assuming you are using the MAS no-blush epoxy (what CLC sells)....no prep necessary. but you have to wait until the first coat kicks and is at least 'plasticy'  (usually around 5 to 8 hours on a warm day..

if it is 'gelly'....you may accidently move the cloth when you try to put another coat of epoxy on. 

hope that helps.

h

   Thanks h. Its just a little confusing since the manual says to sand in between epoxy coats when pre-coating before assembly.  So thought sanding was a "must do".  Sounds like it would be better to re-coat before full cure though.

Rob

Hey Saildog!

Nice to hear from a fellow PM builder.  I built an EP last year, which is very similar and am embarking on a Take-Apart PM.  First, congrats on getting to this stage.  Do you have a build blog?

I believe that the instructions to sand when coating the panels is so that you achieve that museum finish glossy surface if you're going with a bright finish.

If you sanded after first applying the first fill coat, you'd actually be sanding the fibers and damage the strength of the cloth.

Have you checked out any of CLC's great articles?

http://www.clcboats.com/shoptips/epoxy_and_fiberglass/fiberglass_weave_epoxy.html

Sanding between panel coats also helps prep the surface for a successfully glossy paint job.   

Thanks Captain Skully...hadn't noticed the articles yet and no, no blog. 

While the article you doesn't mention roughing the surface between coats...I'm still concerned about putting additional epoxy coats over cured epoxy without any surface prep at all.  Certainly would be a time saver though.

 FYI, just called Mas Epoxy and spoke to Dave their technical support guy, who was very helpful.  He said with the slow hardener there is a window of about 4 to 6 hours after coating, at room temperature, where you should recoat to avoid surface prep and get the best bond.  Otherwise he says you should wait 24 hours and lightly scratch the old surface with either 220 sandpaper or a scotch brite pad.

This isn't so bad....do the fiberglassing early in the day, second coat at noon, third coat around 4.

If anyone hasn't done this though, and put new coats over fully cured epoxy, I'd be interested in hearing how that worked out after a number of years.  Maybe it has worked out OK?

Thanks

Rob

I've done that on my WD12 and schooner. I didn't actually fill the weave on their exteriors until after they were structurally complete. I'm still paddling the WD12 after nearly 8 years and the schooner looks just fine after 4 years.

I've also gone more than a day between coats with no surface prep, but that was with System Three Silvertip whose instructions specifically say up to 3 days before sanding is necessary.

Have fun,

Laszlo