Choosing between single scull hull sizes

[Rob]

What are the disadvantages (or advantages) of rowing a single outside of the
stated weight capacity?

For background, I am looking at purchasing a single (specifically the
FluidFirst). My problem comes with my weight: I started the season at about
185 lbs but with all the rowing I've been doing this summer it has come down to
175. However this is also really my first year rowing (although I learned how
last year) so I do not know for sure whether my weight will settle up or down a
little long term (assuming a continued large volume of rowing).

I have had recommendations of both the Midweight (145-180 lbs) from Fluidesign
(which was also my initial thought) and the Intermediate (180-200 lbs) from my
coach.
If I chose the Midweight and ended up weighing more than the stated capacity
(hopefully from muscle!) is that worse than rowing the Intermediate at my
current weight?

[johnf...@gmail.com]

I'd generally go for the lighter rated boat and try to keep my weight down at least to the top of its range. Here's why:
(1) Until anorexia sets in, you'll go faster the lighter you are, particularly for head racing.
(2) Usually lighter range hulls are narrower, and hull width is the #1 determinant of boat speed according to a naval architect/shell designer friend.
The latter would not apply to the Fluid because the widths for the two hulls you are considering are both 11" according to the Fluid website.
(3) The lighter displacement hull will be mashed deeper into the water and thus give you more stability if you need it.

Disadvantages:
(1) You'll have to adjust the rigging up because the boat will sit deeper in the water.
(2) The boat will be harder to turn (only really a problem for head racing).

I've probably forgotten some other things.

[Phil]

On Tuesday, August 13, 2013 1:35:54 AM UTC+1, Rob wrote:
> What are the disadvantages (or advantages) of rowing a single outside of the stated weight capacity? For background, I am looking at purchasing a single (specifically the FluidFirst). My problem comes with my weight: I started the season at about 185 lbs but with all the rowing I've been doing this summer it has come down to 175. However this is also really my first year rowing (although I learned how last year) so I do not know for sure whether my weight will settle up or down a little long term (assuming a continued large volume of rowing). I have had recommendations of both the Midweight (145-180 lbs) from Fluidesign (which was also my initial thought) and the Intermediate (180-200 lbs) from my coach. If I chose the Midweight and ended up weighing more than the stated capacity (hopefully from muscle!) is that worse than rowing the Intermediate at my current weight?

The only piece of advice I'll give is to try them both. A stone here or there will not make any odds at all.
Phil.

[Rob]

I have tried the intermediate, but probably won't get a chance to try a
midweight until September (and I was hoping to order soon so I'll have a chance
to row it this year.

I think that would be my outside limits of weight change either way (a stone
seems to be about 14 lbs). So are you saying that either size should be fine
and I should go more for which I feel better in?

[Rob]

OK, although with my schedule I have more chance to participate in side-by-side
regattas during the summer (1 and 2K races) so I was thinking of trying to put
on some more muscle (whether I succeed or not is up for debate).

Say I went to the outside of what I would expect and got up to 190 lbs in the
midweight. Since the boat would be mashed (slightly) deeper in the water than
designed, would I be able to adjust the rigging to match properly or would I
expect to hit the limits?

Am I over thinking this: is 10 lbs over even worth worrying about?

Why would the boat be more difficult to turn? I would have thought the deeper
depth of the smaller hull would roughly match the difference of the larger
hull's length.

[s...@ku.edu]

Rob,

Life is too short to row a 1x that doesn't fit. I suggest you get the hull that best fits you now and in the near term. If in the future it becomes too small or too big, sell it and buy a different size. I would also follow the advice of the boatbuilder.

John,

I'm curious about the conclusion that skinnier boats are necessarily faster. Can you provide more evidence?

