Back in the '80's I owned the second largest contract FRP molding company in Florida.
We made hundreds of hulls and decks for dozens of boat builders - from liferaft containers to 55 ft sailboats. In the good times, when we were smoking along I was buying 10 55 gal. drums of polyester resin a week.
Good times! I sold the business decades ago.
Since then the total number of times I have used polyester resin = 0.
Boatbuilders use polyester because it works well in a E or S glass matrix laid up in a contact mold, and because it's relatively cheap.
Polyester resin is not a glue. Bonds between polyester and plywood will always fail as any Taiwanese boat owner can tell you.
My shop was temperature and humidity controlled. I cringe when I see someone guesstimating the polyester catalyst with a squeeze bottle outdoors.
Use epoxy for every part of your project. The additional cost will end up as a small item in the final bill. It will last a whole lot longer, and you'll sleep better!
This advice is worth what you paid for it, and no doubt other members will have stories about how they have used polyester successfully. Good for them, but I would not buy their boat.
Mike
Palm Coast FL.
*
