std jantar 2
Neil Bennett
Does anybody have an accurate polar curve for a std jantar2.
I would be very thankfull if somebody could help me
Andreas Maurer
d...@fir124.cray.com (Donald Ingraham) wrote:
> You might be interested in plotting your own polar though. If you've
> refinished and/or sealed your ship like I have, your polar will vary! I
> just finished some tests with mine. I took up a camcorder, aimed it at
> the panel, and recorded 10 different speeds (3 minutes each). Later in
> the quiet of home sipping on a capuccino, I replayed the video. For each
> speed I got exact time (on my camcorders display), speed, altitude lost
> and as a bonus I could compare the calculated sink rate with the reading
> on each vario (I need to file a little off the end of the TE tube)!
> I then plotted the results on a photocopy of the factory polar.
> Over the weekend I plan to do an oil flow test and stick on some home
> made turbulator at the laminar bubble separation line. Maybe something
> magic will happen and I'll produce a Discus killer! :-)
> Cost of all of the above? Four high tows (on calm cold mornings) and some
> fat tape cut with pinking shears. A little more $ if you want to repeat
> the tests ballasted.
Well, I don't want to critisize your technique of getting your
glider's performance, but to me it does not seem to be useful.
At first: How do you detect if you do not fly in sinking or rising
air? Convection is not dependent on sunshine. Just taking off early in
the morning is certainly not enough. Even if the air moves vertically
with only one inch per second it will affect your l/d measurably
(about 2 points). And in any high pressure area the air will sink
faster than one inch per second...
Then there is the second factor: How can you tell that your varios
show the correct value? Any vario with a digital display will only
show the sink rate at a 0.1 m/s grid. But it makes a great difference
whether you have a sink of 0.65 m/s or 0.62 m/s. I still have not been
able to decide whether my sink rate was 0.4 m/s or 0.42...
The same applies for the altimeter. You can check the precision of
your altimeter by simply knocking on it. Then you will see that there
does no altimeter exist that shows your altitude with a precision of
more than about 20 meters.
After having flown nearly any German glider solo (lots of X/C) and
also on competition I have come to the conclusion that it is not
possible to decide about the glider's performance if you have not
another glider you can compare the performance to. That means
formation flight close to another glider for a longer time.
And this is exactly the way the German IDAFLIEG checks out the
performance of the gliders. They use their DG 300, modified to a
wingspan of 17 m, called the "Holy cow". This glider is calibrated
very carefully and the performance of any glider is compared to this.
Because of the very close formation flight of both gliders the
influence of convection is excluded. The tests start at the same
airspeed and the same altitude. After the end of the test the
different altitudes of both aircraft are measured optically to exclude
the instrument's faults.
(Hi Bert: Please correct me if I'm terribly wrong! ;-))
BTW: I know it is tempting to say "My Jantar ist the best ever built"
(I also say this about our club's ASW-20), but be honest to yourself:
Do you fly better with this knowledge? Would you decide in a different
way?
Fly some competitions and try to stay close to other Jantars. After
several flights you might be able to say that your Jantar seems to
glide a little bit better than the other ones, but that's it. Be glad
and enjoy that you lose 20 meters less than other Jantars on the way
to the next thermic.
Of course, the l/d is not all: The qualities of a glider are also very
important while circling the thermic, and also under conditions where
the wing is dirty or wet. These are factors you cannot test at all.
And a last note:
A refinished or resealed glider does not always have to be better than
a new one as it is quite easy to destroy the airfoil's shape....
Bye
Andreas
Donald Ingraham
Hi Andreas,
>Well, I don't want to critisize your technique of getting your
>glider's performance, but to me it does not seem to be useful.
I think they are *at least* as useful as the "sales polar"
where so much was at stake to produce good numbers! I think (judging only
from my years of contact with the human race) that a little extra effort
might go into that "test" glider that is not likely to be spent on every
production unit. A few extra flights might be made until "good" numbers
are recorded, etc. Bottom line, the ship I get new (let alone a 20 year old
Jantar like mine) is not likely to perform that polar. A friend of mine
suggests anyone who disagrees should be towed up 5,280ft and 'best L/D' number
of miles out to sea and released :-)) In their ship, of course.
>At first: How do you detect if you do not fly in sinking or rising
>air? Convection is not dependent on sunshine. Just taking off early in
>the morning is certainly not enough. Even if the air moves vertically
>with only one inch per second it will affect your l/d measurably
>(about 2 points). And in any high pressure area the air will sink
>faster than one inch per second...
No offense to you Andreas, since you have given me *lots* of useful information
in the past, but why is the immediate response to this kind of testing always
a *defense* of the factory polar???? I would think the odds are that
half the time the polar would come out better (the atmosphere rising 1 inch per
second) and half the time it would be worse. Doesn't it make you suspicious that
few tests of this kind show a better-than-factory polar with a 50/50 chance
like that?
You are correct that a perfectly stable atmosphere is ideal. I don't expect
to win the "Dick Johnson flight evaluation methodology" controversy here, but I
do believe it is very useful to have statistics even if they are off by
"one inch per second". Hmmmm. let's see....
