How To Repair Gelcoat Cracks

Past Terry Monville – GBI Technical Advisor

Knowing how or why your gunkhole'south gelcoat cracks occurred in the starting time place is the central to a successful repair. For example, if hitting a seawall or dropping a champagne bottle on deck is what caused the cracks, after fixing them yous will know how to prevent them in the future: Don't potable the champagne causing you to hit the seawall and drop the bottle.

And so in that location are those cracks that seem to appear in the gelcoat from nowhere: in cabin and cockpit corners, around screw holes, or in the middle of the deck. Information technology tin exist difficult to figure out what caused them.

So, What is Gelcoat?

Gelcoat is a pigmented, high-quality polyester resin used every bit the finish on fiberglass boats. Like any other polyester resin, information technology has skilful points and bad. Let's wait at some of the bad points that lead to cracking.

Afterwards it's applied, gelcoat shrinks 4 to 7 per centum during the cure and can have less than i pct elongation. This contributes to gelcoat'south nice hard terminate which we similar, only also makes gelcoat brittle, particularly if it was practical thicker than recommended.

Gelcoat should exist about 20 mils (.020 of an inch) thick when the manufacturer properly applies it to the mold. Just when the architect sprays gelcoat on the mold of a boat deck with cabin top corners and seat backs, the edges tend to become more than needed. Or the gelcoat runs down and builds up in an within corner, or as well much or too little gelcoat gets sprayed on the whole mold.

Minor Single Line Gelcoat Cracks

A minor single-line gelcoat scissure.

Thick areas of gelcoat don't have reinforcing textile to help hold information technology together. The stress is relieved in the form of a crack. This tin happen when the part is pulled from the mold or years downward the road, where a little more stress is introduced from the part flexing. Generally, these cracks volition appear as single-line gelcoat cracks in the cabin or cockpit. This blazon of great is hard to avert and is role of boat ownership. Luckily, the repair is simple and straightforward, as I'll explicate later.

Another common crack is a screw hole fissure: a hairline crack or 2 coming from a piece of deck hardware. This tin happen after a self-borer or sheet metal screw is used to add together a piece of hardware, fifty-fifty if you've used a proper airplane pilot pigsty for the spiral. The threads on the screw create pressure level on the gelcoat causing it to crack. Not using a pilot hole, or using one that is too small, will create even more of an outcome. They are frequently seen effectually snaps for canvas and beverage holders. When mounting hardware with cocky-tapping screws, you should drill the pilot hole and then countersink to remove the gel-coat to the threads' bore. This will forbid the threads from creating force per unit area on the gelcoat and make a small pocket for sealant to help seal the screw.

Repairing Pocket-sized Gelcoat Cracks

1. Use a rotary tool or scraping tool to open the crack into a "Five" shape. You will need to go through the gelcoat to the fiberglass and open the full length of the crack. Next, use eighty-dust sandpaper to scuff up the opening yous created. Fold the sandpaper and so you can get a corner of information technology into the opened crack.
2. After removing the dust, you can make full the crack with One thousand/flex® 655, Six10® or W System 105 Epoxy Resin®/20X Hardener thickened with 406 Colloidal Silica Adhesive Filler.
3. After the epoxy has fully cured, wash it with water to remove any amine chroma. The blush is water-soluble, which ways water is the best pick to remove information technology. Y'all tin can at present sand and use a color matching gelcoat to the area.

If the gelcoat cracks were caused past fiberglass flexing, add some fiberglass reinforcement to the backside to aid prevent future cracks.

If a screw hole repair has a fiberglass core behind information technology, seal the core with epoxy. With balsa or foam core, employ a bent nail to remove a small amount of core from behind the fiberglass, so fill the surface area with 105/20X thickened with 404 High-Density Adhesive Filler. For plywood or other woods core, brand an oversized hole and fill information technology with 105/20X and 404 High-Density filler. Both methods provide a good seal on the core and more holding strength for the fasteners. For greater detail on fastener bonding, read the Fiberglass Gunkhole Repair & Maintenance manual's section on hardware bonding or visit westsystem.com/hardware-bonding.

Stress Neat

These gelcoat cracks are stress cracks at the corner of a companionway.

A concentrated group of cracks generally running in the same direction indicates a more severe problem. This is often found on the leading edge of the motel meridian where information technology meets the deck. This tin be the upshot of a high flex surface area enduring heavy seas or too much load on the boat. Cracks may also form at a bulkhead or other hard spots behind the fiberglass when the gunkhole flexes, creating pressure.

To repair this type of cracking, remove the gelcoat from the area and inspect the fiberglass for deeper cracks. Just wipe the expanse with a moisture cloth so the cracks or fractured fiberglass volition appear as white lines in the laminate.

Continue until the fractured laminate is removed, then practise a traditional fiberglass repair following these steps:

Grind out the area to a taper of 12 to i from the deepest signal.

Cutting fiberglass patches starting with the largest start, working your mode smaller to fill the area that has been ground away.

Using WEST Organization Epoxy, wet out the fiberglass pieces and apply them to the repair area, starting with the largest patch starting time and working your way to the smallest. Let the epoxy cure.

Wash the area with water and a nylon scrub pad to remove whatever amine blush, and sand the repair fair with the surrounding area. If there are low spots, thicken West Organisation Epoxy with 407 Low-Density Fairing Filler and use it as a fairing compound to fill up in low areas. Allow the epoxy cure, wash it, and sand it to shape.

Afterward concluding fairing, apply two coats of unthickened Due west System Epoxy to seal the repair area.

Wash and sand the cured seal glaze of epoxy then apply a topcoat of paint or gelcoat. Encounter Fiberglass Boat Repair & Maintenance, pages 19-25 for detailed instructions.

Thermal Fatigue Gelcoat Cracks

Short, random cracks are called "crazing."

The environs can dramatically affect gelcoat. Wax can protect information technology from fading but in that location is no way to protect gelcoat confronting the repetitive expansion and contraction of temperature change. This motion can cause cracking, which may announced in a parallel or a random pattern.

Parallel patterned cracks will vary in length from short to several inches and are a few to several inches apart. I have heard them referred to as former historic period cracks. Oftentimes these are caused by an expansion of the deck laminate, making the gelcoat more than susceptible to flexural stress.

Short, random cracks are also referred to as gelcoat crazing. Crazing can be localized to a pocket-size surface area or completely embrace a deck. I have seen cockpit soles that remind me of a shattered car window. Crazing is caused by the gelcoat expanding and contracting over a given area.

Nosotros get customer calls asking if sanding the gelcoat and rolling epoxy over it will fill the gelcoat cracks and preclude them from returning. Sadly, the answer is no. Croaky gelcoat should be removed. Later on gelcoat removal, sand the fiberglass laminate with fourscore-grit sandpaper. Afterwards sanding, make any needed repairs to the surface area. Scroll on a minimum of 3 coats of WEST Organization® Epoxy to seal the fiberglass before applying a finish coat of paint or gelcoat.

When gelcoat dandy is a symptom of another problem, repairing the crack and not repairing the underlying cause could lead to repeated neat. In the example of a thick gelcoat, thinning the gelcoat is not practical.

Afterward the repairs are completed, some boats remain cleft-free for years. Taking your time and doing the job right will pay dividends in time and coin.

Our Fiberglass Boat Repair & Maintenance manual has illustrated instructions on many aspects of fiberglass gunkhole repair, including gelcoat repairs. It's bachelor for free download in the pedagogy department on westsystem.com.

Source: https://www.epoxyworks.com/index.php/repairing-gelcoat-cracks/

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