On Fri, 7 Dec 2007 15:33:51 -0500, "Sal's Dad"
wrote:

Aluminum at 171 lb/cu ft. Divide by (12*8) to get approx. 1.78 lb/SF for
0.125 aluminum.
Plywood (5/8 thickness construction grade) is 1.77 lb/SF (or 34 lb/cu ft)

So I stand corrected. 1/8 aluminum weighs about the same as 5/8 construction
grade ply

I thought a figure was a bit high. It is, slightly, but had I known
the difference was a small as it is[I will take your figures] I don't
think I would have bother to post anything. It did smoke out some
interesting figures. Plywood tends to be about as dense as the wood it
is made from, it seems. The texts seem to give the density of woods in
pounds per cubic foot but with a modern calculator[HP48] any and all
units are convenient.

Casady