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All Aboard Boats: Antifouling Comparison Part 2 – Creating the Test Panel

The antifouling series continues with steps for making a test panel of fiberglass-encapsulated plywood.

June 14, 2010
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To compare the performance of Interlux Pacifica Plus, Pettit Hydrocoat and Easy-On Bottom Wax, I made a test panel of fiberglass-encapsulated plywood, replicating the myriad of boat transoms on the water. Even if you aren’t interested in bottom paint, it serves as a quick and dirty fiberglass repair tutorial. Here it is in detail.

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•Step I: I pre-coated a 1-by-3-foot piece of half-inch marine plywood with catalyzed polyester resin. If you don’t pre-coat wood with resin, when you apply the cloth, the wood will suck away the resin applied to the cloth and hinder adhesion, resulting in resin starvation, aka “never bond.”

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•Step II: After about 15 minutes, once the resin “kicked” and got a little tacky, I rolled a layer of biaxial cloth that I had wrapped around a dowel onto the panel. I then brushed on more resin — just enough to make the cloth go translucent, with no white spots showing. After this coat cured, I applied two more coats of catalyzed resin to fill the weave of the cloth.

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•Step III: Since I used a roller to smooth on a piece of 6-mil greenhouse plastic (available at hardware stores) on top of the last coat of resin, I didn’t have much sanding to do. Once the resin cured, I peeled off the plastic sheet, gave the panel a few swipes with some 120-grit paper on a block and then applied gelcoat using a Preval sprayer. I’ve been using these handy aerosol sprayers for all sorts of repair projects for decades. They are cheap and work well. Gelcoat was applied to a 20-mil wet film thickness, which is typical for production boats. How do I know how thick the film is? I have a film thickness gauge — doesn’t everybody? — which I will describe in a subsequent post.

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•Step IV: When the gel cured, I divided the panel in three using masking tape. Each 1-by-1-foot square will get the manufacturer-recommended number of coats and film thickness, as measured by my trusty wet-film thickness gauge.

In Part Three I’ll discuss the application of each product and how each differs with respect to ease of use, re-coat times and times to launch, plus some subjective musings from an experienced user of marine coatings. (That would be me.)

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Click Here for Part 2
Click Here for Part 3
Click Here for Part 4
Click Here for Part 4a
Click Here for Part 5
Click Here for Part 6
Click Here for Part 7

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