One inch per second= 60" per minute= 5ft per minute= 2% error at 250fpm,
2.5% error at 200fpm, and 3.3% at l50fpm, 4% at 125fpm....
So, if you sink 150fpm at 60knots...that's 40:1, then 3.3% error means you could
really be at 41.21:1 or 38.79:1 (assuming the 1 inch per second movement).
All speeds faster than this produce smaller and smaller errors. I can live with
that.
> Then there is the second factor: How can you tell that your varios
> show the correct value? Any vario with a digital display will only
> show the sink rate at a 0.1 m/s grid. But it makes a great difference
> whether you have a sink of 0.65 m/s or 0.62 m/s. I still have not been
> able to decide whether my sink rate was 0.4 m/s or 0.42...
What I suggested was that when you review the video tape, calculate your
sink based on altitude lost (altimeter) over time. Then watch the same video
again (fast-forward is interesting) and this time see if your varios agree with
what you calculated. I was not suggesting using the vario reading to calculate
your sink rate, only to confirm it.
> The same applies for the altimeter. You can check the precision of
> your altimeter by simply knocking on it. Then you will see that there
> does no altimeter exist that shows your altitude with a precision of
> more than about 20 meters.
Ah, but I don't need the altitude precisely. I just need the difference
between two altitudes after a few minutes flying. The error is much less than
20 meters in this case. My methodology:
I tapped the altimeter, flew 3 minutes at a certain speed, then tapped it again
before selecting another speed. There's always going to be *some* error like you
say...but I think it is minimal. When I land, it is the same as when I launched!
<snipped some text from original posting>
> BTW: I know it is tempting to say "My Jantar ist the best ever built"
> (I also say this about our club's ASW-20), but be honest to yourself:
> Do you fly better with this knowledge? Would you decide in a different
> way?
I don't understand what you mean here....the purpose of the testing is to stick
accurate numbers on my McCready ring!!
> Fly some competitions and try to stay close to other Jantars. After
> several flights you might be able to say that your Jantar seems to
> glide a little bit better than the other ones, but that's it. Be glad
> and enjoy that you lose 20 meters less than other Jantars on the way
> to the next thermic.
Again, I'm looking to fly inter-thermally as efficiently as possible, and
knowing one's true polar is the only way to do this. I don't see how it could
help to compare two unknown quantities....
> And a last note:
> A refinished or resealed glider does not always have to be better than
> a new one as it is quite easy to destroy the airfoil's shape....
Exactly! So get out your camera and do some tests!!! :-))
Bye,
Don Ingraham
P.S. Bottom line, Andreas, I don't have a glider like the "Holy Cow" you
mentioned :-( But I figure most of gliding involves "measuring it with a
micrometer, marking it with a grease pencil and cutting it with an axe"
anyway :-)
Have a good weekend!
Dennis Brown
< snip >
>with only one inch per second it will affect your l/d measurably
>(about 2 points). And in any high pressure area the air will sink
>faster than one inch per second...
>
>The same applies for the altimeter. You can check the precision of
>your altimeter by simply knocking on it. Then you will see that
there
>does no altimeter exist that shows your altitude with a precision
of
>more than about 20 meters.
>
>After having flown nearly any German glider solo (lots of X/C) and
>also on competition I have come to the conclusion that it is not
>possible to decide about the glider's performance if you have not
>another glider you can compare the performance to. That means
>formation flight close to another glider for a longer time.
>
>And this is exactly the way the German IDAFLIEG checks out the
>performance of the gliders. They use their DG 300, modified to a
>wingspan of 17 m, called the "Holy cow". This glider is calibrated
>very carefully and the performance of any glider is compared to
this.
<snip>>
>
>Bye
>Andreas
>
>
>
>
1 inch per sec is 5 ft per min. On a 4 min. run, the delta would be
20 feet, which is readable. But you are right, unless you have a
sizeable number of points, it is highly debateable to measure to the
nearest tenth of an L/D point.
Don't you use an instrument shaker to take the friction out of the
altimeter and the airspeed?
There is no doubt in my mind that side beside comparison is the
most desireable cheap method of calibration. But just how did they
calibrate the Holy Cow? Dennis Brown
Bob May
Neil Bennett wrote:
>
> Does anybody have an accurate polar curve for a std jantar2.
> I would be very thankfull if somebody could help me
I could send you the plot out of the manual for my Jantar std 3. Someone
else has already offered a copy ot the standard 1 polar. Perhaps if you
interpolate between them ...:-)
BTW, the manual for the 3 also has the "landing in high plantation
section". It also has the following advice:
"In case the excessive wet of the structure inside is found the sailplane
should be dried."
Seems like theres big bucks to be made for a good Polish to English
technical translator.
Bob May
cul...@netdoor.com
In article <55sbfu$b...@news.mel.aone.net.au> <55tf00$i...@walter.cray.com> <55vjoe$8...@nz12.rz.uni-karlsruhe.de> <560c8r$8...@opal.southwind.net>,
gli...@southwind.net (Dennis Brown) wrote:
They use their DG 300, modified to a
> >wingspan of 17 m, called the "Holy cow". This glider is calibrated
> >very carefully and the performance of any glider is compared to
> this.
