You would have thought this was easy to get information about but all
I can find is repetitive waffling telling me what I already know but
no actual comparative figures.
I (think I) know as follows:-
Timber is somewhat stronger lengthwise than plywood for bending
Plywood is much stronger than timber across the grain
OSB is probably similar to plywood (but how close is it?)
I actually found one bit of quantitative information on this:-
https://www.fpl.fs.usda.gov/documnts/fpltn/fpltn-131-1952.pdf
... dated 1952! Has no one bothered since then? :-) The trouble is
that it compares 'ordinary wood' with 3-ply plywood which isn't what
one tends to get nowadays. I'm specifically interested in comparing
'ordinary' planks with 7-ply plywood (that's 5 + 2 thin veneers) so
the above probably isn't very accurate. My (modern) plywood probably
isn't so close to ordinary planks but is likely to be similar strength
in both directions.
I can find no actual values for the relative strength of OSB (sterling
board) compared with plywood or ordinary planks.
What I **really** want to know is how much stronger ordinary timber is
than comparable thickness plywood or OSB. It would also be quite good
to know how much stiffer it is (not quite the same thing) but that's
probably a bit less important.
This doesn't have to be accurate to the n'th degree, but I do want
some sort of quantitive indication, like is ordinary wood twice as
strong as plywood and OSB, or only 10% stronger, or what? (OK, there's
lots of variables but the US Forest Service managed the sort of thing
I wanted back in 1952!)
--
Chris Green
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