The most horrifying hole in a fiberglass hull is quickly healed with a bit of glass fabric, Fiberglass Repair By Don Casey. Revised by BoatUS editors in April 2012.
How to Patch a Fiberglass Hull
Edit Article How to Fiberglass a Boat. Fiberglass is used to build boats for many reasons. Chief among these are its durability, but also its easy to repair.
A holed fiberglass sailboat or canoe looks bad, but unless the boat is structurally damaged, it's easy to repair. With patience, you can rebuild the hull as good as new. Tools: disc sander or electric drill with sanding disc, buffing attachment for sander or drill, scissors, mixing can and stir stick, paintbrushes, sanding block. Materials: medium-grit sanding discs, soft cloths, acetone, light cardboard, plastic wrap, masking tape; quart-size polyester resin fiberglass repair kit, or polyester resin and hardener, 10-ounce roving, and 7 1/2-ounce fiberglass cloth; fine, very fine, and extra-fine wet-or-dry sandpaper; gel coat to match hull, fiberglass rubbing compound, car wax. Time: about 2 days, depending on size of hole. To patch the hole, buy a quart-size polyester resin fiberglass repair kit at a marine store; from the boat's manufacturer, buy gel coat to match the color of your boat. If you can't find a repair Kit buy 1 quart of polyester resin and hardener, and 2 square feet each of 10-ounce roving and 7 1/2-ounce fiberglass cloth. Buy fiberglass rubbing compound to finish the repair. To prepare a firm base for the patch, enlarge the hole. Grind down the edges of the hole to firm fiberglass with a disc sander or an electric drill with a sanding attachment, and a medium-grit sanding disc. When you've exposed sound fiberglass all around the hole, taper the ground hole out into the sound hull, so that the outside edge of the hole is at least 2 or 3 inches wider than the inside edge. This provides a firm bonding surface for the patching material. When the hole is completely sanded, wipe the dust off with a soft cloth and then clean the damaged area with a cloth soaked in acetone. Caution: Acetone is extremely flammable. Work in a well-ventilated area, and don't smoke; dispose of acetone-saturated cloths immediately in an outside vented container. To contour the patch to match the shape of the hull, cut a backing piece from light cardboard. Cut the cardboard at least 2 inches larger than the hole all around. Cover the piece of cardboard smoothly with plastic wrap, taped into place, so that the patch won't stick to it, and then set the backing into place on the inside of the hull; it should cover the hole completely. Carefully bend the cardboard to match the curve of the hull, and tape it firmly into place with masking tape. The curve of the cardboard must match the hull contour precisely or the patch will be weak. When the hole is backed, prepare the patching material. The hole will be filled with pieces of 10-ounce roving to the thickness of the hull; the top layer is cut from 7 1/2-ounce fiberglass cloth to match the hull surface. Cut the first layer of roving to fit the inside diameter of the hole, at its smallest point. Cut successive layers slightly larger, to overlap the inside layers and feather out over the tapering edges of the hole. Stack the layers of roving in the hole as you cut them so you can see how many thicknesses to cut. When you have enough layers of roving to make the depression just level with the surrounding hull surface, cut a piece of fiberglass cloth to complete the patch, overlapping well onto the sound hull surface. Lay the pieces of roving and fiberglass out in order on a clean surface near the boat. Then, with your patching material at hand, mix polyester resin and hardener in a can as directed by the manufacturer. Mix only as much resin as you can apply in less than 1/2 hour; it hardens quickly. Make sure the temperature in your work area is at least 60° F. Set the first patch of roving -- the smallest one -- on a clean piece of cardboard near the boat. Working quickly, apply catalyzed resin to the roving with a small paintbrush; brush the resin well into the roving to soak it thoroughly. The roving should be completely wet through, but not dripping. Pick up the piece of wet roving and set it into the prepared hole in the hull, centered in the bottom of the depression. Press it smoothly into place with the brush, dabbing it from the center toward the edges. Set the next smallest patch of roving on the cardboard and apply catalyzed resin to it as above; soak it thoroughly. Position the saturated roving over the first layer in the hole, and smooth it into place with the brush. Repeat, applying resin and smoothing each roving layer into place, to build up a smoothly graduated patch of new material in the hole, tapering with the edges of the hole to match the contour of the hull. When all the layers of roving have been applied, close the patch with the prepared piece of fiberglass cloth. Instead of soaking the cloth with resin, set it directly over the patch, dry, and work it down into the resin-soaked roving with the paintbrush. If necessary, add a small amount of additional resin to saturate the edges of the fiberglass cloth, but be sparing; too much resin will weaken the patch. Use only enough resin to thoroughly wet and darken all the roving and cloth. Let the completed patch dry for at least 8 hours, as specified by the resin manufacturer. When the patch is completely dry, remove the cardboard backing from the inside of the hull; the patch should follow the contour of the hull exactly. Remove