I have a bottle of gelcoat paste (GCP, Seattle WA) that I am trying to use to fill scratches on the hull bottoms. While the paste matches my boat color perfectly, the paste is a bit too thick, in my opinion. Can anyone tell me what type of solvent I can use to thin this paste so that it spreads more evenly? I have access to a whole array of organic solvents so please let me know if you have tried to thin this stuff. Maybe I just have to expect that it won't spread very well and I will have to do more sanding than I really want.

Finally, one of my boards looks like something took a bite out of the trailing edge (figuratively speaking). I am having a heck of a time filling this in.

I really appreciate the help people provide on this site. My questions are naive since I am new to many aspects of sailing and sailboat repair.


Thanks in advance.

Bob Klein
Inter 18

Bob

re: Thinning the gelcoat

I understand (but have not yet tried this) that you can heat both the gel and the surface (25 degrees celsius) and that thins it out. Sounds worth a try (but I suggest you work fast and only test it with a small quantity first!!)

Trailing edge

This is alway tough. I usually open the nick out a bit (particularly if it's small) with a small metal file. Then I use packaging tape and/or some smooth plastic along one side (parallel to the trailing edge) to make a molding surface. Then I place the board so the tape is on the bottom and fill the nick and tape with gelcoat. If you do a reasonable job with the 'mold', you shouldn't need to sand too much. Sorry this is hard to explain in words. Maybe someone else has a better method/description too!
cheers

Using gel coat only is often not enough, when you really want a smooth surface you use:
1. Gel-coat
2. Hardener
3. Parafine (which makes the gel-coat less sticky)

This way the gel-coat can be applied with a small brush and later be sanded with some 400 paper.

I did my Nacra 6.0 last winter and it really looks like new.

Good luck

Bob,

The Gelcoat can be thinned with acetone - you can even thin it enough to spray it if you wanted. I believe the key to getting a smooth finish on it is to coat it with something after application. This keeps the air from affecting the cure. For small repairs, use a piece of saran wrap stretched tight. If the bite out of the trailing edge of your board is more than .1875" or so, you will probably need to put in some glass. Some Gelcoats require to be coated so they can cure. Some other folks spray a PVA mold release over the gel to facilitate a cure.

For a sizeable 'bite' I would first take a dremel and clean up the edges and then taper them so I have a spot to build up some glass on. I then take a piece of duct tape with wax paper on it (leaving adhesive of the duct tape all the way around the wax paper) and place it over the area on one side. Depending on what the area looks like, I might first lay up some glass and epoxy on a piece of waxed lexan to get a solid sheet that I can cut some pieces from. Then trim and epoxy a few pieces of the glass in the wound. If the wound is thick, I would only use this on the outside edges and would build up the inside with un-epoxied glass and more epoxy. For the final finish, I mix the epoxy with some micro-balloons to achieve an easier sandable finish.

I want to thank all of you for your responses. I will pull out my board this weekend and see if I can fill that bite.

I'll try thinning the gelcoat paste and I will cover the surface as suggested. Warming the paste seems like a reasonible idea except
the catalyst will work that much faster so I would have to move faster.

I also found this article by Don Casey on the BOATU.S. website.
Nice article on fixing scratches including the use of styrene to activiate the gelcoat

http://www.boatus.com/boattech/casey/02.htm


Cheers and thanks

bob klein
inter 18

you use styrene to thin gel and mekp to catalyze it. if you add air dry or air wax (up to 5%) it
will take out the sticky.

Okay, you got me. what is air wax?

thanks

bob klein

Wax is typically parafin disolved in styrene. It foats to the surface of the patch and keeps the air off. Gel coat is air inhibited and will not fully cure on the surface while exposed. It will feel cured but when you go to sand it will quickly gum up your paper. If you have styrene, use it to thin the gel coat past, or striaght resin, the use of acetone greatly affects the cure. The prefered way to fill where you need thickened material is to use the original color gel coat and thicken with fumed silica to the desired consistancy. This will give the correct color and take the minimum of work to bring to the original finish. Another product that will be available for gelcoats and putties is called Patch Aid. It provides the same function as the wax but helps the cure even more. Its the way to go for secondary gel coat applications and patching

Hey Matt;

Who makes Patch Aid or is this a generic name?

Thanks
bob klein