shouldn't be a problem. 

in fact, you typically want to do the wetting out and fill coats in fairly close proximity when you can still get a chemical bond.  Once a layer completely cures, it needs to be mechanically roughed up (sanded with coarse paper) to provide a good surface for the new layer of epoxy to attach to.

if your first layer is solid enough that the glass is not moving around and it won't stick to or/move with whatever you are using to apply the new thin layer....you should be fine.

fairly easy to get two coats in on a single day if you finsh your first session before noon and have reasonable temperatures.

good luck.

howard

Thanks much, Howard...

I'm in a real hurry with a deadline to go to Maine this spring with the boat, so I'm trying to compress cycles wherever I can....so if I did one early one morning (like get ready today and do some in the morning) I could do even 3 thin coats if the second coat tacks up nice?  (of course, I appreciate that after 3 coats, I certainly would need to wait a day and sand)

Any reason not to do 3 thin coats if I start early and  it tacks up nicely?

thanks!

Curt, 

I'm no expert here but I used the Q-tip trick that others here pointed me to - I thnk I found it on Nick Shade's site. 

Basically, you use a Q-tip to, in a sense, let you know when it's time to put the next coat on. If you lightly touch it to the surface of newly applied resin, then pull it away slowly, it won't tend to "stick" - the fibers of the Q-tip will pull away cleanly. 

If you wait a little while (temparture dependant on how long this is), then touch the Q-tip to the "greening" resin, it will stick a little - the fibers wil tend to pull away from the Q-tip as they want to stick to the resin. Now's the time for the next coat as it will chemically bond to the previous coat. 

If you wait too long, the same thing will result in the first example - the Q-tip wont stick, as the resin has cured too much. In this case, you will need to wait until it is fully cured then sand it out prior to re-coating. You will need a rough surface for a mechanical bond of the next coat. 

Once again, I'm no expert, but I don't see why you couldn't put on three coats in a day using this technique, if the temparture is such that it allows the resin to cure in time to get three coats on in one day? 

I know that in my shop, with a winter temp of "cooler than I'd like", this process would take too long to get three coats on in one day. In the middle of the summer, well that's another story!

Not sure if that helps, but hopefully it will. 

Cheers, 

Rob

agree with Rob.

no problem doing three coats in a day if your temperature/epoxy combination supports that.  i have been known to do late night/early am sessions to complete the wet-out fill-coat process in minimum elapsed time and avoid the need to re-sand.

that said, i don't myself use the 'q-tip' method, but something pretty similar with a latex-gloved hand.

if i touch the hull and epoxy comes off on my glove, it's too soon.  if i touch it and my glove sticks to it (kind of like the feeling of a post-it note), but when i pull away there is no expoxy on my glove, i'm ready for another coat. 

fwiw, i  also keep a thermometer/thermostat in my shop.....and note the cure times wetting out so for my subsequent fill coats i know roughly when to come back (hence the early AM/late night sesssions)

best

howard

I've done 4 coats in a day, but it was 95 degrees in the shop at 9:00 pm. Even with the slow hardener I got 4 coats on starting before sunrise and going til 11:00 pm. That was a long, messy and sweaty day. As far as the "chemical" vs "mechanical" bond thing goes, I can't get excited about it. None of my boats have fallen apart yet. The stresses on the kind of boats built here are just not enough to justify the concern. Aircraft would be a different story, but muscle-powered boats don't need that last little increment of strength. Epoxy takes at least a few days to fully cure once it's no longer tacky. At first it'll be soft enough to ding with a fingernail. Next, it will feel hard, but will clog the paper and form little balls when sanded. Only when it forms a fine dry dust when sanded is it anywhere near a a full cure. Anytime after it's no longer tacky and before it's fully cured is OK for a new coat without sanding. Happy New Year, Laszlo

Thanks so much for the great input!!   I appreciate all the tips above...these would be good notes to have on the shop notes.