Steven M-M

[Phil]

On Tuesday, August 13, 2013 1:01:31 PM UTC+1, Rob wrote:
> On 08/12/2013 09:10 PM, johnf...@gmail.com wrote: > I'd generally go for the lighter rated boat and try to keep my weight down at least to the top of its range. Here's why: > (1) Until anorexia sets in, you'll go faster the lighter you are, particularly for head racing. > (2) Usually lighter range hulls are narrower, and hull width is the #1 determinant of boat speed according to a naval architect/shell designer friend. > The latter would not apply to the Fluid because the widths for the two hulls you are considering are both 11" according to the Fluid website. > (3) The lighter displacement hull will be mashed deeper into the water and thus give you more stability if you need it. > > Disadvantages: > (1) You'll have to adjust the rigging up because the boat will sit deeper in the water. > (2) The boat will be harder to turn (only really a problem for head racing). > > I've probably forgotten some other things. OK, although with my schedule I have more chance to participate in side-by-side regattas during the summer (1 and 2K races) so I was thinking of trying to put on some more muscle (whether I succeed or not is up for debate). Say I went to the outside of what I would expect and got up to 190 lbs in the midweight. Since the boat would be mashed (slightly) deeper in the water than designed, would I be able to adjust the rigging to match properly or would I expect to hit the limits? Am I over thinking this: is 10 lbs over even worth worrying about? Why would the boat be more difficult to turn? I would have thought the deeper depth of the smaller hull would roughly match the difference of the larger hull's length.

You could work out, or even try an experiment to determine, how much further the boat is in the water for each 10 lb. I suspect it won't be that much, especially as the volume increases more rapidly the more the boat is loaded.

Phil.

[johnf...@gmail.com]

On Tuesday, August 13, 2013 9:33:32 AM UTC-4, s...@ku.edu wrote:
> Life is too short to row a 1x that doesn't fit. I suggest you get the hull that best fits you now and in the near term. If in the future it becomes too small or too big, sell it and buy a different size. I would also follow the advice of the boatbuilder.
>

+1

> John,
> I'm curious about the conclusion that skinnier boats are necessarily faster. Can you provide more evidence?
>

I should have added the disclaimer: "as long as they are stable enough that the sculler can use his/her full effort without being handcuffed by issues with the boat's set."

As I said, I relied on the expertise of a friend who is a marine architect (and was a blindingly fast lightweight sculler in his day). I also rely on Ted Van Dusen's line of development. Ted, an MIT-educated engineer, initially produced a line of 1x's that were very narrow and very fast - if you could set them. His initial LW design was only 8.9" wide at waterline and reputedly twitchy. The second generation "Advantage" LW hull has greater stability thanks partly to a wider design (9.6") and partly to a lower seat deck (stability varies as the cube of the height above the water surface). This hull has rocker (a curved keel line) so it tends to rock fore and aft unless one is smooth. Rocker helps to reduce wetted surface area and therefore drag.

I had problems handling a Vespoli MW 1x which has a similar shape, so my coach had me row a used Empacher K-18 for several years, a very stable hull in both axes. Once my skills had improved, I moved into a Van Dusen. My GF, who has a far steeper learning curve than I, rowed various boats, mainly a Peinert, for a season before trying a V-D. She was instantly comfortable and bought a used one this spring.

To the OP:

I dieted off about 10lbs so I could fit into a V-D LW (they don't make a MW Advantage hull). I discovered I got faster as a result.

Unfortunately there are no objective standards for boat weight capacity, it's an educated call by the boatbuilder and the standards may vary from builder to builder.

In terms of rigging height, there is also the factor of variation in people's torso lengths. People with longer torsos will generally need more oarlock height than people with relatively short torsos.

For reference, my GF and I have identical V-D LW hulls. She weighs 140lbs, has a short torso, and is rigged all the way DOWN on the pin. I weigh about 172lbs, have a typical torso length, and am rigged all the way UP. I imagine that narrower boats like the V-D sink more than wider boats under a given added load, assuming that the lengths are about the same.

As for steering, the deeper a hull is in the water (particularly in the bow) the harder it is to drag the bow laterally to turn the boat. Boats built with almost no rocker are deep in the bows and therefore very difficult to turn. The skeg tends to keep the stern from moving laterally, which is why steering happens in the bow.

