"Joe Barta" wrote in message
...
todd wrote:

We're in luck. I'm a mechanical engineer who specialized in
materials engineering.

I have a couple questions for you then. Something I always wondered.

Imagine a torsion box, well made with 1/4" ply top and bottom and 1-
1/2" thick. Let's say it's for a shelf 6ft long and 11-1/4" wide. Now
imagine a solid plank, 2x12 construction lumber (not fir). Would you
think the torsion box would be stiffer or would the solid plank be
stiffer?

I would imagine that if one used oak instead of spf, the oak plank
would be stronger than both.

Also, would I be correct in thinking that 2 pieces of 1x12 laminated
together would be stiffer than a solid 2x12? If so, why? (other than
minimizing and spreading out defects, which is pretty obvious)

I know I could probably do some homework and look this stuff up... but
you're here, right?

Tell me about the construction of the insides of the torsion box. The
makeup of the longitudinal pieces will have the greatest effect on
stiffness. I imagine it will be 3/4x1 SPF of some kind.

todd