----------------------------------------------------
> There is no doubt in my mind that side beside comparison is the
> most desireable cheap method of calibration. But just how did they
> calibrate the Holy Cow? Dennis Brown
They probably compared it to the mother of the Holy Cow,
the Holy Mother Cirrus, which was the predecessor to the
DG 300 as the reference test sailplane used for comparison
flights by the Idaflieg.
I do not remember how many years
they had her (Cirrus) in her comparative service but it
was quite long. When they decided to retire her to be
replaced by the maiden DG, I'll bet a lot of pilots felt
a little sad to see her go.
How they set the baseline data for the Cirrus
I do not know but I am sure that many out there, such as Dick
Johnson, do know and perhaps some of the Germans can give us
more information on the dates of service of the Mother Cirrus
and the date that the DG went into comparison service.
Keep it up!
Jim Culp USA
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Andreas Maurer
Hi Donald,
d...@fir124.cray.com (Donald Ingraham) wrote:
> No offense to you Andreas, since you have given me *lots* of useful information
> in the past, but why is the immediate response to this kind of testing always
> a *defense* of the factory polar????
Well, it is not meant to be a defense. ;-))
But as a poor student I always compare the costs and the effect, and
this ratio seems to be quite bad in this case... ;-))
And a word about factory polars:
I was really looking forward to fly our new DG-505 (the first one)
against Duo at several occasions last year, including two
competitions. According to the factory polar we should have had real a
chance. But in fact we could only hold them when the wheather was very
bad. As speed increased at good days over 140 km/h, we always saw the
Duos disappear at the horizon...from behind and below...
So much about factory polars.
> I would think the odds are that
> half the time the polar would come out better (the atmosphere rising 1 inch per
> second) and half the time it would be worse. Doesn't it make you suspicious that
> few tests of this kind show a better-than-factory polar with a 50/50 chance
> like that?
Well, it makes me suspicious that Dick Johnsons measured polars are
nearly always better than the idaflieg's ones...!?
(Flames will be ignored!) ;-))
Most of the manufactuerer's polars are also simply the calculated
ones.
In my opinion the only polars one can rely on are the ones of the
idaflieg as the method of measurement ignores convection.
If you are interested in this topic: try
http://www.akaflieg.uni-karlsruhe.de/idaflieg/ !!
>So, if you sink 150fpm at 60knots...that's 40:1, then 3.3% error means you could
>really be at 41.21:1 or 38.79:1 (assuming the 1 inch per second movement).
>All speeds faster than this produce smaller and smaller errors. I can live with
>that.
Well, I couldn't. The one is Club class, the other latest Standard
class.. ;-))
Makes a difference of 50.000 DM.... ;-)
>Ah, but I don't need the altitude precisely. I just need the difference
>between two altitudes after a few minutes flying. The error is much less than
>20 meters in this case. My methodology:
>I tapped the altimeter, flew 3 minutes at a certain speed, then tapped it again
>before selecting another speed. There's always going to be *some* error like you
>say...but I think it is minimal. When I land, it is the same as when I launched!
Hmmm...I simply doubt that this method is precisely enough... but this
is only my humble opinion, of course!
>> BTW: I know it is tempting to say "My Jantar ist the best ever built"
>> (I also say this about our club's ASW-20), but be honest to yourself:
>> Do you fly better with this knowledge? Would you decide in a different
>> way?
>I don't understand what you mean here...
Would you fly more offensively if you knew that you have a better L/D?
I know, my English is a little bit rusty...
>.the purpose of the testing is to stick
>accurate numbers on my McCready ring!!
Well, another humble opinion of me: Fly like this certain guy Ingo
Renner (do you know him? With this method he was three times World
Champion ;-)) ) and forget your Mc Cready. This constant pushing and
pulling changes your angle of attack, and any change of angle of
attack will always produce drag. I usually fly at one airspeed
(dependent on the weather - about the speed recommended by McCready)
and adjust it only briefly to the current airmass sink. As I usually
fly flapped aircraft this method also stops me from moving the flaps
into the false position when pulling up...
>Again, I'm looking to fly inter-thermally as efficiently as possible, and
>knowing one's true polar is the only way to do this. I don't see how it could
>help to compare two unknown quantities....
Whether you fly five knots faster or slower will not have a great
effect on your effectivness. I rather use the time of the
inter-thermally flight to relax, look at the others and think about
the next tactical decicion instead of always looking at (or listening
to) the speed commander. In my opinion the more relaxed pilot will
make fewer faults (that usually cost me much more time than flying
precisely the "optimal speed", whatever this is).
>Exactly! So get out your camera and do some tests!!! :-))
I rather look outside and enjoy the landscape... ;-))
BTW: How can you fly precisely with a camera in front of you? Do you
have an autopilot? ;-)
>P.S. Bottom line, Andreas, I don't have a glider like the "Holy Cow" you
>mentioned :-( But I figure most of gliding involves "measuring it with a
>micrometer, marking it with a grease pencil and cutting it with an axe"
>anyway :-)
Well, semms that you got it.. ;-))
>Have a good weekend!
