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  #111  
Old November 12th 04, 06:05 PM
Bill Daniels
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"Bob Kuykendall" wrote in message
om...
Eric Greenwell wrote:

A few have suggested 40:1 is not possible at less than 15 meter span,
but when 15 meter spans can now do 48:1 or better, this is not sensible.


Now we're getting to the crux of the matter. In order to continue this
discussion, we need to avoid comparing apples to oranges.

The 40:1 best L/D performance that you're seeking to match for an LS4
equivalent is the actual Johnson-tested and verified best glide
performance of the LS4. It really does go 40:1 at best glide. I can't
remember what the factory claimed for it, but it is probably on the
close order of 43:1, right in the ballpark of what I'm claiming for
the HP-24.

The 48:1 best L/D performance that you say that 15m ships can do or
better is just a claim. It is salesspeak. It is not verified by any
impartial body. It is, in my mind at least, false until demonstrated
true. When a well-designed 18 meter ship like your ASH-26E can barely
hit 50:1, even when you feather in the squeakiest data points, you
just have to wonder how good you really can do with three whole meters
less.

Now, I'm not going to say that I think that 48:1 or 50:1 is outside
the realm of possibility for a 15m ship. But I will say that I don't
see it in the impartial test reports that I have read.

And I will note that this is a pretty sore topic with me. I'm
developing a 15/18m sailplane for which I have released what I think
is a reasonable best L/D claim. It has a well-designed wing, courtesy
of my Stanford phd friend who does low-speed aero engineering for NASA
Ames and campaigns in 15m national competition. So I think I have good
reason to believe that my ship will meet my claims. And I also have a
pretty good idea that there's no magic out there that is going to let
you pull 50:1 out of 15 meters like you'd extract a rabbit from the
eye of a needle.

As for real, tested best glide performance available from a 15m ship,
a good example is the Ventus. When Johnson tested the Ventus A in
1981, he got 45:1 out of it. Just incredible. Not many people were
particularly enamored of its handling characteristics, but it went
like stink.

And after 15 years of evolution that produced a new fuselage and a new
wing, Johnson tested the Ventus again in 1996 - this time the 2B
model. His results show that the best L/D increased an entire negative
1 to 44:1. It was definitely a nicer glider, with the auto-connects
and nicer cockpit and other improvements, but somehow the best L/D
didn't go up.

Going forward, I propose that if we're going to be tossing a lot of
best L/D claims around, that we restrict ourselves to tested, verified
best L/D performance values, for example the idaflieg or Johnson
results. Otherwise I'm just going to have to join the Liar's Dice game
and claim a patently unobtainable 50:1 for the HP-24. And I'd like to
think of myself as a more honest person than that.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com


Well said, Bob.

All else equal, span determines performance. Clearly performance is a
highly desired quality for the buyers of new sailplanes. I think is true
that any cost savings due to a shorter span will not offset the lesser
performance with the majority of buyers.

If you really want a short span glider, wait until the first generation of
owners dump them on the used market when they move up to larger spans.
Then, short span gliders will be really cheap.

15 meter gliders are popular for a reason. They are still small enough to
be easy to assemble while delivering excellent performance. However, I
suspect that if costs were equal, 18 meters would be still more popular.

Bill Daniels
(20 meter driver)

  #113  
Old November 12th 04, 06:50 PM
Shawn
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"Eric Greenwell" wrote in message


A few have suggested 40:1 is not possible at less than 15 meter span, but
when 15 meter spans can now do 48:1 or better, this is not sensible.

Most people that have objected to this smaller span solution have done so
mainly on the "it doesn't cost THAT much more to ..." grounds; i.e.,
proposing a more expensive glider than one that will just match the LS4.
This might indeed yield a more viable product, but it doesn't meet the
goal of a "cheaper LS4".

Which would you prefer, at the same price: a new LS4, or an new 13 meter
with identical performance, handling, and safety? I would choose the 13
meter glider, but many/most would not, even though it's smaller size and
lighter weight would make it easier to rig, to push around, to retrieve,
to tow (in it's trailer or behind a tow plane), even to wax!

Old habits and dreams die slowly, I think. Glider pilots are mostly a very
conservative bunch.