any irregularities in the patch surface, and correct contour as necessary, with a disc sander or an electric drill with a sanding attachment, and a medium-grit sanding disc; do not oversand, but smooth the area to match the hull contour exactly. Then smooth the sanded surface by hand with a sanding block and fine-grit wet-or-dry sandpaper, using long back-and-forth strokes over the patch. When the patch is smooth and matches the hull contour, clean the area with acetone to remove all dust. Finish the patch with gel coat, to match the color of the hull. Mix the gel coat as directed by the manufacturer. Brush a thin layer of gel coat onto the patch area, to cover the patch completely and evenly. Then, working quickly, carefully smooth a large piece of plastic wrap directly over the wet gel coat, smoothing out all air bubbles and wrinkles, to cover the patch completely. If necessary, use overlapping strips of plastic to cover the patch completely. You must cover the gel coat with plastic or it won't dry smooth. Let the gel coat dry for at least 8 hours, as directed by the manufacturer. When the gel coat is completely dry, peel off the plastic wrap; the patch surface should be very smooth. Carefully hand-sand the patch area with fine-grit wet-or-dry sandpaper to remove any excess gel coat and contour the patch to match the hull exactly. Smooth the sanded patch carefully and remove any scratches with very fine and then extra-fine wet-or-dry sandpaper; use enough water to prevent scratching the gel coat. Finally, clean the rebuilt hull area thoroughly with a wet cloth. To polish the patch, apply fiberglass rubbing compound to the sanded gel coat and buff the surface as directed by the manufacturer; use the buffing attachment of the disc sander or electric drill. After buffing the patch, apply a protective coat of car wax to the hull surface. Now that your boat's hull is patched and buffed, let's turn our attention to the interior of the boat. Learn how to make built-in waterproof cockpit cushions on the next page. For tips on caring for and repairing other types of sports equipment, try the following links: From its inception in 1977, the Chicago Marathon has held sway as one of the world's largest marathons. Why is the Windy City such a popular race destination, and how can speedsters register to compete for the substantial cash prize? How Black Water Rafting Works Black water rafting is a new take on both spelunking and tubing. What's it like to tube through a cave?
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To begin you will need to purchase a polyester resin fiberglass repair kit from your local boat store that works with the manufacturer of the boat. It will need.
How to Patch a Fiberglass Hull. A holed fiberglass sailboat or canoe looks bad, but unless the boat is structurally damaged, it s easy to repair.
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Revised by BoatUS editors in April 2012 Few things are more disheartening to the boatowner than staring at the fuzzy edge of broken fiberglass. However, the repairability of fiberglass is one of its best characteristics. The most horrifying hole in a fiberglass hull is quickly healed with a bit of glass fabric, a supply of resin, and equal parts skill and care. And the repair is less patch than graft--a new piece of skin indistinguishable from the old. Fiberglass lay-up is nothing more than layers of glass fabric saturated with polyester (or epoxy) resin, yet most boatowners imagine a self-applied repair as only slightly more durable than a wet Band-Aid. This is a false concern. Follow a few simple rules and your lay-up will be just as durable as the rest of the boat. Cut Away the Damage Impact damage nearly always results in some associated delamination. Tap the impact area with the end of a plastic screwdriver handle to determine the extent of the damage; solid laminate sounds sharp, delamination dull. Check inside the boat to make sure nothing is in the way, then make a circular or oval cut to remove the damaged area. Never try to save damaged fiberglass; always cut it out and replace it with new laminate. Check all the edges and enlarge the hole if you find any additional delamination. Working from Inside If the damage area is small and above the waterline, make the repair from inside the hull, if possible. You are going to bevel the edge of the hole with a 12-to-1 chamfer, so if you repair a 3-inch diameter hole through a 1/2-inch-thick hull from the outside, you end up with about 15 inches (diameter) of surface damage to refinish. Repair it from the inside and you have only a 3-inch hole to refinish. A second reason to make the repair from the inside is that you can back the hole on the outside with a polished surface, creating a mold that allows you to lay-up the repair the same way the boat was built--gelcoat first. Very little finish work will be required. Dewax Before grinding, always wash the area around the hole thoroughly with a dewaxing solvent. The original fiberglass will have traces of mold release on the outer surface and wax surfactant on the inner surface. If you fail to remove the wax first, grinding will drag it into the bottom of the scratches and weaken the bond. Grind During the lay-up process, because each layer is applied before the previous one fully cures, each application of resin links chemically with the previous one to form a solid structure--as though all the layers were saturated at once. Unfortunately, no matter how strong the laminate-to-laminate bond, the initial