Let's see. Lots of work...
Bye
Andreas
Jeffry Stetson
In article <55vjoe$8...@nz12.rz.uni-karlsruhe.de>, uq...@rz.uni-karlsruhe.de says...
>
>The same applies for the altimeter. You can check the precision of
>your altimeter by simply knocking on it. Then you will see that there
>does no altimeter exist that shows your altitude with a precision of
>more than about 20 meters.
Accuracy, no. Precision, yes. It helps to use an altimeter displaying
feet! Small altitude changes with 1000 feet/revolution are much easier
to see than similar changes with a 1000m /revolution instrument. (On
weak days I find altimeter changes or 20-40 feet to give useful
information.)
--
Jeffry Stetson ... Comm ASEL, Pvt SES & Glider, Instrument Airplane
EAA, SSA, AOPA, IAC, MAPA
Mooney M20E "Superduper 21"
Salto H-101 "Shiva - The Cosmic Dancer"
Andreas Maurer
Hi Donald!
d...@fir124.cray.com (Donald Ingraham) wrote:
>>Well, it makes me suspicious that Dick Johnsons measured polars are
>>nearly always better than the idaflieg's ones...!?
>It seems to me that Dick's tests rarely upheld the factory claim. Is it
>common for idaflieg and the factory polars to differ by more than a couple points?
>I'll check out idaflieg's web page....thanks
Hmm...you will not find any polars there (if I remember correctly),
but you will find a neat description how they get their polars
measured.
>>Would you fly more offensively if you knew that you have a better L/D?
>I think so. There's enough guess work *outside* the cockpit...one less thing to
>question during a long final glide is welcome :-)
Hmmm...and what about these three hundred dead flies on your leading
edge? ;-))
Well, it's the same with me: It's always a physological advantage to
know that you have the better glider (<vbg>), but I only base my
decisions about the current situation and my calculators...
Planning an approach from a longer distance I do not count on the 1:42
my glider shoud have but only 1:30 under perfect circumstances (no
wind, no thermals anymore and no pollution of the wing).
At low altitudes I do not plan an approach, I decide visually as I do
not want to reach the airfield at only 50 ft.
And even very weak winds and low pollution will require lost of extra
hight to reach the airfield (this is being calculated by my
calculators).
>I agree 100% (even though I can't help following the needle when I'm in the
>lower 1/3 of the thermal strength band) *but*, sorry to nit-pick...the 'speed
>recommended by McCready' is based on your true (not factory or idaflieg or Dick's)
>polar.
Of course it is. But in my opinion it does not make any difference
whether you fly at 90 mph or 100 mph...
>For me, some of the benefit of this testing is psychological: I have "seen" my
>polar and I think I'll be able to relax a little more when I "call" on it.
True.
> It sounds like you have access
>to excellent ships at your club, and I don't know if you own one yet (poor
>student :-), but if you did, you too might consider spending only 500DM doing a
>testing-modifying-testing cycle: where testing means (moving the CG, sealing it
>up, sanding out imperfections, trying some turblator, instrument calibration,
>etc).
Hihihi...
I DID! But without spending a penny on it...
Indeed I have access to rather nice aircraft in my club or belonging
to friends: My club owns an ASW-24 (although I did not fly it often
lately) and the new DG-505 (In 1998 we will get an ASW-27). But you
will usually find me in our club's old ASW-20L with a large "7Z" on
the wing... ;-))
And I have access to my temporary boss' ASH-25 or LS-7 and to the
AS-22-2 (the prototype of the 25)... ;-))
Without having to spend a penny... ;-))
But to come back to the topic: Some years ago (I guess it was in 1991)
I did a complete re-finishing of the ASW-20, taking three weeks. This
included particular repainting and all the other gimmicks you
mentioned: Sealing, perfect sanding, correction of the CG by putting 3
kg (!) of lead into the vertical stabilizer.
And now to the interesting part:
Apart from the fact that lots of people (who knew this aircraft for
years) thought that we had got a new ASW-20, we found out something
exciting:
Before the re-finishing, the 20 had always worse performance than the
(very good) LS-6 of the Theisinger brothers (perhaps you know Martin
from the last World Championchips). At low airspeeds the L/D was a
little bit worse, but the higher the airspeed became the greater was
the difference.
And suddenly the 20 was exactly as good as the LS-6, independent of
the airspeed. Wow! I really could not believe it when Georg Theisinger
told me about this (he was the first to compare the 20 against the
LS-6's and Ventus at a training of the National team). Klaus Holighaus
said that our 20 was "forbidden" good... ;-))
The only disadvantage it has aginst an LS-6a is the missing water tank
in the vertical stabilizer when loaded with lots of water (at my
weight of 92 kg I cannot take more than 60 kg of water with me), but
this counts only for very good wheather.
Without comparison to other gliders I would not have been able to
detect this outstanding performance (and now we are back at the topic
again)...
But in direct comparison it is obviuos: Without water its L/D is even
better than the L/D of a second 20 stationed at our airfield at
airspeeds up to 170 km/h...and it climbs much better... :-)))
And I did not have to spend lots of costs into an evaluation of the
20...
