PocketShip.net

When I was removing the masking tape that I used to help in fillet cleanup there are places where the tape pulled up a thin layer of epoxy from the side panels that have been fiberglassed and sanded. You can peel it off much like peeling off the thin layers of an onionskin. The remaining fiberglass appears structurally sound. I searched on the web but couldn't find any help on the subject. The side panels were done outside in the garage. Is it possible the last coat of epoxy did not cure enough in cooler weather before I sanded? Other fiberglassing that I did indoors (rudder, centerboard trunk, centerboard) are fine. Being a novice fiberglasser I am anxious to find a solution and to make sure it does not happen again. I am assuming it is not something I should ignore in order to make sure additional layers of fiberglass and paint adhere properly.

What brand of epoxy are you using?

MAS epoxy. I used a roller for 3 coats after using a squeegee to wet-out the glass.

how long did you wait between coats? did you sand at all between coats? I'm by no means an expert but it sounds like an issue of 2 coats not bonding to each other. So my guess is that you waited too long between coats and didn't sand. If you recoat within a day you don't need to sand, but if you wait longer you should scuff up the previous coat for better adhesion. Does this sound possible?

The coats were done within 24 hours, sometimes the same day. I'm wondering if some overzealous sanding before the last coat was fully cured is the problem and weakened that coat. I found a blog where someone had epoxy flaking off a kayak from a vibrating saber saw. I guess the big question is what is the solution. Not all parts of the side panels are equally affected. Right now I am thinking I should peel/scrape off the worst areas; give the panels a light sand and recoat. Or since I put on 3 fill coats and not just 2, peel off the bad sections, and just resand the side panels in preparation for painting.

>>>>Not all parts of the side panels are equally affected.

Hard to say without a close inspection, but I'd bet my beer that the next-to-last coat of epoxy was a bad mix, or there was surface contamination before the last coat. Surface contamination can come from a lot of things. A wipe-down with a rag that has fabric softener or grease in it; a microscopic rain of silicone lubricant from an overhead garage door; a heavy falling dew just before the last coat of epoxy; use of a solvent other than denatured alcohol or lacquer thinner. Really no way to back out of that except to sand off the bad areas.

We've ALL done bad mixes, where the ratio of resin-to-hardener is off somehow. If it's off just a little, sometimes the thorough application of heat will kick off the bad stuff. (Put a space heater in the bilge, pull a tarp over the hull, and let it bake at 100 degrees F for 36 hours or so.) If the mix is off enough, heat won't help, though. USUALLY, though, a second, properly-activated coat will kick off the bad one and you can keep moving. Doesn't sound like that's the case.

I've had every one of these happen to me. Multiple times. You work through it. It's part of the adventure.

I think there was a drizzle of rain and it was damp when the last coat was applied so the surface contamination seems plausible. The problem actually reminds me of when we had some so called professional student painters paint our soffits when it was wet outside. A year later you could peel the paint off in foot long sections.
Thanks, it's great to have this forum to aid this newbie boat builder.
The Pocketship project has been an enjoyable and rewarding adventure so far; people are intrigued by the whole process, and I have even had strangers stop by and visit to see what I am working on in the garage.