CPES, Epoxy and Fiberglass Questions

I'm new to this forum, but I am looking for "outside" opinions. I'm building a 19' douglas fir plywood sailboat (Weekender design). I am already using Smith Coat Clear Penetrating Epoxy Sealer (CPES) inside and out. This reportedly is made with "natural" wood fibers etc....adding a "flexible" finish. My sources (that are building or have built the same boat) say to fiberglass because the sun will "check" the paint eventually...something about the way the wood is milled or something, the uneven moisture throughout the wood will check the paint if glass cloth isn't used. Others swear by the Smith's Coat and as long as I paint the "half-cured" CPES, it will never check. Both sides of the argument is compelling. Also, I really wanted to epoxy the interior of the boat in order to add a durable finish (in case I drop an anchor or something). But some say the wood wont breathe if moisture gets in...so they recommend not epoxying the interior. If the boat is CPES'd, than is moisture intrusion really an issue here? I just can't get a good consensus of the two above situations. By the way, the doug fir plywood ranges from 1/4 to 1/2 inches thick and it is NOT marine grade. I will be painting the hull with some form of interlux paint, and using epoxy, sand, and paint on the deck (for traction). The boat will probably have very few "bright" areas...due to the plywood construction. Any takers on these questions?

[duluthboats]

CPES, is epoxy with solvents nothing else. It is a good sealer and primer. If I was building a quality boat from quality materials, I would treat all the wood with it.

Fir plywood will check marine grade or not. Even with 6oz glass the grain will print through.

If I was building my first boat I might use house quality lumber. I would also use house quality primer and paint. If I kept it painted and didn’t abuse it, it would last many years but it would check. This comes under the heading of, been there, done that.

Gary

[gonzo]

Fir plywood will always check. The only way to prevent it is to laminate a layer of cloth over it. Wood doesn't need to breath. That is one of those miths with no relation to real life. Fungus and bacteria that deteriorate wood can only live at a limited range of temperature and humidity. If you can keep the wood dry or soaked they can't survive. I assume you want the wood dry, so a layer of 10 to 15 oz cloth will solve the problem. If durability is not a problem, just coat over the epoxy with an enamel.

I've decided to use CPES AND Fiberglass on top of that. That way I have waterproofed wood under fiberglass under paint....sounds pretty watertight/proof to me.

[duluthboats]

Go for it, and post pictures.

Gary