Go here: http://www.boatdesigns.com/products.asp?dept=172

Plywood/epoxy building techniques are highly proven and done correctly you should achieve over 20 years of useable life and then some. The debate still rages on total encapsulation verser just the outside and it comes down to a personal choice. If it were areas I could easily check then I would only do the outside and totally encapsulate in hidden areas, but that is my opinion in a sea of opinions on this subject.

If you choose to do this then shop wisely for epoxy because the prices can vary widely for basically the same formula, i.e. as much as $ 30.00/gallon.