The Rot Doctor


Subject: Re: Stain and CPES
Date: Sun, 03 Oct 2004


I believe I spoke to you the other day - about my order. Anyway, I forgot to ask for your recommendation concerning using stain and CPES.

I have what is essentially a plywood foredeck on a 1970's - 15' runabout that I am "renovating." "Essentially," meaning it is only about 1/4" thick. The previous owner took pretty good care of the boat and varnished both the top and bottom (underside) of the wood. Bottom has about 2 coats of varnish. But, it is checking now on the top. I plan on stripping the top/exterior, CPESing to prevent checking, staining, epoxying to build depth and UV-Polyurethaning it.

1. What order of the coatings do you recommend?

Stain first, then CPES, then your topcoat polyurethane varnish. I would build my thickness with the UV resistant varnish rather than a thick epoxy as you propose. A little more work, but will last much longer before needing touchup.

2. What about the issue of oil based stains vs water based stains and epoxy. (West is recommending the water based stains for use with their petro-based epoxy.) If water based, do you have a source/brand that you can recommend?

Either can be used. Our chemist prefers oil-based stains. Just be sure to let either dry as recommended before applying the CPES.

3. The varnish on the underside is fine, but I think I would like to add either CPES and/or your layup resin to seal the wood better. But, stripping the underside would be a PIA. Do I dare do so w/o stripping the old varnish? CPES or just the resin?

CPES or Layup & Laminating Resin can be applied to properly prepped varnish. Scuff sand and wipe clean before applying. I probably wouldn't bother. 3 or more coats of varnish should seal the wood fine.

4. What if I decide to add a layer of cloth to the underside to add strength to the 1/4" foredeck? Would I have to strip the varnish then? If not, do I just use the epoxy and cloth, or CPES first?

Technically you would not have to strip to bare wood. You could scuff sand the surface and bond the fiberglass to the varnish. Practically speaking, you would want to strip the wood bare and apply the fiberglass cloth to the bare wood. If you are after a stiffer deck, I would add some ribs to the underside, bonded with epoxy adhesive instead of the fiberglass. This would add far more strength with very little weight compared to fiberglassing the whole thing.


Richard S.

You are welcome. Let me know if you have further questions about this job.