: Hi Pete,

: The strength of a piece of wood is not determined by whether it is flat sawn
: or vertical grained but how the grains are oriented over the length of the
: piece of wood itself.

: Think of a piece of wood as being comprised of tubes - like a bundle of
: straws held together with glue. If all the fibers are intact, you have
: maximum strength; as more fibers are cut there are less to support the
: load and more stress is placed on the weaker glue - the strength is
: compromised.

: The limbs on a wood bow a subjected to extreme tension and compression
: stresses. It is critical to make sure that the wood grain is not violated.
: Bow limbs are
: typically made by working starting with a single growth ring for reference
: because this is an easy way to make sure that the rings are intact. Edge
: ring [vertical grain] bows are just as strong - it just takes a bit more
: care to do.

: This discussion has more bearing on making paddles than kayaks. A paddle is
: just like a bow - one launches kayaks, the other arrows. Paying attention
: to the grain pattern on a paddle will allow you to make it stronger for
: less weight.

: Is grain orientation important in strip style construction? Well, yes and no.
: Yes, [perfect] flat grain would theoretically be stronger - but the second
: you began to fair the hull you would start cutting the grain fibers. The
: wood strength is not critical in this type of composite construction
: because the wood serves primarily as core for the fiberglass. The
: fiberglass is the grain - it provides the strength.

: IMHO, edge grain strips are easier to fair, flat sawn have a prettier grain
: pattern.

: Hope this helps.

: Hank

Hi there, Hank.

Thanks for trying, but I may be even more confused. If it's true that:

"[t]he wood strength is not critical in this type of construction construction because the wood serves primarily as core for the fiberglas. The fiberglas is the grain-it provides the strength."

then how do you interpret the clear differences in the strip panel test results where the panels deflected more, and failed at, lower forces when the force was applied parallel to the grain than when applied at right angles? Every other factor was factored out, correct? The only difference was the orientation of the wood grain.

Am I imagining the wrong kind of test machine? I thought the 3-point test machines applied a straight knife-like force to the middle of a test coupon supported at each end. Like if you had an 8'- 2"x4" supported by saw horses 8' apart, and you start stacking bricks on it in the middle.