How To Repair A Long Narrow Crack In Fiberglass

Fiberglass Repair: DIY (or Non)

Stress cracks, dock dings and other minor injuries aren't hard to repair yourself. Anything bigger?
Here's some info to help you decide when to telephone call in a pro.

Unless your boat lives her life dockside cuddled up to a couple of fenders, she's going to get a few scrapes and bruises. And almost every fiberglass boat, even the most mollycoddled, somewhen suffers the heartbreak of spider-web and/or stress cracks. These scars of a life well-lived are unsightly, simply usually are only cosmetic. Generally, repair of minor damage is inside the mechanical aptitude of most skippers. DIY'ing these small, just fourth dimension-consuming, jobs will salve big bucks at the boatyard, likewise.

Merely what almost bigger, more serious injuries? I strongly advise against DIY if at that place'southward a pigsty punched through the side of your boat, a deep touch on crater revealing torn fibers or, even worse, coring, or any serious damage to the laminate itself. These are, I'd say, jobs for the pros. Have the fourth dimension, fork over the cash and accept it done right. My rule of thumb is, if I take to buy new tools to do the job, I don't. I suck it up and pay the money.

If the repair you're contemplating requires large swathes of fiberglass cloth, information technology may be time to telephone call in the professionals!

Photos courtesy of Saunders Yachtworks

First, Do No Harm

Stress cracks and crazing themselves aren't usually structurally damaging, only unsightly; left untreated however, they can eventually let water seep into the laminate and perhaps do real damage over the years. Ditto for small-scale dings and gouges. If the underlying laminate isn't damaged—showing broken strands of fabric or cracked resin, for example—many skippers only leave things alone. But are y'all certain the cracks and crazing are merely cosmetic?

M. Boyd Siegel is assistant crafts manager at Saunders Yachtworks in Gulf Shores, Alabama, and he's likewise aces at fixing fiberglass laminates. Sometimes information technology'south hard to tell how serious the harm is, Siegel says. "Gelcoat failure oft shows as unmarried small cracks or crazing, erratic cracks that are rather shallow. Lamination failure will show concentric fractures that radiate outward from a central betoken of impact." Both issues tin can look similar, and the only way to be certain is to open up the damaged expanse and await at the base of operations laminate.

"Opening up" normally means grinding with 60- or 80-grit abrasive disks. In skilled hands, an angle grinder makes short piece of work of removing damaged gelcoat and fiberglass, just enough and no more than. That'southward where many DIY'ers run afoul. They take off too much, and anything that comes off has to be put back on, turning a small job into a large one. The rule of thumb is to grind out a crater around the damage with a 12:1 slope, creating an ample bonding surface area for the replacement fabric. For example, an touch gouge 1/four-inch deep would hateful a xxx-inch radius, or a crater 6 inches across. Grinding to a 3/8-inch depth increases the bore to 9 inches, with 2.25 times the area. That means more than twice equally much fabric will exist needed to fill up the crater, twice as much resin, twice equally much squeegee-ing, twice as much gelcoat, twice as much fairing, sanding and buffing. Go the idea?

Stress cracks around stanchion bases are often compression-related.

Unless you have a close human relationship with your angle grinder, I'd hire a fiberglass pro from the thousand to do the grinding, if not the whole job; he'll as well accept his ain tools and prophylactic gear, which you probably don't. (Article of clothing a respirator, eye protection, long sleeves and gloves when working with fiberglass, by the style. The grinding dust won't do your lungs whatsoever favors, and the acetone, styrene and other solvents aren't so dandy, either. A uncomplicated dust mask isn't plenty.)

Experts recommend using a Dremel or Dremel-style rotary grinder to open stress cracks prior to filling. While easier to handle than a honkin' big bending grinder, a Dremel can cut through eggshell-thin gelcoat and become likewise securely into the laminate underneath if non wielded gently. If you have lots of cracks, get friendly with the Dremel. You tin buy one that's fine for gelcoat piece of work for under $100. To prepare isolated stress cracks, however, I'd take the advice of the folks at West System and apply a simple can opener and sandpaper to widen the cracks. While you might make the same mistakes with mitt tools as you would with power, you won't make them equally fast.

What About Resin?

Shallow gelcoat cracks with undamaged laminate underneath can exist filled with gelcoat alone. Brush it on, or dribble it into the scissure with the aforementioned popsickle stick y'all used to mix in the catalyst. But about repairs will involve resin—polyester, vinylester or epoxy. Information technology wasn't long agone that the only option for almost of us was polyester; that's what marine stores carried. And polyester worked pretty well. Now it's easy to purchase whatever resin. Merely which one is best?

