epoxy recoat question

deckhand · Post by **deckhand** » Thu Nov 01, 2007 2:53 am

does epoxy fairing compound NEED to be sanded before you put on another layer or can it just be "scrubbed". My compound has lots of tiny pits and I really don't want to sand it all down. what says you guys.

Post by **Tim** » Thu Nov 01, 2007 6:08 am

Up to the time of full cure (roughly 24 hours), you can achieve a primary bond between layers of epoxy, and therefore can sometimes avoid the need for sanding.

Beyond that, you need to sand since you're dealing with mechanical (secondary) bonds and the quality of the bond is improved by sanding first.

In practice, I rarely, if ever, forgo the sanding step. I don't see how you can really fair a surface without taking down the high spots during a sanding step between coats.

deckhand · Post by **deckhand** » Thu Nov 01, 2007 10:33 am

I made a form and I'm squeegeeing the fairing putty on the boat with a profile shaped pull. the problem is that the putty develops voids and wants to pull itself off the hull. I'm going to give it a light sanding and a wash. Pictures later

Rachel · Post by **Rachel** » Thu Nov 01, 2007 12:25 pm

I don't know about anyone else, but that's a perennial problem for me (fairing trying to drag itself back out of a void). I've experienced the same type of thing while taping wallboard in houses.

One thing I've found that helps, is to use a very flexible applicator, so that you can bend it as you go. What I mean by this is that you flex the applicator (putty knife, or what-have-you) so that you are using the face of the blade more than the "bottom" edge, and so that that face is as parallel to the work surface as possible. More of a squooge/schmear than a scrape. It's like walking on ice wherein you try not to let the surface know that you're actually trying to do something with it.

I'm not sure that's the best way; just what I've come up with.

Rachel

Hirilondë · Post by **Hirilondë** » Thu Nov 01, 2007 7:58 pm

I have done both wallboard compounding and epoxy fairing as well. I'm not sure you need the really flexible spreader, as a matter of fact I like a steel one for both, but the technique Rachel describes works well. Think of it as forcing the goop into the lows as you pass over them.

deckhand · Post by **deckhand** » Thu Nov 01, 2007 11:16 pm

I did just that today. I also made a sharper edge on my spreader. It took a few passes but its now nice and smooth. It'll take minimal sanding to get it perfect. Now its time do do the other side...