Tim Mara wrote:
I would always choose the 15 meter glider.......following what you

have been
saying the 15 meter would then not be the "same" performance as the

13 meter
glider.....but better!
Also.having flown a lot of different types of glider and airplanes over
several years, including some ultra-lite or 'lite" types there is

still no
way to compare these with the extra mass and groovy feeling of the

(for the
lack of a better word) real sailplanes.....
tim


This thread is reminding me of a Monty Python skit:

Span span span span
Span span span span
Lovely span! Wonderful span!*

The message I'm getting is that the market (us) wants LS-4 like
performance for a lot less money. A number of manufacturers are putting
out gliders that are close, but miss the mark in one way or another. I
suspect they, with good intentions, say to themselves in that self
assured glider pilot kind of way,
"I know what will fix this sport. I'm going to build it, people will
fly it, and I will be their savior."
OK, maybe not the savior part, but I'm sure each of them thinks they've
got the solution.
Or worse, a committee gets together and designs something (nearly) no
one wants.
Do these guys ever do extensive, international, market research that
asks the one true question (that Tim alludes to above)?
"What will YOU buy?" "When push comes to dollars and you picture
yourself in a new glider, what is it like?" Asking participants at the
latest Worlds isn't enough.
From what I read, what we *Really* want to fly sounds like "A big shiny
high performance gliders for half as much money." Is that what you
really want? Works for me.
The price of Russias and PW-5s has dropped over recent years because
IMHO they don't fit into this picture. I think SparrowHawks are very
cool but I won't give up my Mosquito for one.
The whole hand made glider industry is a dead end anachronism and the
end is approaching (see the ASW-28 wing shrinkage, Discus CS AD, sale of
RS threads for recent examples). High tech ultralights, minigliders and
old designs built with cheap labor nibble at the edges, but don't break
down the central dogma of the big manufacturers.

The manufacturers should be asking owners, clubs, students etc. what
they *Really want to buy*, not just "We build these gliders for these
prices. Which do you want?" Then apply some well established material
and manufacturing technology as well as marketing, and try to build it.
At worst they'll end up where they're headed anyway.

Shawn


* http://www.mailmsg.com/sounds/spam-song.wav for the original

  #114  
Old November 12th 04, 07:00 PM
Kirk Stant
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(Bob Kuykendall) wrote in message . com...
Earlier, Eric Greenwell wrote:


The one somewhat-troubling exception that occurs to me is full-on,
no-holds-barred competition. I believe that where the stakes are high,
there can be competitive advantage in a light, very small glider of
15m or slightly less. What we're talking about is a glider for a 5'2"
pilot of about 108 lbs who doesn't mind launching at 11 lbs/ft^2 in a
machine that provides about as much crash protection as a motorcycle
racing suit.


George Moffat was way ahead of you; he brings up this exact subject in
"Winning on the Wind"! His instant solution? Woman contest pilots!

He also had an interesting discussion about the potential of a 13
meter racing class, but unlike the current emphasis on handicapping,
he wanted a really strict one-class ship (much like the theory behind
the PW-5). This came from his experience in sailboat racing.

I think all this discussion about exporting Sparrowhawks to Europe
misses a huge point - European (and probably the rest of the non-US
gliding community) has a strong XC and racing bias. So a glider that
doesn't fit into an existing racing category, or has less XC
capability, will be a tough sell. Club class perhaps, but then you
are competing against much less expensive used ships.

The US on the other hand, seems (IMHO) to have a substantial anti-XC /
racing majority - which would explain the "success" (?) of the
Sparrowhawk and PW-5 over here.

Finally - To me the argument is backwards: I don't want a 13 meter
ship that has the performance of an LS4, I want an LS4 (size, comfort,
handling, cost) that has the performance of an LS6!

Kirk
Ex-partner in an LS4, currently flying an LS6 (and missing the -4s
huge cockpit and wonderful ailerons)
  #115  
Old November 12th 04, 07:32 PM
Eric Greenwell
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Tim Mara wrote:
I would always choose the 15 meter glider.......following what you have been
saying the 15 meter would then not be the "same" performance as the 13 meter
glider.....but better!


Tim, you completely missed the point: the choice was between gliders of
IDENTICAL performance. Even so, you made my point: a lot of RAS pilots
have a bias to 15 meters, REGARDLESS of the performance!

Also.having flown a lot of different types of glider and airplanes over
several years, including some ultra-lite or 'lite" types there is still no
way to compare these with the extra mass and groovy feeling of the (for the
lack of a better word) real sailplanes.....


