I would expect plywood to by somewhat stronger, that is sort of the point of plywood after all. Just speculating, but I would guess that plywood will be slightly weaker than piece of the same wood bent with the grain but much stronger than the same wood bent across the grain. The overall result would be a generally stronger material.

Traditional boats have been built for a long time with thin pieces of wood. Adirondack Guide Boats were 1/4" thick cedar over ribs spaced every 3 or 4 inches. The cedar did not need any longitudinal reinforcement, it just needed help across the grain.

In a strip-built boat the fiberglass serves the same purpose as the ribs. In a stitch-and-glue boat, the alternating layers of wood serve that purpose.

The people looking to truly optimize the fiberglass/wood ratios should also investigate the orientation of the fiberglass. There would appear to be a lot of room for balancing the strength across the grain with the strength parallel to the grain.

To me the data suggests looking into unidirectional cloth if you are looking to optimize weight and strength. I don't yet see enough of a trend with the data to draw any conclusions regarding what the optimum wood thickness vs glass thickness would be.

: Your explanation makes sense. It brings to mind one additional question:
: Would plywood be more durable than wood strips due to it's alternating
: grain orientation? It would seem from the results of your tests that
: plywood should have a consistent strength in all directions of load, which
: might prevent some types of failures. Then again, is there any real data
: on the types of hull failures that are most common in kayaks? I would
: think that impact punctures are probably the most common and that this is
: where a cross laminated wood layup (like plywood) would be superior.