The Rot Doctor


Subject: Deteriorating Floors
Date: Fri, 28 Jan 2000

Dear Dr. Rot, We have a 30' C&C Sailboat, 1979 that has the beginnings of a rotting wood problem, can you help?

The mast is stepped on an oak block approx. 8.5" X 4" X 18" which is screwed into three floors that run athwart ship straddling the bilge. These floors are the problem. They are each made of two pieces of 3/4" plywood. They were not encapsulated in fiber glass on all sides just the fore and aft sides. The top side or edge, which the oak block sits on, is open or bare plywood as is the bottom side. These floors are approx. 7" tall and roughly 24" across on the hull to hull dimension. There has been some minor rotting or deterioration of the plywood but nothing real serious. The problem with this design occurs when moisture in the bilge and moisture that runs down the mast keep these floors wet. I have dried out the floors and am wondering if your product would help to restore any of the plywood that has begun to rot and further protect the existing wood that is still ok. Also, would I need to seal the bottom of the floor to prevent the resin from running straight through the plywood? On another subject, the rudder on this boat absorbs water through a small crack on it's top edge. The water runs down the shaft inside the rudder and then tries to exit the rudder at the end of the stainless shaft 12"up from the bottom of the rudder causing a soft spot in the rudder which has begun to crack the surface of the rudder. Can I use your product to seal up this problem?

Thank you for your help.
I found the link to your website on The Good Old Boat Magazine site.

michael f.

The answer to your mast step problem is definitely yes, the CPES will restore strength to the rotted area and prevent moisture from getting into the wood in the future. The CPES is an aggressive penetrant, so if there are cracks going all the way from the top of the plywood to the bottom, it could run all the way through to the bilge if you start treating the top first. My solution would be to treat the bottom side first with several coats over the whole bottom side, and perhaps some more coats to areas that you think might be a problem, toung and groove joints for instance. This will seal the underside, keeping any CPES that you put on the top from running through. Treat the top side with one good coat, with maybe an additional coat on areas right around the mast step.

You didn't tell me what the materials that you were dealing with on the rudder problem are, but unless there is oil or grease in the crack, the CPES will penetrate no matter what the material, and several coats will give a complete seal. Apply to the crack and allow it to wick in, wiping up any excess with dry rags or paper towels. Keep applying and wiping for about 10 -15 minutes, or until the CPES won't go in, or starts to run out the bottom. As the pot life for the first application nears it's end (1-4 hours, depending on temp.) carefully clean up the excess around the crack with solvent. Try not to get any solvent into the crack itself, although it wouldn't be the end of the world if it did. Our epoxy injection kit would be handy here to get just enough CPES right on the crack.