Jay wrote:

It would appear that 2 short wings can be built lighter
than one long one since the moment arm is half as long
for the shorter wing pair.

There are a lot of benefits to higher aspect ratio
wings that far outweigh the structural advantage of low AR
wings. Reduced drag is but one. Ever wonder why you
don't see any biplane sailplanes?

You'd have a more compact airplane that way with less
weight that had the same drag as an equal wing area monoplane.

'Fast' and 'biplane' just don't go together. Fast "biplanes"(*)
like the Quickie, Mong, etc. do not get their speed and low
drag from the fact that they have two wings, but rather in
spite of it. Induced drag decreases as aspect ratio increases,
so a longer span wing of equivalent area and wing section will
have less induced drag than two wings with a lower AR. Two wings
will also have at least double the interference drag of one,
regardless of whether or not they use interplane struts.

Dave 'dragster' Hyde


(*) Jay has already stated that he knows the
Quickie is not a true biplane. The same principles apply, however.