Gelcoat over Epoxy

[wet-foot]

Looking to do a repair to the aft side of a boat that has a hole punched in it. Damaged area about 3 feet long by 1.5 feet high. The area is not flat has some complex curves. Plan to do the repair with epoxy and glass and top coat it with the original gelcoat color. West System Epoxy says I need to use a vinylester primer between the epoxy and gelcoat. The gelcoat will be the final application and I kknow it will melt the epoxy. Does anyone have any experience topcoating over epoxy with gelcoat?

[gonzo]

Gelcoat will not affect epoxy resin. It is very chemically resistant. The problem is with adhesion. A vinylester primer can help but is not perfect. Your best options are to use an epoxy gelcoat or do the repair with vinylester resin.

[wet-foot]

How does epoxy gelcoat compare to poly-gel? I have mixed fillers with epoxy to make a paste but I was led to believe that epoxy always discolors!!!!!

Gel coat will attack the epoxy.Specificly its the styrean in the gel coat. so if you want to put Gelcoat over epoxy use a BPO(cream )
Hardener fairing compound over the epoxy repair first and then you can Gel Coat. However I recomend Paint to save all the hassell related with Gel Coat.
ps I teach this to profesionals for a living

[wet-foot]

Why would you use BPO hardner vinylester fairing compound instead of vinylester primer? Do you have much experience working with fiberglass without using a mould? Do you know of a fast method of creating a one off mould?
This is my main concern, each project I do is unique so I would like to avoid building a mold if possible.

Really appreciate your input.

Originally Posted by Guest

Gel coat will attack the epoxy.Specificly its the styrean in the gel coat. so if you want to put Gelcoat over epoxy use a BPO(cream )
Hardener fairing compound over the epoxy repair first and then you can Gel Coat. However I recomend Paint to save all the hassell related with Gel Coat.
ps I teach this to profesionals for a living

Hi there, i am new to this forum and very new to all this boat/fiberglass stuff..i understand that you are a Pro. i really need help with this stuff. i do autobody and paint ...but boats are really differant so i need help. i have a 10foot get ski i am working on right now. i am working on the bottom of the boat really want to know what to do next.... i have sanded the bottom with 320grid and looking at gelcoats and paints..the getski is white on the bottom but i want it black and glossy.. what would you recommand. need help with steps like sand 320, then spreay primer and then paint and spreay gelcoat afterward.. That would really help my project to get it done by Augest 1st.......Really, Really , Thankfull...

[freeman]

If your boat is made of polyester, why not just do the repair with polyester resin, fair it with a polyester based fairing compound such as poly fair and then use a polyester based spot putty such as ever coat for the many pin holes and then gel coat it. The trouble with doing a repair with gelcoat is it takes a lot of work to get the gel coat like a factory moulded finish. Theres plenty of wet sanding involved, and then applying more coats of gel coat, its a tedious process. We`ve found if you thin the gelcoat out with duratech`s clear it can be sprayed fairly flat and shiny, but the duratech clear coat will break down after expousure the the sun.

As for the jet-ski?( get ski ) , the same above applies. The easiest thing for you to do is sand the bottom with 150 - 220 grit, and then find a supplier that deals with awl-grip paint and expoxy primers. This paint is fairly expensive, but as anyone here uses it knows its durability. Other than that, find a sand your hull, find a good expoxy primer, and get some good quality automotive paint, emeron works great,international make a good paint also for the marine industry. But you gotta prime the get and sand the gel with 150 - 220 grit, if not the paint will peel right off.

[wet-foot]

I would not re gel the whole bottom, too much work!!!
If you want to change the colour to black from white use a top grade marine epoxy paint. You won't need bottom paint unless the ski sits in the water all day. Just follow the manufactures instructions. The good finishes can be brushed on then sanded out and buffed to look great. They are also easy to touch-up. This could be a 8 hour job with 3 coats or? Gel coat would take much longer and you will have a really tough time getting a smooth glass like finish unless you have unlimited hours to spend on it. Good luck with your projeect!!!!

[DGreenwood]

Gougeon Bros just did some research on this very subject and it looks like if gel is put over fully cured and properly prepped epoxy you can rely on the adhesion. Go to their site and check it out.

[wet-foot]

I think it would be too much work to reglass the entire bottom to to get a colour change.
I would go for a paint job in this situation. Yes I read the west system article on putting gel over epoxy. I am looking to do a bit of custom work with epoxy and was hoping to top it off with poly-gel. Before they recommended using a vinylester primer in between but it looks like that's not necessary now, which is good!!!!