Spray Gun for Gel Coat

I'm thinking about spraying a small gel coat repair. Since this is mostly an expirement to see how well it comes out, I want to get a relatively low cost gun. I was thinking of getting a $40 HVLP gun from Nortern Tool with a 2.3mm nozzle.

This might be a stupid question since I have no experience with spraying paint, but if this goes well I hope to re-gel a 2x3 ft patch in the cockpit floor. Can I use this gun to spray straight down on the deck floor?

My other question is regarding styrene. The gel is a slightly off white color. I am concerned it will yellow over time. Is it possible to shoot the gel out of a 2.3mm gun without thinning it?

Re: Spray Gun for Gel Coat

WOW those are good questions. Gel Coat is quite thick and does need a larger opening then most other sprayable products. You could probably get away with a 2.3mm tip if you can thin the gel coat enough to spray. I see some say 1.7mm but I know for fact that that size tip will be very marginal at best. I'd stay with the 2.3mm if I were you. I use a 1.8mm tip with gravity feed guns for primers and 1.3mm for base coats and clear coat spraying. Start with a practice board and no thinner and if you get a good fan and no problems shooting the gel coat and move on. If you do get problems getting that gel coat out of the gun, add a little thinner at a time and retry till you are pleased with the fan and coverage. But add amounts so you can duplicate the mixture again if need be... And as far as shooting straight down, a partially filled (maybe half full) HVLP gravity gun will work perfectly. If the gun is too full in that position, it may leak through the vent hole in the top of the cup cap... Also most HVLP guns are designed to shoot properly at 10PSI at the tip. So you will need between 30PSI to 40PSI at the gun. Use a regulator/gauge at the input of your gun. Then (without any paint in the gun) squeeze the trigger wide open and adjust the pressure for those numbers. You could also shoot some thinner and adjust for the pressure and the fan pattern at the same time before the gel coat goes in the cup. Then a little adjustment to fine tune the fan pattern would be all you would need if anything. Oh! And one more thing, thoroughly CLEAN that paint gun immediately after finished unless you want to buy another one for the next job... JMHO!