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Sculling Lesson with Gordon Hamilton 12 Aug 2013
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Charles Carroll
Aug 18, 2013, 7:38:07 PM8/18/13
to
Dear all,
The following are notes from my lesson with Gordon Hamilton last Monday.
Some of you know Gordon and have been coached by him. Perhaps you will find
something interesting in these notes.
Cordially,
Charles
The lesson began in the Clubhouse, as it always does. Gordon stressed the
importance of keeping the elbows pronated throughout the entire stroke.
“If you pronate the elbows and hold them high during the recovery, it will
keep the blades off the water,” said Gordon. “And if you keep the elbows
pronated at the catch, it will ensure that you will pull with your whole
body rather than just the arms. In other words keeping your elbows pronated
will ensure that your shoulders and lats will stay connected to your legs.
As the legs push off the stretcher the shoulders and lats should pull back
on the oar handles. This should be done simultaneously. It is a single,
coordinated movement. And if you keep the elbows pronated at the release, it
will ensure that you won’t move the blades after they are released.”
Pronate appears to be a relatively new word in Gordon’s coaching lexicon. I
am always a little uncertain about what it means.
Pro•na•tion [prohneyshuhn] rotation of the hand or forearm so that the
surface of the palm is facing downward or toward the back (opposed to
supination ).
So by pronation Gordon simply means keeping the surface of the palms facing
downward and keeping the elbows higher than the hands. In past lessons
Gordon has said: “Your elbows shouldn’t be drawn back past you. They should
be out alongside you and higher than your hands. Your elbows should always
be higher than your hands.”
A passage from Gordon’s Book, “Sculling in a Nutshell,” immediately leaps to
mind:
“If your release has been executed at the correct time, i.e. just as the
back of your legs has hit the seat deck, your blades will have sprung out of
the water and changed direction almost effortlessly, bringing you seamlessly
into the Recovery. On the other hand, if you are accustomed to making the
Release too late, i.e. your stroke is too long at the back end, you will
have to wrestle your blades out of the water in a disruptive, jerky manner.
The tendency will be to stop at the finish and rest at this point with no
Follow-Through. This rest interrupts the release of energy which has been
stored in the oars during the Drive. Among other things, it is this
utilization of the energy of the Drive which creates a sense of Flow, this
wonderful feeling of ease and rhythm that you are after.”
Gordon is adamant about the release—that it should be concurrent with the
legs hitting the seat deck. According to Gordon, if you release
sequentially, using just your arms after the legs hit the seat deck, your
stroke will be too long at the back end and you will be releasing too late.
Keeping the surface of the palms facing downward and keeping the elbows
higher than the hands will prevent this. Gordon made a point of emphasizing
that the arms because they are the weakest body segment should never be used
by themselves even at the finish.
The one thing one thing he regrets about his book, Gordon said, is that he
wasn’t “polemical enough.”
“I have been rowing and sculling for 55 years. Some of the people I coach I
have been coaching for over 4 decades. After all this time I have formed a
very clear idea of how to scull. I know how sculling ought to be done. I
know the correct way to scull.”
So what Gordon meant when he told me that he hadn’t been “polemical enough”
in his book is that he was regretting not having been more tenacious in
making the case for his ideas about how to scull.
I have been taking lessons from Gordon for ten years. I may not know much,
but I do know a little something about how he thinks.
“It seems to me that everything you are coaching for can be distilled into a
single premise of Steve Fairbairn’s.”
Gordon looked amused. I went on.
“Fairbairn maintains that the legs and back should work together. And you,
ever the student of Fairbairn, are coaching for just that. It seems to me
that coupling the drive and draw is the essence what you are coaching for.”
“Exactly!” said Gordon.
“So your idea of the correct way to scull is that the legs and back should
work together concurrently from the instant you begin applying force against
the oar handles all the way through to the end of the stroke.”
“Yes it is.”
“And what’s more the legs and back should never, never, never, ever be
permitted to become uncoupled. When the knees are down the drive is over. It
is as simple as that.”
“Yes it is,” said Gordon. “It is simple as that.”
“…as the oarsman pushes his weight off the stretcher, instantly he must pull
it on to the rowing pin. Coupling the drive and draw is about the most
difficult art of timing in rowing. Once it has been got correctly, the
oarsman will be able to row truly his full weight the length which the
condition of his muscles will allow him to row.” —Steve Fairbairn
The last thing, which I found interesting about the lesson, is Gordon’s use
of technology. He hangs an iPad around his neck. It is protected by a
LifeProof case which is waterproof, dustproof, etc. The iPad and case is
compact enough to allow Gordon the drive the launch and photograph
simultaneously.
To control the camera he uses a sports video app named The Coach’s Eye. You
come in off the water and Gordon can immediately show you a video which
clearly illustrates what he was trying to get you think about when you were
on the water.
I am probably the only person on RSR that hasn’t heard of the Coaches Eye.
It is really a very nifty little app.
The following are notes from my lesson with Gordon Hamilton last Monday.
Some of you know Gordon and have been coached by him. Perhaps you will find
something interesting in these notes.
Cordially,
Charles
The lesson began in the Clubhouse, as it always does. Gordon stressed the
importance of keeping the elbows pronated throughout the entire stroke.
“If you pronate the elbows and hold them high during the recovery, it will
keep the blades off the water,” said Gordon. “And if you keep the elbows
pronated at the catch, it will ensure that you will pull with your whole
body rather than just the arms. In other words keeping your elbows pronated
will ensure that your shoulders and lats will stay connected to your legs.
As the legs push off the stretcher the shoulders and lats should pull back
on the oar handles. This should be done simultaneously. It is a single,
coordinated movement. And if you keep the elbows pronated at the release, it
will ensure that you won’t move the blades after they are released.”
Pronate appears to be a relatively new word in Gordon’s coaching lexicon. I
am always a little uncertain about what it means.
Pro•na•tion [prohneyshuhn] rotation of the hand or forearm so that the
surface of the palm is facing downward or toward the back (opposed to
supination ).
So by pronation Gordon simply means keeping the surface of the palms facing
downward and keeping the elbows higher than the hands. In past lessons
Gordon has said: “Your elbows shouldn’t be drawn back past you. They should
be out alongside you and higher than your hands. Your elbows should always
be higher than your hands.”
A passage from Gordon’s Book, “Sculling in a Nutshell,” immediately leaps to
mind:
“If your release has been executed at the correct time, i.e. just as the
back of your legs has hit the seat deck, your blades will have sprung out of
the water and changed direction almost effortlessly, bringing you seamlessly
into the Recovery. On the other hand, if you are accustomed to making the
Release too late, i.e. your stroke is too long at the back end, you will
have to wrestle your blades out of the water in a disruptive, jerky manner.
The tendency will be to stop at the finish and rest at this point with no
Follow-Through. This rest interrupts the release of energy which has been
stored in the oars during the Drive. Among other things, it is this
utilization of the energy of the Drive which creates a sense of Flow, this
wonderful feeling of ease and rhythm that you are after.”
Gordon is adamant about the release—that it should be concurrent with the
legs hitting the seat deck. According to Gordon, if you release
sequentially, using just your arms after the legs hit the seat deck, your
stroke will be too long at the back end and you will be releasing too late.
Keeping the surface of the palms facing downward and keeping the elbows
higher than the hands will prevent this. Gordon made a point of emphasizing
that the arms because they are the weakest body segment should never be used
by themselves even at the finish.
The one thing one thing he regrets about his book, Gordon said, is that he
wasn’t “polemical enough.”
“I have been rowing and sculling for 55 years. Some of the people I coach I
have been coaching for over 4 decades. After all this time I have formed a
very clear idea of how to scull. I know how sculling ought to be done. I
know the correct way to scull.”
So what Gordon meant when he told me that he hadn’t been “polemical enough”
in his book is that he was regretting not having been more tenacious in
making the case for his ideas about how to scull.
I have been taking lessons from Gordon for ten years. I may not know much,
but I do know a little something about how he thinks.
“It seems to me that everything you are coaching for can be distilled into a
single premise of Steve Fairbairn’s.”
Gordon looked amused. I went on.
“Fairbairn maintains that the legs and back should work together. And you,
ever the student of Fairbairn, are coaching for just that. It seems to me
that coupling the drive and draw is the essence what you are coaching for.”
“Exactly!” said Gordon.
“So your idea of the correct way to scull is that the legs and back should
work together concurrently from the instant you begin applying force against
the oar handles all the way through to the end of the stroke.”
“Yes it is.”
“And what’s more the legs and back should never, never, never, ever be
permitted to become uncoupled. When the knees are down the drive is over. It
is as simple as that.”
“Yes it is,” said Gordon. “It is simple as that.”
“…as the oarsman pushes his weight off the stretcher, instantly he must pull
it on to the rowing pin. Coupling the drive and draw is about the most
difficult art of timing in rowing. Once it has been got correctly, the
oarsman will be able to row truly his full weight the length which the
condition of his muscles will allow him to row.” —Steve Fairbairn
The last thing, which I found interesting about the lesson, is Gordon’s use
of technology. He hangs an iPad around his neck. It is protected by a
LifeProof case which is waterproof, dustproof, etc. The iPad and case is
compact enough to allow Gordon the drive the launch and photograph
simultaneously.
To control the camera he uses a sports video app named The Coach’s Eye. You
come in off the water and Gordon can immediately show you a video which
clearly illustrates what he was trying to get you think about when you were
on the water.
I am probably the only person on RSR that hasn’t heard of the Coaches Eye.
It is really a very nifty little app.
thomas....@googlemail.com
Aug 19, 2013, 5:54:16 AM8/19/13
to
Coaches eye is a great little app, although taking an ipad out in the launch is a pretty hardcore way of using it IMO!
An alternative is to get a camcorder that records in .mp4 (my faves are the Sanyo "pistol grip" range as they are easier to hold) and then either have the SD card reader for the iPad or use the Eyefi SD card that allows you to wirelessly transfer the video from the camera to the iPad
http://www.eye.fi/
An alternative is to get a camcorder that records in .mp4 (my faves are the Sanyo "pistol grip" range as they are easier to hold) and then either have the SD card reader for the iPad or use the Eyefi SD card that allows you to wirelessly transfer the video from the camera to the iPad
http://www.eye.fi/
Carl
Aug 19, 2013, 7:45:04 AM8/19/13
to
Everyone who sculls, rows or coaches acquires their own internal video
of how everything goes together, but each of us should be ready to
submit that imagery to external appraisal, not least to careful
consideration in terms of the resulting inertial consequences &
neuro-muscular demands.
I'm not qualified to comment on the latter, but maybe can contribute on
the former.
First, an observation: I like the idea of everything acting together &
finishing together, but so many fast scullers continue their hand
movement well after the legs are down that it does raise serious
questions about the validity of the all-together rule.
So one ought to consider what happens at the point where the legs cease
extension & the seat stops (although some do extend the feet for more
length). As it reaches full range the seat first must decelerate - over
a measurable distance - WRT the boat. This brings boat & the
overwhelming part of crew mass to the same velocity over the water, but
already the load on the blades has substantially fallen. Indeed, if the
blades are not to be extracted while still under load, we must just
previously have ceased pulling. However, if we still can draw the hands
further into the bow, why is this a bad thing? Are we to suppose that
sustaining load & work is actually a bad thing, even though we know that
propulsive efficiency is rising as we move the blades astern? And if
so, why?
Then at the catch I still have difficulty with the notion that
everything kicks off at the same instant. As previously discussed on
RSR, the oars are very bendy & it takes time & distance (better
expressed as speed, maybe) to get them bent & loaded (a continuous
process of bend increasing with load, during which energy is stored in
the bending of the oar which does nothing, until much later, to propel
the boat). So hitting the stretcher & handles simultaneously can do
nothing at that point but generate a backwards kick on the boat well
before the oars can sustain a corresponding load.
And, as we've also discussed, for the sculler the handles at the catch
are moving more towards each other than towards the bow. In that
geometrical situation it makes sense first to draw the hands towards
each other (equal & opposite reactions, no immediate load on the
stretcher) &, as the oars bend & the load increases, only then to
connect in the rest of the body. Yet still you can insert a further
process, based on inertial reactions, by which small contractions of
hands, arms & flexing of the shoulders increase handle loads by reacting
against body mass _before_ the load hits the stretcher.
In other words, were everything inflexible & all actions axial WRT the
boat, then we might with more justice consider feet, hands & everything
else acting simultaneously at the catch. Yet still we could use the
inertial effect of hand movement reacting against body mass to
non-injuriously impose the early load upon our own non-rigid bodies,
rather than applying an early shearing load across the join between
spine & pelvis.
However, the flexibility of the oarshaft means we can't load feet
against hands simultaneously, while the geometry of the sculling catch
means that failing to use the pectorals & arms to initiate the catch
wastes a logical means of getting an earlier oar flexion & load
application. It may well be that, however we are coached, still we row
more naturally than coach's dictum demands, & coach does not see the
difference between what we actually feel & do, & what he/she believes
they've at last got us to do.
Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ca...@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682
URLs: carldouglas.co.uk & now on Facebook @ CarlDouglasRacingShells
James HS
Aug 19, 2013, 9:08:18 AM8/19/13
to
I have to say that I agree with Carl's assessment - though it is not universally recognised - that the hands should move towards each other as the first art of the catch. i recently mentioned this to my coach - who in all other respects I hold in god like reverence (as she helped me start to improve my extraction)and she said NO - you throw your hands outwards and then take the catch PERIOD (so no discussion :) - great thing about coaching is you take from it what works for you!
but my bigger disagreement is the arm discussion - everyone always sais that the biceps are small (well they are not SO small) but when you draw your arms back you use the Latissimus dorsi, the largest muscle of your back. Lats are initially activated to maintain the torso-leg connection and then to complete the stroke with the handle into the body.
The deltoids stabilize the shoulder joint and maintain handle height throughout the movement. The rhomboids (upper back muscles) pull your shoulder blades together at the end of the stroke.
AND biceps are used in pulling the handle into your body at the finish.
Also the relative lack of strength is a bit off - my target squat is 1.2 bodyweight my target behch pull is 0.94 - so while significantly less, by no means useless! - plus that effective range is approximately 400mm!
I certainly notice on the water when I remember to include the feature out arms full on that I get an improvement in pace!
My only worry about orthodoxy is not to be too dogmatic :)
James
but my bigger disagreement is the arm discussion - everyone always sais that the biceps are small (well they are not SO small) but when you draw your arms back you use the Latissimus dorsi, the largest muscle of your back. Lats are initially activated to maintain the torso-leg connection and then to complete the stroke with the handle into the body.
The deltoids stabilize the shoulder joint and maintain handle height throughout the movement. The rhomboids (upper back muscles) pull your shoulder blades together at the end of the stroke.
AND biceps are used in pulling the handle into your body at the finish.
Also the relative lack of strength is a bit off - my target squat is 1.2 bodyweight my target behch pull is 0.94 - so while significantly less, by no means useless! - plus that effective range is approximately 400mm!
I certainly notice on the water when I remember to include the feature out arms full on that I get an improvement in pace!
My only worry about orthodoxy is not to be too dogmatic :)
James
Carl
Aug 19, 2013, 9:15:39 AM8/19/13
to
On 19/08/2013 00:38, Charles Carroll wrote:
> if you are accustomed to making the Release too late, i.e. your stroke
> is too long at the back end, you will have to wrestle your blades out of
> the water in a disruptive, jerky manner. The tendency will be to stop at
> the finish and rest at this point with no Follow-Through. This rest
> interrupts the release of energy which has been stored in the oars
> during the Drive. Among other things, it is this utilization of the
> energy of the Drive which creates a sense of Flow,
And that bit I just don't get.
> is too long at the back end, you will have to wrestle your blades out of
> the water in a disruptive, jerky manner. The tendency will be to stop at
> the finish and rest at this point with no Follow-Through. This rest
> interrupts the release of energy which has been stored in the oars
> during the Drive. Among other things, it is this utilization of the
> energy of the Drive which creates a sense of Flow,
Agreed, we store energy in the oars - up to the point at which we unload
them. But it seems, if I read this aright, that Gordon doesn't want
that energy released propulsively against the water? So my question:
how does this stored energy assist the recovery? Are we being asked to
assume that the backlash/reverberation of a still-bent oar flicks it
forward into the recovery? What if we have part-feathered by the time
it springs towards the bow (it must first flick sternwards)? The act of
feathering will result in the rebound no longer being in the horizontal
plane.
Similarly, if you relax at the finish how does that interrupt the
release of the energy stored in the oars? Indeed, how does doing so
oblige you to "wrestle your blades ... in a jerky manner".
Carl
Aug 19, 2013, 12:41:29 PM8/19/13
to
On 19/08/2013 14:08, James HS wrote:
> I have to say that I agree with Carl's assessment - though it is not universally recognised - that the hands should move towards each other as the first art of the catch. i recently mentioned this to my coach - who in all other respects I hold in god like reverence (as she helped me start to improve my extraction)and she said NO - you throw your hands outwards and then take the catch PERIOD (so no discussion :) - great thing about coaching is you take from it what works for you!
>
When in a teaching role, it can be a disconcerting to be asked a probing
> I have to say that I agree with Carl's assessment - though it is not universally recognised - that the hands should move towards each other as the first art of the catch. i recently mentioned this to my coach - who in all other respects I hold in god like reverence (as she helped me start to improve my extraction)and she said NO - you throw your hands outwards and then take the catch PERIOD (so no discussion :) - great thing about coaching is you take from it what works for you!
>
question. But I think teaching is about learning, so when a bright
student asks a tricky question it's not good enough to bat it away in
that manner. Better to say, if you know your questioner is far from
dumb, "Interesting! Let's discuss when we've both got a free moment".
But a lot of rowing coaching is narrowly didactic & imitative, treated
more as religious instruction than as a tricky puzzle. And most of us
do find it very tough to have to set aside our preconceptions & let in
alien concepts, let alone to then weigh up those concepts. After all,
if you've paid a fair chunk to acquire your coaching qualifications you
are entering a circle where non-conformity is seen as damaging, so you
don't want word getting out that maybe you no longer 'profess the faith'
in every particular.
As you imply, orthodoxy should not become a strait-jacket. It's a
useful structure but should always be open to examination & revision.
Cheers -
Carl
> but my bigger disagreement is the arm discussion - everyone always sais that the biceps are small (well they are not SO small) but when you draw your arms back you use the Latissimus dorsi, the largest muscle of your back. Lats are initially activated to maintain the torso-leg connection and then to complete the stroke with the handle into the body.
>
> The deltoids stabilize the shoulder joint and maintain handle height throughout the movement. The rhomboids (upper back muscles) pull your shoulder blades together at the end of the stroke.
>
> AND biceps are used in pulling the handle into your body at the finish.
>
> Also the relative lack of strength is a bit off - my target squat is 1.2 bodyweight my target behch pull is 0.94 - so while significantly less, by no means useless! - plus that effective range is approximately 400mm!
>
> I certainly notice on the water when I remember to include the feature out arms full on that I get an improvement in pace!
>
> My only worry about orthodoxy is not to be too dogmatic :)
>
> James
>
Charles Carroll
Aug 19, 2013, 12:57:48 PM8/19/13
to
Carl,
I am about to leave for Sausalito and a second lesson with Gordon. But I did
want to post a quick reply to the question about how to load the blades in
the initial phases of the drive.
So far as I am able to tell, there is no disagreement between you and
Gordon. As you have said so eloquently, “You can’t hit something hard which
offers no resistance.” Gordon completely agrees.
Gordon thinks that in the initial phases of the drive the fingers, hands,
and even arms should be used to build tension within the water. And as you
have said elsewhere, assuming I am remembering correctly, most of this
tension can be built simply by placing your blades deep enough. From a
sculler’s point of view, it may seem like it takes forever to build this
tension, but in reality you build it over a few milliseconds.
Once the blades are able to resist force applied to the oar handles — that’s
when Gordon thinks the legs and back should start working together; and keep
working together all the way through the release. As you put it so clearly,
they act together and finish together ...
Gotta run …
Cordially,
Charles
I am about to leave for Sausalito and a second lesson with Gordon. But I did
want to post a quick reply to the question about how to load the blades in
the initial phases of the drive.
So far as I am able to tell, there is no disagreement between you and
Gordon. As you have said so eloquently, “You can’t hit something hard which
offers no resistance.” Gordon completely agrees.
Gordon thinks that in the initial phases of the drive the fingers, hands,
and even arms should be used to build tension within the water. And as you
have said elsewhere, assuming I am remembering correctly, most of this
tension can be built simply by placing your blades deep enough. From a
sculler’s point of view, it may seem like it takes forever to build this
tension, but in reality you build it over a few milliseconds.
Once the blades are able to resist force applied to the oar handles — that’s
when Gordon thinks the legs and back should start working together; and keep
working together all the way through the release. As you put it so clearly,
they act together and finish together ...
Gotta run …
Cordially,
Charles
Carl
Aug 19, 2013, 5:59:06 PM8/19/13
to
I need to correct one point, but how can I put it? Let's try:
Burying the blade, of itself, does nothing. Loading the buried or
burying blade does everything. No load will appear if you wait for it,
& time will pass fruitlessly.
The load comes only because _you_ apply it. When you apply load, if the
blade is buried the shaft will flex under that load. The blade will
then, simultaneously, feel a load proportional to how much you've flexed
the shaft, which will in turn be proportional to how hard you are pulling.
I have an analogy taking shape, but I have a boat to lacquer again right
now so the analogy has to wait & grow awhile. If it develops into
something useful, I'll let you know :)
Charles Carroll
Aug 19, 2013, 6:55:47 PM8/19/13
to
> Hope it went well, Charles?
Hi Carl,
Being out on the water in my spectacular Carl Douglas always goes well. And
the lesson, too -- that went well.
So it has been a good morning.
> I need to correct one point:
> Burying the blade, of itself, does nothing
I agree, provided the boat isn’t moving. But would this be true for a boat
underway?
Assume a scull is inserted in an oarlock which is attached to a moving boat.
Wouldn’t the blade of this scull when buried and held in place build a
tension within the water?
> I have an analogy taking shape,
> but I have a boat to lacquer again right now so the analogy has to wait &
> grow awhile
Brings to mind one of my favorite passages.
And as imagination bodies forth
The forms of things unknown, the poet's pen
Turns them to shapes and gives to airy nothing
A local habitation and a name.
Cordially,
Charles
Carl
Aug 19, 2013, 8:17:39 PM8/19/13
to
On 19/08/2013 23:55, Charles Carroll wrote:
>> Hope it went well, Charles?
>
> Hi Carl,
>
> Being out on the water in my spectacular Carl Douglas always goes well.
> And the lesson, too -- that went well.
>
> So it has been a good morning.
>
>> I need to correct one point:
>> Burying the blade, of itself, does nothing
>
> I agree, provided the boat isn’t moving. But would this be true for a
> boat underway?