[Carl]

Yes. Compute the waterplane area, A m^2 (= length x average waterline
beam). Then the change in displacement per extra kg = 1/(100 x A) mm.
Quite easy to do - you can measure beam at intervals along the tidemark
that any slightly scummy water leaves on the boat.

Cheers -
Carl

--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
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Email: ca...@carldouglas.co.uk Tel: +44(0)1932-570946 Fax: -563682
URLs: carldouglas.co.uk & now on Facebook @ CarlDouglasRacingShells

[Carl]

Once upon a time shells were laid up on stocks, the skin being either a
single veneer or a sheet of bias-laminated plywood bent over formers and
specially-shaped ribs. It was (in theory) easy to scale the hull as the
builder though it should be scaled for a given crew weight. That was
more of a black art than a science as they had no way to calculate the
suitability of a given hull for a particular size.

Then came moulding. At which point the significant investment in fixed
production tooling discouraged making additional moulds to cover other
crew weights. So hulls for lightweights were simply the hulls used for
for larger crews but with an inch or so of freeboard sliced off - a
rather slight reduction in wetted surface since length & beam were not
scaled down. A woman lightweight would thus be sculling in a shell
that, for her, was too wide at & below the waterline & too shallow - a
saucer rather than a bowl in cross-section.

Now we see some slight acceptance that good crews, scullers especially,
come in widely different weights. That realisation does not extend to
FISA's boat-weight regulations which, supposedly in the cause of
fairness, mandate the same minimum shell weight for super-heavy man as
for lightweight women, but that's rule-makers for you.

Even now, most shell builders offer you - at most - 2 weight-scaled
versions of a given hull. And by weight-scaled I mean properly
proportioned for beam, length & depth according to the crew weight, but
I don't think it right for a 59kg sculler to be told it's OK for them to
have a boat supposedly fit also for an 80kg sculler.

We offer 6 discrete sizes, centred about 60kg, 70, 78, 85, 92 & 100+kg.
This does _not_ mean that our shells have a reduced tolerance, when
compared with others, for over- or under-weight crews; the tolerance on
any suitably-sized shell will be similar. It does mean that we fit the
user's chosen weight more accurately.

Let's leave open the intriguing question of how 2 hulls of the same beam
can really be right for different median crew weights. And let's
suppose that, in a hull which may perhaps have been derived from another
commercial product, the vendor does truly know the weight for which that
boat is most appropriate. If you are right on the margin, you have to
decide whether you'll add more muscle than the fat you'll shed, & that
must depend partly on your coach's training regime. So only your coach
can advise.

I would agree with John: be as light as is consistent with sustaining
performance. A lot of heavies pay in lost flexibility for their muscle
bulk & wonder why they get beaten by lighties. no point in being the
strongest boat-stopper on the water ;)

Good luck -

[Rob]

On 08/13/2013 09:33 AM, s...@ku.edu wrote:
>
> Life is too short to row a 1x that doesn't fit. I suggest you get the hull that best fits you now and in the near term. If in the future it becomes too small or too big, sell it and buy a different size. I would also follow the advice of the boatbuilder.
>

OK, I'm thinking my best option is the midweight. My biggest concern was that I
was close to the transition point between the two shells. After all, when I add
a stoke coach, a water bottle, some clothing (and maybe splash a little water
into the boat) I'm right in the middle of the two (especially in the spring at
my 'winter' weight).

So can I conclude that it is better to row the smaller shell given the choice
between the two if I'm close to both sizes?

[johnf...@gmail.com]

On Wednesday, August 14, 2013 7:52:56 AM UTC-4, Carl wrote:
>
> Even now, most shell builders offer you - at most - 2 weight-scaled
> versions of a given hull. And by weight-scaled I mean properly
> proportioned for beam, length & depth according to the crew weight, but
> I don't think it right for a 59kg sculler to be told it's OK for them to
> have a boat supposedly fit also for an 80kg sculler.
>
> We offer 6 discrete sizes, centred about 60kg, 70, 78, 85, 92 & 100+kg.
>

I agree with you about some of the smaller 1x boatbuilders. I have even seen an example listing their boats at different weight ratings and the length and width are the same for all the ratings. Suggesting that they just build the same hull higher for the heavier weights.