>As always, it's a matter of time or money. You usually have one or the other.:-)
At leat the lattr should not be a problem when you read some newsgrous
in the internet...$50.000 per week? No problem...
I think I should try this.
Or work as a gliding instructor at Alice Springs... ;-))
Donald Ingraham
Hi Andreas,
>But as a poor student I always compare the costs and the effect, and
>this ratio seems to be quite bad in this case... ;-))
If only povery went away with student status!:-) Actually the ratio works for me
because I'm too poor to buy a used Discus or the like, so I'm trying to 'tune'
what I've got. Another reason is that I did refinish and seal it, so I want to
know if I helped or hurt the performance...I know the real answer is to
fly, fly, fly...and I do that too. (BTW - the polar looks very good, whew)
>Well, it makes me suspicious that Dick Johnsons measured polars are
>nearly always better than the idaflieg's ones...!?
It seems to me that Dick's tests rarely upheld the factory claim. Is it
common for idaflieg and the factory polars to differ by more than a couple points?
I'll check out idaflieg's web page....thanks
>>So, if you sink 150fpm at 60knots...that's 40:1, then 3.3% error means you could
>>really be at 41.21:1 or 38.79:1 (assuming the 1 inch per second movement).
>>All speeds faster than this produce smaller and smaller errors. I can live with
>>that.
>Well, I couldn't. The one is Club class, the other latest Standard
>class.. ;-))
Maybe that's true for a range of 3 points, but this error is only 1.21 points,
and that's assuming the whole sky is dropping or raising at 5fpm on a single
flight. Three or four flights without seeing the data points scatter too much
should give any gambler...er statistician...a fair degree of confidence.
>Would you fly more offensively if you knew that you have a better L/D?
I think so. There's enough guess work *outside* the cockpit...one less thing to
question during a long final glide is welcome :-)
>Well, another humble opinion of me: Fly like this certain guy Ingo
>Renner (do you know him? With this method he was three times World
>Champion ;-)) ) and forget your Mc Cready. This constant pushing and
>pulling changes your angle of attack, and any change of angle of
>attack will always produce drag. I usually fly at one airspeed
>(dependent on the weather - about the speed recommended by McCready)
I agree 100% (even though I can't help following the needle when I'm in the
lower 1/3 of the thermal strength band) *but*, sorry to nit-pick...the 'speed
recommended by McCready' is based on your true (not factory or idaflieg or Dick's)
polar.
>BTW: How can you fly precisely with a camera in front of you? Do you
>have an autopilot? ;-)
Fly precisely? Damn, is that part of it??
The camera has a 4" LCD on the side that folds out and swivels. As
long as it is pointed at the gauges, it will focus. So I hold it at chest level
and glance at it every 15 secs or so to make sure the guages are on screen.
For me, some of the benefit of this testing is psychological: I have "seen" my
polar and I think I'll be able to relax a little more when I "call" on it.
And some is very practical. You mentioned that the difference between a club ship
and a current standard class ship is 50.000DM. It sounds like you have access
to excellent ships at your club, and I don't know if you own one yet (poor
student :-), but if you did, you too might consider spending only 500DM doing a
testing-modifying-testing cycle: where testing means (moving the CG, sealing it
up, sanding out imperfections, trying some turblator, instrument calibration,
etc).
As always, it's a matter of time or money. You usually have one or the other.:-)
Bye,
Don
Donald Ingraham
Andreas,
<snip>
>And [after refinishing] suddenly the 20 was exactly as good as the LS-6,
>independent of the airspeed. Wow! I really could not believe it when Georg
>Theisinger told me about this (he was the first to compare the 20 against the
>LS-6's and Ventus at a training of the National team). Klaus Holighaus
>said that our 20 was "forbidden" good... ;-))
You might want to consider coming over to the US for a summer and do some
flying out West...while making some big $$ tuning ASW-20s on the off days! Of
course you would need proof that the glider's performance *was* improved...hmmm...
something on film perhaps... :-)
I would guess the weight in the tail produced the biggest gain....?
>Without comparison to other gliders I would not have been able to
>detect this outstanding performance (and now we are back at the topic
>again)...But in direct comparison it is obvious.
Probably true.
For pure performance verification of individual improvements like additional tail
ballast, turbulator, seals, etc....I agree: fly side by side, before and after
the change, with a similar ship. And make one change at a time; you might
improve performance with one change and hurt it with another yet still show a
minor net gain.
(BTW:flying tip to tip is a more accurate measure of "better or worse" although
it still produces no absolute values...beat that dead horse!)
The first thing I would do if I took delivery of a new ship would be to see if
it could perform the polar. Hell, if it didn't at least come very close, I'd
want to return it! I heard Karl Striedeck's ASW-27 came up very short of claimed
performance until a blocked (undrilled?) pitot-pass-through for the in-flap
blow holes was discovered. I wonder what tipped him off?
Any experiences out there verifying the polar of a new ship? (idaflieg's comments
welcome! :-))
Bye,
Don Ingraham
Rick Filipkiewicz
Are the idaflieg polars publicly available & how can I get them ? For
what gliders ?