>
> Assume a scull is inserted in an oarlock which is attached to a moving
> boat. Wouldn’t the blade of this scull when buried and held in place
> build a tension within the water?
Sadly it would not. You would have the flow along the blade which is a
>> Hope it went well, Charles?
>
> Hi Carl,
>
> Being out on the water in my spectacular Carl Douglas always goes well.
> And the lesson, too -- that went well.
>
> So it has been a good morning.
>
>> I need to correct one point:
>> Burying the blade, of itself, does nothing
>
> I agree, provided the boat isn’t moving. But would this be true for a
> boat underway?
>
> Assume a scull is inserted in an oarlock which is attached to a moving
> boat. Wouldn’t the blade of this scull when buried and held in place
> build a tension within the water?
prerequisite for the generation of lift, but without load there would be
no lift.
It's hard to explain this, but I'll try:
Lift on a foil arises only when the foil bears a load, & its magnitude &
direction matches that of the load. If a foil is inserted into a flow &
appropriately aligned, the flow over the foil will generate lift. If
the foil is held firm, the force needed to hold it will, in simple
terms, be equal to the lift. If the angle of the foil's axis to the
flow is increased, the lift will also increase. So far, so simple.
If the grip on the foil is now released, then like a ball rolling down a
hill, it will move in a way which reduces the load & lift. That may
either be by rotating into a direction which reduces the lift (reduced
angle of attack), or by moving with the flowing fluid (which reduces the
relative velocity of fluid & foil, & hence the lift.
If you just place an unrestrained oar's blade into the water in the
catch position, with the boat moving, the oar will swing around the pin
in a manner rather similar to a loaded oar, but not quite as rapidly.
That's because, with no load on the blade, it tries to adopt an AoA
which is lift-neutral. Load it up and the flow will still be tip-first,
but will actually come from a slightly more sternward direction, which
means an increased AoA, & that angle self-adjusts continually to match
the applied load.
Lift is not something which establishes itself. It is the difference of
pressure between opposite faces of the foil. It is AoA which
automatically establishes itself. This it does in response to the
applied load, its own shape & the flow over its surfaces. AoA is
self-adjusting, a direct consequence of what is required in those flow
conditions to create a lift force which balances the applied load.
It is both a simple & a vexing concept, so I fully sympathise with
anyone who finds it intractable. One's own interpretations can
completely obscure the view, & please understand that that is not in any
way a symptom of being dumb.
Glad the outing went well. That's what matters!
Cheers -
Carl
>
>> I have an analogy taking shape,
>> but I have a boat to lacquer again right now so the analogy has to
>> wait & grow awhile
>
> And I hope your analogy takes on a proper shape while you are
> lacquering. Brings to mind one of my favorite passages.
>
> And as imagination bodies forth
> The forms of things unknown, the poet's pen
> Turns them to shapes and gives to airy nothing
> A local habitation and a name.
>
> Cordially,
>
> Charles
>
John Greenly
Aug 20, 2013, 12:57:55 PM8/20/13
to
On Monday, August 19, 2013 6:55:47 PM UTC-4, Charles Carroll wrote:
> > Hope it went well, Charles? Hi Carl, Being out on the water in my spectacular Carl Douglas always goes well. And the lesson, too -- that went well. So it has been a good morning. > I need to correct one point: > Burying the blade, of itself, does nothing I agree, provided the boat isn’t moving. But would this be true for a boat underway? Assume a scull is inserted in an oarlock which is attached to a moving boat. Wouldn’t the blade of this scull when buried and held in place build a tension within the water? > I have an analogy taking shape, > but I have a boat to lacquer again right now so the analogy has to wait & > grow awhile And I hope your analogy takes on a proper shape while you are lacquering. Brings to mind one of my favorite passages. And as imagination bodies forth The forms of things unknown, the poet's pen Turns them to shapes and gives to airy nothing A local habitation and a name. Cordially, Charles
Hi Charles,
> > Hope it went well, Charles? Hi Carl, Being out on the water in my spectacular Carl Douglas always goes well. And the lesson, too -- that went well. So it has been a good morning. > I need to correct one point: > Burying the blade, of itself, does nothing I agree, provided the boat isn’t moving. But would this be true for a boat underway? Assume a scull is inserted in an oarlock which is attached to a moving boat. Wouldn’t the blade of this scull when buried and held in place build a tension within the water? > I have an analogy taking shape, > but I have a boat to lacquer again right now so the analogy has to wait & > grow awhile And I hope your analogy takes on a proper shape while you are lacquering. Brings to mind one of my favorite passages. And as imagination bodies forth The forms of things unknown, the poet's pen Turns them to shapes and gives to airy nothing A local habitation and a name. Cordially, Charles
A wonderful quotation, thanks!
May I have a go at this question? Let's make you the scientist. Do an experiment: get the boat moving, then plunk your blades into the water (at any angle you like- try various) hold them so they can't move, and see what happens! I'm sure you don't need to do this experiment, you already know what will happen- it will put on the brakes, the boat will slow down, because the water is pushing on the blades as it flows by. That does indeed load the oars- you would feel the force at the handles- but it's in the wrong direction! To load the oars in the opposite direction to propel the boat, you need to reverse the force, namely by pulling on the handles. They then move faster than they would if you were to just let them go free, and that relative motion against the water generates the force in the other- propulsive- direction. Until you pull, the oar is not loaded and flexed for propulsion. (If you let go of a handle, that oar will just pivot freely and there will be almost zero load on the oar-- an experiment I once did unintentionally, with interesing results on the roll axis....)
Does this make sense?
By the way, there is really no such thing as a tensile force under water. Fluids generally can't support internal tension. If you manage to get the pressure down to or below zero in a fluid it will separate, or cavitate, as can happen around a powerful propellor blade. What does happen to your oar blade is that the pressure on one side (the back, when you're propelling) is lower than the pressure on the other (front) side, resulting in the net force on the blade. It doesn't take much pressure difference: the pressure right near the water surface is one atmosphere, 15 lb/in^2. A 10% difference in pressure between front and back would be 1.5 lb/in^2, and with a blade area of around a square foot, this would give over 200 lb total force-- not even a monster rower could pull that hard, remembering the adverse lever ratio of the oar.
Cheers,
John G
Carl
Aug 20, 2013, 3:30:48 PM8/20/13
to
On 20/08/2013 17:57, John Greenly wrote:
> On Monday, August 19, 2013 6:55:47 PM UTC-4, Charles Carroll wrote:
>>> Hope it went well, Charles? Hi Carl, Being out on the water in my spectacular Carl Douglas always goes well. And the lesson, too -- that went well. So it has been a good morning. > I need to correct one point: > Burying the blade, of itself, does nothing I agree, provided the boat isn�t moving. But would this be true for a boat underway? Assume a scull is inserted in an oarlock which is attached to a moving boat. Wouldn�t the blade of this scull when buried and held in place build a tension within the water? > I have an analogy taking shape, > but I have a boat to lacquer again right now so the analogy has to wait & > grow awhile And I hope your analogy takes on a proper shape while you are lacquering. Brings to mind one of my favorite passages. And as imagination bodies forth The forms of things unknown, the poet's pen Turns them to shapes and gives to airy nothing A local habitation and a name. Cordially, Charles
> On Monday, August 19, 2013 6:55:47 PM UTC-4, Charles Carroll wrote:
>
> Hi Charles,
>
> A wonderful quotation, thanks!
>
> May I have a go at this question? Let's make you the scientist. Do an experiment: get the boat moving, then plunk your blades into the water (at any angle you like- try various) hold them so they can't move, and see what happens! I'm sure you don't need to do this experiment, you already know what will happen- it will put on the brakes, the boat will slow down, because the water is pushing on the blades as it flows by. That does indeed load the oars- you would feel the force at the handles- but it's in the wrong direction! To load the oars in the opposite direction to propel the boat, you need to reverse the force, namely by pulling on the handles. They then move faster than they would if you were to just let them go free, and that relative motion against the water generates the force in the other- propulsive- direction. Until you pull, the oar is not loaded and flexed for propulsion. (If you let go of a handle, that oar will just pivot freely and there will be almost zer
o load on the oar-- an experiment I once did unintentionally, with interesing results on the roll axis....)
>
> Does this make sense?
>
> By the way, there is really no such thing as a tensile force under water. Fluids generally can't support internal tension. If you manage to get the pressure down to or below zero in a fluid it will separate, or cavitate, as can happen around a powerful propellor blade. What does happen to your oar blade is that the pressure on one side (the back, when you're propelling) is lower than the pressure on the other (front) side, resulting in the net force on the blade. It doesn't take much pressure difference: the pressure right near the water surface is one atmosphere, 15 lb/in^2. A 10% difference in pressure between front and back would be 1.5 lb/in^2, and with a blade area of around a square foot, this would give over 200 lb total force-- not even a monster rower could pull that hard, remembering the adverse lever ratio of the oar.
>
> Cheers,
>
> John G
>
I should politely disagree with you on the tension question, John.
> Hi Charles,
>
> A wonderful quotation, thanks!
>
> May I have a go at this question? Let's make you the scientist. Do an experiment: get the boat moving, then plunk your blades into the water (at any angle you like- try various) hold them so they can't move, and see what happens! I'm sure you don't need to do this experiment, you already know what will happen- it will put on the brakes, the boat will slow down, because the water is pushing on the blades as it flows by. That does indeed load the oars- you would feel the force at the handles- but it's in the wrong direction! To load the oars in the opposite direction to propel the boat, you need to reverse the force, namely by pulling on the handles. They then move faster than they would if you were to just let them go free, and that relative motion against the water generates the force in the other- propulsive- direction. Until you pull, the oar is not loaded and flexed for propulsion. (If you let go of a handle, that oar will just pivot freely and there will be almost zer
o load on the oar-- an experiment I once did unintentionally, with interesing results on the roll axis....)
>
> Does this make sense?
>
> By the way, there is really no such thing as a tensile force under water. Fluids generally can't support internal tension. If you manage to get the pressure down to or below zero in a fluid it will separate, or cavitate, as can happen around a powerful propellor blade. What does happen to your oar blade is that the pressure on one side (the back, when you're propelling) is lower than the pressure on the other (front) side, resulting in the net force on the blade. It doesn't take much pressure difference: the pressure right near the water surface is one atmosphere, 15 lb/in^2. A 10% difference in pressure between front and back would be 1.5 lb/in^2, and with a blade area of around a square foot, this would give over 200 lb total force-- not even a monster rower could pull that hard, remembering the adverse lever ratio of the oar.
>
> Cheers,
>
> John G
>
Water columns ascend capillaries &, indeed, trees not because the water
is pumped up from below but because it is pulled up from above. Water
can, transiently, support colossal tension for a time, subject only to
purity & the lack of fine particles to provide centres for nucleation.
In the shorter term & the more real world, the time taken for nucleation
under large negative internal pressures (internal tension) can be long
enough for incipient cavitation (i.e. boiling) not to affect that situation.
With an oar, as you say, the surface loadings are minute. Indeed it is
arguable that oars are already too large, if only we would make better
use of the ends of the stroke & less use of the middle.
An oar after the catch is acting as a foil or wing, with flow passing
along it from tip to root, & the resistance to its face-first motion
through the water derives almost entirely from pressure reduction across
the convex back of the blade, just as for any wing, with little or no
contribution from any front face pressure rise. Indeed, so effective is
the back-face tension that there is virtually no pressure build up on
the convex face until you approach the mid-stroke stall. Even then, the
tension on the back of a well-covered blade is equal to or greater than
the pressure on its front face.
The better use of oars to win races has been bedevilled by a C19th
illustration, which pops up everywhere, showing a notional oarblade
complete with central spine splitting & turning back on its path an
oncoming flow of water. Drawn by some armchair classics scholar no
doubt ;) That illustration is, of course, total hokum although rarely
recognised as such. But it is hokum which attaches itself seamlessly, &
lends credibility, to the popular belief that the place to do your best
work is "obviously" when the oar is perpendicular to the boat - at the
magically sciency-sounding "orthogonal", egad!
The reason a cavity need not & should not form behind a loaded blade
during the first 1/3 & last 1/4 of the stroke is that the flow of water
along the blade ensures that new water keeps being introduced before
tension & time can lower the water surface enough to expose the back of
the blade (water's inertia is important here). However, this does
require the blade be kept below the current water surface, which is too
often not the case during mid-stroke. In part the mid-stroke is
problematic, with a cavity forming behind the blade there, because
rowers are wrongly told that any amount of 'looming' must immediately
cause deleterious drag & that the right level for the blade is with its
upper edge level with the surface. And without the water behind it, the
blade then slips markedly face-first until flow from root to tip is
established towards the finish. A deeper blade ensures the tension in
teh water does not pull the surface down far enough to expose the back
of the blade in the short time available.
That's more than enough of a lecture from me, & I must apologise in
advance for seeming to jump in with both feet, & for any inadvertent
typos (I'm in a hurry to be elsewhere). Of course I'm more than happy
to answer challenges from all & sundry :)
John Greenly
Aug 20, 2013, 6:25:47 PM8/20/13
to
On Tuesday, August 20, 2013 3:30:48 PM UTC-4, Carl wrote:
> On 20/08/2013 17:57, John Greenly wrote: > On Monday, August 19, 2013 6:55:47 PM UTC-4, Charles Carroll wrote: >>> Hope it went well, Charles? Hi Carl, Being out on the water in my spectacular Carl Douglas always goes well. And the lesson, too -- that went well. So it has been a good morning. > I need to correct one point: > Burying the blade, of itself, does nothing I agree, provided the boat isn’t moving. But would this be true for a boat underway? Assume a scull is inserted in an oarlock which is attached to a moving boat. Wouldn’t the blade of this scull when buried and held in place build a tension within the water? > I have an analogy taking shape, > but I have a boat to lacquer again right now so the analogy has to wait & > grow awhile And I hope your analogy takes on a proper shape while you are lacquering. Brings to mind one of my favorite passages. And as imagination bodies forth The forms of things unknown, the poet's pen Turns them to shapes and gives to airy nothing A local habitation and a name. Cordially, Charles > > Hi Charles, > > A wonderful quotation, thanks! > > May I have a go at this question? Let's make you the scientist. Do an experiment: get the boat moving, then plunk your blades into the water (at any angle you like- try various) hold them so they can't move, and see what happens! I'm sure you don't need to do this experiment, you already know what will happen- it will put on the brakes, the boat will slow down, because the water is pushing on the blades as it flows by. That does indeed load the oars- you would feel the force at the handles- but it's in the wrong direction! To load the oars in the opposite direction to propel the boat, you need to reverse the force, namely by pulling on the handles. They then move faster than they would if you were to just let them go free, and that relative motion against the water generates the force in the other- propulsive- direction. Until you pull, the oar is not loaded and flexed for propulsion. (If you let go of a handle, that oar will just pivot freely and there will be almost zer o load on the oar-- an experiment I once did unintentionally, with interesing results on the roll axis....) > > Does this make sense? > > By the way, there is really no such thing as a tensile force under water. Fluids generally can't support internal tension. If you manage to get the pressure down to or below zero in a fluid it will separate, or cavitate, as can happen around a powerful propellor blade. What does happen to your oar blade is that the pressure on one side (the back, when you're propelling) is lower than the pressure on the other (front) side, resulting in the net force on the blade. It doesn't take much pressure difference: the pressure right near the water surface is one atmosphere, 15 lb/in^2. A 10% difference in pressure between front and back would be 1.5 lb/in^2, and with a blade area of around a square foot, this would give over 200 lb total force-- not even a monster rower could pull that hard, remembering the adverse lever ratio of the oar. > > Cheers, > > John G > I should politely disagree with you on the tension question, John. Water columns ascend capillaries &, indeed, trees not because the water is pumped up from below but because it is pulled up from above. Water can, transiently, support colossal tension for a time, subject only to purity & the lack of fine particles to provide centres for nucleation. In the shorter term & the more real world, the time taken for nucleation under large negative internal pressures (internal tension) can be long enough for incipient cavitation (i.e. boiling) not to affect that situation. With an oar, as you say, the surface loadings are minute. Indeed it is arguable that oars are already too large, if only we would make better use of the ends of the stroke & less use of the middle. An oar after the catch is acting as a foil or wing, with flow passing along it from tip to root, & the resistance to its face-first motion through the water derives almost entirely from pressure reduction across the convex back of the blade, just as for any wing, with little or no contribution from any front face pressure rise. Indeed, so effective is the back-face tension that there is virtually no pressure build up on the convex face until you approach the mid-stroke stall. Even then, the tension on the back of a well-covered blade is equal to or greater than the pressure on its front face. The better use of oars to win races has been bedevilled by a C19th illustration, which pops up everywhere, showing a notional oarblade complete with central spine splitting & turning back on its path an oncoming flow of water. Drawn by some armchair classics scholar no doubt ;) That illustration is, of course, total hokum although rarely recognised as such. But it is hokum which attaches itself seamlessly, & lends credibility, to the popular belief that the place to do your best work is "obviously" when the oar is perpendicular to the boat - at the magically sciency-sounding "orthogonal", egad! The reason a cavity need not & should not form behind a loaded blade during the first 1/3 & last 1/4 of the stroke is that the flow of water along the blade ensures that new water keeps being introduced before tension & time can lower the water surface enough to expose the back of the blade (water's inertia is important here). However, this does require the blade be kept below the current water surface, which is too often not the case during mid-stroke. In part the mid-stroke is problematic, with a cavity forming behind the blade there, because rowers are wrongly told that any amount of 'looming' must immediately cause deleterious drag & that the right level for the blade is with its upper edge level with the surface. And without the water behind it, the blade then slips markedly face-first until flow from root to tip is established towards the finish. A deeper blade ensures the tension in teh water does not pull the surface down far enough to expose the back of the blade in the short time available. That's more than enough of a lecture from me, & I must apologise in advance for seeming to jump in with both feet, & for any inadvertent typos (I'm in a hurry to be elsewhere). Of course I'm more than happy to answer challenges from all & sundry :) Cheers - Carl
Hi Carl,
I apologize for oversimplifying my point- I didn't want to complicate it unnecessarily. In case it will be of interest let's talk about it a bit.
Actually any liquid does certainly have attractive forces, usually called cohesive force between identical molecules; that's what keeps them from wandering away and falling apart into a gas- boiling! Water has particularly strong cohesive intermolecular forces because of the large dipole moment of the molecules (making so-called hydrogen bonds). The amazing ability of tall trees to pull water up to their tops does indeed make use of this cohesive force, which easily holds up to 10 atmospheres of tension in the very narrow capillaries of the xylem tissue- the "pipes" in trees. This classic problem in the physics of cohesion in liquids is complicated by osmotic effects, chemical gradients, not to mention that there is fascinating evidence emerging in recent times that water may develop an entirely different, more ordered structure near hydrophilic surfaces, something like a liquid-crystal state- a discovery that may have revolutionary implications in all sorts of ways.
The cohesive effect shows up strongly at the free surface of water where the force is inward into the volume (classical surface tension) and also it can be very strong at contact with a solid surface; there the magnitude and direction of the force depends upon the interaction of the water molecules with the particular type of surface as well as with each other, and that plays a role in tree xylem. However, the cohesion in bulk water (that is, not within a short distance of a surface) though affecting viscosity, is not a very important effect until the pressure gets very low; there it does indeed inhibit boiling and the formation of cavities, but not very strongly, especially if there are impurities to nucleate bubbles as is always the case in our rivers and seas, as you said.
Here, for instance- I looked it up: the boiling temperature of water at +0.5 psi absolute pressure (0.03 atmospheres) is about 80 degrees farenheit. So at that temperature water begins to fall apart into a gas even while the pressure is still slightly positive, no tension needed. The thermal jiggling energy of the molecules is enough to overcome the cohesive forces. It's a good thing we have an atmosphere applying pressure to the surface of our rivers, otherwise they would boil all away on a nice summer day! That's also one reason why you can't go on a space walk without a pressure suit: your blood would boil at zero pressure. And, the fact that water doesn't boil in tall trees at that temperature even at hugely negative pressure is a good clue that something else is going on there that is not characteristic of bulk water with a free surface....
Now back to oar blades. We agree that the pressure difference on the two faces of the oar blade is only a few percent of atmospheric pressure at most, and you rightly state that it is mostly due to a reduction on the back face, a consequence of the hydrodynamics. So certainly you agree that the pressure on the back face is still positive, not negative; it's just slightly smaller than on the other side. There is no tensile stress, the water is just pushing harder on one side than on the other.
If you don't immerse the blade properly, air will happily rush in and separate the water from the back of the blade, because the air is at atmospheric pressure, and the water behind the blade is a bit below that (a reduction of 0.5psi below atmospheric is enough to let the air push its way down to about a foot below the surface). So the pressure there relative to atmosphere is negative, but again, nowhere is the absolute pressure negative. It's lower than atmosphere, but still way above zero.
I bet we are just dealing with a simple nomenclature problem here. When you suck on a straw, you are reducing the pressure at your end so your drink flows up. You have reduced the pressure at the top relative to the surface of your drink which is open to atmospheric pressure- so you can certainly say that the relative pressure is negative with respect to atmospheric. But it is still far above the zero absolute pressure below which actual tensile stress appears in the liquid. Try it with a pressure gauge- I have had students try that, and nobody can suck the pressure down by more than 2 or 3 psi or so. So, if I just replace your use of the word "tension" with the phrase "reduced pressure", then we're together on all that you have explained. My point is only the minor one that because the absolute pressure is everywhere positive, you don't need to invoke the cohesive strength of water to correctly understand any of it, which is why I left it out in my previous post. There is no tensile stress.
Yes?
--John G
This is good for me- it will help me the next time this subject comes up with a student!
