US Dollar sinks to new low against Euro

Andreas Maurer wrote:
On Wed, 10 Nov 2004 22:57:27 -0800, Eric Greenwell
wrote:



But here's question: we know a modern glider can be smaller than the 24
year old LS4 design and have the same performance.


Do we really know that?

I believe it when I see one. 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 (apart from the fact that the fuselage will be a little
shorter), so there is very little potential to reduce the fuselage
weight compared to a current glider (say, ASW-28). Proof is the PW-5
which is only slightly lighter than an ASW-28 despite the fact that it
has much lower Vne and maximum weight.


Fixed fuselage cross-section with a smaller wing means that the
fraction of fuselage drag on total drag is going to be greater. As a
consequence the wing needs to save drag - and the only chance to do
this is increased aspect ratio... which will lead to wing loading
problems.

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.




I suggest 13 meters
would do it without heroic efforts by the designer, but what do the
citizens of RAS think is the minimum?


It's not the wing span or weight, its acceptance. And I think history
has shown what kind of glider will be accepted (and bought) and which
not.
How many LS-4 have been sold? 1.400?


Let's face it:
At the moment the Sparrowhaw is sold for $33,950, the LS-4 for 39.500
EUR (VAT not included).
The Sparrowhawk is not that much cheaper, especially if we consider
the fact that it is much smaller and much simpler (no retractable
gear). And, of course, it's not certified (the certification alone is
the major part of the development costs - this is what makes an
aircraft so expensive). Shall we bet that if it was certified the
Sparrowhawk would be at least as expensive as an LS-4?


If we had an exchange rate of 1:1 as we had two years ago, you'd get a
lot more bang per buck with an LS-4, wouldn't you?

Have you looked at the exchange rate lately?

On Thu, 11 Nov 2004 09:22:39 -0700, Shawn
wrote:


Have you looked at the exchange rate lately?

Sure I did - but the exchange rate neither reflects the real
production cost nor is it a fixed value. Two years ago the exchange
was 1:1.

Unfortunately it's not the mistake of the European glider
manufacturers that the $ has lost 30 percent of its value compared to
the Euro.



Bye
Andreas

You hopefully don't expect sailplane designers to fix your economy, don't
you? I thought that's what you have a President for...

--
Bert Willing

ASW20 "TW"


"Shawn" a écrit dans le message de
news: ...
If we had an exchange rate of 1:1 as we had two years ago, you'd get a
lot more bang per buck with an LS-4, wouldn't you?

Have you looked at the exchange rate lately?

Andreas Maurer wrote:
On Wed, 10 Nov 2004 22:57:27 -0800, Eric Greenwell

But here's question: we know a modern glider can be smaller than the 24
year old LS4 design and have the same performance.


Do we really know that?

YES! With the newer 15 meter size gliders moving close to or even above
50:1 (like the Diana), there should be no question that 40:1 can be
achieved with less than 15 meters. It might take more than 13 m, maybe
13.5 or 14 meters - I don't know where the limit is.


I believe it when I see one. Frankly spoken, I doubt that this is
possible without major compromises concerning cockpit size and crash
protection.

No compromises are needed to achieve this, and I don't want any
compromises to be made. A crash-worthy cockpit is not an option, in my mind.


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 (apart from the fact that the fuselage will be a little
shorter), so there is very little potential to reduce the fuselage
weight compared to a current glider (say, ASW-28). Proof is the PW-5
which is only slightly lighter than an ASW-28 despite the fact that it
has much lower Vne and maximum weight.

I agree in concept, but the details are important; for example, my
proposal was to match the LS4, not an ASW 28! THe PW5 is not a good
example: it is not a modern design and is made of fiberglass; the ASW 28
is carbon fiber.

Fixed fuselage cross-section with a smaller wing means that the
fraction of fuselage drag on total drag is going to be greater. As a
consequence the wing needs to save drag - and the only chance to do
this is increased aspect ratio... which will lead to wing loading
problems.

What kind of problems? The modern gliders show a trend to smaller and
smaller wing area. A SparrowHawk is the extreme example, with only 11
meter span and 70 sq ft, yet has a wing loading of only 5 to 5.5
pounds/sq ft (24 to 27 kg/m2).


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.

These are all design choices to be made by the designer. Today's
designers know more than they did 25 years ago when the LS4 was
designed, and they now have a broader range of materials to choose from.
Of course they can match the LS4 with a smaller span!

This is not the same as saying it would be a commercially viable product.


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.

Without crash tests or a review by people that are knowledgeable in
glider cockpit design, I can not compare the Apis, LS4, or SparrowHawk
objectively. I would be guessing, just like you.

