CPES and Undercoat

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  • Don Maurer
    Senior Member
    • Jul 1999
    • 543

    CPES and Undercoat

    Okay, I'm about ready to apply the final finish to my boat after 2 years construction. I have waded through all the choices and finally decided to skip epoxy encapsulation. It's a lapstrake plywood boat. The hull is Sapele plywood and hondouras mahogany. I intend to CPES the whole thing and paint the hull inside and out with Kirby's paint. The thwarts, gunwales and sheer strake, transom and trim will all be left bright. My question is whether I should use an undercoat under the Kirby's topcoats, and if so, what undercoater do you recommend? It seems to me that at least some of the effectiveness of the CPES' ability to bond with the paint will be lost if I use an undercoat, especially if most of it gets sanded away anyhow. So, those of you who use CPES, what the best way to obtain a fine finish over CPES?
  • Scott Rosen
    Senior Member
    • Feb 2000
    • 5390

    #2
    Hi Don,

    When I painted my Nutshell, which is plywood lap construction, I started with a couple of coats of CPES, followed by Kirby's primer, followed by Kirby's enamel.

    You could skip the primer, but then the plywood grain would show through the finish coats. I've had excellent adhesion, even on the inside which sometimes collects rain water and sits for week.

    Comment

    • MR. KNOW IT ALL
      Senior Member
      • Nov 2001
      • 1897

      #3
      Don......Remember this post?

      There was some good discussion. You might want to reread this.
      Kevin in Ohio

      Comment

      • Don Maurer
        Senior Member
        • Jul 1999
        • 543

        #4
        Thanks, Kevin. As informitive as that thread was, it really didn't address the question of using undercoater. Thus, my inquiry.

        Comment

        • thechemist
          Senior Member
          • Mar 2000
          • 877

          #5
          Originally posted by Don Maurer:
          Thanks, Kevin. As informitive as that thread was, it really didn't address the question of using undercoater. Thus, my inquiry.
          Undercoaters, sometimes called primers, [an equally multi-definitioned word] have many definitions, related to the various things they do, and why those things are done.

          If you define exactly the purpose(s) you wish your undercoater to fulfill in your particular applications circumstance, then your question can be better answered.

          Comment

          • Don Maurer
            Senior Member
            • Jul 1999
            • 543

            #6
            The reason I would use an undercoater would be to fill the grain and provide a uniform surface for the topcoat.

            Comment

            • thechemist
              Senior Member
              • Mar 2000
              • 877

              #7
              In that case you should probably have two or three coats of Kirby's primer, which I believe will perform the functions you expect of your undercoater, below your topcoat.

              Likely that's where the term "undercoater" came into use.

              Put on two coats, then sand, then put on the third coat and sand again for final leveling.

              If you can have Kirby provide a bit of color-concentrate, you can tint the coats alternate colors. That way, you can tell how far you have sanded, and not go through anywhere.

              Comment

              • paul oman
                .........................
                • Aug 2001
                • 1674

                #8
                Are you sure you want to coat the wood with several coats of epoxy cut nearly 70% with solvents? What's to gain with all those solvents? Consider using a thin epoxy that you've thinned 20-40% with solvent yourself. For the next coat thin the epoxy 10-20%, Then a coat of 0-5% thinned. Use a thin non blushing epoxy (like Low V epoxy). The result will be a 'deep' glass like finish. For the natural wood places, cover the epoxy with several coats of varnish. Paint the other places as you describe. You might consider using a linear polyester polyurethane (algrip is one of these) which is the ultimate brush/spray on durable poly coating.

                regards

                paul oman
                www.epoxyproducts.com/marine.html

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