> On 20/08/2013 17:57, John Greenly wrote: > On Monday, August 19, 2013 6:55:47 PM UTC-4, Charles Carroll wrote: >>> Hope it went well, Charles? Hi Carl, Being out on the water in my spectacular Carl Douglas always goes well. And the lesson, too -- that went well. So it has been a good morning. > I need to correct one point: > Burying the blade, of itself, does nothing I agree, provided the boat isn’t moving. But would this be true for a boat underway? Assume a scull is inserted in an oarlock which is attached to a moving boat. Wouldn’t the blade of this scull when buried and held in place build a tension within the water? > I have an analogy taking shape, > but I have a boat to lacquer again right now so the analogy has to wait & > grow awhile And I hope your analogy takes on a proper shape while you are lacquering. Brings to mind one of my favorite passages. And as imagination bodies forth The forms of things unknown, the poet's pen Turns them to shapes and gives to airy nothing A local habitation and a name. Cordially, Charles > > Hi Charles, > > A wonderful quotation, thanks! > > May I have a go at this question? Let's make you the scientist. Do an experiment: get the boat moving, then plunk your blades into the water (at any angle you like- try various) hold them so they can't move, and see what happens! I'm sure you don't need to do this experiment, you already know what will happen- it will put on the brakes, the boat will slow down, because the water is pushing on the blades as it flows by. That does indeed load the oars- you would feel the force at the handles- but it's in the wrong direction! To load the oars in the opposite direction to propel the boat, you need to reverse the force, namely by pulling on the handles. They then move faster than they would if you were to just let them go free, and that relative motion against the water generates the force in the other- propulsive- direction. Until you pull, the oar is not loaded and flexed for propulsion. (If you let go of a handle, that oar will just pivot freely and there will be almost zer o load on the oar-- an experiment I once did unintentionally, with interesing results on the roll axis....) > > Does this make sense? > > By the way, there is really no such thing as a tensile force under water. Fluids generally can't support internal tension. If you manage to get the pressure down to or below zero in a fluid it will separate, or cavitate, as can happen around a powerful propellor blade. What does happen to your oar blade is that the pressure on one side (the back, when you're propelling) is lower than the pressure on the other (front) side, resulting in the net force on the blade. It doesn't take much pressure difference: the pressure right near the water surface is one atmosphere, 15 lb/in^2. A 10% difference in pressure between front and back would be 1.5 lb/in^2, and with a blade area of around a square foot, this would give over 200 lb total force-- not even a monster rower could pull that hard, remembering the adverse lever ratio of the oar. > > Cheers, > > John G > I should politely disagree with you on the tension question, John. Water columns ascend capillaries &, indeed, trees not because the water is pumped up from below but because it is pulled up from above. Water can, transiently, support colossal tension for a time, subject only to purity & the lack of fine particles to provide centres for nucleation. In the shorter term & the more real world, the time taken for nucleation under large negative internal pressures (internal tension) can be long enough for incipient cavitation (i.e. boiling) not to affect that situation. With an oar, as you say, the surface loadings are minute. Indeed it is arguable that oars are already too large, if only we would make better use of the ends of the stroke & less use of the middle. An oar after the catch is acting as a foil or wing, with flow passing along it from tip to root, & the resistance to its face-first motion through the water derives almost entirely from pressure reduction across the convex back of the blade, just as for any wing, with little or no contribution from any front face pressure rise. Indeed, so effective is the back-face tension that there is virtually no pressure build up on the convex face until you approach the mid-stroke stall. Even then, the tension on the back of a well-covered blade is equal to or greater than the pressure on its front face. The better use of oars to win races has been bedevilled by a C19th illustration, which pops up everywhere, showing a notional oarblade complete with central spine splitting & turning back on its path an oncoming flow of water. Drawn by some armchair classics scholar no doubt ;) That illustration is, of course, total hokum although rarely recognised as such. But it is hokum which attaches itself seamlessly, & lends credibility, to the popular belief that the place to do your best work is "obviously" when the oar is perpendicular to the boat - at the magically sciency-sounding "orthogonal", egad! The reason a cavity need not & should not form behind a loaded blade during the first 1/3 & last 1/4 of the stroke is that the flow of water along the blade ensures that new water keeps being introduced before tension & time can lower the water surface enough to expose the back of the blade (water's inertia is important here). However, this does require the blade be kept below the current water surface, which is too often not the case during mid-stroke. In part the mid-stroke is problematic, with a cavity forming behind the blade there, because rowers are wrongly told that any amount of 'looming' must immediately cause deleterious drag & that the right level for the blade is with its upper edge level with the surface. And without the water behind it, the blade then slips markedly face-first until flow from root to tip is established towards the finish. A deeper blade ensures the tension in teh water does not pull the surface down far enough to expose the back of the blade in the short time available. That's more than enough of a lecture from me, & I must apologise in advance for seeming to jump in with both feet, & for any inadvertent typos (I'm in a hurry to be elsewhere). Of course I'm more than happy to answer challenges from all & sundry :) Cheers - Carl
Hi Carl,
I apologize for oversimplifying my point- I didn't want to complicate it unnecessarily. In case it will be of interest let's talk about it a bit.
Actually any liquid does certainly have attractive forces, usually called cohesive force between identical molecules; that's what keeps them from wandering away and falling apart into a gas- boiling! Water has particularly strong cohesive intermolecular forces because of the large dipole moment of the molecules (making so-called hydrogen bonds). The amazing ability of tall trees to pull water up to their tops does indeed make use of this cohesive force, which easily holds up to 10 atmospheres of tension in the very narrow capillaries of the xylem tissue- the "pipes" in trees. This classic problem in the physics of cohesion in liquids is complicated by osmotic effects, chemical gradients, not to mention that there is fascinating evidence emerging in recent times that water may develop an entirely different, more ordered structure near hydrophilic surfaces, something like a liquid-crystal state- a discovery that may have revolutionary implications in all sorts of ways.
The cohesive effect shows up strongly at the free surface of water where the force is inward into the volume (classical surface tension) and also it can be very strong at contact with a solid surface; there the magnitude and direction of the force depends upon the interaction of the water molecules with the particular type of surface as well as with each other, and that plays a role in tree xylem. However, the cohesion in bulk water (that is, not within a short distance of a surface) though affecting viscosity, is not a very important effect until the pressure gets very low; there it does indeed inhibit boiling and the formation of cavities, but not very strongly, especially if there are impurities to nucleate bubbles as is always the case in our rivers and seas, as you said.
Here, for instance- I looked it up: the boiling temperature of water at +0.5 psi absolute pressure (0.03 atmospheres) is about 80 degrees farenheit. So at that temperature water begins to fall apart into a gas even while the pressure is still slightly positive, no tension needed. The thermal jiggling energy of the molecules is enough to overcome the cohesive forces. It's a good thing we have an atmosphere applying pressure to the surface of our rivers, otherwise they would boil all away on a nice summer day! That's also one reason why you can't go on a space walk without a pressure suit: your blood would boil at zero pressure. And, the fact that water doesn't boil in tall trees at that temperature even at hugely negative pressure is a good clue that something else is going on there that is not characteristic of bulk water with a free surface....
Now back to oar blades. We agree that the pressure difference on the two faces of the oar blade is only a few percent of atmospheric pressure at most, and you rightly state that it is mostly due to a reduction on the back face, a consequence of the hydrodynamics. So certainly you agree that the pressure on the back face is still positive, not negative; it's just slightly smaller than on the other side. There is no tensile stress, the water is just pushing harder on one side than on the other.
If you don't immerse the blade properly, air will happily rush in and separate the water from the back of the blade, because the air is at atmospheric pressure, and the water behind the blade is a bit below that (a reduction of 0.5psi below atmospheric is enough to let the air push its way down to about a foot below the surface). So the pressure there relative to atmosphere is negative, but again, nowhere is the absolute pressure negative. It's lower than atmosphere, but still way above zero.
I bet we are just dealing with a simple nomenclature problem here. When you suck on a straw, you are reducing the pressure at your end so your drink flows up. You have reduced the pressure at the top relative to the surface of your drink which is open to atmospheric pressure- so you can certainly say that the relative pressure is negative with respect to atmospheric. But it is still far above the zero absolute pressure below which actual tensile stress appears in the liquid. Try it with a pressure gauge- I have had students try that, and nobody can suck the pressure down by more than 2 or 3 psi or so. So, if I just replace your use of the word "tension" with the phrase "reduced pressure", then we're together on all that you have explained. My point is only the minor one that because the absolute pressure is everywhere positive, you don't need to invoke the cohesive strength of water to correctly understand any of it, which is why I left it out in my previous post. There is no tensile stress.
Yes?
--John G
This is good for me- it will help me the next time this subject comes up with a student!
Carl
Aug 20, 2013, 7:31:36 PM8/20/13
to
On 20/08/2013 23:25, John Greenly wrote:
> On Tuesday, August 20, 2013 3:30:48 PM UTC-4, Carl wrote:
>> On 20/08/2013 17:57, John Greenly wrote: > On Monday, August 19, 2013 6:55:47 PM UTC-4, Charles Carroll wrote: >>> Hope it went well, Charles? Hi Carl, Being out on the water in my spectacular Carl Douglas always goes well. And the lesson, too -- that went well. So it has been a good morning. > I need to correct one point: > Burying the blade, of itself, does nothing I agree, provided the boat isn�t moving. But would this be true for a boat underway? Assume a scull is inserted in an oarlock which is attached to a moving boat. Wouldn�t the blade of this scull when buried and held in place build a tension within the water? > I have an analogy taking shape, > but I have a boat to lacquer again right now so the analogy has to wait & > grow awhile And I hope your analogy takes on a proper shape while you are lacquering. Brings to mind one of my favorite passages. And as imagination bodies forth The forms of things unknown, the poet's pen Turns them to shapes and gives to airy nothing
> On Tuesday, August 20, 2013 3:30:48 PM UTC-4, Carl wrote:
Atmospheric pressure sits on all we do, which as you say is rather
fortunate for those interested in using liquid water. And it also
imposes itself upon solids, & thus within solids. So when we stretch a
lump of rubber, we say we have it under tension even if that stretch is
rather slight or its modulus quite low. Yet in reality the internal
pressure of that rubber is barely affected.
I see tension & reduced internal pressure as different sides of the same
animal, with tension - the depression of internal pressure - sometimes
the easier beast to envisage. Conversely, if we talk about pressure
being higher on the face of the oarblade, we tend to return the new
reader to their previous view that it is pressure on that face which
propels the boat when the reality is that this pressure barely changes
while the pressure behind the blade falls.
Tension used as an expression of a pressure reduction within a
continuous liquid that's already held together by strong intermolecular
forces as well as by atmospheric pressure does, I hope, lessen the
chance of the new seeker after knowledge slipping back into that sort of
misinterpretation which so impedes rowers' understanding of how their
oar actually works. As with the various ways of interpreting the source
of fluid dynamic lift (e.g. circulation vs Bernoulli), it can be helpful
to use that perspective which most easily explains what goes on & is in
reality is not incorrect. In this case tension, or the depression in
internal pressure, seems useful and not inappropriate.
Comments & amendments, please.
John Greenly
Aug 20, 2013, 10:12:20 PM8/20/13
to
I hope I didn't confuse Charles (Charles, are you still out there after all this??). I guess what I was worrying was that Carl's use of the word tension might be leading Charles to think that the water is somehow pulling on the back side of the blade. That's not true, it's just not pushing quite as hard as on the front side. That's a consequence of the flow of water that develops around the blade when you exert a force on ("load") the oar, and it really is complicated, but don't worry, it'll happen just fine whether we understand it or not- rowing is simple, just put the oar in the water and pull.
Hmmm, if there were no atmospheric pressure, then the flow would probably actually try to produce negative absolute pressure, a tensile stress, in the water behind the blade-- and I don't know what would happen. Would the flow cavitate? Would little puffs of cold steam come out? Aha!! We can propose an experiment on the international space station: we send up a big water tank, and a Carl Douglas shell, and a sculling astronaut... shouldn't cost more than a few hundred million. How would you like to be the first builder to send a shell into orbit?
At this point, I can't resist my favorite quote from Nietzsche:
"When one rows, it is not the rowing which moves the ship: rowing is only a magical ceremony by means of which one compels a demon to move the ship."
Well, I guess that has thrown a monkey wrench into the works....
Cheers,
John G
By the way, I just recently came across this business about a previously unknown state of water near surfaces; it's quite fascinating, even though it probably has nothing to do with rowing, so this paragraph is hopelessly Off Topic. A man named Gerald Pollack at the University of Washington has been the main investigator- you can google him to find something about it.
Carl
Aug 21, 2013, 6:23:42 AM8/21/13
to
of the day.
Our problem with the ISS jaunt (yes, I'm up for that one!) would be the
lack of gravity as well as of pressure. Without gravity, I guess we'd
be rowing over the surface of a large ball of boiling liquid held
together only by its intermolecular forces, so best not make a wave.
And then it'd freeze solid in the middle of our test program, with
vapour subliming off the sunward side (but probably not redepositing on
t'other side). Ah well, back to the drawing board?
I suspect that the great German coach, Karl Adam, knew a bit more about
rowing than the philosopher who thought, "Yhat which does not kill you
makes you stronger", although Nietsche's dictum seems to inspire many
more-sadistic coaches.
Yes, I fear Charles may have run away screaming from the scene of our
discussion. Come back, Charles! We didn't mean it to hurt that much.
Honest! Just remember the philosophical centipede. He was out walking
on a hot day & sat down on a twig for a breather. as he sat, he
pondered, "Now which leg goes down after which". Not a good idea - as
he set off he tangled up & fell over his own feet.
Carl
Aug 21, 2013, 10:35:14 AM8/21/13
to
If there were no gravity & a vacuum, then the pressure inside a large
sphere of a dense, non-volatile liquid would be extremely low
(determined by diameter & surface tension). But the cohesive forces
would remain.
Now pass a convex-surfaced foil through this unique liquid in its unique
situation. According to Bernoulli, there'd be a fall in pressure due to
the conversion of the liquid's internal energy into kinetic energy as it
accelerates (as it must) over the foil's surfaces.
Under such circumstances the internal pressure in those accelerated
regions would fall markedly below zero? Which means they are under tension.
Atmospheric pressure, gravity & volatility come along for the ride in
our considerations of the flow of normal fluids in normal situations.
Pressure stops the liquid from boiling where internal pressure is
reduced, gravity defines & maintains the flattish gas/liquid interface,
while volatility lurks in the background to create problems in more
extreme situations. Otherwise they are irrelevant ;) So if, for a
simpler understanding, we take atmospheric pressure out of the equation
then tension within the water becomes real. And it is the fall in
pressure, rise in tension, which provides the force on the blade in the
propulsive process, just as it is the fall in air pressure above the
wing which stops the plane from dropping. And the tension concept
underlines why the formation of a cavity behind the blade with water
falling away from the blade surface as the surface level falls - through
the interaction of gravity, reduced internal pressure & the inertia of
water - results in a real, loss-making, sternwards slippage of the
blade. The pressure within the water behind the blade is actually
sub-atmospheric.
You see, also, how important coverage of the back of the blade is during
the mid-stroke when you vary the depth of a simple baffle in a flowing
water stream. The drag on the baffle rises as depth increases &
continues rising until you are some way sub-surface.
Just today's tea-time teaser -
John Greenly
Aug 21, 2013, 12:07:03 PM8/21/13
to
On Wednesday, August 21, 2013 10:35:14 AM UTC-4, Carl wrote:
> A couple more thoughts for John G: If there were no gravity & a vacuum, then the pressure inside a large sphere of a dense, non-volatile liquid would be extremely low (determined by diameter & surface tension). But the cohesive forces would remain. Now pass a convex-surfaced foil through this unique liquid in its unique situation. According to Bernoulli, there'd be a fall in pressure due to the conversion of the liquid's internal energy into kinetic energy as it accelerates (as it must) over the foil's surfaces. Under such circumstances the internal pressure in those accelerated regions would fall markedly below zero? Which means they are under tension. Atmospheric pressure, gravity & volatility come along for the ride in our considerations of the flow of normal fluids in normal situations. Pressure stops the liquid from boiling where internal pressure is reduced, gravity defines & maintains the flattish gas/liquid interface, while volatility lurks in the background to create problems in more extreme situations. Otherwise they are irrelevant ;) So if, for a simpler understanding, we take atmospheric pressure out of the equation then tension within the water becomes real. And it is the fall in pressure, rise in tension, which provides the force on the blade in the propulsive process, just as it is the fall in air pressure above the wing which stops the plane from dropping. And the tension concept underlines why the formation of a cavity behind the blade with water falling away from the blade surface as the surface level falls - through the interaction of gravity, reduced internal pressure & the inertia of water - results in a real, loss-making, sternwards slippage of the blade. The pressure within the water behind the blade is actually sub-atmospheric. You see, also, how important coverage of the back of the blade is during the mid-stroke when you vary the depth of a simple baffle in a flowing water stream. The drag on the baffle rises as depth increases & continues rising until you are some way sub-surface. Just today's tea-time teaser - Carl
Carl, yes, I'm with you all the way. Well... yes, there are a few little problems with our space rowing experiment, but what the heck, the frontiers of science always present obstacles!
> A couple more thoughts for John G: If there were no gravity & a vacuum, then the pressure inside a large sphere of a dense, non-volatile liquid would be extremely low (determined by diameter & surface tension). But the cohesive forces would remain. Now pass a convex-surfaced foil through this unique liquid in its unique situation. According to Bernoulli, there'd be a fall in pressure due to the conversion of the liquid's internal energy into kinetic energy as it accelerates (as it must) over the foil's surfaces. Under such circumstances the internal pressure in those accelerated regions would fall markedly below zero? Which means they are under tension. Atmospheric pressure, gravity & volatility come along for the ride in our considerations of the flow of normal fluids in normal situations. Pressure stops the liquid from boiling where internal pressure is reduced, gravity defines & maintains the flattish gas/liquid interface, while volatility lurks in the background to create problems in more extreme situations. Otherwise they are irrelevant ;) So if, for a simpler understanding, we take atmospheric pressure out of the equation then tension within the water becomes real. And it is the fall in pressure, rise in tension, which provides the force on the blade in the propulsive process, just as it is the fall in air pressure above the wing which stops the plane from dropping. And the tension concept underlines why the formation of a cavity behind the blade with water falling away from the blade surface as the surface level falls - through the interaction of gravity, reduced internal pressure & the inertia of water - results in a real, loss-making, sternwards slippage of the blade. The pressure within the water behind the blade is actually sub-atmospheric. You see, also, how important coverage of the back of the blade is during the mid-stroke when you vary the depth of a simple baffle in a flowing water stream. The drag on the baffle rises as depth increases & continues rising until you are some way sub-surface. Just today's tea-time teaser - Carl
I'm glad that image of the boiling sphere of water in space has sparked your thoughts! Absent both gravity and external pressure, as I said and you agree, it seems that the pressure on a blade backside would indeed try to go negative. I imagine the water would cavitate, cease to be a simple homogeneous fluid, and I don't know what would happen. Gases are much simpler than liquids in that way- the air above an airplane wing really, truly can't support tensile stresses, the pressure drops but it can't go negative- the best you can do is zero- vacuum- and that can happen only with supersonic flows. I do that all the time in the laboratory with supersonic nozzles directing gas flow into a vacuum. Even there, all the empty spaces fill up on sound-speed timescales-- "nature abhors a vacuum".
As I indicated with the little calculation before- pressure under water goes up by roughly 0.5 psi per foot of depth, so if you see an open hole with atmospheric air reaching one foot down, you must have reduced the pressure in the water at that depth by at least 0.5 psi. That's a lot, but to make a hole behind the blade that is a few inches deep as is seen with a partially immersed blade, you need only a fraction of that pressure reduction, and that's quite within a rower's strength.
...Lunch-time musings
--John G
Charles Carroll
Aug 22, 2013, 1:08:25 PM8/22/13
to
> Do an experiment: get the boat moving,
> then plunk your blades into the water �
� hold them so they can't move, and
> see what happens!
John,
I have done such an experiment many times. And yes, it does put on the
brakes, as you say
Only not at first!
The first thing I feel is a slight movement of the oar handles bowards. I
want to stress the idea of �slight.� It is really only the slightest of
movements. It happens in mere milliseconds. I also want to stress that I
only feel this movement if I have a relaxed grip on the oar handles and am
holding the handles in my fingertips.
My idea of how to proceed from the feel of this movement is to join it. John
MacArthur in �High Performance Rowing� writes that this is the basic
sequence of good bladework:
Place-feel-squeeze.
Now, is this �slight movement of the oar handles bowards� an indication that
the blades are loading?
If not, what is causing the handles to move bowards?
I thought I was beginning finally to understand how the blades are loading
in the initial phases of the drive. But I guess not, at least not according
to Carl.
I wrote the following a couple of weeks ago. Perhaps if you or Carl or
someone else has the time, you could go through it and tell me what I have
gotten wrong.
By the way, thanks for your explanation. It did a lot to clear things.
Cordially,
Charles
�����
Suction on the Back of the Blade Resists Pressure on the Oar Handles
�It is the deficit in pressure across the area of the back of the blade
(suction, if you like, or tension within the water if you prefer) which
resists the force you apply to the blade, far more than any slight build-up
of pressure on the convex face of the blade.� �Carl Douglas, RSR,
22-Mar-2006, �Re: Lesson on taking the Catch�
So according to Carl it is a deficit in pressure across the area of the back
of the blade generates a pulling force that resists pressure applied against
the oar handles. Can we think of this deficit in pressure as a kind of
suction that counterbalances the pull on the oar handles?
Imagine yourself walking across a mud flat and finding your feet with each
step sinking deeper and deeper into the mud to where it becomes almost
impossible to pull your feet out. Something in the mud holds your feet
firmly in place. Moreover, as you try to lift your feet out of the mud,
doesn�t it feel as if the mud is sucking them down even deeper? The harder
you lift, the stronger the suction!
Could this be a way to think of the pulling force holding on to the back of
an oar blade? Just as what holds your feet in the mud is not the mud on top
of them, but a sucking action, so it is with an oar blade in the water.
This, or something similar, may have inspired Aristotle�s observation that
�Nature abhors a vacuum.� According to Aristotle nature requires every space
to be filled with something. So what holds the blade in the water is not the
slight build-up of pressure on the convex face of the blade, but the deficit
in pressure behind it, the same pulling force that occurs when a foot is
sunk deep in mud and you try to pull it out.
When scullers talk about building resistance against the blades in the
initial phases of the drive what they are really talking about is creating a
deficit in pressure across the area of the back of the blades.
It doesn�t take long to create this deficit in pressure. If all else fails,
won�t the oar handles held in place and the boat moving bowards do it for
you? In fact observations of my own sculling suggest that the faster you are
moving the boat, the faster you create a deficit in pressure across the back
of the blades. As Carl says, it is mostly a matter of placing the blades
deep enough.
The important point to consider is that you should not push off the
stretcher until you feel this deficit in pressure. A slight movement of the
oar handles towards the bow indicates that it has been made. It is this
slight movement that you should strive to feel.
