Rot Doctor


Subject: Fiberglass boat with questionable stringers.
Date: Fri, 02 Jun 2000

Well my spirits are lifted now that I may have a chance at saving my boat by using your products. I was directed to you by someone trying to be helpful in a question/answer forum in the boatdoctor website. He suggested I check you out and see if you might have the answers I need. Let me describe my situation and hopefully we will come to some viable answers and simple solutions.

About 3 years ago I bought a 1977 Angler fiberglass boat. It’s 21 ft. modified-V hull and it has a 140 hp. Evinrude. I knew it was going to be a handyman special when I bought it and since I’m rather handy, I thought it would be a nice project. Besides, it’s the only way my wife would finally agree to me owning a decent size fishing boat without going into hock for the next decade or so. Well, I got the boat and began by removing the rotted plywood floor which opened another can of worms. The stringers which are nothing more than 1″X lumber that were glassed over, were rather soft, especially the top couple inches where the floor fasteners would penetrate. I haven’t been able to come up with any answers as to whether I can get away with repairing the existing stringers or replacing them completely. I’d rather not get involved with the latter for obvious reasons. I wasn’t sure whether the stringers were a vital part of the hulls overall structural strength or if it was basically something to fasten the floor down too. If they were mainly for fastening the floor down too, I think they would be OK with only minor repairs. The hull design is one that is (stepped) on the sides much like beveled clapboard siding on a house. I assume that is for hull strength and rigidity. The stringers are located directly over top of the strakes on the bottom of the boat. I think that’s what they call the several long flat steps that run the length of the hull. The hull itself appears to be in very good condition with no splits, cracks, gouges or soft areas. It just seemed to me that the hull could withstand a pounding in rough water even with the questionable stringers since most of the rigidness of the stringers comes from the heavy glass matt layers of fiberglass that completely covers them. But then again, I’d hate to find out I was wrong once it was too late!

I hope you can steer me in the right direction. If you have any other questions you certainly may e-mail me.
Looking forward to your response.

Thanks, Bob


Your analysis is fundamentally correct: The wood in the stringers is primarily there as a mold for glass that covers them and for something to fasten the floors to. Most of the strength is in glass and the notched hull underneath. You can in a way count yourself lucky (tell your wife it was your very astute foresight!) that the boat is as old as it is and they put all that glass around the stringers. We have a ’90 23′ Bayliner (not exactly the Cadillac of the glass boating world) and the stringers are there but only chopper-glassed over. If they go, we’re in for a hell of a project. We drive the boat a little but use it mostly for research.

I’m not sure how far you’ve gone with evaluating the stringers, but if the wood inside is reasonably dry, I’d just inject CPES (Clear Penetrating Epoxy Sealer) into the fastener holes to stop the rotting process and restore some substance to the wood inside. If you wanted to be obsessive, you’d follow the CPES after about a week with our Layup & Laminating Resin, which would make things inside hard as iron. The downside to this complete solution is that it would probably take 4–6 quarts of the L&L Resin — which is specific for wood repair — and the stuff ain’t cheap. Personal opinion is you can get by without it, although you will probably need some to flood in the fastener holes so you can get the new floor down. You may also want to push in some Fill-It Epoxy Filler if a grip point is needed.

The new flooring can be made from exterior grade ply. After it is measured out, cut and trimmed and ready for installation, coat it thoroughly with CPES, ESPECIALLY the edges and the end grain areas. Pilot-drill your fastener holes, and then give them a good dabbing with the CPES. Fasten it down and secure. Now, give the top portion another coat of the CPES, give it a day or so to dry, and then come back with outdoor carpeting and outdoor carpeting adhesive and put it down. What you have done here is give yourself a new floor over wood that is almost 100% protected from future rot problems. It’s a lot easier than trying to re-glass the surface. To be done right you would need to use epoxy resin, and, like I said, the stuff ain’t cheap.

So, what do I think you would need to complete this project? I would say start with two of the 2-quart units of the CPES, a 2-pint unit of the L&L Resin, and either a 12 oz or 2-pint unit of the Epoxy Filler. That SHOULD do the trick, but if you run out you’ll just have to re-order.

An additional thought: Keep your eye on your transom. If you ever pull a fastening or the motor or expose the wood core of the transom, saturate the exposed wood with CPES. It’ll cost a little bit for product, but it may save you from having to go through the whole process all over again inside the transom shell.

You’ll have some questions, so feel free to come back. We’ll give you all the help that we can.