Here is what I ended up using:
We used the Pre-val sprayers. They are very handy, but:
1) They freeze you hand; wear thicker gloves. This gives you a false sense of security
that you gel coat hasn't started to warm up and set on you, which is not the case.
2) We used the Duratec. Got all my supplies from the "fiberglasswarehouse" folks in Burlington ,Washington. With the Duratec, it is mixed 50/50 with the gelcoat
. The Duratec web site had the best advice on how to use their products. No wax is needed; the Duratec takes care of the cure. You catalize with 2% MEKP catalyst. At 77 degrees F, the Duratec / gelcoat
will gel in 14-16 minutes. They are not kidding about this. You have to move fast, because that includes your mixing time. They recommend MEK (the solvent) as a thinner. To use this with the Pre-val sprayer, we found that 10% MEK worked, 5% did not. Because the Pre-val sprays at a low rate, we found that the largest batch of gel coat / duratec we could mix for the sparyer was about 2 1/2 ounces. More than that, and the remainder gelled in the sprayer jar. One problem we had was that towards the end of a batch, even at 2 1/2 ounces, there would be occasional clogging of the sprayer, at which point it would spirt globs on your new surface. The instructions tell you how to clear the clogs, but once it occurs the second time we generally dumped the remainder of the batch and mixed a new one. To do our stern, about 40 square feet, we used most of 3 sprayers. One of the power units did not last very long. It was definitely a two person job. My wife did the mixing and timing and I did the spraying. The stern has a slight overhang, and I was doing the spraying from scaffolding while hooked to a safety
line. I did not have any runs or sags. I did end up with some dimpling on the surface (supposedly due to the spray losing its solvent before it gets to the surface). However, about half-way into the job, the wind
came up and made it very challenging. All things considered, I really liked the results. Oh, one other thing. If the temperature does not get above 60 degrees F, then the Duratec / gelcoat will not cure. Since we did this in cooler weather
, we really did not get a hard cure for about 4-5 days. Each day we would have a a few hours when the sun would warm the stern, providing that the cool wind
Thanks for all the good advice.
SV Skookum John (a Skookum 53)