Monday Answer
Sepelle is plywood for those folks who like to keep things for a long time--even a generation or two (or more!). It is similar to Meranti plywood, but has a tighter grain, and a darker, more consistent color. When finished with epoxy, top coated with varnish, the texture of the wood doesn't generally show on the finish, like it might with Meranti. It is denser than Fir or Meranti, which makes it a little heavier; the thickness of this plywood is measured in millimeters, so 1/4" is really 6 mm. (a hair thicker than actual 1/4"). Yet it has five veneers (just like Meranti) rather than Fir plywood, which has three. It has no, zero, voids or football shaped patches. According to Greg Boats of Portland Oregon (maker of wooden driftboats) it is as near perfect plywood as can be got. However, it may be three times as expensive as fir plywood of the same relative thickness.
The two wreckers of plywood I was looking for for boats that lead to delaminating damage are sunlight and mold--both are virtually impossible to escape if you are into boating. Of course bad glue in the laminations and at joints enters massively into the mix, but it seems that the most minor of scratches opens the door for irreversible damage once sun and mold damage has begun. Like rust it never sleeps and tiny webs caused by exposure and contact weave their way below the finish surface to weaken the structure. The best one can do is monitor the deterioration and then decide how far to go to get back to an acceptable level to maintain structural integrity.
With a boat there is no free lunch. Fiberglas solves some of the problems of wood, but it comes with a set of trade offs all its own. No matter which you choose, wood or Fiberglas, much of the literature reads as a losing proposition. The solace for the boat owner is great fun while its fun, satisfaction if building it, and an acceptance of maintenance at all times.
