T&T: Gel Coat Repair

[Rudy and Jill Sechez]

> I have some gel coat repair to do. Some places are just hair
> line cracks,
> others are chips. A few are gouges down to the glass. > 

> John Brees

Hi John-

What you want to do is not difficult, but the final step, matching the color of the gel coat, can be somewhat difficult, and may need to be redone a few times, until you get the color close. 

Matching color is a matter of combining the appropriate primary color tints into the resin, to end up matching the color on the boat. If you have trouble accomplishing this, search out someone that works with colors (high school or college art student?), as they usually know how to develop colors. 

It is often doubtful that a perfect match can be accomplished, though a really close match is often possible. Sometimes you can buy the color from the manufacturer or, if you are really lucky, the manufacturer used a standard off-the-shelf color. This applies to gel-coat or paint.

If your hull is made from polyester resins, then you can use the same for the repairs, including gel-coat for the finish. 

If not, or if you are not sure, then it is better to use epoxy resins. With epoxy resin, you probably will not be able to finish with gel-coat and will need to paint the repair.

You will also need a variety of fillers. Fortunately just about all the fillers are compatible with either epoxy or polyester resins. These fillers are produced by various manufacturers and sold under a variety of generic and proprietary names, which, until you become familiar with each, may cause some confusion. Fortunately, you will usually only need two or three different types of fillers. Most epoxy and polyester resin manufacturers/distributors publish information about these fillers and how they are used. 

If the gouge or crack is shallow enough and in polyester resin, you can use gel-coat, thickened with the appropriate thickener, if necessary. If deeper, then you will need to fill with polyester resin or resin/fiberglass, before gel-coating. If using epoxy, use resin/filler or resin/glass/filler, whichever is appropriate, sand, repeat until flush and then paint.

The gouges are easy- clean down to clean glass, fill and paint/gel-coat. If the gouge extends into the glass, ideally you will need to grind the gouge out fairing the edges, layer with fiberglass cloth/resin and when flush, paint/gel-coat.

The cracks are a little more involved. You need to enlarge the crack (enough to comfortably fill with thickened resin), fill it and then let it harden, sand, refill if necessary, and when flush paint/gel-coat. 

If the crack is too large; if it is in an area that is stressed; or, if the crack returns, then the crack will need to be enlarged enough for fiberglass fibers to be layered into the crack, sanded smooth, filled/sanded until flush and finished with paint/gel-coat.

If the crack returns, it will need to be redone, only stronger and this means wider and deeper, reinforced with more glass fibers, with the possibility of glass layers also needing to be applied to the underside of the involved area.

Other than the minutiae needed for the resin work and enlarging the gouge or crack, a sander with sandpaper rough enough to do the rough work (36 grit) and the finer work (80-220 grit) will be needed. If the repairs are extensive, either in size or quantity, you may benefit from a 4.5 inch angle grinder. To finish gel-coat, a slow-speed buffer will be needed. Otherwise, any tool that will accomplish the job can be used. Before buying anything special, see what you can do with what you have or what you can borrow. Once you decide you love the work, then go crazy buying all those other tools. Keep one idea stuck to the back of your mind- no matter how bad the repair turns out, it can always be ground out and redone.

I know that this may be a little too vague, but it is easily learned and you will become comfortable with doing this fairly quickly. Plus, there is usually someone around the boatyard/marina that can give you more individual guidance. 

A couple weeks ago, I spent a few hours with a couple who wanted to do this on their boat. This was their first time too. They were able to finish the job on their own, with only a few questions here and there, mostly confidence-building questions. Believe me, they were not rocket scientists either.

There are many books published that can help you understand how to do this in more detail. (There are too many tips and details to mentioned here.) I would not be surprised if your library had some, and if not, they are available from most nautical book sellers and from many chandleries. The same companies that supply you with information on fillers may also be able to supply you with how-to information.

I hope this gives you the confidence to try it.

Rudy
Briney Bug, Port St Joe, Fl