'Nother PW-5/World Class question

On Fri, 28 Nov 2003 23:18:07 +1300, Bruce Hoult
wrote:


The PW-5 wings are like feathers compared to anything else I've rigged.


I rigged the prototype of the Russia-1 - at 11 meters span (L/D of 27
iirc) each wing had a weight of 22 kg. Now this is what I'd call
feather weight...

The test pilot Yuri Kuznezov displayed some nice aerobatics to
convince us that the wings were string enough before we took flights.


Bye
Andreas

On 27 Nov 2003 23:23:56 -0800, (Marcel
Duenner) wrote:


The last LS4s built by Schneider costed about 15% less than an LS8.
Take production to Lithuania and cut another 10-15%.
Your new LS4-WC price is still double the PW5's! Talking of prices ex
works. Of course, shipping overeas will cost about the same.

Of course, you are correct. But let's face it: The PW-5 is a little
smaller (very little) than the LS-4...but this is the only difference
(if you build an LS-4 with fixed gear, no water bags and similar
finish). I still see no cause why workers with the same wages would
make an LS-4 a lot more expensive.


Saving money by having a fixed gear - I don't know. Might save
3000Euros or so but also costs 2 points L/D. I think the original idea
of choosing the LS4 was to have a WC with 40/1.

I don't think the L/D is the critical part - it's the acceptance of
clubs to use such an aircraft as a trainer (and create the numbers of
aircraft and pilots) - and an LS-4 would definitely be accepted.
The manufacturer might sell the retracting gear as an option (like it
was done for the DG-300 Club for some years) - but to cut costs a
fixed gear is essential imho.


Save money on the finish? Please! Anyone competing seriously will have
it re-sanded and polished - so what's the point?

If you want to save the money - do the finish yourself... or fly with
the defaut finish. I saw one of the earlier PW-5's... and the finish
was absolutely horrible. But the PW-5 was cheap. Guess why.



Bye
Andreas

Andreas Maurer wrote:

I fail completely to understand why a smaller span (and crippled
performance) should lower production costs significantly. Why no
outgrown glider with up-to-date performance?

Changing wing span to, say, 14 meters will cost about 5 points of L/D,
and I doubt that it will save more than $500 (slightly less material
needed, and three man-hours saved for finish).

There's design, and then there is design for manufacture. If you look at
models for manufacturing costs of things, airplanes included, the
biggest factors are the choice of materials, the mass of whatever it is
you are making, and the complexity. The big things that affect
complexity are parts count and the ease/difficulty of working with the
material. Drops in parts count can have *big* impact on touch labor.
Think fixed wheels, for example.

After that, there are big learning curves for how many you make, with
the cost per unit dropping significantly. Aerospace thingies typically
have about an 80% learning curve, which means each time you double the
number of things you make, you drop the cost of manufacture by 80%. So
if it costs $10K to make the 20th plane, it will cost $8K to make 40th.
That's not saying the manufacture will pass on the savings, of course.

There are probably enough gliders out there against which to do build a
semblance of a cost models for gliders.