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View Full Version : Sanding epoxy before painting - seal? prime? just paint?



tim_r
09-12-2007, 06:25 AM
Hi all,

Another newbie question, but I've never 'glassed anything in my life before this.

The glass is down and covered in 3 layers of epoxy. I've got some runs that I need to sand out before painting (actually many runs - first boat!). After sanding, do I need to do something to prep the epoxy before applying the paint?

Thanks,
Tim

JimD
09-12-2007, 06:29 AM
Sanding is the usual prep for painting. But wash off any possible blush before you sand. Ideally, you will sand off all glossy surface to the epoxy before painting. Most paint seems to stick very well to sanded epoxy without primer.

tim_r
09-12-2007, 06:30 AM
Great Jim, just the information I was looking for.
Tim

JimD
09-12-2007, 06:33 AM
You're welcome, Tim. See this current thread for a few more thoughts on painting: http://www.woodenboatvb.com/vbulletin/upload/showthread.php?t=69700

Eric D
09-12-2007, 10:54 AM
Hi all,
I've got some runs that I need to sand out before painting (actually many runs - first boat!).

Another thing to try is to use a heat gun and a scraper to remove the bulk of the run/gloop first. Then sand, otherwise you may end up with a dished out area on both sides of the sand job and affect your fairing job later even more. Just another fly in the ointment for you to think about.

Ron Paro
09-12-2007, 11:07 AM
The primer is not to improve 'stickability' of the top coat. It is used when a very smooth finish is desired. Theoretically, you could sand the epoxy to the same level of smoothnes as the primer, but what the primer does is allows you to see the imperfections in the epoxy coat that you may not have seen before sanding the primer.

Here are a few shots of my skiff. The first one shows the primer coat prior to sanding, the second one is the hull after sanding the primer. The next one is the result of the extra effort. http://jimmyskiff.blogspot.com

http://bp0.blogger.com/_XuaT2XHyCMw/RmOHgOE3jbI/AAAAAAAAASM/Xy5LHQ7KHa0/s200/IMG_3194.JPG http://bp2.blogger.com/_XuaT2XHyCMw/RmOHguE3jeI/AAAAAAAAASk/SlS2--mZ8nQ/s200/IMG_3211.JPG http://birdsbloomsandbutterflies.com/JSimages/JS%20First%20Launch.jpg

Uncle Braddah
09-13-2007, 10:18 PM
I have put microballons mixed with q-cel and epoxy, as a fairing material(to deal with drips)applied with a drywall spatula blade then sanded it down. Next Im going to use a barrier coat sealing primer such as Corlar. Then Ii will apply the bottom paint.

Klaus
09-14-2007, 07:52 AM
Another thing to try is to use a heat gun and a scraper to remove the bulk of the run/gloop first. Then sand, otherwise you may end up with a dished out area on both sides of the sand job and affect your fairing job later even more. Just another fly in the ointment for you to think about.

In my experience, using a heat gun on an epoxy surface that has glass cloth embedded (I think that's what the OP said) is not a good idea. For removing epoxy globs on just wood, the heat gun method is perfect. But if you try that trick on a glassed surface it may lift off glass strands and look worse than the runs after you finished getting them off.
Klaus

Pericles
09-14-2007, 08:17 AM
Amazing how long new ideas take to be employed. Here's the way to do it.

http://duckworksmagazine.com/03/r/articles/glass/bottom.htm

Pericles

JimD
09-14-2007, 09:20 AM
Amazing how long new ideas take to be employed. Here's the way to do it.

http://duckworksmagazine.com/03/r/articles/glass/bottom.htm

Pericles

I agree that is one way to do it and I'm sure very effective in the situation illustrated. But not necessarily the way to do it under all circumstances. Good grist for the mill, though. Thanks for the link.

Keith Wilson
09-14-2007, 09:41 AM
WOW! Now that's an excellent idea, at least for surfaces on which you can lay a flat sheet of film. Won't work on round-bilged hulls, though.

Thorne
09-14-2007, 09:50 AM
Try scrapeing the runs before sanding.

What paint? At least one brand/type isn't recommended for use over epoxy directly, but most go on just fine.