John Greenly
Aug 22, 2013, 3:24:10 PM8/22/13
to
On Thursday, August 22, 2013 1:08:25 PM UTC-4, Charles Carroll wrote:
> > Do an experiment: get the boat moving, > then plunk your blades into the water … … hold them so they can't move, and > see what happens! John, I have done such an experiment many times. And yes, it does put on the brakes, as you say Only not at first! The first thing I feel is a slight movement of the oar handles bowards. I want to stress the idea of “slight.” It is really only the slightest of movements. It happens in mere milliseconds. I also want to stress that I only feel this movement if I have a relaxed grip on the oar handles and am holding the handles in my fingertips. My idea of how to proceed from the feel of this movement is to join it. John MacArthur in “High Performance Rowing” writes that this is the basic sequence of good bladework: Place-feel-squeeze. Now, is this “slight movement of the oar handles bowards” an indication that the blades are loading? If not, what is causing the handles to move bowards? I thought I was beginning finally to understand how the blades are loading in the initial phases of the drive. But I guess not, at least not according to Carl. I wrote the following a couple of weeks ago. Perhaps if you or Carl or someone else has the time, you could go through it and tell me what I have gotten wrong. By the way, thanks for your explanation. It did a lot to clear things. Cordially, Charles ————— Suction on the Back of the Blade Resists Pressure on the Oar Handles “It is the deficit in pressure across the area of the back of the blade (suction, if you like, or tension within the water if you prefer) which resists the force you apply to the blade, far more than any slight build-up of pressure on the convex face of the blade.” —Carl Douglas, RSR, 22-Mar-2006, “Re: Lesson on taking the Catch” So according to Carl it is a deficit in pressure across the area of the back of the blade generates a pulling force that resists pressure applied against the oar handles. Can we think of this deficit in pressure as a kind of suction that counterbalances the pull on the oar handles? Imagine yourself walking across a mud flat and finding your feet with each step sinking deeper and deeper into the mud to where it becomes almost impossible to pull your feet out. Something in the mud holds your feet firmly in place. Moreover, as you try to lift your feet out of the mud, doesn’t it feel as if the mud is sucking them down even deeper? The harder you lift, the stronger the suction! Could this be a way to think of the pulling force holding on to the back of an oar blade? Just as what holds your feet in the mud is not the mud on top of them, but a sucking action, so it is with an oar blade in the water. This, or something similar, may have inspired Aristotle’s observation that “Nature abhors a vacuum.” According to Aristotle nature requires every space to be filled with something. So what holds the blade in the water is not the slight build-up of pressure on the convex face of the blade, but the deficit in pressure behind it, the same pulling force that occurs when a foot is sunk deep in mud and you try to pull it out. When scullers talk about building resistance against the blades in the initial phases of the drive what they are really talking about is creating a deficit in pressure across the area of the back of the blades. It doesn’t take long to create this deficit in pressure. If all else fails, won’t the oar handles held in place and the boat moving bowards do it for you? In fact observations of my own sculling suggest that the faster you are moving the boat, the faster you create a deficit in pressure across the back of the blades. As Carl says, it is mostly a matter of placing the blades deep enough.
Hi Charles,
Glad you're still with us!!
Just a quick reply for now. If you feel the handles move toward the bow against your hands, you're putting a little bit of load on the oars all right- in the wrong direction! That is the beginning of stopping the boat. If it were enough to be visible, you'd see that the oar shafts are bending very, very slightly the wrong way.
Maybe we need to carefully define "loading" the oars. In physics and engineering, a "load" is just a force exerted on an object. Forces have a direction. To "load" the oars for the drive, you need to pull on the handles in the direction of the drive, not the reverse. So until you pull the handles hard enough to move the oars faster than they would have if they just coasted, you're not loading the oars for the drive. You apply the load, the force, by pulling when the blade is underwater. That's all there is to it.
Just a quick note about "suction"-- If you read Carl's and my conversation above, you'll see that this is what I was worried you might be misinterpreting. The blade is never stuck in the water like your foot in mud- thank goodness, or we'd never get it out to take a second stroke! The fact is that when you pull, you apply the force- load- on the oar that makes the blade move through the water in a way that generates a complex flow around the blade. It happens that a main result of that flow is a slight lowering of the pressure on the back side of the blade. That slight difference in pressure between front and back is enough to transmit all your pull to the water. There is nothing you can do to make this happen but get the blades underwater and pull. That's all!
So, as to your last paragraph,
>The important point to consider is that you should not push off the stretcher until you feel this deficit in pressure. A slight movement of the oar handles towards the bow indicates that it has been made. It is this slight movement that you should strive to feel.
You need to pull. Otherwise you are establishing the pressure deficit on the wrong side of the blade, the load's in the wrong direction, and you will be wasting effort and motion to reverse it when you start to pull. What you need to feel is strong resistance to your pull. That's the sign that the oars are under water and under load, and you want to make that happen as quickly as ever you can. And, if you really insist on thinking about it, that's the sign that the pressure deficit exists on the correct side- back side- of the blade... but please, forget about that, it takes care of itself!!
I'm thinking that the place-feel-squeeze idea has to do with feeling when the blades are all the way in the water as you start to pull- that seems like a nice way of saying it- but gee, it happens so fast... that's what makes it tricky!
hope this helps,
--John
> > Do an experiment: get the boat moving, > then plunk your blades into the water … … hold them so they can't move, and > see what happens! John, I have done such an experiment many times. And yes, it does put on the brakes, as you say Only not at first! The first thing I feel is a slight movement of the oar handles bowards. I want to stress the idea of “slight.” It is really only the slightest of movements. It happens in mere milliseconds. I also want to stress that I only feel this movement if I have a relaxed grip on the oar handles and am holding the handles in my fingertips. My idea of how to proceed from the feel of this movement is to join it. John MacArthur in “High Performance Rowing” writes that this is the basic sequence of good bladework: Place-feel-squeeze. Now, is this “slight movement of the oar handles bowards” an indication that the blades are loading? If not, what is causing the handles to move bowards? I thought I was beginning finally to understand how the blades are loading in the initial phases of the drive. But I guess not, at least not according to Carl. I wrote the following a couple of weeks ago. Perhaps if you or Carl or someone else has the time, you could go through it and tell me what I have gotten wrong. By the way, thanks for your explanation. It did a lot to clear things. Cordially, Charles ————— Suction on the Back of the Blade Resists Pressure on the Oar Handles “It is the deficit in pressure across the area of the back of the blade (suction, if you like, or tension within the water if you prefer) which resists the force you apply to the blade, far more than any slight build-up of pressure on the convex face of the blade.” —Carl Douglas, RSR, 22-Mar-2006, “Re: Lesson on taking the Catch” So according to Carl it is a deficit in pressure across the area of the back of the blade generates a pulling force that resists pressure applied against the oar handles. Can we think of this deficit in pressure as a kind of suction that counterbalances the pull on the oar handles? Imagine yourself walking across a mud flat and finding your feet with each step sinking deeper and deeper into the mud to where it becomes almost impossible to pull your feet out. Something in the mud holds your feet firmly in place. Moreover, as you try to lift your feet out of the mud, doesn’t it feel as if the mud is sucking them down even deeper? The harder you lift, the stronger the suction! Could this be a way to think of the pulling force holding on to the back of an oar blade? Just as what holds your feet in the mud is not the mud on top of them, but a sucking action, so it is with an oar blade in the water. This, or something similar, may have inspired Aristotle’s observation that “Nature abhors a vacuum.” According to Aristotle nature requires every space to be filled with something. So what holds the blade in the water is not the slight build-up of pressure on the convex face of the blade, but the deficit in pressure behind it, the same pulling force that occurs when a foot is sunk deep in mud and you try to pull it out. When scullers talk about building resistance against the blades in the initial phases of the drive what they are really talking about is creating a deficit in pressure across the area of the back of the blades. It doesn’t take long to create this deficit in pressure. If all else fails, won’t the oar handles held in place and the boat moving bowards do it for you? In fact observations of my own sculling suggest that the faster you are moving the boat, the faster you create a deficit in pressure across the back of the blades. As Carl says, it is mostly a matter of placing the blades deep enough.
Hi Charles,
Glad you're still with us!!
Just a quick reply for now. If you feel the handles move toward the bow against your hands, you're putting a little bit of load on the oars all right- in the wrong direction! That is the beginning of stopping the boat. If it were enough to be visible, you'd see that the oar shafts are bending very, very slightly the wrong way.
Maybe we need to carefully define "loading" the oars. In physics and engineering, a "load" is just a force exerted on an object. Forces have a direction. To "load" the oars for the drive, you need to pull on the handles in the direction of the drive, not the reverse. So until you pull the handles hard enough to move the oars faster than they would have if they just coasted, you're not loading the oars for the drive. You apply the load, the force, by pulling when the blade is underwater. That's all there is to it.
Just a quick note about "suction"-- If you read Carl's and my conversation above, you'll see that this is what I was worried you might be misinterpreting. The blade is never stuck in the water like your foot in mud- thank goodness, or we'd never get it out to take a second stroke! The fact is that when you pull, you apply the force- load- on the oar that makes the blade move through the water in a way that generates a complex flow around the blade. It happens that a main result of that flow is a slight lowering of the pressure on the back side of the blade. That slight difference in pressure between front and back is enough to transmit all your pull to the water. There is nothing you can do to make this happen but get the blades underwater and pull. That's all!
So, as to your last paragraph,
>The important point to consider is that you should not push off the stretcher until you feel this deficit in pressure. A slight movement of the oar handles towards the bow indicates that it has been made. It is this slight movement that you should strive to feel.
I'm thinking that the place-feel-squeeze idea has to do with feeling when the blades are all the way in the water as you start to pull- that seems like a nice way of saying it- but gee, it happens so fast... that's what makes it tricky!
hope this helps,
--John
Charles Carroll
Aug 22, 2013, 6:07:08 PM8/22/13
to
Hi John,
I have two minutes before I have to take the second walk, so this, too, will
be a quick reply.
You wrote that "If you feel the handles move toward the bow against your
agree. But if you feel them moving bowards and join this movement -- i.e.
pull the oar handles bowards -- wouldn't you be going in the right
direction?
Cordially,
Charles
I have two minutes before I have to take the second walk, so this, too, will
be a quick reply.
You wrote that "If you feel the handles move toward the bow against your
hands, you're putting a little bit of load on the oars all right- in the
wrong direction!"
If you hold the oar handles and keep them from moving bowards, I readily
wrong direction!"
agree. But if you feel them moving bowards and join this movement -- i.e.
pull the oar handles bowards -- wouldn't you be going in the right
direction?
Cordially,
Charles
John Greenly
Aug 22, 2013, 6:38:58 PM8/22/13
to
On Thursday, August 22, 2013 6:07:08 PM UTC-4, Charles Carroll wrote:
> Hi John, I have two minutes before I have to take the second walk, so this, too, will be a quick reply. You wrote that "If you feel the handles move toward the bow against your hands, you're putting a little bit of load on the oars all right- in the wrong direction!" If you hold the oar handles and keep them from moving bowards, I readily agree. But if you feel them moving bowards and join this movement -- i.e. pull the oar handles bowards -- wouldn't you be going in the right direction? Cordially, Charles
Hi Charles,
> Hi John, I have two minutes before I have to take the second walk, so this, too, will be a quick reply. You wrote that "If you feel the handles move toward the bow against your hands, you're putting a little bit of load on the oars all right- in the wrong direction!" If you hold the oar handles and keep them from moving bowards, I readily agree. But if you feel them moving bowards and join this movement -- i.e. pull the oar handles bowards -- wouldn't you be going in the right direction? Cordially, Charles
yes sure, yes you would! If you can do that instantly and avoid backwards push you're much quicker than I am. If I were to wait to feel that I would be too late. I'm working on trying to feel the resistance to my pull with the inward motion of hands just before I push off the stretcher. When I do it right, I immediately pick up a few tenths of a mile per hour in speed. As a musician I think of every motion in terms of rhythm. This is a sort of ka-thump rhythm, with the ka being the feeling of resistance to my hands, and the thump being the feet on the stretcher. Actually at a higher rate it just becomes, maybe... Kthump.
Cheers,
John G
By the way, I really hope I didn't sound dismissive of your interest in understanding the blade hydrodynamics- I think it's just great that you're interested, and it's fun for me to put my oar in, trying to help Carl explain it- not that he needs help. I have always found that I didn't really understand something until I figured out how to explain it to somebody. I think most teachers know that. Thanks for your tolerance!
Charles Carroll
Aug 22, 2013, 9:21:36 PM8/22/13
to
John,
I don’t think we are too far apart on any of this. If I have understood you,
we are both trying to scull more efficiently and effectively, and we are
both working on timing.
I am finding that I scull as much as 1 meter-per-second faster with
significantly less perceived effort if I can just get my full reach and keep
myself from pushing off the stretcher before there is resistance on the
blades.
So I am working on getting as much useful reach as I can, staying relaxed as
I place the blades, and trying not to push off the stretcher before the
blades can resist the pressure applied to the oar handles. To this end I am
doing lots of low rate/low pressure work.
Sculling a low pressure/low rates I can feel when I have resistance on the
blades and it is time to push off. When I find my rhythm and my SpeedCoach
says that I am moving well, I then increase the rate and pressure until
things fall apart.
At high rates everything becomes more about timing then feeling. This is why
rhythm is so important.
Actually what it all comes down to is trying to enjoy my sculling, get a
good work out, and keep my stern level.
What follows is the passage from John McArthur that I mentioned earlier this
afternoon.
Cordially,
Charles
——————
PLACEMENT DRILLS:
“Correct placement of the blade at the catch is perhaps the most difficult
part of rowing effectively. Thankfully there are many exercises that can be
used to improve this.
“In order to execute a quick and effective catch it is necessary to be
totally relaxed as the blade enters the water. Unfortunately this is not an
easy skill to master, as the temptation is to tense the body just before the
catch. The key to it is to be preparing to change direction from the moment
that the blade leaves the water at the finish of the previous stroke; and if
the body is in the correct position to take the next stroke all the way
through the recovery, it will be easier to change direction quickly and with
little fuss.
“It is important to stress again that the body plays no part in covering the
blade, and no discernible upward movement of the shoulders should be
observed. The hands should rise quickly whilst the body remains perfectly
still.
“This is known as hooking or placing the blade. When the blade is covered,
the rower should feel the pressure build up in front of the spoon and should
then push the legs down rapidly. The coordination of the hand movement and
the legs is critical in ensuring effective boat propulsion: if the legs come
on too soon, the rower will shoot the slide; and if they come on too late,
the strain will be felt in the arms. Both of these circumstances will lead
to ineffective, slow boats.
“Achieving this coordination between the arm and leg movements should
therefore be one of the main goals of all rowers wishing to move boats
quickly and efficiently. One of the keys to this is to be able to feel the
water, to feel the pressure building up on the spoon, and placement drills
are an excellent way to help achieve this. Moreover since many rowers seem
to have difficulty in achieving this feeling, such drills should constitute
a high proportion of the technical exercises performed. The aim of placement
drills may therefore be said to be to enable the rower to place the blade in
the water quickly and efficiently, with the minimum of disturbance to the
movement of the boat.
“Placement drills can be broken down into three different types that
concentrate primarily on the following:
1. the recovery movement, i.e. preparing for the catch;
2. the placing of the blade at the catch;
3. the feeling for the buildup of pressure.
“Although they have different emphases, the important thing is that they all
rein-force the basic sequence of good bladework, namely place—feel—squeeze.”
(“High Performance Rowing,” pp. 38-39)
I don’t think we are too far apart on any of this. If I have understood you,
we are both trying to scull more efficiently and effectively, and we are
both working on timing.
I am finding that I scull as much as 1 meter-per-second faster with
significantly less perceived effort if I can just get my full reach and keep
myself from pushing off the stretcher before there is resistance on the
blades.
So I am working on getting as much useful reach as I can, staying relaxed as
I place the blades, and trying not to push off the stretcher before the
blades can resist the pressure applied to the oar handles. To this end I am
doing lots of low rate/low pressure work.
Sculling a low pressure/low rates I can feel when I have resistance on the
blades and it is time to push off. When I find my rhythm and my SpeedCoach
says that I am moving well, I then increase the rate and pressure until
things fall apart.
At high rates everything becomes more about timing then feeling. This is why
rhythm is so important.
Actually what it all comes down to is trying to enjoy my sculling, get a
good work out, and keep my stern level.
What follows is the passage from John McArthur that I mentioned earlier this
afternoon.
Cordially,
Charles
——————
PLACEMENT DRILLS:
“Correct placement of the blade at the catch is perhaps the most difficult
part of rowing effectively. Thankfully there are many exercises that can be
used to improve this.
“In order to execute a quick and effective catch it is necessary to be
totally relaxed as the blade enters the water. Unfortunately this is not an
easy skill to master, as the temptation is to tense the body just before the
catch. The key to it is to be preparing to change direction from the moment
that the blade leaves the water at the finish of the previous stroke; and if
the body is in the correct position to take the next stroke all the way
through the recovery, it will be easier to change direction quickly and with
little fuss.
“It is important to stress again that the body plays no part in covering the
blade, and no discernible upward movement of the shoulders should be
observed. The hands should rise quickly whilst the body remains perfectly
still.
“This is known as hooking or placing the blade. When the blade is covered,
the rower should feel the pressure build up in front of the spoon and should
then push the legs down rapidly. The coordination of the hand movement and
the legs is critical in ensuring effective boat propulsion: if the legs come
on too soon, the rower will shoot the slide; and if they come on too late,
the strain will be felt in the arms. Both of these circumstances will lead
to ineffective, slow boats.
“Achieving this coordination between the arm and leg movements should
therefore be one of the main goals of all rowers wishing to move boats
quickly and efficiently. One of the keys to this is to be able to feel the
water, to feel the pressure building up on the spoon, and placement drills
are an excellent way to help achieve this. Moreover since many rowers seem
to have difficulty in achieving this feeling, such drills should constitute
a high proportion of the technical exercises performed. The aim of placement
drills may therefore be said to be to enable the rower to place the blade in
the water quickly and efficiently, with the minimum of disturbance to the
movement of the boat.
“Placement drills can be broken down into three different types that
concentrate primarily on the following:
1. the recovery movement, i.e. preparing for the catch;
2. the placing of the blade at the catch;
3. the feeling for the buildup of pressure.
“Although they have different emphases, the important thing is that they all
rein-force the basic sequence of good bladework, namely place—feel—squeeze.”
(“High Performance Rowing,” pp. 38-39)
Carl
Aug 23, 2013, 9:10:46 AM8/23/13
to
On 23/08/2013 02:21, Charles Carroll wrote:
> “Placement drills can be broken down into three different types that
> concentrate primarily on the following:
>
> 1. the recovery movement, i.e. preparing for the catch;
> 2. the placing of the blade at the catch;
> 3. the feeling for the buildup of pressure.
Sorry to say it, Charles, but there is no way on earth that pressure
> “Placement drills can be broken down into three different types that
> concentrate primarily on the following:
>
> 1. the recovery movement, i.e. preparing for the catch;
> 2. the placing of the blade at the catch;
> 3. the feeling for the buildup of pressure.
will start, or build up, as a result of "placing" the blade in the
water. John McArthur is a great coach, but even the greatest harbour a
few irrational concepts. This placement & feeling for the pressure
build-up is wholly irrational. It can't possibly, & simply doesn't,
happen like that.
The only pressure there will be if you "place" the blade is a slight
pressure the wrong way (resulting in drag) needed to rotate the unloaded
blade sternwards about the pin.
The trouble is with the non-scientific, touchy-feely stuff that creeps
in from the motivational side of coaching & infects the purely technical
underpinnings. Now it might be that if you _tell_ people to do this
they may avoid doing something worse at the catch, but that still
doesn't justify the pseudo-science explanation that's offered but stands
reality on its head.
The reality is that the blade is driven in at the catch. Seen from the
bank it is driven slightly sternwards - maybe at 10 degrees to the
vertical. Seen from the boat it is driven in at more like 45 degrees,
due to the forward component of velocity provided by the boat. Anything
less results in backwatering. Too much results in scooping the water.
The good catch gets it right, it is clean. It's a matter of practice.
Importantly: as the blade meets the water there should be no delay in
commencing the loading process.
Let's address that last statement:
You have to apply a small load to the handles even to execute the "hook"
which does indeed reverse the motion of the blades immediately before
their entry. And hooking is just the right way to describe it - you are
hooking hard into a moving object (the water). Obviously there can be
hardly any load on the blade at the moment of first contact, when it is
hardly touching the water, but there can be a lot more load by the time
it is covered, the load should be building all the way through the entry
& building a whole lot more into the main part of the stroke.
But, again, I don't buy this obsession with the fineness of timing of
hands & feet. There's a large, somewhat inert mass of body between feet
& handles, & in any case the sculling catch can/should first be taken
more across the boat than along it, due to acute angle of the blades to
the boat at the catch. It's what your pecs are for!
Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ca...@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682
and now, at last, we're back on carldouglasusa.com
robin_d...@hotmail.com
Aug 23, 2013, 12:01:04 PM8/23/13
to
I have little time to write because of needing to leg it in a few minutes to fetch my 20-month old WJ1x from childcare, but something just struck me after reading the last few pages of well-thought out theory about what is going on at the back of the blade.
Somewhere in the regulations is the bit in the rules disallowing coatings on boats that (to paraphrase) tinker with the behaviour of water - ie preventing people from using waxes or textures or other stuff that would impinge on fluid drag.
Does this rule only apply to the rowing shell or is it to all parts of the rowing equipment that interact with the water?
The reason why I ask this is the following - if it was permissible - and the back of the blade was coated with something which increased the local hydrophilicity slightly compared to normal paint or coatings, would this make it even fractionally less likely that the water would "disengage" with the back of the blade to be displaced with air when someone washes out close to the surface, and consequently switches the mode of action of the blade from "moving boat forwards" to "moving water backwards". Conversely are the current coatings "hydrophobic" enough to impact on "loss of grip" of the back of the blade and would blade performance be enhanced by making the coatings have nil net hydrophobicity / philicity.
Probably completely barking up the wrong tree, but something that I've not had a chance to think about much on my own.
