Effect of CPES on wood's reserve buoyancy

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Effect of CPES on wood's reserve buoyancy

Post by Locutus »

I expect this would apply mainly to plywood but may have a significant affect on veneer cold molded hulls as well. I'm curious about how much penetrating epoxy affects the reserve buoyancy of the wood it is applied to, and whether there is a way to way to quantitatively measure this.

I assume that wood, which is a porous material, gets some of its reserve buoyancy from the pores themselves, since they are essentially microscopic empty spaces. I further assume that penetrating epoxy works its penetrating magic through capillary action, filling the spaces of the pores. The third assumption I'm making is that solid epoxy is somewhat heavier than water, just like a fiberglass hull is.

Let's say that you apply a couple coats of CPES to both the inside and outside of a hull made of 3/8" Okoume plywood. If the CPES effectively penetrates 1/8" deep into the plywood, since both sides are coated that leaves only 1/3 of the plywood left with empty pore space. If the CPES and subsequent fiberglass coating plus paint is also sufficiently heavier than the untreated wood, there may be no reserve buoyancy left to the wood after treatment.

Of course at this point I don't know how deeply the CPES will penetrate a given wood, nor do I know whether or by how much the cured CPES is heavier than an equivalent volume of untreated wood. But if one is calculating the total reserve buoyancy of a finished boat with sealed chambers and foam, it seems to me that it would be important to include an accurate calculation of the hull material's reserve buoyancy after sealing with CPES, as well as the addition of a fiberglass skin and paint.

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Re: Effect of CPES on wood's reserve buoyancy

Post by Bill Edmundson »


I did some test on new plywood. CPES only had very slightly more penetration than straight epoxy. It is probably a much better product on bad wood/rot. My personal opinion, on new wood, is it's a waste of time and money. I don't know about Total Boat, I have some that I haven't tried. Smith's stinks to high heaven!

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Re: Effect of CPES on wood's reserve buoyancy

Post by hoodman »

I doubt that CPES can penetrate much beyond the face ply of the plywood. There's no way it will penetrate 1/8" in new wood.

Testing the assumption that epoxy sinks, I did a little test. Two pucks of cured epoxy, one thickened with wood flour and the other unthickened but full of tiny air bubbles. Both sink.

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