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Bubbles in fillet

PostPosted: Wed Apr 05, 2023 3:24 pm
by slash2
Yeah, another question…

So I’ve had problems in the past with air bubbles popping up when I fiberglass. I think it’s usual due to working while the boat is warming up. So when I went to do the fillets on the keel, I first went in yesterday and filled the stitch holes and any gaps between plywood sheets. I also made a thin coat of plain epoxy over the fillet area hoping that would seal any areas air might escape from. Well I did my fillets this morning and now I see air pockets in it. Yes, we have a bit of a heat wave and it was warming up through the day, but I thought the pre-sealing would help. Evidently not. So is it basically impossible to epoxy while the day is warming?

I’ve never seen bubbles in fillets before…

Re: Bubbles in fillet

PostPosted: Wed Apr 05, 2023 7:39 pm
Weird! I have made two CLC boats, and I never had any trouble with bubbles or outgassing.


Re: Bubbles in fillet

PostPosted: Wed Apr 05, 2023 8:36 pm
by Brent65
I have experienced this on occasion. I would try dipping a tooth pick in alcohol and popping the bubble. If the fillet is wet enough, the epoxy will fill in and close the hole.

Re: Bubbles in fillet

PostPosted: Wed Apr 05, 2023 9:09 pm
by slash2
Yeah- by the time I noticed it, it was firmed up pretty well.

I’ve had continuous trouble with bubbles- though never before in a fillet. Mostly when I’m wetting out the fiberglass. They generally don’t show up immediately, but after an hour or so (when I’m not looking). It was common to see them around brads. It does seem associated with doing epoxy early in the day while things are warming up. That was certainly today. We went from 60 to mid 80s. Going to make it tough when I go to fiberglass the bottom. I know others have mentioned starting in the evening and going late.

Or just stick around and pop bubbles.

Re: Bubbles in fillet

PostPosted: Wed May 24, 2023 7:09 pm
by slash2
I’ve discovered another reason not to epoxy in warming temperatures. I fiberglassed the transom and the first two coats went on well. Temperature was about 65 and the day was starting to warm. The second coat had set up well so I decided to do the third. At the time the temperatures were warming up appreciably but I wasn’t concerned about bubbles as I had two layers on. Put a nice thin coat on and quit for the night. Next day I found terrible drips and runs - real bad. I first thought all the coats must have slumped but it was just the third one. Sanded it down and reapplying the third coat in pretty steady temperatures and it came out great. I think what happened is that as temperature went up the epoxy viscosity went down quicker than it hardened and that caused the runs. I’ve never had an epoxy coat go so wrong, but then I don’t think I have epoxied on such a rapidly warming day.

Anyway, something to keep in mind.

Good side is that I’m getting a sneak peak at the finished boat. The transom looks like it’s been varnished and it looks great!