> The instructions tell you to
> complete all 3 coats within 72 hours. Then it also says to never wait more
> than 72 hours between coats of epoxy. Which is it?

A maximum of 72 hours/ 3 days between coats is OK. See page 12 in "The Epoxy Book" you should have got along with your kit. You will still get a decent bond after that, but the epoxy gurus say that you won't get the best possible bond. In my non-formal testing (read messing with scraps), pieces with older epoxy coatings that have been 'glued' together with epoxy still break apart in the wood rather than the epoxy. I think this is one reason repairs are possible in an already completed boat (or canopy in my case); with a little preparatory sanding, adhesion is sufficiently effective.

> I put my first coat on Sunday evening, a second Monday, a third plus
> taping the keel on Tuesday. Then, as luck would have it, the temp dipped
> into the 40's last night and barely topped 60 today (plus lots of
> humidity.) I was all set to add another coat tonight, but the previous
> coat is still really tacky. I was using hardener 2 from System 3. I think
> I need additional coats because I can still see a lot of the weave of the
> glass.

> I'd appreciate any clarifications/suggestions. Nancy

You may still see the weave after 3 coats, but unless you put on very thin coats, you probably have enough on. I do four, but I flatter myself that I'm putting on thin coats. It may be the 'telegraphing' effect that you are seeing, as others have suggested. In general, we beginners tend to overdo it rather than underdo it. It sounds like you have enough time left since the last coat to do another without bonding problems if you really think you need another. At worst, you'll be sanding it off later or have a boat that's one or two pounds heavier than it need be.

If your last coat is still tacky now, look at your resin/hardener measuring and mixing techniques; without more information, the odds are that's where the problem originated. I had so much trouble with air getting into those 'volumetric' pumps that I abandoned them in favor of measuring by weight only. Then I mix a minimum of three minutes by the clock.