Quote:
Originally Posted by Kutscha
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The weight of the balsa sandwich is about right, but the aluminium calculation is 10x out. Should be 9.1lb. And you are not calculating like with like or calculating what was available in 1940. Aluminium composites were not in use. Wood composites were. An unstiffened sheet of aluminium that size 1/16" thick would weigh 9.5 lb by itself.
The ratio also changes if you make the plywood thinner and the balsa thicker. For example 1/16" ply and 1/2" balsa comes out to about 8lb and is probably stronger.
Today, if you want to go really light, you use epoxy graphite with a protective surface of Kevlar against impact damage.