John Greenly
Aug 23, 2013, 12:05:12 PM8/23/13
to
On Thursday, August 22, 2013 9:21:36 PM UTC-4, Charles Carroll wrote:
> John, I don’t think we are too far apart on any of this. If I have understood you, we are both trying to scull more efficiently and effectively, and we are both working on timing. I am finding that I scull as much as 1 meter-per-second faster with significantly less perceived effort if I can just get my full reach and keep myself from pushing off the stretcher before there is resistance on the blades. So I am working on getting as much useful reach as I can, staying relaxed as I place the blades, and trying not to push off the stretcher before the blades can resist the pressure applied to the oar handles. To this end I am doing lots of low rate/low pressure work. Sculling a low pressure/low rates I can feel when I have resistance on the blades and it is time to push off. When I find my rhythm and my SpeedCoach says that I am moving well, I then increase the rate and pressure until things fall apart. At high rates everything becomes more about timing then feeling. This is why rhythm is so important. Actually what it all comes down to is trying to enjoy my sculling, get a good work out, and keep my stern level. What follows is the passage from John McArthur that I mentioned earlier this afternoon. Cordially, Charles —————— PLACEMENT DRILLS: “Correct placement of the blade at the catch is perhaps the most difficult part of rowing effectively. Thankfully there are many exercises that can be used to improve this. “In order to execute a quick and effective catch it is necessary to be totally relaxed as the blade enters the water. Unfortunately this is not an easy skill to master, as the temptation is to tense the body just before the catch. The key to it is to be preparing to change direction from the moment that the blade leaves the water at the finish of the previous stroke; and if the body is in the correct position to take the next stroke all the way through the recovery, it will be easier to change direction quickly and with little fuss. “It is important to stress again that the body plays no part in covering the blade, and no discernible upward movement of the shoulders should be observed. The hands should rise quickly whilst the body remains perfectly still. “This is known as hooking or placing the blade. When the blade is covered, the rower should feel the pressure build up in front of the spoon and should then push the legs down rapidly. The coordination of the hand movement and the legs is critical in ensuring effective boat propulsion: if the legs come on too soon, the rower will shoot the slide; and if they come on too late, the strain will be felt in the arms. Both of these circumstances will lead to ineffective, slow boats. “Achieving this coordination between the arm and leg movements should therefore be one of the main goals of all rowers wishing to move boats quickly and efficiently. One of the keys to this is to be able to feel the water, to feel the pressure building up on the spoon, and placement drills are an excellent way to help achieve this. Moreover since many rowers seem to have difficulty in achieving this feeling, such drills should constitute a high proportion of the technical exercises performed. The aim of placement drills may therefore be said to be to enable the rower to place the blade in the water quickly and efficiently, with the minimum of disturbance to the movement of the boat. “Placement drills can be broken down into three different types that concentrate primarily on the following: 1. the recovery movement, i.e. preparing for the catch; 2. the placing of the blade at the catch; 3. the feeling for the buildup of pressure. “Although they have different emphases, the important thing is that they all rein-force the basic sequence of good bladework, namely place—feel—squeeze.” (“High Performance Rowing,” pp. 38-39)
-------
> John, I don’t think we are too far apart on any of this. If I have understood you, we are both trying to scull more efficiently and effectively, and we are both working on timing. I am finding that I scull as much as 1 meter-per-second faster with significantly less perceived effort if I can just get my full reach and keep myself from pushing off the stretcher before there is resistance on the blades. So I am working on getting as much useful reach as I can, staying relaxed as I place the blades, and trying not to push off the stretcher before the blades can resist the pressure applied to the oar handles. To this end I am doing lots of low rate/low pressure work. Sculling a low pressure/low rates I can feel when I have resistance on the blades and it is time to push off. When I find my rhythm and my SpeedCoach says that I am moving well, I then increase the rate and pressure until things fall apart. At high rates everything becomes more about timing then feeling. This is why rhythm is so important. Actually what it all comes down to is trying to enjoy my sculling, get a good work out, and keep my stern level. What follows is the passage from John McArthur that I mentioned earlier this afternoon. Cordially, Charles —————— PLACEMENT DRILLS: “Correct placement of the blade at the catch is perhaps the most difficult part of rowing effectively. Thankfully there are many exercises that can be used to improve this. “In order to execute a quick and effective catch it is necessary to be totally relaxed as the blade enters the water. Unfortunately this is not an easy skill to master, as the temptation is to tense the body just before the catch. The key to it is to be preparing to change direction from the moment that the blade leaves the water at the finish of the previous stroke; and if the body is in the correct position to take the next stroke all the way through the recovery, it will be easier to change direction quickly and with little fuss. “It is important to stress again that the body plays no part in covering the blade, and no discernible upward movement of the shoulders should be observed. The hands should rise quickly whilst the body remains perfectly still. “This is known as hooking or placing the blade. When the blade is covered, the rower should feel the pressure build up in front of the spoon and should then push the legs down rapidly. The coordination of the hand movement and the legs is critical in ensuring effective boat propulsion: if the legs come on too soon, the rower will shoot the slide; and if they come on too late, the strain will be felt in the arms. Both of these circumstances will lead to ineffective, slow boats. “Achieving this coordination between the arm and leg movements should therefore be one of the main goals of all rowers wishing to move boats quickly and efficiently. One of the keys to this is to be able to feel the water, to feel the pressure building up on the spoon, and placement drills are an excellent way to help achieve this. Moreover since many rowers seem to have difficulty in achieving this feeling, such drills should constitute a high proportion of the technical exercises performed. The aim of placement drills may therefore be said to be to enable the rower to place the blade in the water quickly and efficiently, with the minimum of disturbance to the movement of the boat. “Placement drills can be broken down into three different types that concentrate primarily on the following: 1. the recovery movement, i.e. preparing for the catch; 2. the placing of the blade at the catch; 3. the feeling for the buildup of pressure. “Although they have different emphases, the important thing is that they all rein-force the basic sequence of good bladework, namely place—feel—squeeze.” (“High Performance Rowing,” pp. 38-39)
Here's something that may help illuminate this issue. I was talking this morning with somebocy who studies the nervous system, and asked her about nerve conduction times and mental reaction times. The question is: given that with a good, fast catch the time from blade just touching the surface to being fully immersed and loaded and the feet pushing is no more than about a tenth of a second, or 100 msec (this from looking at slow-motion videos), can you in fact detect and respond to anything during that time?
Her answer was interesting and, simply,it's: no! Turns out that the nerves responsible for proprioception (sensing our own body position) have very high conduction speeds, around 100 m/s, so getting the information to the brain is not the worst limiting factor. It's mental reaction time that is too slow. They call the study of that "mental chronometry". A typical test is to have somebody push a button when they sense some particular stimulus. The time to receive and respond to a stimulus is around 160 msec minimum, for young adults, so if you wait to sense something about the catch, by the time you respond it's all over.
What you can do is to monitor the relative timing- the rhythm- of events like pulling with your hands and pushing with your feet. Your nervous system is quite good at judging the relative times of stimuli, even though it's farther to your feet than to your hands. That's, I guess, what I am doing feeling my Kthump rhythm of hands and feet. You observe it, and if it isn't what you want, you can adjust it from one repetition to the next. But you can't wait to feel and respond to anything within the course of a catch. Much too slow.
Cheers,
--John G
Charles Carroll
Aug 23, 2013, 1:25:22 PM8/23/13
to
For anyone interested in Gordon Hamilton’s coaching, or his use of the Coach’s
Eye on an iPad, I put three videos on YouTube of the recent Lessons. We had
the lessons in the morning and by late afternoon Gordon had emailed the
videos with his commentary.
The first video is how Gordon coaches for the release — relatively little
layback, arms pronated, weight over the oar handles. Gordon does not want
you to drop your center of gravity into the bow. Doing your weight into the
bow, according to Gordon, will disturb your stability.
https://www.youtube.com/watch?v=bl956rCF5Fo
The second video is about grip on the oar handles and losing the pins. In
this video Gordon also recommends changing the height of the oarlocks.
https://www.youtube.com/watch?v=S2KrudtO7Fo
The third video I am including because by some miracle I was able get Gordon
to say that I actually took a few good strokes.
https://www.youtube.com/watch?v=TWRc_hHPt_0
Eye on an iPad, I put three videos on YouTube of the recent Lessons. We had
the lessons in the morning and by late afternoon Gordon had emailed the
videos with his commentary.
The first video is how Gordon coaches for the release — relatively little
layback, arms pronated, weight over the oar handles. Gordon does not want
you to drop your center of gravity into the bow. Doing your weight into the
bow, according to Gordon, will disturb your stability.
https://www.youtube.com/watch?v=bl956rCF5Fo
The second video is about grip on the oar handles and losing the pins. In
this video Gordon also recommends changing the height of the oarlocks.
https://www.youtube.com/watch?v=S2KrudtO7Fo
The third video I am including because by some miracle I was able get Gordon
to say that I actually took a few good strokes.
https://www.youtube.com/watch?v=TWRc_hHPt_0
Carl
Aug 23, 2013, 1:39:49 PM8/23/13
to
On 23/08/2013 17:05, John Greenly wrote:
> On Thursday, August 22, 2013 9:21:36 PM UTC-4, Charles Carroll wrote:
>> John, I don�t think we are too far apart on any of this. If I have understood you, we are both trying to scull more efficiently and effectively, and we are both working on timing. I am finding that I scull as much as 1 meter-per-second faster with significantly less perceived effort if I can just get my full reach and keep myself from pushing off the stretcher before there is resistance on the blades. So I am working on getting as much useful reach as I can, staying relaxed as I place the blades, and trying not to push off the stretcher before the blades can resist the pressure applied to the oar handles. To this end I am doing lots of low rate/low pressure work. Sculling a low pressure/low rates I can feel when I have resistance on the blades and it is time to push off. When I find my rhythm and my SpeedCoach says that I am moving well, I then increase the rate and pressure until things fall apart. At high rates everything becomes more about timing then feeling. This is why rhyt
> On Thursday, August 22, 2013 9:21:36 PM UTC-4, Charles Carroll wrote:
hm is so important. Actually what it all comes down to is trying to enjoy my sculling, get a good work out, and keep my stern level. What follows is the passage from John McArthur that I mentioned earlier this afternoon. Cordially, Charles ������ PLACEMENT DRILLS: �Correct placement of the blade at the catch is perhaps the most difficult part of rowing effectively. Thankfully there are many exercises that can be used to improve this. �In order to execute a quick and effective catch it is necessary to be totally relaxed as the blade enters the water. Unfortunately this is not an easy skill to master, as the temptation is to tense the body just before the catch. The key to it is to be preparing to change direction from the moment that the blade leaves the water at the finish of the previous stroke; and if the body is in the correct position to take the next stroke all the way through the recovery, it will be easier to change direction quickly and with little fuss. �It is important to s
tress again that the body plays no part in covering the blade, and no discernible upward movement of the shoulders should be observed. The hands should rise quickly whilst the body remains perfectly still. �This is known as hooking or placing the blade. When the blade is covered, the rower should feel the pressure build up in front of the spoon and should then push the legs down rapidly. The coordination of the hand movement and the legs is critical in ensuring effective boat propulsion: if the legs come on too soon, the rower will shoot the slide; and if they come on too late, the strain will be felt in the arms. Both of these circumstances will lead to ineffective, slow boats. �Achieving this coordination between the arm and leg movements should therefore be one of the main goals of all rowers wishing to move boats quickly and efficiently. One of the keys to this is to be able to feel the water, to feel the pressure building up on the spoon, and placement drills are an excellent wa
y to help achieve this. Moreover since many rowers seem to have difficulty in achieving this feeling, such drills should constitute a high proportion of the technical exercises performed. The aim of placement drills may therefore be said to be to enable the rower to place the blade in the water quickly and efficiently, with the minimum of disturbance to the movement of the boat. �Placement drills can be broken down into three different types that concentrate primarily on the following: 1. the recovery movement, i.e. preparing for the catch; 2. the placing of the blade at the catch; 3. the feeling for the buildup of pressure. �Although they have different emphases, the important thing is that they all rein-force the basic sequence of good bladework, namely place�feel�squeeze.� (�High Performance Rowing,� pp. 38-39)
>
> -------
>
> Here's something that may help illuminate this issue. I was talking this morning with somebocy who studies the nervous system, and asked her about nerve conduction times and mental reaction times. The question is: given that with a good, fast catch the time from blade just touching the surface to being fully immersed and loaded and the feet pushing is no more than about a tenth of a second, or 100 msec (this from looking at slow-motion videos), can you in fact detect and respond to anything during that time?
>
> Her answer was interesting and, simply,it's: no! Turns out that the nerves responsible for proprioception (sensing our own body position) have very high conduction speeds, around 100 m/s, so getting the information to the brain is not the worst limiting factor. It's mental reaction time that is too slow. They call the study of that "mental chronometry". A typical test is to have somebody push a button when they sense some particular stimulus. The time to receive and respond to a stimulus is around 160 msec minimum, for young adults, so if you wait to sense something about the catch, by the time you respond it's all over.
>
> What you can do is to monitor the relative timing- the rhythm- of events like pulling with your hands and pushing with your feet. Your nervous system is quite good at judging the relative times of stimuli, even though it's farther to your feet than to your hands. That's, I guess, what I am doing feeling my Kthump rhythm of hands and feet. You observe it, and if it isn't what you want, you can adjust it from one repetition to the next. But you can't wait to feel and respond to anything within the course of a catch. Much too slow.
>
> Cheers,
>
> --John G
>
In some circles they call this latency? Same problem a church organist
> -------
>
> Here's something that may help illuminate this issue. I was talking this morning with somebocy who studies the nervous system, and asked her about nerve conduction times and mental reaction times. The question is: given that with a good, fast catch the time from blade just touching the surface to being fully immersed and loaded and the feet pushing is no more than about a tenth of a second, or 100 msec (this from looking at slow-motion videos), can you in fact detect and respond to anything during that time?
>
> Her answer was interesting and, simply,it's: no! Turns out that the nerves responsible for proprioception (sensing our own body position) have very high conduction speeds, around 100 m/s, so getting the information to the brain is not the worst limiting factor. It's mental reaction time that is too slow. They call the study of that "mental chronometry". A typical test is to have somebody push a button when they sense some particular stimulus. The time to receive and respond to a stimulus is around 160 msec minimum, for young adults, so if you wait to sense something about the catch, by the time you respond it's all over.
>
> What you can do is to monitor the relative timing- the rhythm- of events like pulling with your hands and pushing with your feet. Your nervous system is quite good at judging the relative times of stimuli, even though it's farther to your feet than to your hands. That's, I guess, what I am doing feeling my Kthump rhythm of hands and feet. You observe it, and if it isn't what you want, you can adjust it from one repetition to the next. But you can't wait to feel and respond to anything within the course of a catch. Much too slow.
>
> Cheers,
>
> --John G
>
sometimes has (or did where I was once a non-angelic chorister): organ
console at the opposite end of the aisle from the pipes but the choir
close to the organist. Organist had to anticipate everything:
compensate for the time lag by playing every note ahead of the sounds
reaching him & direct the choir according to when they'd hear the organ.
We've had this sort of discussion before - about learned responses (or
sets thereof). The question remains as to whether every element of
these very repetitious actions is controlled only from the brain or some
of it more locally mediated &, if so, how?
As you say, the inherent music/rhythm of the stroke is important in
keeping the action smooth & coherent. We do have an exquisite sense of
timing, sensitive to changes of just a few milliseconds, though you
might not think that when watching some of us on the water.
Cheers -
Carl
--
Carl Douglas Racing Shells -
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James HS
Aug 23, 2013, 3:22:40 PM8/23/13
to
As an 'ologist' from one of our venerable universities I would agree that the concept that one 'waits to feel the pressure' then pushes is going to be physiologically outside of the system's response time - but that it not to say that it is not possible for you to use information from the last stroke and apply it to the next - look how fast a tennis player adjusts to the change in tactics of his/her opponent - often not making the first, one, but soon homing in.
I am afraid I think that the sequence is "what Carl said" - blade in, if anything unhelpful movement from where it is and check on the boat, but by swiftly pulling the hands together and slightly tensing(bending) the arms you have taken the slack up in the physiology and slightly bent the blades. My coach then instructs me to use 30% power to prime the system until about half slide, and then accelerate up to full power at the most advantageous part of the stroke (towards the end.)
My coach has shown me that putting the blade in at the catch, at as acute an angle as I can, will do little to check the boat as it is pointing substantially backwards - as opposed to putting it in at 90 degrees :) - so I worry about that little and concentrate on the bending/tension of the system before I start to apply power for the early phase of the drive.
I do think it feels different when I get it right - but I also think that I am using a feedback loop to get it to feel right each stroke by adjusting AFTER the last one rather than responding to the stimulous DURING the stroke.
But it does not harm to describe what you are supposed to feel as a HUGE amount of beneficial 'priming' of the system can be done through imagery! (IMHO)
James
I am afraid I think that the sequence is "what Carl said" - blade in, if anything unhelpful movement from where it is and check on the boat, but by swiftly pulling the hands together and slightly tensing(bending) the arms you have taken the slack up in the physiology and slightly bent the blades. My coach then instructs me to use 30% power to prime the system until about half slide, and then accelerate up to full power at the most advantageous part of the stroke (towards the end.)
My coach has shown me that putting the blade in at the catch, at as acute an angle as I can, will do little to check the boat as it is pointing substantially backwards - as opposed to putting it in at 90 degrees :) - so I worry about that little and concentrate on the bending/tension of the system before I start to apply power for the early phase of the drive.
I do think it feels different when I get it right - but I also think that I am using a feedback loop to get it to feel right each stroke by adjusting AFTER the last one rather than responding to the stimulous DURING the stroke.
But it does not harm to describe what you are supposed to feel as a HUGE amount of beneficial 'priming' of the system can be done through imagery! (IMHO)
James
mruscoe
Aug 23, 2013, 5:21:47 PM8/23/13
to
people who through stature or age can't get the range of the elite athletes.
Part of the feel for the stroke, particularly the catch, comes from the
way the blade works in the lift phases at the ends of the stroke that
Carl loves to talk about. Good sweep rowing gets about 55 degrees
forward past the pin, and elite scullers can be 65+ degrees forward of
the pin. It makes a huge difference to the feel of the stroke, and how
quickly you have to move to get connected. You're getting maybe 35
degrees forward of the pin, guessing from the separation of the handle
ends, and losing 10+ degrees getting the blade buried, which is
inevitable because you've got to move quicker without the advantage of
the angle - that's make it pretty difficult to get a stroke that feels
as good as it could do.
I can't help thinking that shorter oars, shorter inboard, and
appropriate span would make for a much better experience i.e. scaled rig
to increase the stroke angles.
Just my opinion, but I remember the huge difference it made in the more
extreme case of the adaptive A1x when they made radical rigging changes
to increase the stroke angles, and it went from high rate paddlewheeling
to a much more efficient stroke.
gsl...@gmail.com
Aug 23, 2013, 9:10:18 PM8/23/13
to
On Friday, August 23, 2013 2:21:47 PM UTC-7, mruscoe wrote:
> On 23/08/2013 18:25, Charles Carroll wrote:
> I can't help thinking that shorter oars, shorter inboard, and
> appropriate span would make for a much better experience i.e. scaled rig
> to increase the stroke angles.
I had a coach that did just that years ago for this exact reason. Makes a lot of sense. Valery Kleshnov has data to back that up. See his rigging chart: http://www.biorow.com/RigChart.aspx
> On 23/08/2013 18:25, Charles Carroll wrote:
> I can't help thinking that shorter oars, shorter inboard, and
> appropriate span would make for a much better experience i.e. scaled rig
> to increase the stroke angles.
I'll post a link to the article that talks about this when I get a chance to dig it up.
John Greenly
Aug 24, 2013, 5:15:20 PM8/24/13
to
Here's something I wonder about though. Absolutely agreed, the higher the catch angle the less chance to check the boat as the blades go in. But the other side of that coin is that the force on the pin as you load the oars is more sideways as the angle goes up, the forward component gets smaller, so it doesn't resist the foot pressure as well when it comes on the stretcher. The pin forward force has to be bigger than the stretcher backward force-- if not, then the boat is slowing down. So, how much angle is too much??
Cheers,
--John
by the way, what kind of ology do you do, James??
wmar...@gmail.com
Aug 24, 2013, 9:15:45 PM8/24/13
to
Walter
James HS
Aug 25, 2013, 5:28:54 AM8/25/13
to
> by the way, what kind of ology do you do, James??
Rarefied world of Experimental Psychology at Oxford in the 80's, then ergonomics in industrial control rooms, then gerontology (study of old age) then architecture :) - so I am now a qualified architect that specialises in how people (mainly disabled) interact with buildings (mainly arts buildings)and I build stuff up to about UKP 2 million - but I am more of a process brain than a designer, though that process sadly does not include an ability to manipulate figures, which is a real pity as I have an ability to manipulate 3 dimensional space and understand materials - and LOVE 3D software and 3D printing :)
So most of my professional life is spent working through the senses/musculo/sceletal/anthopometrics to predict how people interact with the built environment.
The whole rowing stroke thing is really interesting in this respect as there are plenty of postulated neural connections that unlock other things (like a real difficulty defecating if the feet are not under load) - so the whole sequence thing is really interesting, as is the muscle memory thing - takes me a few strokes to make the change, but 000,s of strokes to make it "permanent" and how quickly the system reverts to 'old' habits.
I don't ski much but when I do I am always told to take my elbows away from my chest to help balance .... less embryo like body shape, and since I have started coaching I have noticed how beginners go into that shape - not a strong one, not a stable one, but armadillo like. This has helped me think about my own stroke and 'open up' as long as it feels strong (not over-open) it seems to be better!
James
A. Dumas
Aug 25, 2013, 5:48:41 AM8/25/13
to
wmar...@gmail.com wrote:
> All the "big" guys get really long catch angles - If you look at
> overhead shots of Karpinnen, Porter, Drysdale (the three for whom
> I've taken measurements) they get about 70 degrees "past the pin"
> catch-angle.
http://ewoud.home.xs4all.nl/rowing/mahe.gif
> All the "big" guys get really long catch angles - If you look at
> overhead shots of Karpinnen, Porter, Drysdale (the three for whom
> I've taken measurements) they get about 70 degrees "past the pin"
> catch-angle.
John Greenly
Aug 25, 2013, 11:35:25 AM8/25/13
to
On Saturday, August 24, 2013 9:15:45 PM UTC-4, wmar...@gmail.com wrote:
> All the "big" guys get really long catch angles - If you look at overhead shots of Karpinnen, Porter, Drysdale (the three for whom I've taken measurements) they get about 70 degrees "past the pin" catch-angle. Pushing outwards on the water from both sides at these angles (once the boat is moving) is a bit like the sideways push in speed-skating - generates a "reaction thrust" (I'm told that's what it's called) which is likely augmented by the lift-forces on the backs of the blades (the reduced pressure due partly to the tip-on movement through the water in the early stages of the stroke and partly to the fact that you're pulling the handle).
>
> Walter
It's totally and only that you're pulling the handle. "lift" is nothing more nor less than one of the forces that arises at the blade in reaction to your pull, and it happens to result in more efficient coupling of your force to the water. That's all. The blade does not and cannot pull you more than you pull it.
> All the "big" guys get really long catch angles - If you look at overhead shots of Karpinnen, Porter, Drysdale (the three for whom I've taken measurements) they get about 70 degrees "past the pin" catch-angle. Pushing outwards on the water from both sides at these angles (once the boat is moving) is a bit like the sideways push in speed-skating - generates a "reaction thrust" (I'm told that's what it's called) which is likely augmented by the lift-forces on the backs of the blades (the reduced pressure due partly to the tip-on movement through the water in the early stages of the stroke and partly to the fact that you're pulling the handle).
>
> Walter
Yes, right, I think the big guys actually have two advantages: they can reach those extreme angles, but also they are strong enough to support the pressure at those angles despite the unfavorable geometry. You're right, the angle is like the skater's angle of push- it's like an inclined plane that gives an effective "gear ratio" that transforms a very large sideways force at low velocity into a smaller forward force at high velocity. But there's no magic- you don't get something for nothing, you only get a more, or less, efficient use of your own work.
