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George
 
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Angy! Wow great reply!

Ok so why does it strain that way, that is the real question. Why does
it shrink on the outside more than the inside?

The reason I think is this. When I look at a round disk of wood, as its
drying, you can see the darkness change as it dries. It dries faster on
the outside of the disk, than the inside. That's why it splits.

Why does it dry faster on the outside of the disk? Because it has more
surfaces through which to evaporate (i.e. the outer surface, where the
bark may be). The inside part of the disk can only evaporate through
the front of back of the disk. Anyway, the disk does look like its
darker on the inside and dry on the edge, when I look at one, its
fairly obvious.

Well, anyway, that's my hypothesis anyway.

Comments?

Had you read the information in the FPL post, you'd have the answer without
having to hypothesize. And it's not greater surface. The side of a straw
is greater in surface than the walls, but the water runs end to end, anyway.

"With respect to shrinkage characteristics, wood is an anisotropic
material. It shrinks most in the direction of the annual
growth rings (tangentially), about half as much across the
rings (radially), and only slightly along the grain (longitudinally).
The combined effects of radial and tangential
shrinkage can distort the shape of wood pieces because of the
difference in shrinkage and the curvature of annual rings."