Andreas Maurer
>You might want to consider coming over to the US for a summer and do some
>flying out West...while making some big $$ tuning ASW-20s on the off days! Of
>course you would need proof that the glider's performance *was* improved...hmmm...
>something on film perhaps... :-)
Okay. You pay the flight? ;-))
Il arrive on Aug 1st, 13:45 o'clock...(but where?) ;-))
>I would guess the weight in the tail produced the biggest gain....?
Good question.
Certainly it did improve the performances at low airspeeds. But the
gain at high airspeeds was surely caused by the "clean" surface and
the sealings.
BTW: Afterwards we tried to find out why the performance had improved
so dramatically: We had unintentionally destroyed the airfoil: The
leading edge was a little bit "sharper", that means that the leading
edge radius was decreased...
Ang guess what, big surprise: Now the stall qualities have become a
little bit worse. Now our 20 spins like any other 20...
>Probably true.
>For pure performance verification of individual improvements like additional tail
>ballast, turbulator, seals, etc....I agree: fly side by side, before and after
>the change, with a similar ship. And make one change at a time; you might
>improve performance with one change and hurt it with another yet still show a
>minor net gain.
>(BTW:flying tip to tip is a more accurate measure of "better or worse" although
>it still produces no absolute values...beat that dead horse!)
Well, I prefer to do longer XC-flights together with several other
gliders. Then you measure not only the L/D but the overal performance
of the ship (if you know about the performances of the other gliders
and their pilots).
>The first thing I would do if I took delivery of a new ship would be to see if
>it could perform the polar. Hell, if it didn't at least come very close, I'd
>want to return it!
Well, that's a true point. Gliders are simply much too expensive to
allow them to be worse than promised.
>Any experiences out there verifying the polar of a new ship? (idaflieg's comments
>welcome! :-))
Well, as already said: I had the pleasure of verifying the performance
of the new 505 at two competitions...
It was not really a pleasure. :-((
Bye
Andreas
jnbe...@aol.com
In article <566htl$4...@walter.cray.com>, d...@fir124.cray.com (Donald
Ingraham) writes:
>If only povery went away with student status!:-) Actually the ratio works
for
>me
>because I'm too poor to buy a used Discus or the like, so I'm trying to
>'tune'
>what I've got. Another reason is that I did refinish and seal it, so I
want
>to
>know if I helped or hurt the performance...I know the real answer is to
>fly, fly, fly...and I do that too.
You may be able to have your own "sacred cow" to fly your sailplane
against to help determine the effectiveness of various performance
enhancements. Just make arrangements with another interested pilot with a
similar ship and make a habit of consistently doing a lot of comparison
flying: one of you flies the thermal while the other tracks exactly
behind; one navigates to the next thermal while the other forms up closely
off one wingtip, etc. Real world stuff, not just best glide angle in still
air (which we hardly ever use).
Some cautions: This is not loose, casual flying with your buddy. It
demands concentration, precision, control, and brutal objectivity (no
wishful thinking allowed). You need someone you can trust to hold things
constant while you try out different techniques and/or hardware. And
obviously both pilots must be competent and comfortable with close-in
flying to make this work.
The performance of the two gliders should be pretty close but they don't
have to be equal. Practice estimating the height difference between them
at the end of a glide in terms of fuselage lengths to add some precision
to the measurement and allow you to determine whether that latest change
helped or hurt your performance.
It would have been nice if you could have gotten a baseline reading BEFORE
you refinished and sealed your glider but it sounds like you're in the
tinkering mode so you probably have more improvements in mind anyway.
If you're careful, you'll be able to see the effects of minor changes in
both sailplane performance and piloting technique fairly quickly. I got a
real education in this technique years ago flying my former LS-3 against
George Moffat in his Ventus. I had tweaked my ship considerably the
previous winter and was experimenting with turbulator tape and different
flap positions. He was evaluating various winglets and was only too happy
to tutor me in a subject I had learned about in his articles years before
I ever met him. I had to write down what was the same/different for each
flight and make notes throughout in order to keep everything straight
(both of us were changing things every weekend) but it paid off
handsomely.
Will this tell you what your actual performance is? No. But you'll know
right away if what you did helps or hurts. Then when you get everything
dialed in just right, you can run your glide test.
Chip Bearden
ASW-24 "JB"
SSA Vice Chairman and Director, Region 2
Donald Ingraham
Andreas,
> Okay. You pay the flight? ;-))
Just jump in that ASH-25, take a high tow....a HIGH tow.....fill the back seat
up with food, drink and a couple cigars and aim for Virginia!! I'll pay for the
264,000ft tow (when you get here:-).....oh yeah, try to avoid bugs on tow...
> Il arrive on Aug 1st, 13:45 o'clock...(but where?) ;-))
Don't push your luck, just put it down on the first beach. I'll keep an eye
out for you on the evening news.....
>
> BTW: Afterwards we tried to find out why the performance had improved
> so dramatically: We had unintentionally destroyed the airfoil: The
> leading edge was a little bit "sharper", that means that the leading
> edge radius was decreased...
