: Hey, Sam-

: I agree, with an important caveat: The failure will initiate and propogate
: through the wood IF the glue joint is a good one.

: From a wood technology standpoint, a good glue joint requires two things: a
: mechanically coplanar and fresh (not oxidized) surface, and 100-250 psi
: clamping pressure. So, if these conditions are met (B&C or planed edge),
: there will be a strong glue joint that will not fail prior to wood fiber
: failure.

: Clamping pressure is not a problem for strips : duct tape, bungees, whatever-
: it doesn't take much to develop 200 psi along a 1/4-1/8 inch thick piece
: of wood.

: But as far as B&C or planed joints, I'll revert to woodworking to analyze.
: When gluing up a table top or cutting board, a good way is with a freshly
: hand planed or machine jointed surface. Any alignment dowels or biscuits
: should not be glued, and the flat, planar surface will glue better than a
: tongue and groove or other fancy joint. The T&G prevents the generation of
: the clamping pressure (due to gaps) required for an optimum joint. (Glue
: does not have much strength across gaps) And, of course, it takes some
: mondo clamping to develop that pressure.

: This was also my experience with strips: due to tiny amounts of tearout while
: milling the B&C joints, I had more gaps than with the hand-planed edges.
: More gaps equals less strength.

: Of course, this is not important because epoxy and glass save the day.

: If, however, one desires to shift some of the structural resposibility for
: the boat's seaworthiness from glass to wood, then methinks that
: eliminating gaps might be a happy thing.
: Mike

Mike,

You’re right, if the glue line isn’t sound, then it doesn’t matter what the shape of the surface is. And I agree with your analysis based on sound wood working practice. So allow me to modify my previous post: When building a cedar strip boat, it doesn’t matter - C&B or plane edge, failure will propagate through the wood.

For folks like you, who use strong hardwoods, more attention to the wood bond lines may be a good idea. If one really wanted to get the most from a hardwood glue joint, slightly thickened epoxy would be a good choice. In that case, the joint geometry and clamping pressure would be of little importance.

Cheers,
Sam