Epoxy issue

Problems, how to use. Also see: "EPOXY", in the left-hand column of the Home page.

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SamsBoat
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Joined: Fri Oct 16, 2015 12:08 pm
Location: Florida

Epoxy issue

Postby SamsBoat » Mon Sep 05, 2016 7:18 pm

An epoxy question. We have several thin coats of epoxy resin on the boat including a base layer of fiberglass which all went on very smoothly. This last layer reacted oddly. After sanding the bottom and side down with a 200 grit paper, and vacuuming and wiping clean several times with damp cloths we applied another coat. The epoxy appeared to lay down normally. However when it dried there are very small areas where the resin appears to have beaded up, (see the attached photo.) For the most part this happened only on the bottom of the boat. There are a few similar spots on the sides but really not noticeable and again very very few. All of the coats were done within 24-hours of one another with the exception of this one which was probably 7 or more days. It’s warm here of course being Florida but this particular day was quite a bit cooler than the others, in the low 90’s. I’m using Silver Tip with the slow hardener.

Any thoughts on why this layer reacted this way? Any fix for it? Thank you.
Attachments
overall_view.jpg
detail_boat_bottom.jpg

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billy c
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Re: Epoxy issue

Postby billy c » Tue Sep 06, 2016 4:34 am

...from the System three epoxy book
"Sometimes a coating will try to crater. This is most common with recoated surfaces that have been sanded, but may happen on other surfaces as well. While the cause of cratering is quite complex, the solution is pretty simple. Immediately after coating a surface look at it from an angle, sweeping your eyes over the whole surface. Craters will usually form within ten minutes after first applying the coating. Take the heel of the foam roller and really grind it in the area that has cratered. This wets out the dry spots in the crater center. Then, re-roll the area treated to even out the coating."
(insert Witty phrase here)
Billy's Belle Isle website

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Roberta
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Re: Epoxy issue

Postby Roberta » Tue Sep 06, 2016 4:45 am

What Billy relayed plus, sometimes sandpaper gets clogged and becomes more like a finer grit, giving you a smoother surface than desired for recoating. When coating within 24 hrs, you get a good chemical bond. After that, you rely on a mechanical bond, so the surface needs to be rough enough for the coating to bite into the subsequent coats.

Also, it helps to clean the surface prior to sanding so you don't imbed impurities into the surface when sanding. Then clean again before coating.

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

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vupilot
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Re: Epoxy issue

Postby vupilot » Tue Sep 06, 2016 7:21 am

Pretty common, I got the same with another brand of epoxy, Chalked it up to some type of contaminant, I just sanded down and recoated the small area, took a couple coats, then sanded to blend and smooth the epoxy into the surrounding area and moved on.

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Bill Edmundson
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Re: Epoxy issue

Postby Bill Edmundson » Tue Sep 06, 2016 7:43 am

I had it happen on the cockpit sole with MAS. Cleaned it, light sanding, cleaned it, and recoat. I could find it now. But, you would really have to look for it.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build


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