Own a boat long enough; you’ll likely need some gel coat repair. Fortunately, patience and simple tools can make the task quite doable. Clean the damaged area before applying the gel coat. Wear a mask and disposable gloves to protect yourself from the noxious resin fumes. Mix the gel coat according to the manufacturer’s instructions.
Scratches
Sc scratches are an inevitable part of boat ownership, from rope chafing on coamings to impact damage from winch handles. Surface scratches can often be buffed away with polishing compound, but deeper ones require filler to blend them into the surrounding gel coat. Gelcoat paste offers both filler and finish in a single application, but it must be applied carefully to ensure that the finished repair is smooth and even.
Start by thoroughly cleaning the area to be repaired with a cloth dampened with acetone. This removes any contamination that might interfere with the adhesion of the new gelcoat. Once the area is clean, use 80-grit sandpaper to roughen the affected surface and create a shallow bevel for better bonding. This will also improve the flow of water over the hull. Carefully tape off the area around the scratch with 2-inch 3M Scotchbrite Painter’s Tape. This protects adjacent areas from gelcoat spatter and accidental sanding.
When applying the gelcoat paste, make sure it’s a generous amount. Using too little will result in an uneven repair. Once the application is complete, let it cure for about 15 minutes and then wipe down with a lint-free cloth soaked in acetone to remove any excess. Allow the gelcoat to dry completely before proceeding with sanding and buffing.
Deeper gelcoat scratches are a bit more difficult to repair, but not impossible. Instead of simply spreading the gelcoat paste over the entire scratch, work a screwdriver or some other tool into the crack to open it up. This will allow the gelcoat to bridge the crack, but will leave a void in the middle that you must fill with more of the paste.
Once you have color-matched the gelcoat, add the catalyst per the manufacturer’s instructions. Mix it well and apply to the scratch, sprinkling lightly for best coverage. The mixture will be slightly fluid at first, but it will begin to thicken as it sets up. Use a plastic putty spreader to work the paste into the crack, filling it slightly higher than the surrounding surface to allow for sanding later.
Gouges
Seeing scratches in your boat gelcoat is never good, but the sinking feeling you get when those scratches turn into gouges is even worse. Gouges in the gel coat of a fiberglass vessel are not only unsightly but can cause problems with the structural integrity of your boat’s hull. It is important to deal with gouges in gelcoat as soon as they appear.
Repairing deep gouges in gelcoat can be a bit more difficult than dealing with scratched surfaces. In some cases, you will need to use epoxy resin and fillers instead of gelcoat paste. This process is a little more time-consuming and requires more knowledge of fiberglass construction, but it can be done. It is also important to know that the repairing of deep gouges in gelcoat can often require additional structural fiberglass work or filler to ensure a strong and long-lasting finish.
Before beginning a gelcoat gouge repair, it is important to remove any loose or flaking material from the area. This can be done with a small wood or plastic putty knife, but can also be done using a power sander with a medium grit. It is also important to be certain that the area is clean, dry and free of wax or grease.
Once the area is clean, it is important to tint the batch of gelcoat you are working with to match the color of the surrounding surface. This can be done by adding pigments to the mixture before you add the catalyst or by purchasing a gelcoat repair kit that comes with tinted gelcoat in your desired shade. In addition, it is important to be sure that the gelcoat you are using is UV-resistant, as this will help extend the life of your repair.
If you are repairing a large area, you can use a brush or spray-on application to apply the gelcoat. It is important to work fast, as the gelcoat will start to harden within about 15 minutes of adding the catalyst. It is also important to be certain that you are applying the gelcoat evenly across the affected area.
Cracks
From abrasions caused by rope chafing on cockpit coamings to the occasional dropped winch handle, gelcoat chips are an unfortunate reality of boat ownership. But fixing them can be a fairly simple task if the proper preparation and processes are followed. A good mix of tools and materials along with a clean work area will help to ensure success.
When repairing crazing, it is important to take the time to properly sand the damaged area with medium-grit sandpaper. Be sure to sand until there is no shine left; this will help ensure that the new gel coat adheres properly. In the case of deep crazing, it may be necessary to wet-sand the surface in order to remove any remaining blemishes.
Linear cracks are a natural part of the flexing process of fiberglass parts and can occur both immediately after the mold pull or years down the road. These cracks can either be cosmetic or indicate structural problems that must be addressed. Fortunately, these cracks are usually confined to the gelcoat and do not extend into the laminate.
Spider cracks, on the other hand, often indicate serious structural problems and should be dealt with as soon as they are noticed. These cracks are generally a result of excessive bending of the fiberglass parts themselves, or they can be caused by fixtures that are putting a strain on certain areas – such as bolted attachments – and are not flexible enough themselves.
When attempting to repair cracks in the gelcoat, it is important that the cracks be opened for inspection in order to determine how far they extend into the laminate. To do this, a putty knife can be used to open the crack so that you can see where it is going. Once you have inspected the crack, it is important that the area is sealed off from air in order to allow the gel coat to cure correctly. This can be done by using a PVA curing agent or a piece of plastic wrap or wax paper.
Once the area is sealed off, the cracked gelcoat can be filled with a pigmented gel coat paste. Be sure to use a product that is formulated for gelcoat, such as G/flex 655, Six10 or WEST SYSTEM 105 Epoxy Resin/20X Hardener thickened with 406 Colloidal Silica Adhesive Filler. Once the gel coat is cured, it can be sanded smooth (wet sanding works well with gelcoat) and polished for a beautiful finish.
Oxidation
The hull and deck of your sailboat take a beating from environmental forces. Seawater — the universal solvent — and sun’s plastic-killing UV radiation wear down gel coat, causing everything from stains and scuffs to gouges and structural damage. But a bit of regular preventative maintenance goes a long way toward prolonging your fiberglass’s lifespan. Fortunately, most do-it-yourself sailors are willing to roll up their sleeves and annually clean the slate with a bit of elbow grease.
First, thoroughly clean the affected area of any oil and grease. Then mask the surrounding areas with tape to protect them from sanding particles that can oversaturate the new surface and cause the paint job to fail. Next, select a portion of the hull that is identical in color to the damaged area. This will serve as your mixing palette and allow you to match the gelcoat color precisely. Sand the affected area lightly using 320 and then 800 grit sandpaper. This will smooth the damaged gel coat and prepare it to accept a fresh layer of paint.
Before you apply any gelcoat repair products, check the manufacturer’s instructions to make sure that you have the correct ratio of hardener and base. Different gelcoat kits require different amounts of each to cure properly. Mix enough of the product to allow you to spread it over the sanded area using a putty knife. You’ll have about 10-15 minutes to work before the gelcoat starts to harden.
Using an acid-based stain remover, such as a black streak or rust stain remover, can help you get rid of any darkened blemishes. If the stain is stubborn, you may need to use a stronger chemical, such as an alkaline or carbolic acid cleaner.
Cracks in gel coat occur when stress reaches a point where the fibers and resin that make up the fiberglass fabric begin to separate. The stress may be caused by a sudden impact or simply from years of gradual flexing of the part.
Cracks in gel coat should be repaired as soon as possible to prevent water from seeping into the fiberglass structure and rusting metal components. While this type of deterioration can’t be completely prevented, proper maintenance of your gelcoat will significantly extend the life of your boat.
