"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?

Depends on what sort of plywood it is.
Likely to be close. But make the box 2" thick and it will win. 3" and the
plank has no chance.

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)

No, it would be the same unless you had trouble finding 2x without splits
and things.

j