Traditional wisdom says to match repair resin with the original (i.e., any the boat was built with), but in this example tradition is backside the times. Most boats are even so laid-up with ortho- or isophthalic polyester, but frequently at that place's a layer of vinylester, a hybrid of polyester and epoxy, right behind the gelcoat to ameliorate osmosis resistance. Maybe it gets footing off during the repair, or maybe not. And some higher-end boats are built entirely of vinylester. Vinylester resin sticks fine to polyester, and then maybe that'due south the option? Nope—it's easier than that. One resin fits all, and that's epoxy. It'll stick to nigh anything, and has other advantages, likewise.

"While vinylester and polyester both accept their places in vessel repair, whatsoever chance I go I will utilise epoxy," says Siegel. "Epoxy may be more expensive, but it's a far superior resin." Repairs don't use mass quantities of resin, then the extra price will more pay off in a higher-quality job, he adds. Epoxy is also more user-friendly, specially for the DIY'er. Information technology can be mixed with ho-hum-cure activators to extend working time, and fillers to make a thick adhesive putty or an like shooting fish in a barrel-to-sand fairing compound. "Using the proper fillers, glass and activators can really help an inexperienced do-information technology-yourselfer turn out a nice, production-strength repair," says Siegel.

Most DIY angle grinders are electric. This one is a pro-grade pneumatic.

When you surf the spider web for information on fiberglass repair, you'll surely come up across sure "experts" warning that polyester gelcoat won't stick to epoxy. Not truthful, according to the folks at West. Equally long as the surface is properly prepared, gelcoat volition stick fine to epoxy. But you must first remove its "amine blush," a waxy chemical compound that forms on the surface of the epoxy during cure. It scrubs off easily with water and an annoying pad. Polyester resin should be cleaned the aforementioned way after cure, to remove wax that floats to the surface to seal out air and allow total cure. Laminating resin doesn't have wax, so information technology stays tacky, an reward when edifice up layers of fabric. If repairing fiberglass with polyester resin, be certain to buy it with wax, or else you'll have to seal it somehow to make information technology cure all the way; ordinarily, "cures tack-free" will be somewhere on the label. If you used the wrong resin and need to seal information technology, plastic wrap works, or you can spray information technology with polyvinyl alcohol (PVA). It'south easy to remove once the resin has cured. Same affair with gelcoat: It comes with or without wax. For repairs, you want it waxed.

An Eye for Colour

The Achilles' heel of many repairs is matching new gelcoat to old. With luck you tin purchase the correct color from the boatbuilder or an aftermarket supplier; otherwise you'll accept to become a set of pigments and tint the gelcoat yourself. I have no eye for color, then for me this means lots of trial and mistake. Siegel advises making information technology easier by first cleaning and polishing the area you're trying to match, removing any grime or oxidation; and then add small amounts of tint to the gelcoat. Keep rail of how many drops of this color and that colour you're calculation, so you can mix it again for the next repair job. Become slow—a lilliputian pigment goes a long mode.

When y'all're close to a match, daub a sparse layer of united nations-catalyzed gelcoat on the existing surface and let it dry. "Gelcoat color volition change slightly every bit the solvents evaporate; information technology typically tends to get slightly darker," says Siegel. A sunny 24-hour interval makes this happen faster, and the un-catalyzed gelcoat will wipe off with solvent. Once you accept a lucifer, catalyze the gelcoat and apply it to the repair. Pros volition spray it on, simply DIY'ers usually brush; there are brushable gelcoats on the marketplace that can exist used right out of the can, without thinners or additives. Either method involves plenty of moisture-sanding and buffing to get that new-gunkhole shine.

A major color-matching repair calls for both experience and artistry.

Homo, is this stuff complicated or what? Isn't there an easier mode, short of doing nothing at all? Siegel concludes, "In that location are always easy fixes, but they typically come at a cost. How long will the repair last? One day or twenty years? It all depends. The all-time way is to grind and outset fresh."

If removing sometime, damaged material and replacing information technology with new is the only mode to ensure you don't accept to repair the same place twice, possibly it's ameliorate to tap a professional and just pay once.

This commodity originally appeared in the September 2022 upshot of Power & Motoryacht magazine.

Source: https://www.powerandmotoryacht.com/maintenance/how-to-repair-fiberglass

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