Oh, yes, that's good, isn't it-- in that analogy the oar blade with good lift is like a nice sharp skate blade that doesn't slip sideways, while a stalled blade is like a dull skate that doesn't get a good grip.
Cheers,
--John G
John Greenly
Aug 25, 2013, 11:50:43 AM8/25/13
to
What is "muscle memory" really? As a musician, I rely on it absolutely. We use several redundant systems to remember music: We learn the structure of the piece, can be done by studying the score; we have it in aural memory, we can "listen" to it and play what we are hearing in our head; but when those fail we just let the fingers do it and try not to interfere mentally. I've always assumed it's really a pattern established in the brain (though not a conscious part of the brain), not actually in the muscles-- right?
--John G
Carl
Aug 25, 2013, 4:08:11 PM8/25/13
to
achieves a hard mechanical connection to the ice through the fin groove
that it cuts. So you can apply a simple triangle of forces to resolve
the forward component from this angled lateral thrust. The lateral
force component is resisted in part inertially against the skater's body
mass & in part by the horizontal component resulting from that mass
hanging away from the axis of the skate.
In rowing (as in sailing or flying) your blade's firm connection with
the working fluid results from that fluid being accelerated around the
curve of the back face of the blade, causing a pressure reduction over
that face which works almost as well as the interlock between ice &
skate to prevent lateral (= face-first) blade motion through the water &
to confine the blade's actual path through the water to near-enough tip
first.
Skaters know that the first few strides are more like a run but once up
to speed they're into to the familiar side-push & sway action whose
mechanism I've outlined above. The important factor here, as in rowing
or sailing, is gearing. When moving slowly & needing to accelerate you
select a low gear but as speed builds up you move to progressively
higher, more severe, gearing. When the skater is at speed the
relatively slow side-push at high pressure generates a lower force along
the direction of travel, just as the highest gearing on a bike generates
the lowest propulsive force between tyre & road, but in each case it
results in the feet moving at the optimum speed for power being generated.
So it is in rowing. The first strokes are relatively short but, as the
boat gains speed, the stroke should get progressively longer. That way
the catch speed (movement around the pin) slows down WRT boat speed but,
as the boat speed rises you keep catching & loading at much the same
speed. A shorter catch would need to be uneconomically fast & the
shorter resulting stroke would be too short to give time/length in which
to do the necessary work. In rowing, as in skating, the longer catch is
not inefficient, in fact it is more efficient as a means of converting
input effort into net propulsive power, but it does make the gearing
higher (more severe). And this tuning of gearing to vehicle speed is
what we observe in every process in which an engine drives a machine.
You gear the output to keep the engine running at that speed which
allows it to deliver its best power.
In rowing, length is another expression of gearing, & a lot more
meaningful than the little changes in spread & inboard which so
preoccupy many rowers. Thus the faster scullers tend to have the longer
catches, & I hope this explanation shows why you'd expect this to be so.
Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ca...@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682
URLs: carldouglas.co.uk, on Facebook @ CarlDouglasRacingShells
wmar...@gmail.com
Aug 25, 2013, 4:22:17 PM8/25/13
to
The "lift" - in that it's perpendicular to the blade going tip-on through the water during the early part of the stroke, creating a reduced pressure behind (on the convex surface of the blade) partly because it's being driven through the water tip first, part of the reduced pressure on the back of the blade is also due to you pulling on the handle and making the blade go around in the direction of the finish - Carl insists that lift only happens because you load it by pulling the handle, but if you're pulling the handle, AND the blade is going tip first through the water, doesn't the lift force further reduce the pressure behind the blade? A wing goes convex up, and with the flaps fully extended for slow speeds it's also tilted up generally, but the engines are driving the wings into the air, and it's the air having to go farther across the top (analogous in a small way to the back of the blade) as the wing passes through the air that gets the darned 747 off the ground. The wings are "loaded" I guess because of their angle of attack and because they've got that darned fuselage hanging off them and the wing root not letting them drift into a no-lift angle of attack...
Yeah, you've gotta be strong at the catch to hold onto those forces - I wonder when anyone's going to figure out how to measure it, or publish it (and a translation of it into layman's terms).
Then there's depth - early in the stroke does it not help to be a bit deeper so that there is less possibility of sucking air in behind the blade - I asked Kleshnev at another of those conferences, he said - half a blade-width of water above the top edge of the blade - (paraphrased). I asked Sliasas if he had run his simulations at various blade depths, and he tried a simulation with the top edge 10 cm below the surface - it worked out "better" - but he hadn't (and may not yet have) investigated it farther. I've noticed most of the big guys going deep until there's nearly a metre of shaft under the water. At the 1999 FISA conference (Canberra) the Italian coach was queried on the depth of the blades of his lightweight M2X, and his response (bad English) was yes, deeper, but it's good because it's better for speed... Again, paraphrased.
Whatever the case, people I've coached in the area of the catch early in their careers have gone on to some reasonably good results (T. Cameron, K. Heddle, for example)... So I may not have the physics/fluid dynamics of it thoroughly understood, but something's working.
W
Carl
Aug 25, 2013, 4:23:01 PM8/25/13
to
On 25/08/2013 21:08, Carl wrote:
> In rowing, length is another expression of gearing, & a lot more
> meaningful than the little changes in spread & inboard which so
> preoccupy many rowers. Thus the faster scullers tend to have the longer
> catches, & I hope this explanation shows why you'd expect this to be so.
>
> Cheers -
> Carl
Oops! I had the above post sitting on my computer since lunch time UK,
> In rowing, length is another expression of gearing, & a lot more
> meaningful than the little changes in spread & inboard which so
> preoccupy many rowers. Thus the faster scullers tend to have the longer
> catches, & I hope this explanation shows why you'd expect this to be so.
>
> Cheers -
> Carl
finished except for proof-reading & ready to post, while attending to
the needs of a client coming over to collect his 10-yr old Avodire 1x
after its first re-furb. Now he'll take it to Varese looking as new, in
its shimmering, glowing, golden & seemingly holographic best. If you're
in Varese, see if you can spot it, along with the similarly spectacular
sectional Avodire 2x from Poland (if it's there as I'd expect).
But I see, immediately after posting my treatise, that John G had
meanwhile rather more succinctly made most of the points which I'd
laboured to make.
Well, we do agree, so that's good :). But it would be good for the
standard of rowing if this interpretation were to filter out into the
wider world too.
Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ca...@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682
wmar...@gmail.com
Aug 25, 2013, 4:29:11 PM8/25/13
to
wmar...@gmail.com
Aug 25, 2013, 4:30:25 PM8/25/13
to
On Sunday, 25 August 2013 16:23:01 UTC-4, Carl wrote:
> On 25/08/2013 21:08, Carl wrote:
>
> > In rowing, length is another expression of gearing, & a lot more
>
> > meaningful than the little changes in spread & inboard which so
>
> > preoccupy many rowers. Thus the faster scullers tend to have the longer
>
> > catches, & I hope this explanation shows why you'd expect this to be so.
>
> >
>
> > Cheers -
>
> > Carl
>
>
>
> Oops! I had the above post sitting on my computer since lunch time UK,
>
> finished except for proof-reading & ready to post, while attending to
>
> the needs of a client coming over to collect his 10-yr old Avodire 1x
>
> after its first re-furb. Now he'll take it to Varese looking as new, in
>
> its shimmering, glowing, golden & seemingly holographic best. If you're
>
> in Varese, see if you can spot it, along with the similarly spectacular
>
> sectional Avodire 2x from Poland (if it's there as I'd expect).
>
I'll have a look for the boat in Varese!.
> On 25/08/2013 21:08, Carl wrote:
>
> > In rowing, length is another expression of gearing, & a lot more
>
> > meaningful than the little changes in spread & inboard which so
>
> > preoccupy many rowers. Thus the faster scullers tend to have the longer
>
> > catches, & I hope this explanation shows why you'd expect this to be so.
>
> >
>
> > Cheers -
>
> > Carl
>
>
>
> Oops! I had the above post sitting on my computer since lunch time UK,
>
> finished except for proof-reading & ready to post, while attending to
>
> the needs of a client coming over to collect his 10-yr old Avodire 1x
>
> after its first re-furb. Now he'll take it to Varese looking as new, in
>
> its shimmering, glowing, golden & seemingly holographic best. If you're
>
> in Varese, see if you can spot it, along with the similarly spectacular
>
> sectional Avodire 2x from Poland (if it's there as I'd expect).
>
Cheers,
Walter
John Greenly
Aug 25, 2013, 4:43:34 PM8/25/13
to
On Sunday, August 25, 2013 4:23:01 PM UTC-4, Carl wrote:
> On 25/08/2013 21:08, Carl wrote:
>
> > In rowing, length is another expression of gearing, & a lot more
>
> > meaningful than the little changes in spread & inboard which so
>
> > preoccupy many rowers. Thus the faster scullers tend to have the longer
>
> > catches, & I hope this explanation shows why you'd expect this to be so.
>
> >
>
> > Cheers -
>
> > Carl
>
>
>
> Oops! I had the above post sitting on my computer since lunch time UK,
>
> finished except for proof-reading & ready to post, while attending to
>
> the needs of a client coming over to collect his 10-yr old Avodire 1x
>
> after its first re-furb. Now he'll take it to Varese looking as new, in
>
> its shimmering, glowing, golden & seemingly holographic best. If you're
>
> in Varese, see if you can spot it, along with the similarly spectacular
>
> sectional Avodire 2x from Poland (if it's there as I'd expect).
>
>
>
> But I see, immediately after posting my treatise, that John G had
>
> meanwhile rather more succinctly made most of the points which I'd
>
> laboured to make.
>
>
>
> Well, we do agree, so that's good :). But it would be good for the
>
> standard of rowing if this interpretation were to filter out into the
>
> wider world too.
>
>
>
> Cheers -
>
> Carl
Hi Carl,
> On 25/08/2013 21:08, Carl wrote:
>
> > In rowing, length is another expression of gearing, & a lot more
>
> > meaningful than the little changes in spread & inboard which so
>
> > preoccupy many rowers. Thus the faster scullers tend to have the longer
>
> > catches, & I hope this explanation shows why you'd expect this to be so.
>
> >
>
> > Cheers -
>
> > Carl
>
>
>
> Oops! I had the above post sitting on my computer since lunch time UK,
>
> finished except for proof-reading & ready to post, while attending to
>
> the needs of a client coming over to collect his 10-yr old Avodire 1x
>
> after its first re-furb. Now he'll take it to Varese looking as new, in
>
> its shimmering, glowing, golden & seemingly holographic best. If you're
>
> in Varese, see if you can spot it, along with the similarly spectacular
>
> sectional Avodire 2x from Poland (if it's there as I'd expect).
>
>
>
> But I see, immediately after posting my treatise, that John G had
>
> meanwhile rather more succinctly made most of the points which I'd
>
> laboured to make.
>
>
>
> Well, we do agree, so that's good :). But it would be good for the
>
> standard of rowing if this interpretation were to filter out into the
>
> wider world too.
>
>
>
> Cheers -
>
> Carl
your explanation seemed clearer to me than mine did- I have such a hard time trying to make these things clear without being able to draw diagrams!
Cheers
--John G
Carl
Aug 25, 2013, 4:57:16 PM8/25/13
to
The tip-first motion of the oarblade is no different to the
leading-edge-first movement of a plane's wing & the lift that's
generated arises in exactly the same way. Because in rowing the power
application is cyclic, it is your momentum which drives the boat forward
as the blade enters with the water, & for a while thereafter, whereas
for the plane the power generation is continuous.
It is the acceleration of flow around the convexity of the wing or the
blade which creates the right conditions for there to be lift, but if
there were no load the effective angle of attack would immediately
self-adjust so that there was no lift on the wing or on the blade. It
is the application of load, whether from the handle to the blade by
yourself in the boat, or the force resulting from gravity or some
manoeuvre acting on the mass of the plane, which changes the effective
AoA until the lift that results equals the load that's applied.
Perhaps an easy way of explaining this otherwise intangible cause &
effect conundrum is to consider hanging a weighty object onto a spring?
Without that object there is no spring force; when you attach the
object the spring stretches, increasing in tension but only op to that
exact point at which its tension = the object's weight. In short, the
spring self-adjusts its length & tension to the load applied, & the wing
or oarblade & the surrounding flows self-adjust until lift is generate
which exactly matches the applied load. We see this as an adjustment of
AoA (if we carefully observe the flow)
In the case of the plane, I should note that this self-adjustment of AoA
to make the resulting lift match the weight of the plane does nothing to
ensure that the plane is in level flight. Depending on load, speed,
pitch & settings of control surfaces (ailerons, etc.) the plane might be
rising or descending, & it's the job of the pilot to make the necessary
in-flight adjustments to ensure the required flight altitude & path.
HTH?
Meanwhile no reasonable observer can any more argue that blades should
not go deeper that is recommended by popular teaching. There is no
measurable penalty from a fair bit of looming but considerable gain in
stroke efficiency from the deeper blade. Any aeration/exposure of the
back of the blade during the stroke immediately reduces the area over
which the reduced pressure or lift force (what I like to call tension!)
can act. Such a reduction reduces the total lioft on the blade,
resulting in a bit more face-first movement which manifests itself in an
increase in AoA which, in other terms, might be aptly termed slippage.
Finally (FWIW & just to complicate matters unnecessarily ;) ) any
asymmetric foil (e.g aircraft wing, sail or oarblade) will generate lift
in a flow if held even at zero or a moderately negative AoA. That's why
these foils are shaped that way - thus a passenger plane's wings are
very flat beneath & quite convex above & will generate some upward lift
at significant negative AoA. A stunt plane, which needs to be able to
fly well when inverted, will have wings for which the upper & lower
surfaces are both convex.
Cheers -
Carl
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ca...@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ca...@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682
greg2...@yahoo.com
Aug 26, 2013, 6:20:30 PM8/26/13
to
On Sunday, August 25, 2013 1:08:11 PM UTC-7, Carl wrot
The large catch angle does allow more time for the catch so would be advantageous to anyone regardless of boat speed.
The fashion is to keep the span in relatively narrow range and a larger catch angle does require more flexibility and more skill to keep the boat set up, which you would expect in faster elite rowers. Volker Nolte has been arguing for smaller span and shorter oars and more similar catch angles more similar catch angles (especially for smaller rowers) for quite some time
If a faster boat can take more advantage of blade life during the first part of the stroke and hence may benefit from a larger catch angle, but I don't have any idea if this is the case.
You may be right but I don't think you have made the case--or at least you haven't convince me yet.
Best,
Nosmo
> In rowing, length is another expression of gearing, & a lot more
> meaningful than the little changes in spread & inboard which so
> preoccupy many rowers. Thus the faster scullers tend to have the longer
> catches, & I hope this explanation shows why you'd expect this to be so.
Of course you would adjust the catch angle on the start to adjust the gearing--that is the only option one has, but when one is up to maximum speed it is not at all obvious that slower rowers would use a smaller catch angle. Why wouldn't you just use some other method to lower the gear for slower boats e.g. shorter oars, smaller blades, more inboard.
> meaningful than the little changes in spread & inboard which so
> preoccupy many rowers. Thus the faster scullers tend to have the longer
> catches, & I hope this explanation shows why you'd expect this to be so.
The large catch angle does allow more time for the catch so would be advantageous to anyone regardless of boat speed.
The fashion is to keep the span in relatively narrow range and a larger catch angle does require more flexibility and more skill to keep the boat set up, which you would expect in faster elite rowers. Volker Nolte has been arguing for smaller span and shorter oars and more similar catch angles more similar catch angles (especially for smaller rowers) for quite some time
If a faster boat can take more advantage of blade life during the first part of the stroke and hence may benefit from a larger catch angle, but I don't have any idea if this is the case.
You may be right but I don't think you have made the case--or at least you haven't convince me yet.
Best,
Nosmo
gsl...@gmail.com
Aug 26, 2013, 6:33:04 PM8/26/13
to
> If a faster boat can take more advantage of blade life during the first part of
err, blade "lift" not "life"
Carl
Aug 27, 2013, 7:16:40 AM8/27/13
to
everyone or "make the case" to the satisfaction of all. This is a
debate, in which I do try to explain those aspects of the rowing stroke
on which my own areas of technical expertise qualify me to talk. But I
also understand that these are conceptually knotty, even
counter-intuitive, matters. I do try to provided other entries into
understanding what's going on, but I can't win 'em all. And it is hard
to let go of long-held interpretations in the face of new (to us)
explanations. However, I do think you'll find those who do have the
relevant technical background are in broad agreement with what I say.
There's no reason not to play with rig, but I was attempting to explain
that your greatest scope for re-gearing your stroke comes from catch
angle. Also, to provide a logical underpinning for varying stroke
length according to boat speed (which would include headwind effects,
sprinting, etc.). That does not rule out more radical rig changes, & I
have a lot of regard for the work such as Nolte & Kleshnev have done in
that direction. But it does put into perspective the small, fiddling
rig changes - 5mm here or there - which waste so much time on the bank
&, frankly, don't make nearly as much difference as, say, moving the
stretcher out to take a more acute-angled catch, or drawing a tad
further past the body (in sculling), or simply wasting less time &
distance by slow catches.
It is not simply a case of taking more advantage of blade lift by
lengthening the catch. It is about accepting that there is a mechanism
(lift) which efficiently converts side-forces into axial propulsive
forces (just as with the skater), but accepting that as you reach
further forward your effective gearing becomes progressively more
severe. Nowt wrong with a severe gearing, provided it's what you can
manage under those conditions to enable you to maximise you own power
application
Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ca...@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682
Nosmo
Aug 27, 2013, 2:47:50 PM8/27/13
to
On Tuesday, August 27, 2013 4:16:40 AM UTC-7, Carl wrote:
> > On Sunday, August 25, 2013 1:08:11 PM UTC-7, Carl wrot
> >> In rowing, length is another expression of gearing, & a lot more
> >> meaningful than the little changes in spread & inboard which so
> >> preoccupy many rowers. Thus the faster scullers tend to have the longer
> >> catches, & I hope this explanation shows why you'd expect this to be so.
> > Of course you would adjust the catch angle on the start to adjust the gearing--that is the only option one has, but when one is up to maximum speed it is not at all obvious that slower rowers would use a smaller catch angle. Why wouldn't you just use some other method to lower the gear for slower boats e.g. shorter oars, smaller blades, more inboard.
>
> > The large catch angle does allow more time for the catch so would be advantageous to anyone regardless of boat speed.
> >
> > The fashion is to keep the span in relatively narrow range and a larger catch angle does require more flexibility and more skill to keep the boat set up, which you would expect in faster elite rowers. Volker Nolte has been arguing for smaller span and shorter oars and more similar catch angles more similar catch angles (especially for smaller rowers) for quite some time
>
> > If a faster boat can take more advantage of blade life during the first part of the stroke and hence may benefit from a larger catch angle, but I don't have any idea if this is the case.
> >
> > You may be right but I don't think you have made the case--or at least you haven't convince me yet.
> >
> > On Sunday, August 25, 2013 1:08:11 PM UTC-7, Carl wrot
> >> In rowing, length is another expression of gearing, & a lot more
> >> meaningful than the little changes in spread & inboard which so
> >> preoccupy many rowers. Thus the faster scullers tend to have the longer
> >> catches, & I hope this explanation shows why you'd expect this to be so.
> > Of course you would adjust the catch angle on the start to adjust the gearing--that is the only option one has, but when one is up to maximum speed it is not at all obvious that slower rowers would use a smaller catch angle. Why wouldn't you just use some other method to lower the gear for slower boats e.g. shorter oars, smaller blades, more inboard.
>
> > The large catch angle does allow more time for the catch so would be advantageous to anyone regardless of boat speed.
> >
> > The fashion is to keep the span in relatively narrow range and a larger catch angle does require more flexibility and more skill to keep the boat set up, which you would expect in faster elite rowers. Volker Nolte has been arguing for smaller span and shorter oars and more similar catch angles more similar catch angles (especially for smaller rowers) for quite some time
>
> > If a faster boat can take more advantage of blade life during the first part of the stroke and hence may benefit from a larger catch angle, but I don't have any idea if this is the case.
> >
> > You may be right but I don't think you have made the case--or at least you haven't convince me yet.
> >
You also seem to be saying that Mehe should using a much greater catch angle then me (a 5'7" 53 year old light weight) because he is so much faster. Kelshnev seems to be saying that I should be rowing with about the same catch angle but smaller span shorter oars and less inboard. His data indicates that I may be ~1.5 percent faster if I changed my rigging.
1.5% is a pretty significant speed change--but it does involve spending >$1500 to find out(new oars and my own set of riggers for a shared Van Dusen).
Carl
Aug 27, 2013, 4:12:00 PM8/27/13
to
> Apologize if I seemed argumentative. I was not trying to be, but rather truly understand what you are saying. I pretty much agree with everything you are saying: Faster boats need higher gearing, lift is a mechanism to convert side forces in to forward motion, and small rigging changes don't matter much.
>
> You also seem to be saying that Mehe should using a much greater catch angle then me (a 5'7" 53 year old light weight) because he is so much faster. Kelshnev seems to be saying that I should be rowing with about the same catch angle but smaller span shorter oars and less inboard. His data indicates that I may be ~1.5 percent faster if I changed my rigging.
> 1.5% is a pretty significant speed change--but it does involve spending >$1500 to find out(new oars and my own set of riggers for a shared Van Dusen).
>
>
No apology sought or appropriate. This is Usenet, where we can speak
>
> You also seem to be saying that Mehe should using a much greater catch angle then me (a 5'7" 53 year old light weight) because he is so much faster. Kelshnev seems to be saying that I should be rowing with about the same catch angle but smaller span shorter oars and less inboard. His data indicates that I may be ~1.5 percent faster if I changed my rigging.
> 1.5% is a pretty significant speed change--but it does involve spending >$1500 to find out(new oars and my own set of riggers for a shared Van Dusen).
>
>
directly without dressing up our words with a smoother, more muffled
touch in which meaning gets buried in all the politesse. Besides, I
like a challenge :)
If you hear 2 supposed experts on a subject you may hear 2 parallel
lines of the same argument. I have already express my respect for
Valery Kleshnev, and for Volke Nolte. Years ago, for instance, Nolte
proposed certain equipment changes to give you a more acute angle at the
catch.
What I'm putting to you is the opportunity, before laying out
significant sums on rigging, to consider and explore the influence of
catch angle on boat speed under different conditions, how to use it over
the first few strokes of a race, and how it provides you with an
infinitely variable gearing system - once you appreciate how it can work
in that way. And I'd say the same if you had made radical rigging
changes as Kleshnev suggests. These 2 approaches are not mutually
exclusive, but what I find is that crews & scullers so often think that
their arc & its starting point are fixed & that small rig changes
determine all. Just as you shorten stride & maybe increase cadence when
running up hill (& certainly when cycling up hill), so you should
shorten catch angle to match boat speed because everything is going that
bit slower.
