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Old 10-10-2012, 12:38 PM   #109 (permalink)
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Originally Posted by JRP3 View Post
It's not as easy to sand as regular polyester bondo, if it's just a thin layer to be sanded down for cosmetics I'm not sure I'd bother to use epoxy resin and silica/microbaloon.
I'll agree about the ease of sanding with polyester, but I've developed a tendency over the years to prefer to stay with one resin system on a given job. I don't use polyester at all anymore, so epoxy is a given for me. I just wanted to point out that it was fairly trivial to make epoxy fairing compound as long as the resin is handy.

That said, I don't see why not to use regular bondo, as long as there's enough post-cure time on the sanded/peel-ply finished epoxy for the excess amine to blush out and get washed off prior to using to polyester. Peel ply is a real finishing problem-solver. Make sure the peel ply extends well past the edge of your layup so it's easy to grab and start pulling. Easier to peel off when the resin is still green, but not too difficult even after full cure - waiting to full cure will resolve amine blush issues as well. Post-curing in a heat tent or out in the sun (120-130F part temperature) for 4-8 hours will make it work even better and ensure best possible amine crosslinking prior to peeling and finishing.

As for applying the cloth over pre-wetted foam, I usually lay it out dry, cut and mark as necessary, roll it up, wet the foam, and then unroll it. It's more difficult to get set right the first try, and extra hands are nice to have, but it tends to wet through better and stays in place better than when I'm wetting through the cloth first. YMMV, and experimentation is your best buddy.

Gojo Natural Orange Pumice Hand Cleaner does a great job of isolating uncured epoxy and making little tiny balls out of it - perfect for getting those little bits off your skin and out of your hair.

I just love all this composites stuff, and hope you're having fun too! Can't wait to read the numbers at the end!

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