Spraying two color of gelcoat

I am a small back yard boat builder getting ready to do my first two color hull, I am planning on doing the sides of the boat in a color and the hull bottom white, my question is how do you get the nice distinction difference, I understand you use tape but I was told today that i can use masking tape, next question, all varibles considered, at what point can you safely remove the tape and begin with your second color? Any help or suggestions would be greatly appreciated.

 

Since no one else has responded I might as well weigh in with what I know about it.

I spray gelcoat into a female mould when vacuum bagging hulls and decks. I thin about 40% using Duratec Hi-Gloss. Thin too much and the stuff runs down into the bottom of the mould or beads up around waxy areas. You still have to use a pressure pot with a fairly large aperture on the gun: took me a while to figure out that smaller apertures means the stuff is coming out of the gun too fast to be properly atomized.

I peel the tape while the gelcoat is still wet. Otherwise, you peel off part of a layer of dried gelcoat from the mould.

I generally do the hull in several passes. I do the very bow and stern, then wait about 12h to do the rest of the hull, which I do in three or four passes. The bow and stern are very narrow, and if I try to cover them in one application I end up blowing ribbons into the gelcoat and making a mess. Any little divots get filled in by hand later. It'll depend on what sort of thinners you use, of course. I don't have any problems with Duratec.

It wasn't really clear from your post if you were spraying an existing hull or a mould. I've no experience spraying hulls, other than the observation that it's easier to spray a hull with automotive paint. You can get stuff to add to gelcoats, but the surface finish always needs a lot of sanding in my experience, which is limited, and mostly from observations of building up layers of vinylester black tooling gelcoat on plugs.

Hope that helps a bit.

Regards,

Matt Turner
Turner Racing Shells Ltd.

 

Matt,

Thank you for your reply, I did fail to mention that I am spraying a mold, When I spray it looks like it be a matter of testing the gelcoat to see how fast it cures. Just courious, what type of hulls do you build?
Again, thank you for your reply.

 

Check out:

http://www.turnershells.com/CONSTRUC2.HTM

I should have mentioned that I catalyse at 0.5% MEKP for a pot life of about 1/2h. Using a 1gal. mix I can do the entire hull in about 20min. leaving time to cleanup, but I've switched to spraying about 1 or 2qt. at a time, since it's easy to build up layers. I have been caught about three times with gelcoat going off in the gun and pot, so it's worthwhile my sticking to the 1qt. set up. I've now got a full supply of taps and dies for cleaning up gelcoat off threaded parts.

I also fooled around at one point with refridgerating the gelcoat beforehand but gave it up when I started to suspect water drops were condensing in the spray.

Happy spraying!

Matt

 

Use 3M fineline tape for your edge line. Mask off everything you dont want painted. Make sure everything is clean. As soon as you are done spraying the gel coat, and the overspray has been removed by the fans. Start pulling your tape line. Have someone else flush your spraygun while you do this so the gelcoat doesn't set up in your gun. As soon as you can touch the gelcoat without getting any on your fingers you can spray your next color. Usually about 2 hrs. I am an expert at this I can help you through this e mail me with any questions that you have.