Quote Originally Posted by BoKu View Post
I don't think that's exactly true. I'm not an engineer, but I'm pretty sure that the foam is indeed loaded in shear as it reacts lift loads out of the skin and into the spar.
Eh, a little bit, but Mr. Lewis is pretty much correct at least in the case of the blue flotation foam used in the wings, canard and winglets of canard aircraft. Mostly, it's there for ease of fabrication (gives shape without a mold) as well as supporting the skin against sheet buckling.


Quote Originally Posted by BoKu View Post
An engineer like Marc Z. could tell us for sure, and probably exactly how much.
Well, if we had an engineer like Marc Z. hiding somewhere around here, maybe he could tell us for sure (and how much), but thankfully, I know of none. Marc Z. himself, however, cannot tell us for sure (or how much) - only what his understanding of the situation is :-). Which is that the actual shear transferred by the foam is a very small percentage of the total, if even measurable.

However, the facts are clear that composite materials (foam, fiberglass, epoxy) are completely capable materials for the construction of both experimental and certificated aircraft, when designed and used appropriately.