Fiberglass over plywood is ridiculously tough. There are wood and fiberglass boats still around after 50 years. However, fiberglass has an Achillis Heel — sunshine. Fiberglass rapidly degrades with exposure to UV rays.
Thus, it is recommended to paint or varnish fiberglass with something offering UV protection.
We wanted the boat to show off it’s lovely woodiness, so we chose varnish. There are fancy marine varnishes that are made for marine applications. Spar Varnish is one example. They are relatively expensive (though not compared to epoxy which is ridiculously expensive). However, there are exterior varnishes that are equally good that you can pick up at the hardware store/lumberyard which are just as good.
In a moment of insecurity, I called and checked in with Gayle at Glen-L just to make sure. She gave me a thumbs up on my selection of exterior UV varnish.
After varnishing, it looked pretty much the same as after the last finish coat of epoxy. But in my mind, I knew I’d protected the fiberglass from it’s Nemesis the big ball of fire in the sky.