No sag gelcoat??

[billr]

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 wasn't around.
Thanks for all the good advice.
Bill
SV Skookum John (a Skookum 53)

[Maine Sail]

Originally Posted by Alan Wheeler

You can not use Gelcoat on the outside. Gelcoat will only harden in a Female mold between the mold and glass/resin. In other words, it has to be kept from air.
You are best to fill the gouges with filler, fair and sand and paint with a two pot paint. Paint will allow you to roll it on.

I have done gelcoat repairs for years and years and it can most certainly be done but you need to know the tricks and secrets.

In order for gelcoat to kick and cure it must be sealed off from air. Mixing a little Wax-Sol Made by Kardol (LINK) into the gelcoat before spraying or rolling it does the trick. If you need another coat the wax must be thoroughly removed from the surface and it must be sanded before the next coat.

I usually "hot coat" my second coat by spraying the first application without wax then letting it kick until almost tacky. I then mix my second coat with wax (waxsol) and spray it over the first. This gives enough thickness to wet-sand out the orange peel and buff it to match..

Gecoat repair is not easy, and it does take practice, but it can be done. One trick I use for gouges is to over fill the hole with un-waxed gel coat. The next day you take the top off with a razor blade or sharp chisel. What's underneath will be cured as it was sealed from air by the top layer you shave off...

Gelcoat MUST be thinned to spray it and this becomes even more tricky!!

Polyester resin also needs to be kept from air! That's why there are two types; "laminating resin", which is un-waxed and will cure tacky and "finishing resin", which has wax added so it will fully kick and cure...