And yet, one of the elements cited most by the people that own the
shorter span sailplanes is the improved response of the glider, so you
can "feel the air" better and maneuver more quickly while thermalling.
Your preference might just be habit and lack of exposure to the modern
small span gliders, like the SparrowHawk, Apis, Silent, etc. These are
not your father's 1-26! (This is not disparagement of the 1-26, but a
recognition of how different the new gliders are).

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA
  #116  
Old November 12th 04, 08:32 PM
Eric Greenwell
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Kirk Stant wrote:


The US on the other hand, seems (IMHO) to have a substantial anti-XC /
racing majority - which would explain the "success" (?) of the
Sparrowhawk and PW-5 over here.


(Sound of loud buzzer for wrong answer) The people buying and flying the
SparrowHawk are most definitely cross-country pilots! You don't buy a
glider like that to float around the airport. It'd be a heck of fun ship
for that purpose, but the people that want to do that seem to buy
cheaper gliders or use the club ships.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA
  #117  
Old November 12th 04, 09:23 PM
Fred Mueller
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Tim Mara wrote:
.. there is still no
way to compare these with the extra mass and groovy feeling of the (for the
lack of a better word) real sailplanes.....
tim



Groovy. That is the perfect word.

Fred
  #118  
Old November 12th 04, 11:19 PM
Steve Hill
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It seems to me that as long as there is such a disparity amongst the ranks
of sailplane enthusiasts financially, we'll never really be able to reach
any meaningful solution...I for one wouldn't consider a sailplane that
didn't have the ability to self launch and then turn into a pretty high
performance soaring machine, simply because it suits my goals...There's lots
of 1-26's and many other veritable gliders in the under 10k price range that
there should always be a home for...If it seems one thing is missing, it
seems like that is a self launched kit sailplane, for the enthusiast who
truly wants to be free of the encumbrance of waiting in line for tows...and
all the associated headaches of retrieves...it would seem to me that the
HP-24 project could place itself into being one of a kind in that regard,
instead of simply another nice sailplane...for the money the LAK-12 and
numerous other longer winged mounts seem to be plentiful and I agree with
Bob Kuykendal about L/D claims being largely over-rated...

the one thing I notice more and more, is that self launchers are turning up
on the State records and badge flights more and more...and I think it will
continue...I don't think the overall performance is near as much an issue,
as the convenience and ability to go...when the weather is good...I started
in hang gliders and have owned wood, aluminum and glass...I don't want to go
back in performance any more than anyone...a less expensive self launcher
would seem to me to be much more meaningful for growing our sport...than
just another sailplane to add to the long and confusing list that is already
out there...



Steve.




  #119  
Old November 13th 04, 01:31 AM
Eric Greenwell
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Steve Hill wrote:

the one thing I notice more and more, is that self launchers are turning up
on the State records and badge flights more and more...and I think it will
continue...I don't think the overall performance is near as much an issue,
as the convenience and ability to go...when the weather is good...I started
in hang gliders and have owned wood, aluminum and glass...I don't want to go
back in performance any more than anyone...a less expensive self launcher
would seem to me to be much more meaningful for growing our sport...than
just another sailplane to add to the long and confusing list that is already
out there...


I agree with Steve. As an example, the Russia AC-5 sold very well
because it had a good price and decent performance. It has about 70% of
the L/D of ASH 26 E, but was about 40% of the price, and 30+ pilots
found that very attractive. Unfortunately, it's not available new now,
and the manufacturer's intentions aren't known.

L/D is somewhat overrated as Bob K and others point out, especially for
a motorglider. A Russia pilot might have to use his engine more often
than I do in my ASH 26, but what's an extra 10-15 minutes of engine, 5
or 6 times a year? Nothing really, but it sure can expand your soaring
options.


--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA
  #120  
Old November 13th 04, 01:51 AM
Robertmudd1u
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..If it seems one thing is missing, it
seems like that is a self launched kit sailplane, for the enthusiast who
truly wants to be free of the encumbrance of waiting in line for tows...and

all the associated headaches of retrieves.

It is not missing it already exists, the Apis M is a selflaunch 15meter span
glider available in kit form. It uses modern design concepts and materials. The
39hp. engine assures good climb rates even at high density altitudes.

Visit the web site for more information. www.apisgliders.com

In all fairness I must mention that the Silent selflaunch is also available in
kit form but is 13meters in span.

Robert Mudd
Apis Sailplanes Inc.

 




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