US Dollar sinks to new low against Euro

Bob Kuykendall wrote:

I tend to believe that the legacy of span-limited competition classes
is such that sailplane buyers will tend to gravitate towards
competition spans, even those with very weak inclination to ever
compete. That's one of the reasons I'd like to see a distinct
competition class for sub-15m ships; and I think that 13m would be a
perfectly good place to draw the line.

This effect should not be an issue here, since we are talking about
performance identical to an LS4. So, it would do exactly as well in any
contest as an LS4. I don't know if it would be immediately accepted into
the club class since I'm not familiar with the rules, but if has the
same performance as an LS4 and the same price, why not?

A 13-meter class would collect all the Russias, Apii (Apia?), PW5s,
and Sparrowhawks, though sadly leave the 14m L33 (TG-10D for
USAFAians) out in the cold. It would give people at least a plausable
excuse to buy these little gliders, and give developers an economic
basis for developing them. And I think that it would be a kick-ass fun
class to fly in, since I'm just the right size for it and I'm used to
flying a few points short of a Libelle.

I like the idea of encouraging smaller gliders with a class, but I'm
more in favor of "performance bracket" classes than span classes. THe
European club class is such a class. By handicapping over a small range
of performance, say 10%, it's easier to accommodate performance
differences fairly.

Instead of the Sports Class we have in the US, I'd like to see something
like "Sports A" (handicaps from 1.05 and up), and "Sports B" (handicaps
from 1.04 and lower). Or maybe 3 classes?

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

Eric Greenwell
Washington State
USA

Robert Ehrlich wrote in message ...
Kirk Stant wrote:
...
I must be the only guy who thinks Rutan's designs are ugly and
over-optimized.
...

Certainly not, concerning the optimization.
See http://inter.action.free.fr/publicat...ds/canards.htm
Sorry, it is in French.

Merci, c'est interessant!

Eh oui, un amerloque qui parle Francais...et qui a vote pour W.

Kirk

At 15:36 11 November 2004, Andreas Maurer wrote:

Frankly spoken, I doubt that this is possible without
major compromises concerning cockpit size and crash
protection. I need a certain cockpit cross-section
to be able to sit comfortably, so the cross-section
of the fuselage (which defines most of its drag) is
fixed, independent of the wing span. Fuselage surface
area is also fixed.... One solution could be to build
the whole glider extremely light (like the Apis or
Sparrowhawk) to get normal wing loadings of about 33
kg/m^2 at a high aspect ratio, but this is going to
result in the inability to carry water, low Vne (hence
the comparably bad penetration of the Apis compared
to club class gliders with similar L/D and wing loading)
and questionable crash protection. The Sparrowhawk
and Apis look really good and are definitely state
of the art - but to be honest, I would not like to
rely on their cockpit shell strength when I impact
at 50 kts or above.


As to the question of fuselage integrety in smaller,
lighter gliders the Apis manufactures seem to have
given this some thought. See: http://www.albastar.si/
and look under construction on the menu bar

Mike

At 02:12 12 November 2004, Mike Ziaskas wrote:
At 15:36 11 November 2004, Andreas Maurer wrote:

Well, Andreas wrote to the effect that he did not
want compromise in fuselage crashworthyness in the
lightweight gliders (MZ)

As to the question of fuselage integrety in smaller,
lighter gliders the Apis manufactures seem to have
given this some thought. See: http://www.albastar.si/
and look under construction on the menu bar

Mike



Mike Z

In article ,
(Erik mann) wrote:
Or, maybe the design goal should be 40:1 performance at the lowest cost,
irrespective of span?

40:1 isn't actually what people want, otherwise the Phoebus would be a
lot more popular than it is.

What is the reason for more span? It decreases induced drag at high
angles of attack. So less span is worse because it means you won't be
able to thermal slowly and efficiently, right? Just like the PW-5.
Well, no, the PW5 thermals beautifully. The problem with it is that it
needs very thick wings to do that, and this actually penalises it at
*high* speed, not low speed. A glider similar to the PW-5 could easily
have thinner wings, a better best L/D and *much* better high speed
performance. It just wouldn't be able to fly as slowly for thermalling
and -- perhaps more importantly for low time pilots -- for landing.

