repair a floor

Question
Ron -
I have a 1987 Searay Seville open bow. I have some rot from the pass through way about 12 inches into the bow and about six inches onto the left side around the ski locker opening.
I have heard that i can use CDX or pressure treated plywood, instead of marine plywood. I have also heard that you can use sealer and varnish instead of fiberglass.
What are your thoughts on those two subjects?

Answer
Hi Bob...Thanks for selecting the undersigned to reply to your question.

Waterproof glue or adheasive material is used to join each laminate of marine plywood. Construction grade or pressure treated plywoods utilize an ordinary adheasive, which is not waterproof, and the laminates will eventually delaminate. The chemical used to pre-treat wood does not penetrate to the ultimate inner core of the material, and on average, it only exists within the first 1/8th of an inch.

Fiberglass consists of two primary substances, first a cloth or woven type of material is used, and second, an epoxy resin (adheasive) binds the fiberglass material to the surface of the plywood. Fiberglass increases the rigidity and strength of the plywood, as well as protecting it from exposure to moisture.

If you prefer to use a sealer and/or varnish on pre-treated plywood, it will not be properly nor adequately absorbed, because of the chemical used to extend the life of the plywood, and to a certain degree, make it somewhat waterproof. Initially, a top coat of varnish will look great, but it just won't last very long, and additional coats will have to be applied, which makes for more work.

So, do it right the first time and avoid unnecessary extra costs. You'll end up with better results that will offer durability, longevity and less maintenance when you use marine grade plywood.

Safe Boating
Ron Blanchet