BoatworksToday · video

What this video covers

Polyester gel coat applied to a boat transom failed to cure, leaving a tacky, unworkable surface that gummed up sandpaper.1:47 Troubleshooting revealed the issue was not expired gel coat or catalyst, but insufficient film thickness caused by using a thick-nap roller.5:10 Polyester resins require a minimum film thickness of approximately 20 mils to cure properly; the heavy-nap roller spread the material too thinly to fill the texture of the 1708 fiberglass cloth.6:37 To resolve the failure, the surface was cleaned with a dedicated de-waxer—as acetone does not effectively remove wax—and recoated with a fresh, thicker layer of gel coat applied with a short-nap mohair roller.10:55 Testing confirmed that applying the material more liberally allowed it to cure fully.14:33 The primary takeaway is that gel coat application requires a short-nap roller or brush to ensure adequate thickness, and any questionable materials should be verified with a small test batch before application to the boat.

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