Quote Originally Posted by mquast200 View Post
That's what it's called Cajun secret. It doesn't look that hard the hardest part looks like finding material. Marine plywood is almost impossible to find around here. If you do find it , it's pretty expensive.

If you can get marine plywood, you'll find it easier to work with and better in the long run.

Exterior ply works, but both pine and fir ply will check over time. And that requires some maintenance to cure or it must be covered in fiberglass cloth. Pure epoxy isn't enough to prevent checking.

I'm building a small boat this summer, and I'll use Integraply underlayment in 1.4 inch. This stuff, like most underlayment, uses exterior glue. It's a hardwood, so it should not check like the fir or pine. Plus, the website says it passes the "two-hour boil test." That is where a small piece is chucked into water and boiled for two hours. Most boat sites say a one-hour test is enough to prove that a suspicious plywood is good enough for boats.