bond of any repair is mechanical, not chemical. Consequently, grinding is the key to getting a strong repair. Use a disk sander loaded with a 36-grit disk to grind a 12-to-1 bevel around the perimeter of the hole inside. Also grind a rectangular area of the inner surface a few inches beyond the bevel to accommodate a finishing layer of cloth. Protect your eyes with goggles and your lungs with a good dust mask. Long sleeves will reduce skin irritation. Tilt the sander so that only one side of the disk is touching the surface and the dust is thrown away from you. After you brush away the dust and wipe the area with an acetone-dampened rag, the sanded surface should have a uniform dull look. Mask and Mold To prevent any resin runs from adhering, give the exterior surface of the skin around the hole a heavy coat of paste wax, taking care not to get any on the edge or inside the hole. Mask the area below the hole. Cut a scrap of smooth plastic laminate (Formica) or thin clear acrylic (Plexiglas) a foot larger than the hole. Wax this backer, then spritz it with polyvinyl alcohol (PVA) mold release. Screw or tape the backer to the outer surface. If the hull is flat or curving in only one direction in the damage area, the backer will assume the correct curve. If the hull is spherical, i.e. curving in two directions, acrylic screwed to the hull can sometimes be coaxed into the correct shape if warmed with a heat gun (before applying the mold release). Fabric Cut sufficient fiberglass fabric to fit the hole. Unless you have reason to follow a different schedule, begin with two layers of 1 1/2-ounce mat, then alternate mat and 6-ounce cloth. The number of laminates will be determined by the thickness of the hull; you will roughly need one layer for every 1/32 inch. Cut the first layer of mat the full size of the ground depression, then cut subsequent pieces about an inch smaller. This order of largest piece first, then progressively smaller pieces is how you are going to apply the new fabric. We do it this counterintuitive way, particularly with polyester resin, because it maximizes the area of the secondary bond, the adhesion of the new cloth to the old laminate. Using Polyester or Vinylester Resin For above-the-waterline repairs you can use either polyester or vinylester resin. Of course, for an even stronger repair you can also use epoxy, but not if the surface of the repair will be gelcoat. (You should use epoxy for underwater repairs.) If you are doing your repair with polyester or vinylester resin, you need laminating resin. Laminating resin does not fully cure while exposed to air, which allows you to get a chemical bond between the multiple laminates you will be applying. To get the final laminate to cure, you simply seal it from the air, either with a plastic or by coating it with polyvinyl alcohol (PVA) mold release. Catalyst The catalyst for both polyester and vinylester resin is methyl ethyl ketone peroxide, or MEKP. Do not confuse MEKP with the common solvent MEK; they are not the same. Polyester resin usually requires 1 to 2 percent of hardener by volume (follow the manufacturer's instructions). As a rule of thumb, four drops of hardener will catalyze 1 ounce of resin at 1 percent. Be certain to stir the catalyst in thoroughly or part of the resin will be undercured, weakening the lay-up. You can adjust the cure time by adding more or less catalyst. Temperature, weather, and the thickness of the laminate all affect curing times. Some experimentation is generally required. The mix shouldn't kick (start to harden) in less than 30 minutes. Hardening in about two hours is probably ideal, but overnight is just as good unless the wait will hold you up. Always err on the side of too little catalyst; if you add too much, the resin will "cook," resulting in a weak lamination. Gelcoat Gelcoat is essentially pigmented polyester resin. Start the repair by spraying or brushing about 20 mils of color-matched gelcoat onto the waxed backer. Check the gelcoat thickness with a toothpick; 1/32 is about 30 mils. Lay-up When the gelcoat kicks, wet it with polyester resin and lay-up the first two layers of mat and one layer of cloth, compressing them against the gelcoat and working out all voids and bubbles with a resin roller and/or a squeegee. Let the first three plies kick, then lay up four additional plies. Never lay up more than four plies at a time or the generated heat may "cook" the resin and weaken it. Continue the lay-up four plies at a time until the repair is flush with the interior surface. Finish For a finished look, cut a rectangular piece of mat and one slightly larger of cloth and apply these over the patch, smoothing them with a squeegee. Seal this top layer with plastic or PVA to allow a full cure. Remove the backer from the exterior surface. Fill imperfections in the new gelcoat with gelcoat paste and allow it to cure fully. Clean the area around the patch, then sand--if necessary--and polish the repair area. Don Casey has been one of the most consulted experts on boat care and upgrades for 30 years, and a panelist on our "Ask The Experts" website for a decade. He and his wife cruise aboard their 30-footer part of the year in the eastern Caribbean. His books include Don Casey’s Complete Illustrated Sailboat Maintenance Manual, and the recently updated This Old Boat, the bible for do-it-yourself boaters.
Technical Staff Report. First, we will classify the types of holes we are discussing as ones that are round and have been machined, probably with a drill, as opposed.