A friend who flys an ASW-22 (sharp leading edge) suggesting I look into
sharpening the leading edge on my Jantar during refinishing. So I thought:
of all the aerodynamic qualities a wing possesses, a sharp leading edge is the
most intuitively obvious drag-reducing feature and should greatly enhance
the wing's ability to *slice* through the air. Then I pondered how that thought
could have possibly eluded the designer, followed quickly by the decision that
it couldn't have, and there was NO WAY I should even *consider* changing it!! :-)
Which I didn't.
Sounds like you unknowingly produced a winner though....
Don
Donald Ingraham
___________________________________________________
>(Rick Filipkiewicz) writes:
>Are the idaflieg polars publicly available & how can I get them ? For
>what gliders ?
Rick, if you get an answer sent to your personal e-mail address I'd be
interested to know it, too.
Thanks,
Don
____________________________________________________
>Chip Bearden (jnbe...@aol.com) writes:
<snip>
>If you're careful, you'll be able to see the effects of minor changes in
>both sailplane performance and piloting technique fairly quickly. I got a
>real education in this technique years ago flying my former LS-3 against
>George Moffat in his Ventus. I had tweaked my ship considerably the
>previous winter and was experimenting with turbulator tape and different
>flap positions. He was evaluating various winglets and was only too happy
>to tutor me in a subject I had learned about in his articles years before
>I ever met him. I had to write down what was the same/different for each
>flight and make notes throughout in order to keep everything straight
>(both of us were changing things every weekend) but it paid off
>handsomely.
<snip>
Chip,
Thanks for the advice. The "sacred cow" ("stand-in cow":-) approach to
testing each mod also lets you fly during "normal" thermal conditions. I
hate early morning high tows. I guess there's also fewer tows involved
(<$) because neither ship *has* to land unless you want to alter/re-test
something that same day. I guess that's what Andreas meant about
comparison flying being cheaper. I like your idea of measuring/recording
the affect of each mod, rather than after many. Three questions:
1) How handsome *was* the pay-off?
2) I've read articles here and there about improving performance, but
nothing written *recently* and nothing *complete*. Anything you can
recommend?
3) Do you think *approximate* McCready numbers are sufficient or do
you think numbers based on an accurate polar (which, say, allow you to fly
within 10MPH of "perfect") are important?
Someday my secret bank account will have enough in it for a flight
computer, then I can experiment with different polars more easily...at
least until my wife notices something new and shiny in the panel :-)
Why, it's an ELT, honey...wouldn't want you to worry. ;-))
Thanks in advance,
Don
mhamm...@aol.com
I think it was just about this time last year that I asked about
the building of a Woodstock and received some excellent input. Well, I
joined the Sailplane Homebuilders Association last Summer and even took a
little dual in a 2-33. It looks like the Woodstock plans are coming for
Christmas. I have a couple new questions. Regarding flight
characteristics, will the Woodstock be a good sailplane for a novice (I'm
a power pilot with 600 hrs almost all tailwheel) glider pilot. In other
words, If I get my glider rating next Summer then construct a Woodstock,
is it within the avergae new glider pilot's capabilities? The way I read
it the answer is YES which leads me to the other question. Does the
Woodstock offer enough performance to keep a novice's attention for a
while? I'm interested in building some glider time enjoying local
thermalling and perhaps some short X/C flights. Thanks in advance for your
input!
Paul E. Remde
You might try reaching Bob Wander at 7161...@compuserve.com. He is a
very respected instructor here in Minnesota. He built a very nice
woodstock a few years ago and loves flying it when he gets a chance. He
has done some cross-country in it. He even flew it in a regional
contest a few years ago. I would guess that it is about as capable of
cross-country flying as a 1-26. Maybe even a little better.
Paul
--
Paul E. Remde
Product Marketing Manager
Emerson Electronic Motion Controls
Chanhassen, Minnesota
Sailplane: Schweizer 1-35c (EX)
Soaring rewards with freedom, beauty and challenge.
F.L. Whiteley
Wasn't the leading leading edge mod responsible for some of the performance
increase in the fully Schuemannized Libelle? Never seen one. Of course
you could affect a number of variables and become a test pilot. Of course,
it's easier if your glider is experimental on the US registry.
FLW
Donald Ingraham <d...@fir124.cray.com> wrote in article
<56b18j$h...@walter.cray.com>...
S. Steve Adkins
My glider instructor, Bob Wander (a well known name), with many hours
of flying and instruction, still loves to fly the Woodstock he built.
My experience is much like your experience. A power pilot; 450 hours;
much of it tail wheel; joined SHA; and, became obsessed with gliding
just after clearing the trees on R/W 27 at Stanton Minnesota on the
first dual instruction flight with Bob. I too started in the 2-33, then
moved to the Super Blanik after solo. I now fly Bob Wander's Blanik
Solo (just like a minature fighter) and club gliders: 1-23, K8, K7,
K-21 and Puhacz (Owl). Also, I still enjoy the 2-33.