But glancing at the Filippi and Empacher websites, I find:

Filippi offers 10 1x molds with various widths (from 10.32" to 11.7"), lengths, and weight ratings, so I would assume that they are not simply variations on a single shape??:
http://www.filippiboats.it/boats.asp?s=2

Empacher offers 7 1x molds, likewise apparently different:
http://www.empacher.com/rennboote/Einer_e-30-07-10.php

In each case, two molds have identical ratings but the lengths and widths are different, suggesting that the shapes differ???

Actually this situation creates problems for an overseas customer! It can be difficult if not impossible to find examples of several different hull shapes (from Filippi OR Empacher) to test to find which shape suits better.

[Carl]

I think, John, that you've answered that last point: narrow should be
faster - if all other factors can be omitted from the calculation.
However, there's a difference between being faster & having the
potential to be faster, since length & 3-dimensional form (including,
but not only, cross-section) will affect the result, as will sculler power.

So the smaller, slower sculler (I don't necessarily equate small with
slow) will not generate the power to go fast enough to warrant having a
longer boat, while the longer boat trades reduced wave drag (a function
of length & speed) against increased surface & slightly increase
frictional drag.

Incidentally, I am interested to know, when they talk about different
moulds, how many are different moulds and how many are different levels
of sheerline (the point I made earlier).

Vance Packard's hidden persuaders have so advanced their art that they
have very much taken over our brains, & with them our wallets, so it is
tough today for anyone wanting to choose the "right" boat. At the same
time, I think we have become more conformist - wanting to be seen to
have made "the right choice". As I've said before, we fall under peer
pressure & advertising hype to choose certain shells, but this hype is
poorly supported by relevant facts. X may just have won the World
Championships in boat A, but was that because X was good enough to
overcome the possible inferior performance of that boat? And what about
its longevity & robustness? Most buyers will never be world champions,
but it may be the average buyer's money which puts free boats under
world champions.

Cheers -

[Phil]

On Wednesday, August 14, 2013 12:52:56 PM UTC+1, Carl wrote:
> SNIP < according to the crew weight, but I don't think it right for a 59kg sculler to be told it's OK for them to have a boat supposedly fit also for an 80kg sculler. We offer 6 discrete sizes, centred about 60kg, 70, 78, 85, 92 & 100+kg. This does _not_ mean that our shells have a reduced tolerance, when compared with others, for over- or under-weight crews; the tolerance on any suitably-sized shell will be similar. <SNIP>

I'll vouch for the CDX tolerances, as my wife (8.5 st) has the 60Kg hull. While varnishing my own shell recently, I used hers(I'm 10.5 st), with no noticeable ill effects. She did complain that her shoes had 'grown' a bit though ;-)

Phil.

[Douglas MacFarlane]

In article <1a21f9f8-fcaf-4eba...@googlegroups.com>,

Very interesting discussion.

I guess there are a couple of questions I would have.

1) For Carl perhaps - if a sculler was exactly in the middle between two
of your design weights, 74Kg for example, and their weight was fairly
constant, would you recommend they go for the smaller or the larger
hull. Is it better to be at the top end or the bottom end of the weight
range for a hull?

2) It would also be useful to know from those builders who seem from the
info on their web sites to produce a range of weight targeted boats
using the same basic hull (length and width are constant across a range
of sizes) what weight the original design was actually targeted for.

