"Duane Bozarth" wrote in message
...
Leon wrote:

"BobN" wrote in message
oups.com...
You can try the "sagulator" - a calculator for determining wood
deflection. For your dimensions (36x22), red oak sagged .04". They
didn't have oak plywood. Maybe someone can tell us how oak plywood
compares to solid oak strength-wise.

Here's the URL for the calculator:
http://www.woodbin.com/calcs/sagulator.htm

...bob

IIRC that is for solid wood, not plywood.

Correct, but follow the link I posted--their testing indicated on the
order of a 20% or so discrepancy from solid material on a quick
perusal...

Duane, from an engineering point of view if you take a xsection of a piece
of plywood and assume the center ply to be the neutral axis [ the axis about
which the plywood bends ] and then consider the plywood sheet as a simple
beam then each of the plies running the same direction as the center ply
will contribute to the bending strength.per the "engineers simple beam
bending theory"
The cross plies will contribute little to the bending strength directly, but
indirectley they separate by varing degrees the contributing plies from
the neutral axis there by acting as webs and allowing the contributing plies
to act as caps . So in my view even though the separation is small some
additional bending strengthis should be added.......mjh