"Richard Riley" wrote in message
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snip
As always, RSH is right. The proof is in the pudding. Or in the
putting in this case, of a large number of bags full of lead weights.

The calculations for a composite wing are possible, but orders of
magnitude more complex than an aluminum one. And the final product is
so sensitive to building technique that the calcs are just a place to
start for ordering your lead weights.

The plane I'm working on right now is a single surface sail wing.
(Coincidentally, for those of you who work for Ma Boeing - know who
got the patent on the sail wing? Phill Condit.)

Some of the loads - like those on the lift strut - are
straightforward. But the horizontal bending on the front and aft spar
are infinitely beyond me. And the structures guy I dug up at work
said it would take him months. The way to test it? Put it on a truck
and run it down the road till you hit 4 G's.

I think the number of builders that would do something smart with
those calcs is smaller than the number of builders that would do
something dumb. And both groups combined are vastly smaller than the
rest, who wouldn't do anything with them.

If you want to know how strong *your* airplane is, with all your
(inevitable) building imperfections. proof load it.

So, are you gonna build the truck, or contract with one of the hang glider
manufacturers that already have the instrumentation? (and the Nitrous
injection to get everything up to 80 mph).

Tim Ward