On Sep 10, 10:00 am, "Toller" wrote:
What is the story on plywood? Is nothing suitable for marine use without
being fiberglassed?

As others have pointed out, you have to be careful fiberglassing
plywood.
I build driftboats with marine fir and/or mahogany, covered with
glass.
But only for sides and seats. For the bottoms I use a plastic
honeycomb
core from Nida Core or Plascore. Plywood that stays in contact with
the water will eventually get nicked or dinged. Water will migrate
into
the plywood and then you're toast--well, soggy french toast maybe.
At that point you have to grind off the fiberglass and move to Arizona
for a month or two.

You could make your rudder with 3/4" Plascore, stiffened up with
glass on both sides, with puttied and taped edges. It's a quick and
easy way to
make lightweight, stiff, water proof parts.