Jo wrote:Looking under the trailer, I can see that the marine grade plywood has no protection.
What do you suggest to protect it?
I am going to go against the conventional wisdom here, and say that you should leave it bare like the factory did.
When I was picking up my trailer, I asked the dealer what he recommended I use to seal the underside of the plywood. He said that the factory uses latex paint on the interior side, and left the underside bare for a reason. Plywood needs to breathe, and sealing both sides stops it from breathing and makes it rot quicker. He even went on to say that just about every CT that he's seen with a rotted deck was because the owner added extra sealer trying to prevent it from rotting!
So, even though it goes against my own common sense, I'm going to leave mine bare and let it breathe. I figure if it does rot, I'll make an improvement and put in an upgraded all aluminum deck that will never rot again.....