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#21
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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 |
#22
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#23
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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. |
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