Applying gelcoat as top coat

[wet-foot]

Redoing a transom ( 7' x 3' ) with a gelcoat finish. What is the best method to get it to a glass like finish. I have brushable gel in white. Can I brush a few coats sand and trowel or????

[Corpus Skipper]

The surface MUST be flat and smooth before the gelcoat goes on. Roll it on, at least 2 coats, 3 leaves more room for sanding. Then get ready to sand, sand, sand . I'd start with 80 grit on a dual action sander to knock down the high spots. Keep your pad FLAT!!! Go to 150 grit, then 220, then 400, then buff with a good medium compound, and finally a fine compound, or rouge (better if you can find it, check with local repair shops or builders). Finally wax (mold release works EXCELLENT, once again, if you can find it).

[wet-foot]

What type of roller sleeve would you recommend? Also, could you use the sleeve more than once or do you need a new one per application? I could see getting the surface much more level with a roller over a brush. Thx.

[Corpus Skipper]

I use a 4 or 5 inch roller, can't remenber who makes them, but I get 'em at Home Depot. They're white with an orange spiral stripe and they're really plush. A good swishing in acetone after use keeps them usable indefinitely. MUCH smoother than a brush.

[wet-foot]

Will certainly give it a try. Should be able to roll out a large area much faster than brushing. I've been using a 1/4" sheet palm sander, would a 1/2 sheet sander be worth the investment? Plan to do a number of flat panels in the not to distant future. One other thing, Would a premix gelcoat gun do a better job? I'm refering to the same type of project where the gelcoat is the final coat and has to be sanded and polished.

[lprimina]

What style boat are you building? We use board sanders (one foot to 3 foot)
The larger area you can sand at one time the less chance of making valleys on the boat.Sand at a 45 degree angle in one direction then sand at 45 degree angle in opposit direction.
I dont know if this is helps or not, and there are probably better ways than mine out there but it makes for a smooth finnish.(Well after the pro seal, fairing compound, and 8 other sandings

[Corpus Skipper]

Would a premix gelcoat gun do a better job?

Not really. Gelcoat is not self leveling like paint, and sprayers tend to ripple up the gelcoat unless you're really good. I only use them for spraying up molds, and use a Binks paint gun with a pot for spraying decks and large parts. For a one time project, the roller works fine.

We use board sanders

These are good, but expensive for a one time job. I'd recommend a small random orbital, or DA sander if you have a compressor. Good luck.

[wet-foot]

A large sander to keep everything flat makes sense but will go with something more manageable ( price ) for now. What is pro seal? Yes I do have a compressor but not really clear on what a "DA Sander" is!

My next project will be reshape a contoured surface and finish with gelcoat - slow peaks and valleys. Should I make shaped sanding blocks from styrofoam?
Also what's the best way to get a mirror shape for the other side? Hope this makes sense? Have to do a duplicate on the other side. Area about 6 feet long by 18" wide , or there about.

[Corpus Skipper]

DA= Dual Action (random orbital). For shapes the DA works well, for close contours I usually hand sand. Not sure what you mean by mirror shape of other side, are you trying to fabricate a part?

[wet-foot]

I actually have a DA!!!!!!!

Mirror image is what I should of said. Will be doing some modifications to the boat side and will have to duplicate it "in reverse" on the other side.
Was wondering what technique is used to create an exact reverse copy for the other side? Like a car fender, you build the left side, how do you make a perfect reverse copy for the right side? 50% of the boat is a reverse copy of the other side. Any idea how this is done to perfection?

[lprimina]

Pro seal is just a name of a paint that is made to level out some of the valleys (epoxy paint) I will get you the real name next week when I go back to the shop (Monday)
Ben

[Corpus Skipper]

You can pick up the shape, if it is constant, by making a pattern jig. if the shape is more complex, you may just have to wing it.

[wet-foot]

Where does one learn of pattern jigs and plug making.
Is there away to get an exact reverse copy for the other side?

[Corpus Skipper]

None that I know of, other than making careful measurements, then making a mold or a jig.

[wet-foot]

Always hoping for a easy fix!
Wax issue}
I also made a few flat panels using a mold. 2 of 5 came out great - 2 were usable a bit of sticking in the mold - 1 was really bad, 1/5 of the gelcoat would not release and actually stuck to the mold. I used a mold release wax 4 coats and even let it dry overnight. Was really surprised to see it stick with that much wax on the mold! Do I just need more coats of wax or is there something else I should be doing to make this work? The panels I can repair but have to solve this before proceeding onto more elaborate pieces.