Funny thing. A man named Geo Calkins (still kicking at 95!) designed and
built a series of boats called Bartenders. Double ended made of Doug Fir
marine plywood. He put fiberglass ONLY on the sides mainly for cosmetics.
The bottoms got bottom paint only and as the paint sloughs off, bare wood
begins to show in spots.
My Bartender was factory built in '69 and has been used as a 4 man charter,
a commercial salmon troller and now a sport fishing boat. It has spent a LOT
of time in the water.
The bottom is still sound!
Gordon

"Klaus" wrote in message
...
Gary, one should never let a plywood hull absorb water if one wants to
keep the boat for a while.
Any wood will expand when it absorbs water, with plywood the waterproof
glue might stop the absorption past the surface veneer layer but I
would not bet on that. Water would readily be absorbed by the end grain
of plywood joins.
My plywood sharpie hull is fully encapsulated with epoxy + glass on the
outside and also paint on both sides. There is nil water absorption.

If your Chris Craft absorbs water you'd better fix that before the boat
rots away.

Klaus

Gary Warner wrote:

I know planked hulls absorb water and expland - do plywood?

How much water are we talking here? A few gallons, tens
of gallons. (22' Chris Craft 1958)

Thanks,
Gary