None of these aircraft are high performance craft but after three years
and about 100 hours, they are still fun to fly. You should enjoy your
Woodstock. On weak days, it's a hoot to climb in a thermal in the
high lift core in a K8 while a club member in a high performance
private ship helplessly circles wide in sink ... of course, it is more
fun if we are both climbing. So high performance isn't always where the
fun is ... other why are so many Beech drivers now restoring Cubs?
Be sure to attend the Eastern or Western SHA workshops (with a Central
Workshop coming). I made it to both this year. I bought plans for the
Carbon Dragon. You will benefit if you buy Clint Brooks book,
"Woodstock Sailplane Sketchbook" and buy all the back issues of
Sailplane Builder with articles on the Woodstock. Go for it! Keep me
posted at s.s.a...@cdev.com (don't use the Email in this letter as I
rarely check the mail slot).
In <19961113122...@ladder01.news.aol.com> mhamm...@aol.com
writes:
>
> I think it was just about this time last year that
>I asked about the building of a Woodstock and
>received some excellent input. Well, I
>joined the Sailplane Homebuilders Association
>last Summer and even took a
>little dual in a 2-33. It looks like the
>Woodstock plans are coming for
>Christmas. I have a couple new questions. Regarding
>light characteristics, will the Woodstock be a good
mhamm...@aol.com
In article <56ecak$7...@dfw-ixnews10.ix.netcom.com>,
s.ad...@ix.netcom.com(S. Steve Adkins) writes:
>Be sure to attend the Eastern or Western SHA workshops (with a Central
>Workshop coming). I made it to both this year. I bought plans for the
>Carbon Dragon. You will benefit if you buy Clint Brooks book,
>"Woodstock Sailplane Sketchbook" and buy all the back issues of
>Sailplane Builder with articles on the Woodstock.
I wish I could attend but I just took off work this week to
study for powered plane Commercial written. From what I understand there
is only the original carbon dragon flying? As for the back issues I'm
certainly planning on purchasing those but I wasn't too sure about the
sketch book. I wonder if it's really worth it? The Woodstock will not be
my first wood airplane project.
gfos...@aol.com
Just one person's view....I started out soaring in 1994 and bought a
Breigleb BG12 sailplane after about 20 hours of soaring instruction in a
Grob. I had about 100 hours of power flying before that but it was about
30 years previously. I never flew the BG because I soon started renting
a single place Grob and knew I would not be satisfied with the lower
performance and very difficult ground handling of the BG compared to a
glass plane. I sold the BG and ultimately bought a Standard Cirrus. I
soloed the Cirrus with about 70 hours of glider time in Grobs and an L23
Blanik. I've never been in a Schweizer. I now have about 150 hours in
gliders. Getting back to the Woodstock. A close friend bought a
Woodstock and flew it locally for a couple of years. He just told me
yesterday that it was very easy to fly and such things as spin recovery
was achieved simply by taking his hands off the controls. No real spin
recovery techniques required. He also said that the speed range was very
narrow, i.e., it stalled at about 38 but it took quite a bit of nose down
to get it going much above 55 or 60 and by then it was going down pretty
fast. In other words it just didn't penetrate well at all. If flown
slowly though, it could easily out climb anyone on the field because of
the very low sink rate. Assembly was easy for one person because the wing
panels were so light. The lack of penetration caused him to generally
follow the rule that he NEVER flew down wind of the airport for fear the
wind would come up and he would not be able to get back. So for local
flying it is probably a fun plane if you're small and light but marginal
at best for even short cross countries. It would not satisfy me after
about one summer. The amount of work required to build a Woodstock would
not seem to be justified if your main goal is flying. If it is building,
it sure is a good plane to build to start on. Now the coupe de gras,
there is a Woodstock for sale at our local airport(in Southern California)
and it is probably the finest Woodstock in the USA. It and a sistership
were built by a cabinet maker and they have both won several awards for
construction. This is the same plane that use to belong to my friend but
is owned by someone else now. I'm not sure who the owner is but if you're
interested I will track it down for you. It is currently in an enclosed
trailer and I think the price is under $5000. Hope this helps a little.
Greg Foster
mhamm...@aol.com
In article <19961115214...@ladder01.news.aol.com>,
gfos...@aol.com writes:
> The amount of work required to build a Woodstock would
>not seem to be justified if your main goal is flying. If it is building,
>it sure is a good plane to build to start on. Now the coupe de gras,
>there is a Woodstock for sale at our local airport(in Southern
California)
>and it is probably the finest Woodstock in the USA. It and a sistership
>were built by a cabinet maker and they have both won several awards for
>construction. This is the same plane that use to belong to my friend but
>is owned by someone else now. I'm not sure who the owner is but if
you're
>interested I will track it down for you. It is currently in an enclosed
>trailer and I think the price is under $5000. Hope this helps a little.
This helps more than a little. I'd like to think that something
was amiss with the Woodstock you were talking about though as the
"advertised" cruise is 78 mph and you mentioned this example was hard
pressed to do better than 60. I'm both interested in building and flying.
Seeing how I'm located in Indiana, I don't think coming to California is
gonna happen. Thank you very much for your input though. I hope someone
else with Woodstock experience can address the penetration question you
raise. Thanks again!