"frank1492" wrote in message
...

I have an old plywood rowboat which periodically is repaired with
fiberglass cloth. This has worked very welll- the boat is now about 70
years old! . . .
For years it has seemed to me that painting the entire bottom with
fiberglass resin (no cloth) would make an extremely durable and
water-resistant primer, to be painted over with polyurethane marine
paint.

After being patched with fibreglass, no wood boat maintains its
antique value (if any.) Main considerations seem to be:
1. Total weight of a boat with resin skin
2. Possible effects of the resin on the adhesive holding
together the wood plies (and no plywood glue made 70
years ago was expected to last long in a wet environment.)
So long as the resin skin were perfect, you might be OK.
Any scrape or imperfection might fatally weaken the whole.

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)