Cheers,

Douglas

[Carl]

On 15/08/2013 10:21, Douglas MacFarlane wrote:
> In article <1a21f9f8-fcaf-4eba...@googlegroups.com>,
> Phil <philip_b...@yahoo.com> wrote:
>
>> On Wednesday, August 14, 2013 12:52:56 PM UTC+1, Carl wrote:
>>> SNIP < according to the crew weight, but I don't think it right for a 59kg
>>> sculler to be told it's OK for them to have a boat supposedly fit also for
>>> an 80kg sculler. We offer 6 discrete sizes, centred about 60kg, 70, 78, 85,
>>> 92 & 100+kg. This does _not_ mean that our shells have a reduced tolerance,
>>> when compared with others, for over- or under-weight crews; the tolerance
>>> on any suitably-sized shell will be similar. <SNIP>
>>
>> I'll vouch for the CDX tolerances, as my wife (8.5 st) has the 60Kg hull.
>> While varnishing my own shell recently, I used hers(I'm 10.5 st), with no
>> noticeable ill effects. She did complain that her shoes had 'grown' a bit
>> though ;-)
>>
>> Phil.
>
> Very interesting discussion.
>
> I guess there are a couple of questions I would have.
>
> 1) For Carl perhaps - if a sculler was exactly in the middle between two
> of your design weights, 74Kg for example, and their weight was fairly
> constant, would you recommend they go for the smaller or the larger
> hull. Is it better to be at the top end or the bottom end of the weight
> range for a hull?

My first response is that we design our consecutive shell sizes so they
will change-over seamlessly at the intermediate points of weight. Thus
we've had many winners at men's Lightweight in our 78kg hulls, and many
clients still very happy & winning in their 70kg hulls despite now
racing at ~78kg (or more!).

However, if you're rather tall for your weight, & nudging up in weight
towards the next hull size, we might advise the larger hull. And it
depends, too, on whether your 74kg sculler is a man expecting to slim
down for lightweight competitions. If so, then the nominal 70kg is the
right size for him. Similarly for a normally 74+kg woman who again
expects to lose weight during the racing season. If your theoretical
74kg candidate is a smooth sculler of 'normal stature', not prone to big
weight changes, I'd still advise the smaller hull. But if the sculler
expects to add weight (let's say as muscle?), or is rather tall for
their weight, then we might look at the 78kg hull.

We think we have designed the transition so that the differences will
not be very significant. Which is why we offer this continuum of hull
sizes. We complicate our life to improve yours :)

>
> 2) It would also be useful to know from those builders who seem from the
> info on their web sites to produce a range of weight targeted boats
> using the same basic hull (length and width are constant across a range
> of sizes) what weight the original design was actually targeted for.
>

On that, I wish you the best of luck.

> Cheers,
>
> Douglas
>

Cheers -

[johnf...@gmail.com]

On Wednesday, August 14, 2013 10:29:53 AM UTC-4, Carl wrote:
> I think, John, that you've answered that last point: narrow should be
> faster - if all other factors can be omitted from the calculation.
> However, there's a difference between being faster & having the
> potential to be faster, since length & 3-dimensional form (including,
> but not only, cross-section) will affect the result, as will sculler power.
>
> So the smaller, slower sculler (I don't necessarily equate small with
> slow) will not generate the power to go fast enough to warrant having a
> longer boat, while the longer boat trades reduced wave drag (a function
> of length & speed) against increased surface & slightly increase
> frictional drag.
>

Let's just say "slower". Some of us average-sized folks manage to be slower without being smaller. And some small people are annoyingly fast.

So I have to ask: suppose you have a slower and a faster sculler, how much different would the optimal boats for them be? Let's suppose 2K racing, and take a HW elite male who goes 6:33 (not sure what the WR is but it must be somewhere around there?). And an identical HW male (same weight and body dimensions, same sculling skill level) who can't go faster than say 8:30. Of course, dead flat water, no wind, same water and air temperatures. Unless my math skills have deserted me, 6:33 is around 5.1 meters/sec; 8:30 is 3.9 m/s, or about a 30% difference.

So what would that translate to in terms of boat dimensions for the "optimal" boat for each? For example, should the boat for the faster guy be 30% longer?

Of course it's unlikely that a boatmaker would ever design a fine boat for a slow sculler!!

