Novice Attempt at Gel Coat Repair and Finishing

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Wesley Tucker
1961-2013 (RIP)
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Novice Attempt at Gel Coat Repair and Finishing

Post by Wesley Tucker » Mon Oct 10, 2005 9:57 pm

I'm starting a new hobby this week.

Some of you have seen my custom Ick Sticks that I got last fall (the lime green and lemon yellow boards.) Well, because most skaters now grip tape the boards from edge to edge, Rick didn't bother with "finishing" the tops. They are just painted resin glass. I like to doodle with my grip tape, though, because my attitude is that if you pay that kind of money for a custom racing board, I want to SEE IT, not just black sand paper.

This has nothing to do with performance or change the characteristics of the board, just making it look different. Some people put stickers on their their boards, custom paint jobs and even custom stickers. I want to finish the tops of my Icks.

So I went online and found all the stuff: Epoxy, hardener, neutral gel coat w/hardener and tinting solutions (a bottle of bright yellow and blue to mix and make green.) So it's time to strip off the year-old grip tape (which needed replacing anyway,) and mix up some plastics, break out the 300-grit sandpaper and see what happens?

If you don't hear from me within a week, send the paramedics!
Last edited by Wesley Tucker on Mon Oct 10, 2005 10:18 pm, edited 1 time in total.

Wesley Tucker
1961-2013 (RIP)
1961-2013 (RIP)
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Tips and techniques from online

Post by Wesley Tucker » Mon Oct 10, 2005 9:58 pm

For anyone's who's interested in this kind of stuff, I found this online at:

http://www.jamestowndistributors.com/de ... elcoat.jsp

Jamestown Distributors is also where I ordered the "stuff." From what I could see in their catalog, they have everything necessary for glas board construction EXCEPT foam material. Maybe it's there and I can't recognize it, but nothing in the way of foam sheets, foam-making chemicals or any other possible permutation was apparent to me.

**********************

What is Gel Coat?
Boat builders start with a fiberglass mold that is supported by metal on the outside (to make it structurally sound) and on the inside, a gelcoat over top of the fiberglass to make it smooth. To get the mold to pop out, a release wax is used. After waxing the mold thoroughly, a polyester-based material called "gelcoat" is sprayed on every square inch of the mold. Gel Coat is a unique material. Vendors classify it one of three categories: a paint, a fiberglass supply, or an epoxy.
Though smooth and relatively durable, gelcoat, like any finish, is prone to dings and scratches. This handy guide gives a DIY boat owner the ability to repair gelcoat using WEST System Epoxy and a few other simple materials which can be obtained overnight.

Gelcoat Repair Techniques

1. One of the steps that is frequently left out when working with gel coat is to apply a sealer coat of epoxy to the repair area. This is necessary to fill any porosity in the patch. Apply two or three very thin coats of epoxy, extending each coat slightly beyond the previous one. Warm the area with a heat lamp to speed the cure and to help the epoxy flow out nicely.

2. When the sealer coat has cured, wash thoroughly with water and a 3M Scotch-brite pad to remove any amine blush. Any blush left on the surface may inhibit the cure of the gelcoat. This very important step is often forgotten, and the result is usually an unsatisfactory repair.

3. Sand the epoxy coated repair area with progressively finer grits of sandpaper. Finish with 220 wet or dry.

4. De-wax an area twice as large as the diameter of the repair. Apply tape around the perimeter of the de-waxed area. Use masking paper to protect the boat from overspray. If there is a molded bodyline or corner near the repair, you may want to extend the color patch to that point. The same is true for a painted or vinyl stripe.

5. Sand the additional area out to the tape line with 320-grit paper. This will be the total area to be gelcoated.

6. Determine the gelcoat batch size for the size of the repair--approximately 80 square feet per gallon of gelcoat (20 sq. ft. per qt.).