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

For what it is worth, I offer you 'Rollings Law of
Price and Performance'. 'For a given state of the
art, performance increases with the square root of
wingspan; price increases with the square of wing span.'

At 07:36 12 November 2004, Bruce Hoult wrote:
In article ,
(Erik mann) wrote:
Or, maybe the design goal should be 40:1 performance
at the lowest cost,
irrespective of span?

40:1 isn't actually what people want, otherwise the
Phoebus would be a
lot more popular than it is.

What is the reason for more span? It decreases induced
drag at high
angles of attack. So less span is worse because it
means you won't be
able to thermal slowly and efficiently, right? Just
like the PW-5.
Well, no, the PW5 thermals beautifully. The problem
with it is that it
needs very thick wings to do that, and this actually
penalises it at
*high* speed, not low speed. A glider similar to the
PW-5 could easily
have thinner wings, a better best L/D and *much* better
high speed
performance. It just wouldn't be able to fly as slowly
for thermalling
and -- perhaps more importantly for low time pilots
-- for landing.

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

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

"Eric Greenwell" wrote in message
...
Erik mann wrote:

What is it that economists always throw out... ceteris paribus...

I agree that if one started with a clean sheet of paper, then maybe you
can lop off a few pounds on the fuselage, change the planform, etc.
(though, having looked at the structure of some of these ships,
I'm not so sure I would want to fly them or land them off-field...
but I digress). Keeping everthing else equal, is the "best" use of
engineering to start with a shorter span as a design goal? Maybe it
is, as the weight savings on the spar and carry-through structure allows
for a good range of wingloading while bringing along the other
benefits mentioned elswhere (ease of assembly, transport, etc.)?
Or, maybe the design goal should be 40:1 performance at the lowest
cost, irrespective of span?

That was my proposed goal: LS4 performance at the lowest manufacturing
cost. The obvious solution will be a smaller glider, made possible by
the improved aerodynamics, design, and materials that became available in
the 24 years since the LS4 was designed.

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.

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

Eric Greenwell
Washington State
USA

On 11 Nov 2004 12:10:00 -0800, (Brad) wrote:


Since I am 3-d modeler by trade I have been designing up my "dream"
sailplane that would probably end up with a 15m span, but it would be
built using Apis/Russia/TST-10 technolgy, thus would have a empty
weight around 450 pounds or so.

You can already buy this - it's the Apis 2 ultralight motorglider,
certified according to the German ultralight regulations.

Price: 60.000 Euro.
Not quite a bargain, isn't it?



Bye
Andreas

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

Bob Kuykendall wrote:

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.

How about the L/D ten years later after 1000 hours of exposure in the
sun, 300 assemblys by trained monkeys, blowing dust and sand over the wings,
and repeatedly forcing the canopy and gear up and down?

I think there are more interesting questions than just some L/D figure.
Does polyurethane keep airflow better after years of the conditions
I just described than other finishes? How about wing flexing causing
cracks? Do longer wings inevitably mean more cracks unless they get
another $10k worth of finishing?

Is a side opening canopy going to deform (like our L-13 canopy)
over the course of many years? How heavy/sturdy does a canopy
frame need to be to maintain it's shape (I remember watching Bob
look at the HP canopy frame matching to the body with a careful eye)?

And who sells a glider that has parts that don't fit flush with
the disclaimer "in a year or two the parts will stretch and fit perfectly"?

So I personally don't look too hard at the L/D by itself.
The stall speed, the 80 knot sink speed, the possibility of ballast,
and the tradeoffs of flaps vs. no flaps and how this is integrated,
and retract gear, seem to be better indicators than some number.

A glider with 1000+ hours, no refinish or new parts since manufacture,
and then a flight test, is what I'm talking about. If it beats
350 fpm sink at 80kts, and stalls under 35kts at MGW, then it's
time to move on and ask about other flight characteristics
(stall/spin like SZD 50-3 and tricky takeoffs like PIK-20).

In this sense the World Class concept I think was apt, because
the goal was not L/D (perhaps with the knowledge that
waviness and rough handling would negate the cost put into a
high L/D anyway).

--

------------+
Mark J. Boyd