[tony....@gmail.com]

On Wednesday, August 14, 2013 10:29:53 AM UTC-4, Carl wrote:

On a slight tangent, I was startled to notice at the Canada Summer games in Sherbrooke Quebec two boats on a rack marked for woman's lightweight doubles. There was a Filippi 2X on a rack over a Hudson and the Hudson was almost 3 feet longer. So we are referring to a specific weight category here, indicating a very different manufacturing philosphy. Didn't think to look at the beam of the 2 boats unfortunately.
Tony

[johnf...@gmail.com]

On Thursday, August 15, 2013 8:57:13 AM UTC-4, tony....@gmail.com wrote:
> On a slight tangent, I was startled to notice at the Canada Summer games in Sherbrooke Quebec two >boats on a rack marked for woman's lightweight doubles. There was a Filippi 2X on a rack over a Hudson >and the Hudson was almost 3 feet longer. So we are referring to a specific weight category here, >indicating a very different manufacturing philosophy.

It's important to keep in mind that some manufacturers offer different hull shapes in similar weight categories. In this case, FIlippi offers two hulls in this general size range: the F13 and the F36:
http://www.filippiboats.it/boats.asp?s=2
They have the same width but differ in length by 0.4m or about 16", and they are offered in parallel.

Hudson's strategy is (or used to be anyway) to bring in naval architects to computer-design hull shapes, use computer-controlled machines to create plugs of those shapes, and then make moulds from those plugs. This allows them to change shapes quickly. They can save money on the moulds by not making them to close tolerances, and use filler and paint to smooth the surface. So Hudson shapes may change from year to year according to their thinking about what will be fast, hence the length of a Hudson 2x might vary from year to year. AFAIK they do not offer different shapes in the same weight class in parallel. Hopefully someone will correct me if I've got all this wrong.

Empacher and Filippi appear to make moulds in various overlapping and sometimes duplicated weight classes and offer these shapes in parallel. Sometimes the moulds are retired, as was the case for the Empacher -18 midweight 1x mould which was replaced by the -15.

Another strategy (used by Van Dusen and probably some others) is to make a high precision (expensive!!) mould, spray the color directly into the inside of the mold, build the boat in it, and pop out the finished hull with little or no touchup needed. But this approach makes modifying shapes very expensive.

Of course it is also possible that someone put the wrong boat in that rack!!

[andymck...@gmail.com]

On Thursday, August 15, 2013 4:52:19 PM UTC+1, johnf...@gmail.com wrote:
>
> Of course it is also possible that someone put the wrong boat in that rack!!

Say it ain't so! - no rower would ever put a boat back on the wrong rack.........

[Carl]

So much homework!

First thing to note is that wave length is proportional to the square
root of boat speed, and as a first assumption we might apply the rule:
L^2=kV

Rowing shells being very slim, & working at non-constant velocity, &
since a longer hull has more surface & thus incurs greater frictional
drag, & skin friction being a major component of total drag, such simple
rules get blurred by realities.

That's the background, but let's say that the slower sculler might do
better in a shorter boat.

I've had very practical demonstrations of this. Years ago I did a
certain amount of marathon canoeing (200km). We used to build some
rather nice & slippy open canoes & raced these in such events. Our
boats were 18-footers, but a popular racing class in the US is 21ft long.

Anyway, in races, crews in 21-footers were somewhat dismissive of our
prospects in the shorter boat. We did try to explain to them than in
such long marathons your sustainable power output is considerably lower
than for shorter distances, so you moved slower, & at those slower
speeds the 18ft hull length & lesser wetted surface gave you less drag
than for the longer boat. Conversely, if you were sprinting at full
power, then the 21ft boat would easily be the faster.

Since they didn't understand the science, we had to demonstrate the
truth the only way we knew - by leaving them way behind.

All of that said, you have the general picture so I hope you'll excuse
me for not digging deeper into the details for your hypothetical
situation? Were I paid to do it, that'd be a different story.