7. Tint the batch of gelcoat to match the color of the boat. If the boat is fairly new and the manufacturer is still in business, you may be able to get gelcoat that will be a very close color match. If this is not an option, you will need to get the gelcoat from a FRP product supplier. Many marine distributors handle the gelcoats from various resin manufacturers. You will also need pigments to tint the base color to obtain a good match. These pigments are generally available from the gelcoat suppliers. Frequently, local repair yards that do fiberglass repairs will sell these products to the project user.
There are several gelcoat additives that, when used properly, make matching a repair easier. These are clear, low-viscosity resins which are not air inhibited. These products are mixed with the pigmented gelcoat in place of a wax solution to provide a tack-free cured surface. They also provide the added benefit of thinning the gelcoat without changing the color of the cured patch the way acetone or styrene can. A simple gelcoat repair kit is available for small, simple repairs.
Matching the repair color to the color of the boat is probably the hardest part of the entire job. You will find that most gelcoat colors change as they cure. As you tint the gelcoat to match, apply a small amount of uncatalyzed material to the sanded area surrounding the repair. Use your gloved finger to spread this into a sample the size of a quarter. Wait a couple of minutes for the solvents to flash off. Any color variation will be evident. If the color match is not acceptable, change the color by adding small amounts of tinting pigments. As you adjust the gel coat color, try to think in terms of the basic colors, i.e.; the color needs to be blacker or redder or bluer or greener... This will help you identify which of the pigments to use. Use very small amounts of the pigments. You may even need to dilute the pigment with white gelcoat to weaken the effects. Apply an uncatalyzed smear with each change of color no matter how small. Leave each of these smears on the surface until you have the color as close to the boat color as you can get it. When you are satisfied with the color match, wipe away all of the test smears with acetone or lacquer thinner.

8. Divide the batch into a 2/3 portion and a 1/3 portion. Our technique for using the patching additives is slightly different than the recommended procedure. Mix the patching additive with equal parts of the 2/3 portion of the matched gelcoat. Catalyze following the recommendations of the gelcoat supplier. Over or under catalyzation may prevent the product from reaching a proper cure. Apply this mixed gelcoat to the surface of the repair with a spray gun. Apply several light coats, feathering each one farther from the repair area. Allow the solvent to flash off between coats. You may need to apply five or six coats to hide the shadow of the repair. Most gelcoats colors will dry lighter in color if they are too thin. Most manufacturers recommend a total film thickness of 15 to 20 mils. A common mistake is to apply two or three heavy coats, causing solvent entrapment and improper curing. This may also have an effect on the color of the cured repair.

9. Make another mixture with the 1/3 portion of gelcoat and patching additive. This time use about three parts of patching additive with one part gelcoat. Spray the first coat of this mixture over the previously sprayed area. Then apply two or three more coats of this mixture over the entire area. Extend each coat farther than the previous one, with the last coat out to the tape line. The semi-transparent film of lightly tinted clear patching additive will allow the original gelcoat color to show through around the perimeter of the patch. This will help blend any subtle color change into the original gelcoat.

10. Once the gel coat has reached a full cure, pull the tape and sand the tape line smooth. Start with 320-grit wet or dry paper and work up to 600-grit. Sand the surface of the repair if necessary.

11. Buff the surface with a white, medium-cut rubbing compound. Take your time and do not overheat the surface while buffing. The excess heat can cause a stain which will be very difficult to remove. Finish with a fine compound and wax the area.


There are times when the repair will not match simply because the original gelcoat color has faded. You may need to polish the entire side of the boat to restore the original color.
Patience and experience are the two most important ingredients for a well matched color repair. The mixing of the color is guaranteed to teach patience. And since you may need to try more than once for a proper match, the experience comes quickly. So get to it..

Wesley Tucker
1961-2013 (RIP)
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Post by Wesley Tucker » Sun Oct 16, 2005 5:39 pm

Ok, stupid question time.

I'm starting to play with my epoxies and hardeners and there's something rather glaring left out of all the tips and instructions I have found:

What's the best surface or container to use as a mixing vessel for putting the resin and hardener together before spreading it on the board?

Will epoxy harden and stick to glass? Or is there a preferred plastic material that's used as a work surface? Maybe a teflon-lined pot or pan? I've seen videos of glassers working on surfboards and boats, but they always seem to have their agent mixed and ready to go. I just don't want to pour out this stuff and find out what I'm pouring it on makes for a terrible surface for working and mixing these materials together. I'm assuming glass would work best, but don't want to jump to any conclusions if someone gives better advice.
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Gary Saenz
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Post by Gary Saenz » Fri Nov 11, 2005 9:26 pm

Wes, go over to the board building forum at silverfishlongboarding.com Lots of builders info there.

