The Rot Doctor


Subject: plywood hull restoration
Date: Sat, 11 Jan 2003


I've taken the outside of my 24' Oregon Dory down to bare plywood. The wood was very dry from being stored inside for 25 years, but I didn't find any rot. I've applied two coats of CPES, caulked the seams with Dymonic® FC, filled the nail marks and voids with Fill-It, and painted it with two coats of Uniflex 225*. I'm very pleased with with your products. A piece of angle iron on a dock gouged the side of the hull about 3/16" deep and 2"s long and it didn't break that paint. Anyway I'd like to do what I can to protect the inside of the hull, especially under the floor boards. All it's ever had applied to it is oil. I think it was a mixture of Watkin's and linseed oil. If I sand it down some and wipe off as much oil as possible can I apply CPES? caulk the joints? paint? Hopefully there will be a lot of fish guts, slime, seaweed, etc. getting washed down regularly.


If water will absorb into the wood on the interior, so will CPES. So if it passes this test, go ahead and seal the inside as you suggest. Many people will tell you not to seal both the inside and the outside of the boat. They recommend that you leave one side (the inside) semi-permeable, so that moisture can move out of the wood and you don't get a buildup of moisture in the wood. This is what often happens to fiberglass boats. Water gets past the 'glass, and can't get out, accelerating the decay of the wood.

Generally, I agree with this philosophy of sealing only the outside of the boat, and leaving the inside so that it can breathe somewhat. If you want to seal the inside, there are two things that are critical to success. One, to have the wood really dry, you've already done. The second is to do a good job sealing the wood, and check the seal periodically to make sure that it stays intact. On fiberglass boats it is common for the manufacturer to drill drain holes through the fiberglass encapsulated wood, and then never seal them. Also, when deck fittings are mounted, the bedding compound is either poorly applied, or breaks down over time, allowing water into the wood. If you seal the inside well, and check the corners and seams as often as necessary, repairing any cracks quickly, I think that it would be fine to seal the inside of the boat.


* Since Uniflex 255 Aliphatic is no longer available, we suggest our Elasta-Tuff™ 6000-AL-HS instead.