That said, if you're in the USA we can build and ship you a pair of new
riggers (with pins & oarlocks) for an all-up cost of <$650 (unless yours
are wings), so maybe you have some exceptionally pricey sculls in mind?
gsl...@gmail.com
Aug 27, 2013, 5:06:03 PM8/27/13
to
OK, so you are really saying is that one should adjust the catch angle depending on the boat speed--something I already do--not that faster boats "need" bigger catch angles. No argument there.
Van Dusen riggers are wings and cost over $1000.
Van Dusen riggers are wings and cost over $1000.
Charles Carroll
Sep 4, 2013, 2:20:47 PM9/4/13
to
> My main thought looking at those videos is
You have hit on a terrible sore point for me.
I spent several years adjusting my rigging in an attempt to improve the
catch angle. I have had the span as narrow as I could get it (156 cm), and
my oars as short as I could adjust them (282 cm), and have pushed the
stretcher sternwards almost all the way to the last notch.
While these adjustments gave me better catch angle, they virtually
extinguished my finish. Ric Ricci, a coach I respect very much, said my
finish made him “ill.” He said he despised the idea of frontloading the
catch at the expense of the finish.
I have had my oars, span, and stretcher at almost every possible combination
I could try. Interestingly enough once I adapted myself to a particular
combination it didn’t seem to work any better than any other combination.
I am sure you know the oft repeated phrase “Power gets you lengths,
technique gets you inches.” Well I have come to think of rigging changes in
much the same way.
If you are near the top of the pyramid, sculling at an elite level, and
winning and losing by inches, then rigging could make the difference between
crossing the finish line forward of your closest competitor. If, on the
other hand, you are an old guy like me, and fairly small, and not too good
at sculling, there are so many other things to work on first.
But this doesn’t mean I can’t dream. Here are the impressive catch angles of
two elite scullers. C'est incroyable!
https://www.youtube.com/watch?v=AKXLHZ2ErQU
Cordially,
Charles
> about appropriate rigging for people who through stature or age
> can't get the range of the elite athletes.
>
> Part of the feel for the stroke,
> particularly the catch, comes from the way the blade works in the lift
> phases at the ends of the stroke that Carl loves to talk about.
> Good sweep rowing gets about 55 degrees forward past the pin, and elite
> scullers can be 65+ degrees forward of the pin. It makes a huge difference
> to
> the feel of the stroke, and how quickly you have to move to get connected.
> You're getting maybe 35 degrees forward of the pin,
> can't get the range of the elite athletes.
>
> Part of the feel for the stroke,
> particularly the catch, comes from the way the blade works in the lift
> phases at the ends of the stroke that Carl loves to talk about.
> Good sweep rowing gets about 55 degrees forward past the pin, and elite
> scullers can be 65+ degrees forward of the pin. It makes a huge difference
> to
> the feel of the stroke, and how quickly you have to move to get connected.
> You're getting maybe 35 degrees forward of the pin,
> I can't help thinking that shorter oars,
> shorter inboard, and appropriate span would make
> for a much better experience
Ah Mark!
> shorter inboard, and appropriate span would make
> for a much better experience
You have hit on a terrible sore point for me.
I spent several years adjusting my rigging in an attempt to improve the
catch angle. I have had the span as narrow as I could get it (156 cm), and
my oars as short as I could adjust them (282 cm), and have pushed the
stretcher sternwards almost all the way to the last notch.
While these adjustments gave me better catch angle, they virtually
extinguished my finish. Ric Ricci, a coach I respect very much, said my
finish made him “ill.” He said he despised the idea of frontloading the
catch at the expense of the finish.
I have had my oars, span, and stretcher at almost every possible combination
I could try. Interestingly enough once I adapted myself to a particular
combination it didn’t seem to work any better than any other combination.
I am sure you know the oft repeated phrase “Power gets you lengths,
technique gets you inches.” Well I have come to think of rigging changes in
much the same way.
If you are near the top of the pyramid, sculling at an elite level, and
winning and losing by inches, then rigging could make the difference between
crossing the finish line forward of your closest competitor. If, on the
other hand, you are an old guy like me, and fairly small, and not too good
at sculling, there are so many other things to work on first.
But this doesn’t mean I can’t dream. Here are the impressive catch angles of
two elite scullers. C'est incroyable!
https://www.youtube.com/watch?v=AKXLHZ2ErQU
Cordially,
Charles
Carl
Sep 4, 2013, 3:29:58 PM9/4/13
to
to you before, Charles, of the elusive character of performance gain
from rig changes.
When you make a change, you start by sculling/rowing in the same way
that you did before the change. This means you load up in parts of the
stroke in which it has now become harder to sustain that load (the
gearing there has become more severe. At first you continue as before,
& you see a performance gain. Gradually you adapt to avoid the extra
stress your changed rig without changed technique imposed, & in that
process the boat slows down to what was previously normal.
I've made a similar point also WRT to changes which should result in a
more efficient stroke. A stroke only becomes more efficient (converts
more of your input power into propulsive effect) because it slips less.
When it slips less, it takes longer to complete the stroke, which you
interpret as "being heavier". In reality, it feels heavier only because
you are finely attuned to the duration & speed variations of what was
your normal stroke, so you are now trying to complete the stroke in the
same time as before the rig change, which you can only do by pulling
harder. And, as we all know, pulling harder is a mug's game because it
knackers us sooner.
What we should do when making a rig or technique change is to sustain
the same work rate (e.g. by pulse monitoring) & give the stroke the time
it requires rather than clipping its ends or pulling harder. If the
stroke is indeed more efficient, that then requires you to be a little
faster on the recovery. And Ivanov shows you how you do that: not by
speed around the finish but by speed over the stretcher, by an absolute
lack of "hang" at the catch & by that catch being very swiftly struck &
loaded.
Simple, really ;)
>
> If you are near the top of the pyramid, sculling at an elite level, and
> winning and losing by inches, then rigging could make the difference
> between crossing the finish line forward of your closest competitor. If,
> on the other hand, you are an old guy like me, and fairly small, and not
> too good at sculling, there are so many other things to work on first.
>
> But this doesn’t mean I can’t dream. Here are the impressive catch
> angles of two elite scullers. C'est incroyable!
>
> https://www.youtube.com/watch?v=AKXLHZ2ErQU
>
> Cordially,
>
> Charles
>
>
at a lower boat speed would, due to the severity of its inherent
gearing, seem unduly heavy. The sculler on the left, in a very aged
Carl Douglas single, is Rogier Blink from the Dutch club, Gyas, who was
racing in the pair last week. I don't know the other one.
sully
Sep 4, 2013, 6:25:02 PM9/4/13
to
him a beer for that.
I'm so hated at the RC club now by some of the members. One morning a
couple quads docked as I was orienting a new member. I have a standing
bet with every new person that I check out sculling that if they can hold
water correctly without me teaching them, I'll buy them a beer and sandwich
at a local pub of their choice. I have only had to pay off once in about
ten years. This new fellow did it beautifully, taught by his coach up
in Lake Sammamish Wa (I need to find him). So I loudly made that announcement
to the masters' ppl all docking, many of whom learn to hold correctly from
me and abandon it when going to the team boats and descending to the lowest
common denominator. I called out to one woman that she used to hold water correctly just as I saw her doing it pathetically wrong, she answered rather
bitterly "this way works for me".
I answered "it's still wrong, and it's not sculling".
the stare she gave me almost burned my hair off.
It's happening a lot!
I think when I was in my 50s this attitude might have looked authoritative,
but now I bet I just sound like a crazy cat lady.
Ric is my age, I wonder how many rowers hate him too!
:^)
Charles Carroll
Sep 5, 2013, 1:26:11 PM9/5/13
to
> The sculler on the left, in a very aged Carl Douglas single, is Rogier
> Blink
> from the Dutch club, Gyas, who was racing in the pair last week. I don't
> know the other one.
Carl,
> Blink
> from the Dutch club, Gyas, who was racing in the pair last week. I don't
> know the other one.
If memory serves me, the photograph of the other sculler comes from Volker
Nolte. My understanding is that Volker uses this photograph to illustrate
“an ideal catch angle.”
Am I wrong to think that a 14-deg catch angle is really extreme?
I suspect a 14-deg catch angle is out of the reach of most of us. Or should
I re-phrase that statement and say I suspect that it wouldn't be very
beneficial to most of us because we can't move a boat fast enough to make
good use of it. As you say, a catch angle that acute at a lower boat speed
would be unduly heavy because of the severity of its inherent gearing.
Cordially,
Charles
Charles Carroll
Sep 5, 2013, 1:50:28 PM9/5/13
to
Mike,
You and Ric have many things in common. You are about the same height and
weight. You are good athletes. You have been rowing and sculling for
decades. You�ve both raced at the elite level. In fact you have raced
against each other, haven�t you? You both coach. And, if I may paraphrase
Lillian Hellman, neither of you particularly cares to cut your opinions to
fit this year�s fads. If you think something is wrong, you say so plainly.
It is the last quality that I admire most in the two of you.
I know other people don�t feel this way. I know people feel insulted when
someone uses plain words to tell them that they are wrong.
But what sense is there in asking someone to teach you something about
rowing just so you can tell him what you think rowing is?
This goes way back to my school days and Epictetus. �What is the first
business of the philosopher? To cast away conceit; for it is impossible for
a man to begin learning what he thinks he knows.�
If you are not questioning what you think, you are not thinking. But the
problem is, most people hate to be questioned.
Keep at it, crazy cat lady �
Cordially,
Charles
You and Ric have many things in common. You are about the same height and
weight. You are good athletes. You have been rowing and sculling for
decades. You�ve both raced at the elite level. In fact you have raced
against each other, haven�t you? You both coach. And, if I may paraphrase
Lillian Hellman, neither of you particularly cares to cut your opinions to
fit this year�s fads. If you think something is wrong, you say so plainly.
It is the last quality that I admire most in the two of you.
I know other people don�t feel this way. I know people feel insulted when
someone uses plain words to tell them that they are wrong.
But what sense is there in asking someone to teach you something about
rowing just so you can tell him what you think rowing is?
This goes way back to my school days and Epictetus. �What is the first
business of the philosopher? To cast away conceit; for it is impossible for
a man to begin learning what he thinks he knows.�
If you are not questioning what you think, you are not thinking. But the
problem is, most people hate to be questioned.
Keep at it, crazy cat lady �
Cordially,
Charles
Carl
Sep 5, 2013, 5:51:57 PM9/5/13
to
us are not built to reach such lengths & anyway go too slow to benefit
from gearing that's that long (in bike terms).
I see great scope in your case for crisping up your catches at their
existing reach - when the shoulder has mended. Do that & you'll already
have an effectively longer catch - & the boat'll be moving faster too.
What more should you want?
gsl...@gmail.com
Sep 5, 2013, 6:21:59 PM9/5/13
to
The more I think about the catch angle, the more I think the explanation given here isn't quite right.
The issue is not merely that the large catch angle is a high gear and that a faster boat is more efficient with a high gear. This does not explain why one would not choose a bigger blade or longer oar to get that higher gear. Nor does it explain why one would not choose the same catch angle in a slower boat and get the lower gear with shorter oars and/or a smaller blade.
The larger the catch angle, the bigger the gear at the catch relative to other parts of the stroke. Other things being equal one would want a lower gear at the start of the stoke when the boat is moving slower, and a bigger gear closer to mid-drive when the boat is moving faster and the body is in a more powerful position. A faster boat also decelerates faster further exacerbating the difference in relative speed between different parts of the stroke.
Other considerations...
Faster boats usually have more skilled rowers, who can get more compression and are more stable. They may also have people with the physical proportions to get the increase angle (longer arms and/or longer torso?). Boats are also more stable the faster they go so a faster more skilled rower can get that angle and still be stable. Less skilled rowers have a harder time getting compression and opening up.
The increased catch angle does give one more time to make the catch. A faster needs more time to make the catch, so a bigger catch angle makes more of a difference when the boat is faster.
The issue is not merely that the large catch angle is a high gear and that a faster boat is more efficient with a high gear. This does not explain why one would not choose a bigger blade or longer oar to get that higher gear. Nor does it explain why one would not choose the same catch angle in a slower boat and get the lower gear with shorter oars and/or a smaller blade.
The larger the catch angle, the bigger the gear at the catch relative to other parts of the stroke. Other things being equal one would want a lower gear at the start of the stoke when the boat is moving slower, and a bigger gear closer to mid-drive when the boat is moving faster and the body is in a more powerful position. A faster boat also decelerates faster further exacerbating the difference in relative speed between different parts of the stroke.
Other considerations...
Faster boats usually have more skilled rowers, who can get more compression and are more stable. They may also have people with the physical proportions to get the increase angle (longer arms and/or longer torso?). Boats are also more stable the faster they go so a faster more skilled rower can get that angle and still be stable. Less skilled rowers have a harder time getting compression and opening up.
The increased catch angle does give one more time to make the catch. A faster needs more time to make the catch, so a bigger catch angle makes more of a difference when the boat is faster.
gsl...@gmail.com
Sep 5, 2013, 6:27:32 PM9/5/13
to
Is there a video of the proper way to hold water? Not sure I understand completely.
At first I was just blade as if backing, but it really grabs the water and is quite scary. I finally figured out that the top (what was the bottom edge) should be pointed towards the bow so it doesn't just crap. Do I have that right?
At first I was just blade as if backing, but it really grabs the water and is quite scary. I finally figured out that the top (what was the bottom edge) should be pointed towards the bow so it doesn't just crap. Do I have that right?
Charles Carroll
Sep 5, 2013, 8:22:47 PM9/5/13
to
The following are from notes I made on how to Hold Water. Sorry for the
length. Sometimes, as must be very obvious to everyone, I get carried away
...
MIKE SULLIVAN ON HOW TO HOLD WATER:
Lay blades flat on the water Shift grip on handles and feather SLIGHTLY
backward (this is the actual definition of reverse feathering) As the boat
slows continue the rotation into backing position
And Mike is absolutely right. Holding water is just that uncomplicated.
The oar handles do not have to be moved either up or down in the process.
The only load that should be applied to the handles is horizontal.
As for reverse feathering the blades, all that is required is a featherlike,
barely perceptible turn on the oar handles towards yourself. The blades will
descend slowly and their rate of descent can be controlled by varying the
amount of reverse feather.
At first the idea of reverse feathering confused me. In my mind I imagined a
feathered blade off the water. And to reverse feather such a blade meant to
overturn it, that is, to turn it upside down so that its concave side faced
the water. I then imagined the sculler laying the reverse feathered blade on
the water and turning the oar handles away from himself.
A brief 30 second demonstration of how to hold water would have cleared up
everything.
For me – and I am speaking only for myself – it was the written instruction
that created the confusion. Watching Mike Sullivan’s video of Ian and Chris
demonstrating how to hold water demystified the process.
Then Carl’s further elaboration sorted out whatever confusion was still left
in my mind …
——-
CARL DOUGLAS ON HOW TO HOLD WATER
You don't have to move the handles either up or down. If you reverse feather
just a little bit, the blades will descend quite slowly & you can safely let
them do so. You control their rate of de-scent just by unconsciously varying
the amount of reverse feather & even, at will, "fly" them either up or down
through the water.
Because the blades are foiling through the water edge-on, they act like
wings & there's no point in holding the handles either up or down. All that
will do is to give you severe balance problems since the up or down force,
if you choose to resist it, will initially be very high. It'd be like trying
to push a car sideways against the direction of its front wheels.
The only load you should apply to the handles is horizontal - to hold them
away from the body. It is not, in the main, the force on the blades which
stops the boat but that of the water dragging past the largish amount of the
buried shaft. By stopping thus you're applying science, not brute force. The
deeper the blades go (i.e. are flown) the more of their shafts that are
buried & the faster you'll stop. Vertical loading does nothing useful – if
the blades are inclined so that they will go down, then down they'll go –
until the boat has almost stopped.
As you learn this method, you'll see how relatively slowly the blades do
descend under their own steam & how controllable their speed of descent
really is. And you'll find yourself increasing the blades' forward pitch
progressively as the speed falls – just to sustain the load. The speed comes
off the boat so quickly that what I think you secretly fear – that the
blades might keep on diving uncontrollably – really can't happen. There just
isn't enough time or travel.
——-
CARL DOUGLAS ON HOW TO HOLD WATER, CONT
Stopping is normally an emergency measure. There is only one effective, safe
way to stop the boat, & that is to reverse feather, allow the blades to
descend into the water & press against them. As the blades descend, the load
moves inboard to sustain the maximum deceleration de-spite the rapid fall in
the (V-squared) frictional force per unit area.
If stopping, you need to halt in the shortest possible time, not play games
with technique. The emergency stop procedure described above & properly
taught is safe & effective, every time. Emergencies give no time for
internal or external debate, so the emergency stop needs to become a reflex
action, not deliberation. And to suggest there may be alternative ways to
stop, as opposed to slowing down, is dangerous to all.
In a car you may decelerate by easing the pedal, or by lifting off the gas,
but if you need to stop in a hurry you clap the brakes on without a second
thought. Yet unlike rowing, such a response can be harmful: if there's ice,
a wet or greasy road, or other problems of adhesion, you may then lose
control, so emergency stopping used to require an element of skill &
judgement. When ABS was introduced there were crashes due to driver
unfamiliarity with the system, leading them to lift off the brakes on
feeling the characteristic juddering of the pedal - well-learned caution
obstructed the intentions of advanced engineering - so they crashed
needlessly. And probably some of them were driving too fast only because
they knew they had ABS!
In a shell you don't have the problem of adhesion, only of stopping fast
enough. If you do the sloppy thing of pressing the backs of your blades
against the surface & rolling off the feather you _are_ skidding & you will
travel much further before stopping. You will have less directional control.
And you will more likely contribute to the very accident you meant to
prevent. So it's a no-brainer.
——
CARL DOUGLAS ON HOW TO HOLD WATER, CONT
Charles thinks we slam the blades into the water, but that's not what really
happens. Water is too darned hard to let you do that. When I or others say
"allow to descend", we are telling what happens whether or not you allow it.
The angling forwards & downwards of the blade, coupled with the forward
motion of the boat, takes the blades down fast enough. They "fly" downwards
as wings, & any added downforce hardly affects their trajectory. And the
stopping force comes in significant part from the drag on the increasing
buried lengths of the shafts, while the final stopping results from the
reverse squaring & pushing of the deeply buried blades which by that time
may well be rising back up to the surface.
———
CARL DOUGLAS ON HOW TO HOLD WATER, CONT
Put very simply, your blades can descend through the water only at the angle
to which you set them – a steep angle gives a rapid descent, a shallow angle
gives a gradual descent.
This is because, when underwater & attached to your moving boat, the blades
act as any foil would – by resisting forces perpendicular to their surface
through the agency of induced hydro-dynamic lift.
You do want the blades to descend swiftly, but you get that swift descent by
progressively steepening the angle of attack, not by pressing the blades
down harder.
I thought it important to make this point because who are wrongly fearful of
angling their blades into the water may prefer to believe that they can get
the same effect by having the blades flat (or nearly so) & trying to lift
the hands faster than the blades' rate of descent will allow. They will not
stop their boats either so rapidly or under such good control. They will
divert their strength into the uplift instead of the thrust against the drag
that the submerged blades & shaft would otherwise generate.
Another way of putting it is to say that if the blades are just feathered
what you are doing is try-ing to lift the boat up by surfing on the blades.
If they are angled down, they _will_ descend & you can concentrate on
providing the full force that stops the boat. Done in this way, you stop in
an amazingly short distance. Done the other way you may skitter along
aimlessly for several boat lengths.
——
DEFINITION OF HOLD WATER
The idea of hold water appears to have come from sweep rowing:
Hold Water (USA) Emergency stop, also used after the command way enough. It
instructs the rowers to square their blades in the water to stop the
boat. –Glossary of rowing terms, Wikipedia
So the crew is commanded to lay their blades flat on the water, and then
commanded to shift grip on the handles and feather slightly backward to
bring the shell to a full stop.
length. Sometimes, as must be very obvious to everyone, I get carried away
...
MIKE SULLIVAN ON HOW TO HOLD WATER:
Lay blades flat on the water Shift grip on handles and feather SLIGHTLY
backward (this is the actual definition of reverse feathering) As the boat
slows continue the rotation into backing position
And Mike is absolutely right. Holding water is just that uncomplicated.
The oar handles do not have to be moved either up or down in the process.
The only load that should be applied to the handles is horizontal.
As for reverse feathering the blades, all that is required is a featherlike,
barely perceptible turn on the oar handles towards yourself. The blades will
descend slowly and their rate of descent can be controlled by varying the
amount of reverse feather.
At first the idea of reverse feathering confused me. In my mind I imagined a
feathered blade off the water. And to reverse feather such a blade meant to
overturn it, that is, to turn it upside down so that its concave side faced
the water. I then imagined the sculler laying the reverse feathered blade on
the water and turning the oar handles away from himself.
A brief 30 second demonstration of how to hold water would have cleared up
everything.
For me – and I am speaking only for myself – it was the written instruction
that created the confusion. Watching Mike Sullivan’s video of Ian and Chris
demonstrating how to hold water demystified the process.
Then Carl’s further elaboration sorted out whatever confusion was still left
in my mind …
——-
CARL DOUGLAS ON HOW TO HOLD WATER
You don't have to move the handles either up or down. If you reverse feather
just a little bit, the blades will descend quite slowly & you can safely let
them do so. You control their rate of de-scent just by unconsciously varying
the amount of reverse feather & even, at will, "fly" them either up or down
through the water.
Because the blades are foiling through the water edge-on, they act like
wings & there's no point in holding the handles either up or down. All that
will do is to give you severe balance problems since the up or down force,
if you choose to resist it, will initially be very high. It'd be like trying
to push a car sideways against the direction of its front wheels.
The only load you should apply to the handles is horizontal - to hold them
away from the body. It is not, in the main, the force on the blades which
stops the boat but that of the water dragging past the largish amount of the
buried shaft. By stopping thus you're applying science, not brute force. The
deeper the blades go (i.e. are flown) the more of their shafts that are
buried & the faster you'll stop. Vertical loading does nothing useful – if
the blades are inclined so that they will go down, then down they'll go –
until the boat has almost stopped.
As you learn this method, you'll see how relatively slowly the blades do
descend under their own steam & how controllable their speed of descent
really is. And you'll find yourself increasing the blades' forward pitch
progressively as the speed falls – just to sustain the load. The speed comes
off the boat so quickly that what I think you secretly fear – that the
blades might keep on diving uncontrollably – really can't happen. There just
isn't enough time or travel.