Wesley Tucker
1961-2013 (RIP)
1961-2013 (RIP)
Posts: 3279
Joined: Tue Aug 27, 2002 2:00 am

Post by Wesley Tucker » Tue Nov 15, 2005 1:56 pm

Well, I'm well on my way to ruining my Ick Stick.

No, not really.

I've learned a couple of things this week that isn't in the instructions. First of all, the guys who do this for a living aren't exaggerating when they say so much is dependent on the weather. Knowing just how much hardener to add to the base is not an exact science. You just have to get a "feel" for the right amount depending on the temperature and the humidity. Also, I found what is the near-perfect vessel for mixing individual batches of hardened gelcoat: those little 3 oz. Dixie Cups for the bathroom. It really has to be a paper cup because a plastic or foam cup will MELT when you add the hardener. The only trick to using paper is to add the base first then the hardener to it. If you put the hardener in first, the paper will absorb it and you'll lose your proportionate mix. So adding the hardener and stirring at the same time insures you get hardener in the base and not soaked into the cup. You do have to stir, too, because if you don't the hardener just sits on top of the base in a seperated layer and THAT will then soak into the paper cup and again you lose your proportinal mix. Like I said, none of this is in the instructions and you learn by doing it . . . several times.

Another thing I've learned is that gel coat is not fun to play with. What I've found is the most puzzling about the stuff is that it's TRANSPARENT. How Rick gets his so opaque and rich has me stumped. The only solution I've found is put on coat after coat and pray that when it sets it'll be thick enough to hide the blemishes underneath that I set out to eliminate in the first place.

Finally, if you want to play with fibreglas and resins and gelcoats and foams and all this other stuff, take just one piece of advice: learn to use SANDPAPER. Knowing how much to sand, what grit to use, whether to do it by hand or by power tool and most important WHEN TO QUIT is the difference between a cool skateboard and a joke. One instant you're making headway to a fine polished surface and the next you're looking at raw glas where you went thought your finely layed layer of gelcoat.

Fortunately, you can fix anything with enough time and money. It's not like anything is ever "ruined." You can always sand it down to glas and start over again . . . which I have done so far on several occassions with this project.

Oh, and one last thing. Sanding gelcoat produces the most fine, obtrusive and all-pervading dust you can imagine. It's a very fine powder that's made out of sticky hardened styrene plastic (model airplane plastic.) It goes everywhere and is a BITCH to clean up. Make sure if you start playing with this stuff you do away from the fine furniture and upholstered seat covers. If you don't, you'll be living with ploofs of gelcoat dust for a long, long time.
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Frank Henn
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Post by Frank Henn » Wed Nov 16, 2005 1:30 pm

I use glad plastic storage containers to mix my resin up. It has measuring lines and they are disposable. Although I knock the hardend resin out and reuse them casue I'm cheap. If your resin is melting the plastic you might be doing something wrong. Resin will not stick to plastic. I get my resin from here http://www.jgreer.com/index.htm
It dosent have to be a perfect mix, has a long working life, and dries clear.

Some people add color to the resin itself. I've never tried it.

oh and use the resin in a well ventilated area, while wearing long sleeves and a mask.

Ben Buckles
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Post by Ben Buckles » Fri Feb 17, 2006 8:24 am

Frank Henn wrote:oh and use the resin in a well ventilated area, while wearing long sleeves and a mask.
Or you'll end up like Frank.
Rabid Rodent Racing-charter member

Eric Brassard
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Post by Eric Brassard » Thu Oct 18, 2007 12:31 am

Be careful Wesley,Each time you put a coating you put 50 grammes on your board if it 's epoxy whit fiberglass you put more. And if you make a wrong mix your board was always sticky.....


Eric Brassard ( Québec Ramp)

Pat Chewning
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Post by Pat Chewning » Thu Oct 18, 2007 4:33 am

Wes:

I use disposable plastic drinking cups for mixing (the clear plastic kind, not the white styrofoam).

Use heat to cure the epoxy-- warm temperatures are your friend (AFTER it is applied).

Use wet sandpaper (black oxide kind) works much better than dry sandpaper.

Mix small batches. A large batch of epoxy will reach "critical mass" and heat up to the boiling point.

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