One factor in favor of the Apis and Sparrowhawk is their lower speeds
will mean they crash more slowly than an LS4, which is a very important
feature for crash safety.

snip

Let's face it:
At the moment the Sparrowhaw is sold for $33,950, the LS-4 for 39.500
EUR (VAT not included).
The Sparrowhawk is not that much cheaper, especially if we consider
the fact that it is much smaller and much simpler (no retractable
gear). And, of course, it's not certified (the certification alone is
the major part of the development costs - this is what makes an
aircraft so expensive). Shall we bet that if it was certified the
Sparrowhawk would be at least as expensive as an LS-4?

These comparisons are irrelevant for several reasons: The SparrowHawk is
not intended to compete with the LS4; currency issues make price
comparisons change year-to-year; Windward Performance (SparrowHawk
manufacturer) is a new company with a much different situation than an
established one. To talk about the cost of two different _designs_
sensibly means we must eliminate these other factors and consider what
it would cost to build them in the same factory.

THe problem of commercial success is a much more complex problem: you
must determine a particular design, how to build it, and where to build
it. These and other factors besides the effect of span on the cost
become more important and are very difficult to resolve.

If we had an exchange rate of 1:1 as we had two years ago, you'd get a
lot more bang per buck with an LS-4, wouldn't you?

They are two very different gliders, so you can only guess at what the
"bang" is for each pilot. All the people that have purchased a
SparrowHawk could have just as easily bought a used LS4, but chose not to.

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

Eric Greenwell
Washington State
USA

Bert Willing wrote:
You hopefully don't expect sailplane designers to fix your economy, don't
you? I thought that's what you have a President for...


Bert, Bert, don't you know Real Americans (tm) elect a president for the
same reason they buy big SUVs, to stroke their egos.
Also, our economic problems are always someone else's fault.
As for gliders, the Sparrowhawk should be priced very attractively for
Euro holders.

Shawn

Bob Kuykendall wrote:

Earlier, Eric Greenwell wrote:


But here's question: we know a modern glider can be smaller than the 24
year old LS4 design and have the same performance. I suggest 13 meters
would do it without heroic efforts by the designer, but what do the
citizens of RAS think is the minimum?


I dunno about the others, but I'm betting on the range of about 14.3m
to 14.6m for normal sized US pilots. And that the very first guy who
buys one will ask "So, when will I be able to get 15m tips for it?"

I agree. I've noticed when the conversation turns lamenting the cost of
new gliders, someone suggests achieving this goal with sub-15 meter
ships, and the very next posting is "well, it doesn't cost THAT much
more to make it 15 meter...". Certainly for RAS, there is strong bias
for 15 meter span, even though people claim they would be quite happy
with LS4 performance. I am beginning to think a lot of people don't want
a cheap glider with LS4 performance; they want a cheap LS4.

Maybe outside of RAS, there is a good market for a sub-15 meter LS4
equivalent. Certainly some are trying, like the AC4, Apis, Silent, and
the SparrowHawk. Though these are not the same as an LS4, it does give
some idea of the market potential.

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

Eric Greenwell
Washington State
USA

Eric Greenwell wrote in message Compare the 113 sq ft, 15 M, 513 pound LS4 with the 82 sq ft, 12.6 M,
290 pound AC4 Russia: that's a 27% reduction in wing area and a 43%
reduction in weight! The fuselage is smaller, too, but not as much a
reduction as the wing. That seems to me a significant reduction in
finishing is possible, and also in the construction. Of course, an
obvious difference in materials cost (these are both fiberglass gliders).


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?

The use of flaps (somewhat) mitigates the need for water. Only time
will tell if the flaps increase the insurance rates.

I really like the fixed gear, and suspect the insurance rates of the
LS-4 vs. Apis will reflect this.

Beyond that, as I am not so girthy as some americans, I fit in even quite
small cockpits. The larger cockpits are simply a waste for me.

If one wants water, retract, and no flaps, and doesn't mind the
extra weight of ground handling, the LS-4 may be a better choice for
some people.

Of more interest to me, however, is the insurance rates for these
gliders. This is something I'd really like to see a comparison of...

Andreas Maurer wrote:

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.
--

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

While I am an advocate of the "short span" sailplane, I also realize
that what I truly want is the ability to self launch. Unfortunatley,
in my opinion, the short span gliders do not have adequate wing area
to allow for the additional weight a power plant will add.

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.

I believe that 40:1 would be easily achieved, my mission goals would
be a ship that would excel in a climate typical of western Washington,
not looking for a flat out racer, but would rather tailor towards what
I am used to with my Apis 13 while having the ability to self-launch
and retrieve.

What I find encouraging and at the same time deceiving, is that
designing in solids produces very exciting results in a relatively
short time.....but to get from what is on the computer screen to
something you can sit in on the shop floor is another matter entirely!
However that being said.....I do have the ability to create just about
everything required to get the project underway in terms of templates,
parts, etc.......

Cheers,
Brad
N199AK

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