——-
CARL DOUGLAS ON HOW TO HOLD WATER, CONT
Stopping is normally an emergency measure. There is only one effective, safe
way to stop the boat, & that is to reverse feather, allow the blades to
descend into the water & press against them. As the blades descend, the load
moves inboard to sustain the maximum deceleration de-spite the rapid fall in
the (V-squared) frictional force per unit area.
If stopping, you need to halt in the shortest possible time, not play games
with technique. The emergency stop procedure described above & properly
taught is safe & effective, every time. Emergencies give no time for
internal or external debate, so the emergency stop needs to become a reflex
action, not deliberation. And to suggest there may be alternative ways to
stop, as opposed to slowing down, is dangerous to all.
In a car you may decelerate by easing the pedal, or by lifting off the gas,
but if you need to stop in a hurry you clap the brakes on without a second
thought. Yet unlike rowing, such a response can be harmful: if there's ice,
a wet or greasy road, or other problems of adhesion, you may then lose
control, so emergency stopping used to require an element of skill &
judgement. When ABS was introduced there were crashes due to driver
unfamiliarity with the system, leading them to lift off the brakes on
feeling the characteristic juddering of the pedal - well-learned caution
obstructed the intentions of advanced engineering - so they crashed
needlessly. And probably some of them were driving too fast only because
they knew they had ABS!
In a shell you don't have the problem of adhesion, only of stopping fast
enough. If you do the sloppy thing of pressing the backs of your blades
against the surface & rolling off the feather you _are_ skidding & you will
travel much further before stopping. You will have less directional control.
And you will more likely contribute to the very accident you meant to
prevent. So it's a no-brainer.
——
CARL DOUGLAS ON HOW TO HOLD WATER, CONT
Charles thinks we slam the blades into the water, but that's not what really
happens. Water is too darned hard to let you do that. When I or others say
"allow to descend", we are telling what happens whether or not you allow it.
The angling forwards & downwards of the blade, coupled with the forward
motion of the boat, takes the blades down fast enough. They "fly" downwards
as wings, & any added downforce hardly affects their trajectory. And the
stopping force comes in significant part from the drag on the increasing
buried lengths of the shafts, while the final stopping results from the
reverse squaring & pushing of the deeply buried blades which by that time
may well be rising back up to the surface.
———
CARL DOUGLAS ON HOW TO HOLD WATER, CONT
Put very simply, your blades can descend through the water only at the angle
to which you set them – a steep angle gives a rapid descent, a shallow angle
gives a gradual descent.
This is because, when underwater & attached to your moving boat, the blades
act as any foil would – by resisting forces perpendicular to their surface
through the agency of induced hydro-dynamic lift.
You do want the blades to descend swiftly, but you get that swift descent by
progressively steepening the angle of attack, not by pressing the blades
down harder.
I thought it important to make this point because who are wrongly fearful of
angling their blades into the water may prefer to believe that they can get
the same effect by having the blades flat (or nearly so) & trying to lift
the hands faster than the blades' rate of descent will allow. They will not
stop their boats either so rapidly or under such good control. They will
divert their strength into the uplift instead of the thrust against the drag
that the submerged blades & shaft would otherwise generate.
Another way of putting it is to say that if the blades are just feathered
what you are doing is try-ing to lift the boat up by surfing on the blades.
If they are angled down, they _will_ descend & you can concentrate on
providing the full force that stops the boat. Done in this way, you stop in
an amazingly short distance. Done the other way you may skitter along
aimlessly for several boat lengths.
——
DEFINITION OF HOLD WATER
The idea of hold water appears to have come from sweep rowing:
Hold Water (USA) Emergency stop, also used after the command way enough. It
instructs the rowers to square their blades in the water to stop the
boat. –Glossary of rowing terms, Wikipedia
So the crew is commanded to lay their blades flat on the water, and then
commanded to shift grip on the handles and feather slightly backward to
bring the shell to a full stop.
Charles Carroll
Sep 5, 2013, 8:39:07 PM9/5/13
to
Sully will recognize this one.
https://www.youtube.com/watch?v=w-XaE0c36TM
And I am throwing in this line for good measure.
https://www.youtube.com/watch?v=BAkX2KlrAR8
https://www.youtube.com/watch?v=w-XaE0c36TM
And I am throwing in this line for good measure.
https://www.youtube.com/watch?v=BAkX2KlrAR8
Carl
Sep 6, 2013, 7:09:04 AM9/6/13
to
is foiling (as it does in the first 1/3 & last 1/4 of the stroke) the
surface loading is already very low in fluid-dynamic terms & adding area
only increases the drag of the water that flows along its length without
changing the already very shallow angle of attack.
To simplify: the blade is really so lightly loaded (regardless of how
hard we are pulling) that adding to its area does nothing to increase
its propulsive efficiency at the catch & finish.
Where you do incur significant efficiency loss is in mid-stroke, where
the blade has stalled and water flows around it. Even so, the answer is
not to increase blade area but to go deeper, so that water can
completely fill the space behind the blade. This increases the drag
coefficient of the stalled blade, reducing its sternwards slip & hence
the energy wasted in that slip.
BTW, the longer catch is more efficient regardless (within reason) of
the boat speed, as long as the boat is moving reasonably well. The
gearing there is the same, whether you are going faster or slower but in
the slower the action will be intolerably slow & feel heavy.
It is true that the longer catch, by slowing the rate of rotation of oar
about pin at entry, makes it easier to get a clean catch, but you still
need a fast & hard entry as failure to achieve this throws away the
benefits of greater catch length when moving fast.
Rob
Sep 6, 2013, 7:48:45 AM9/6/13
to
On 09/05/2013 08:22 PM, Charles Carroll wrote:
> A brief 30 second demonstration of how to hold water would have cleared up
> everything.
>
> For me – and I am speaking only for myself – it was the written instruction that
> created the confusion. Watching Mike Sullivan’s video of Ian and Chris
> demonstrating how to hold water demystified the process.
There's a good example of how well this works in
> A brief 30 second demonstration of how to hold water would have cleared up
> everything.
>
> For me – and I am speaking only for myself – it was the written instruction that
> created the confusion. Watching Mike Sullivan’s video of Ian and Chris
> demonstrating how to hold water demystified the process.
https://www.youtube.com/watch?v=IUhKzLsOvMs about 43 seconds in.
gsl...@gmail.com
Sep 6, 2013, 8:45:13 AM9/6/13
to
Charles Carroll
Sep 6, 2013, 12:31:44 PM9/6/13
to
> Thanks Rob and Charles.
> I also had though reverse featherin
> I also had though reverse featherin
> was with the concave side down!
> It is much simpler and faster than I imagined.
> Will try tomorrow.
You don�t need to thank me. I�m only a stenographer. Carl Douglas and Mike
> It is much simpler and faster than I imagined.
> Will try tomorrow.
Sullivan are the ones who deserve the credit.
Let us know what happens tomorrow when you practice holding water correctly.
I remember the first time I tried. I flipped myself right out of my shell.
It was a terrible morning to do it. It was cold, the weather was miserable,
and the water was awful. It seemed to take forever to get back into my
shell.
I am sure you will have better luck �
Cordially,
Charles
sully
Sep 6, 2013, 2:27:11 PM9/6/13
to
On Thursday, September 5, 2013 3:27:32 PM UTC-7, gsl...@gmail.com wrote:
> Is there a video of the proper way to hold water? Not sure I understand completely.
>
> At first I was just blade as if backing, but it really grabs the water and is quite scary. I finally figured out that the top (what was the bottom edge) should be pointed towards the bow so it doesn't just crap. Do I have that right?
Charles has it covered. When teaching ppl to do this, I have them go very slowly to begin with, break it into 3 steps.
> Is there a video of the proper way to hold water? Not sure I understand completely.
>
> At first I was just blade as if backing, but it really grabs the water and is quite scary. I finally figured out that the top (what was the bottom edge) should be pointed towards the bow so it doesn't just crap. Do I have that right?
Step 1. stop rowing, relax let oars rest flat on water, legs down, handles away from your body so oars are roughly perpendicular to shell.
step 2. Shift grip of your hands on the handle slightly forward, and very slightly reverse feather both blades. (shifting grip gives you room to feather backward) If you keep the blades shallow, you'll maintain more control, a student used the term 'shaving the water', and I liked it!
step 3. continue feather to backing position. Stops you dead and you're in perfect position to back without futzing around with the oars.
if you allow blades to dive deep, it is as effective at stopping the boat as going to full reverse feather, but the disadvantage is you then need to make some adjustment to begin to back.
I teach to begin to hold with the hands away from your body, thus if you have an emergency stop, you can hold with a steeper pitch and absorb extra pressure into your body.
A really cool way to show how effective this is is to hold water on one side only. You don't need to completely square the blade in this case, but do allow the boat to heel over on the hold side. You can turn your single 90 degrees with this hold if you are going at any sort of hard pressure.
if you have a course you want to do aerobic work on that requires a number of turns and you have for eg: a right hand rule for rowing on the course, a sculler or crew can finish, hold port, approximate a race start across the course, hold port again, another short racing start and be off again without
the heart rate dropping significantly. Crews then of different speeds can
stay roughly together by having the slower shell turn earlier.
I watch some coaches try to run small boat training sessions and it takes as long to get boats turned around and lined up as it does to row the pieces.
It takes about 30 minutes of a practice to teach everyone on a team to hold AND back properly, and if they then practice that over the next week or so during the regular course of their training session, you end up saving hours and hours of training time over the course of a year. Seems so bloody simple to me.
This correct method is more difficult to learn, but if coaches aren't able to teach something as provably effective as holding water correctly, why do they
bother trying to teach the catch? The catch is vastly more difficult to learn, and to demonstrate its' effectiveness.
Of course, by observation, many don't bother teaching that either.
gsl...@gmail.com
Sep 6, 2013, 6:35:54 PM9/6/13
to
On Friday, September 6, 2013 11:27:11 AM UTC-7, sully wrote:.....
Thanks Sully.
I've had a lot of coaches, and none have taught this! That includes three different coaches at my current club each with a lot of experience, going to Craftsbury three times, and a few rows with some world team and Olympic rowers. Can't wait to try it.
Maybe it is just me , but "Over squaring" would have been much clearer--"Reverse squaring" gave me the completely wrong idea.
Our lake does require a lot of turns. The slow turns are a much bigger problem with the big boats than with the singles. If I can get the coaches to teach this to the 8's it will be a huge help.
Thanks Sully.
I've had a lot of coaches, and none have taught this! That includes three different coaches at my current club each with a lot of experience, going to Craftsbury three times, and a few rows with some world team and Olympic rowers. Can't wait to try it.
Maybe it is just me , but "Over squaring" would have been much clearer--"Reverse squaring" gave me the completely wrong idea.
Our lake does require a lot of turns. The slow turns are a much bigger problem with the big boats than with the singles. If I can get the coaches to teach this to the 8's it will be a huge help.
gsl...@gmail.com
Sep 6, 2013, 6:39:31 PM9/6/13
to
Fortunately tomorrow will be hot--I'm just across the bay from you. I'm good at getting back at the boat--I've demonstrated it many times for classes.
sully
Sep 6, 2013, 7:41:02 PM9/6/13
to
On Friday, September 6, 2013 3:35:54 PM UTC-7, gsl...@gmail.com wrote:
> On Friday, September 6, 2013 11:27:11 AM UTC-7, sully wrote:.....
>
>
>
>
>
> Thanks Sully.
>
>
>
> I've had a lot of coaches, and none have taught this! That includes three different coaches at my current club each with a lot of experience, going to Craftsbury three times, and a few rows with some world team and Olympic rowers. Can't wait to try it.
>
>
>
> Maybe it is just me , but "Over squaring" would have been much clearer--"Reverse squaring" gave me the completely wrong idea.
reverse feathering is what you are doing, but start gradually, don't just turn backwards.
> On Friday, September 6, 2013 11:27:11 AM UTC-7, sully wrote:.....
>
>
>
>
>
> Thanks Sully.
>
>
>
> I've had a lot of coaches, and none have taught this! That includes three different coaches at my current club each with a lot of experience, going to Craftsbury three times, and a few rows with some world team and Olympic rowers. Can't wait to try it.
>
>
>
> Maybe it is just me , but "Over squaring" would have been much clearer--"Reverse squaring" gave me the completely wrong idea.
Charles Carroll
Sep 6, 2013, 10:40:43 PM9/6/13
to
Here is a link to an old thread that might interest you:
https://groups.google.com/forum/#!msg/rec.sport.rowing/SegjlDAoLBc/lCQsxUayiyUJ
And here from that thread is a post describing my dunking:
Mike and Carl,
We all know there are not many things in this world that taste as bitter as
humble pie. Nevertheless it is possible to make this dish more palatable if
you season it with a lesson well learned.
I’ll put it simply. You are right and I am wrong.
This morning, Mike, I took your advice and started practicing stopping,
river turns and backing up in the classic way, that is, with the blades
reverse feathered and placed in the water with the blades tips pointing to
the sky.
Morgan says that blades reverse feathered and placed in the water with the
blades tips pointing to the sky is the way she learned how to back up, and
turn, but that she doesn’t use it to stop. She also says that she finds it
difficult to teach this method to novices, particularly in our water.
But I said that I was going to take your advice and practice this method for
a few weeks and test whether it was an improvement over my current method of
backing up, stopping, and doing river turns.
So I pushed off from the dock and sculled into the outer Marina where the
water was protected. Then I started spinning donuts. And as I was going
around I put the port blade in tip up towards the sky.
Wow! The blade held on to the water so firmly that the shell started to spin
around it. I have never turned such a tight donut. I also, however, don’t
know how I didn’t go over. Turning had a completely different feel to it.
Needless to say this got my attention. Who doesn’t want a better method of
stopping, backing up, and turning? I was short for time, however, and didn’t
want to spend what little I had doing drills, I decided to put off work on
all this until tomorrow.
I did a minute of King of the Mountain drills, and then took off.
The water wasn’t very nice. I would say that in the channel it was Force 2
on the Beaufort Scale, a noticeable breeze, small wavelets, crests of glassy
appearance, not breaking. Also I was rowing against a flood tide. Water
washed over the stern deck almost every stroke.
But all in all I thought I was doing pretty well. I was firm on my feet with
a good connection to the stretcher and got the shell moving. I was
confident. I had a good feel for the blades. The shell stayed level and went
straight. And I was making good time.
Then it was time to turn around and head back to the Club.
As I was turning I thought, why not put the port blade in the way Mike
suggests and see if I can’t make a tighter, faster turn?
So I did.
And over I went.
I can tell you that water was cold. It was freezing! And it wasn’t all that
easy getting back into Carl’s shell. The water was bouncing the shell all
over the place, and I was out of practice, and the cold numbed my brain and
made my thinking slow.
It was minutes before I was back in the shell and sculling. By that time I
had an audience. A from one of the anchor outs, a sloop, came up to me in a
kayak to see if he could help, and two power boats motored up. I think there
must have been a total of six or seven people watching over me. I cannot
tell you how impressed I was with their generosity and kindness, or how
em-barrassed I was at my own klutzines.
At one point, about the third or fourth try of righting the shell and
reaching for the starboard oar handle, I must have knocked against the deck
right about where the cutwater ties into the coaming. Or maybe I just
knocked into the coaming. Or the deck! In any event I heard a cracking
sound, similar to the sound of a a sheaf of dry spaghetti snapped in two
over a boiling pot. Instantly I realized that I had cracked my lower rib on
my left side. Or maybe I had torn loose the cartilage around it. I don’t
know. It was painful and I was too embarrassed to tell anyone.
Finally, about the sixth or seventh attempt, I succeeded finally in righting
the boat while keeping hold of both oar handles at the overlap. From that
point on it was easy. I held on to the coaming with my left hand and a quick
scissor kick put me up, over, and straddling the splashbox. Once the boat
felt stable, I slid the seat under my butt, strapped feet into the shoes,
and was back in the business of sculling.
I called a hearty and heartfelt thank you to the knights in shining armor
who were watching over me, explaining that I was late and had to get to
work, and then started sculling as best I know how. My rib hurt, but there
was nothing to be done about that, so I put it out of my mind and
concentrated on getting long and looking smooth and relaxed.
It was amazing how fast I got back to the Club’s dock.
And the lesson learned? That you and Carl are right! Practice the correct
method. Make it second nature, so that you use it without taking time to
deliberate about it. It is the superior method. You will stop faster. You
will turn more tightly. And you will hold water better and back up better.
Thanks once again,
Charles
https://groups.google.com/forum/#!msg/rec.sport.rowing/SegjlDAoLBc/lCQsxUayiyUJ
And here from that thread is a post describing my dunking:
Mike and Carl,
We all know there are not many things in this world that taste as bitter as
humble pie. Nevertheless it is possible to make this dish more palatable if
you season it with a lesson well learned.
I’ll put it simply. You are right and I am wrong.
This morning, Mike, I took your advice and started practicing stopping,
river turns and backing up in the classic way, that is, with the blades
reverse feathered and placed in the water with the blades tips pointing to
the sky.
Morgan says that blades reverse feathered and placed in the water with the
blades tips pointing to the sky is the way she learned how to back up, and
turn, but that she doesn’t use it to stop. She also says that she finds it
difficult to teach this method to novices, particularly in our water.
But I said that I was going to take your advice and practice this method for
a few weeks and test whether it was an improvement over my current method of
backing up, stopping, and doing river turns.
So I pushed off from the dock and sculled into the outer Marina where the
water was protected. Then I started spinning donuts. And as I was going
around I put the port blade in tip up towards the sky.
Wow! The blade held on to the water so firmly that the shell started to spin
around it. I have never turned such a tight donut. I also, however, don’t
know how I didn’t go over. Turning had a completely different feel to it.
Needless to say this got my attention. Who doesn’t want a better method of
stopping, backing up, and turning? I was short for time, however, and didn’t
want to spend what little I had doing drills, I decided to put off work on
all this until tomorrow.
I did a minute of King of the Mountain drills, and then took off.
The water wasn’t very nice. I would say that in the channel it was Force 2
on the Beaufort Scale, a noticeable breeze, small wavelets, crests of glassy
appearance, not breaking. Also I was rowing against a flood tide. Water
washed over the stern deck almost every stroke.
But all in all I thought I was doing pretty well. I was firm on my feet with
a good connection to the stretcher and got the shell moving. I was
confident. I had a good feel for the blades. The shell stayed level and went
straight. And I was making good time.
Then it was time to turn around and head back to the Club.
As I was turning I thought, why not put the port blade in the way Mike
suggests and see if I can’t make a tighter, faster turn?
So I did.
And over I went.
I can tell you that water was cold. It was freezing! And it wasn’t all that
easy getting back into Carl’s shell. The water was bouncing the shell all
over the place, and I was out of practice, and the cold numbed my brain and
made my thinking slow.
It was minutes before I was back in the shell and sculling. By that time I
had an audience. A from one of the anchor outs, a sloop, came up to me in a
kayak to see if he could help, and two power boats motored up. I think there
must have been a total of six or seven people watching over me. I cannot
tell you how impressed I was with their generosity and kindness, or how
em-barrassed I was at my own klutzines.
At one point, about the third or fourth try of righting the shell and
reaching for the starboard oar handle, I must have knocked against the deck
right about where the cutwater ties into the coaming. Or maybe I just
knocked into the coaming. Or the deck! In any event I heard a cracking
sound, similar to the sound of a a sheaf of dry spaghetti snapped in two
over a boiling pot. Instantly I realized that I had cracked my lower rib on
my left side. Or maybe I had torn loose the cartilage around it. I don’t
know. It was painful and I was too embarrassed to tell anyone.
Finally, about the sixth or seventh attempt, I succeeded finally in righting
the boat while keeping hold of both oar handles at the overlap. From that
point on it was easy. I held on to the coaming with my left hand and a quick
scissor kick put me up, over, and straddling the splashbox. Once the boat
felt stable, I slid the seat under my butt, strapped feet into the shoes,
and was back in the business of sculling.
I called a hearty and heartfelt thank you to the knights in shining armor
who were watching over me, explaining that I was late and had to get to
work, and then started sculling as best I know how. My rib hurt, but there
was nothing to be done about that, so I put it out of my mind and
concentrated on getting long and looking smooth and relaxed.
It was amazing how fast I got back to the Club’s dock.
And the lesson learned? That you and Carl are right! Practice the correct
method. Make it second nature, so that you use it without taking time to
deliberate about it. It is the superior method. You will stop faster. You
will turn more tightly. And you will hold water better and back up better.
Thanks once again,
Charles
gsl...@gmail.com
Sep 8, 2013, 11:24:00 AM9/8/13
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On Friday, September 6, 2013 4:41:02 PM UTC-7, sully wrote:
> On Friday, September 6, 2013 3:35:54 PM UTC-7, gsl...@gmail.com wrote:
>
> > On Friday, September 6, 2013 11:27:11 AM UTC-7, sully wrote:.....
>
> On Friday, September 6, 2013 3:35:54 PM UTC-7, gsl...@gmail.com wrote:
>
> > On Friday, September 6, 2013 11:27:11 AM UTC-7, sully wrote:.....
>
> reverse feathering is what you are doing, but start gradually, don't just turn backwards.
What I meant to write was "over feathering" not "over squaring". In any case reverse feather gave me the idea that the blade was rotated in the opposite direction of normal.
I tried it yesterday, although I need to gain confidence and relax a whole lot more before I will try it at full speed, it was no problem at all. My workout yesterday was with a bungee cord which kept the speed lower and made it easier.
My club does teach backing with the blades upside down. The excuse for not doing that is because one may forget to put the blade correctly at the start of a race--something I've never seen. Interestingly one of those Olympians I've rowed with keeps the blade in the normal position when backing. He also didn't use any power on turns.
John Greenly
Sep 8, 2013, 1:51:08 PM9/8/13
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I also, though infinitely far from being an Olympian, have never bothered to reverse blades to back. Sure, they're not as efficient, but I never need to go all that fast backward anyway and it doesn't seem bothersome at all.
Charles Carroll
Sep 8, 2013, 5:03:06 PM9/8/13
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> I'm just across the bay from you
Across the bay from me? Where? North? East? Marin? Oakland Estuary?
I suspect we may know some of the same people.
Cordially,
Charles
gsl...@gmail.com
Sep 8, 2013, 5:35:05 PM9/8/13
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I row on Lake Merritt. Yes we do know some of the same people. The people I have seen mentioned on this newsgroup that we both know include Ellen, Morgan, and Ric Ricky. I did do an open water race several years ago out of OWRC and had a lesson with Ric there also. I first met Ric at Craftsbury. Ellen I probably first met in 2007. Stoked a quad that her husband at the SW Regionals in 2011. I know Morgan from when she was coaching at the Estuary. I'm sure there are many many others we both know.
Do you race at all these days?
Greg
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