How To Do Boat Fiberglass Repair

How To Repair a Fiberglass Boat

Few things are more than disheartening to the boat owner than staring at the fuzzy edge of cleaved fiberglass. However, the repairability of fiberglass is one of its all-time characteristics. The most horrifying hole in a fiberglass hull is apace healed with a fleck of glass cloth, a supply of resin, and equal parts skill and care. And the repair is less patch than graft — a new slice of pare indistinguishable from the old.

Fiberglass lay-up is nada more than than layers of glass fabric saturated with polyester (or epoxy) resin, nonetheless most boatowners imagine a self-applied repair every bit only slightly more durable than a wet Rough-and-tumble. This is a false concern. Follow a few elementary rules and your lay-upwardly will be just every bit durable as the residual of the boat.

Cut Away the Damage

Impact impairment well-nigh always results in some associated delamination. Tap the touch area with the end of a plastic screwdriver handle to determine the extent of the impairment; solid laminate sounds sharp, delamination dull. Bank check inside the boat to make sure goose egg is in the way, and so make a circular or oval cut to remove the damaged area. Never try to salvage damaged fiberglass; always cut it out and supercede it with new laminate. Cheque all the edges and enlarge the hole if you find whatsoever additional delamination.

Working from Inside

If the damage area is small and higher up the waterline, make the repair from inside the hull, if possible. You lot are going to bevel the edge of the hole with a 12-to-one chamfer, and so if yous repair a 3-inch diameter hole through a i/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 three-inch hole to refinish.

A 2d reason to make the repair from the within is that you can back the pigsty on the outside with a polished surface, creating a mold that allows you to lay-upward the repair the same way the boat was built--gelcoat first. Very trivial cease work volition be required.

Dewax

Before grinding, always wash the area around the hole thoroughly with a dewaxing solvent. The original fiberglass volition have traces of mold release on the outer surface and wax surfactant on the inner surface. If yous neglect to remove the wax kickoff, grinding will drag it into the bottom of the scratches and weaken the bond.

Grind

During the lay-upwards process, because each layer is applied earlier the previous one fully cures, each application of resin links chemically with the previous one to grade a solid structure--every bit though all the layers were saturated at once. Unfortunately, no matter how strong the laminate-to-laminate bond, the initial bond of whatsoever 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-one bevel around the perimeter of the pigsty inside. Also grind a rectangular expanse of the inner surface a few inches across the bevel to accommodate a finishing layer of cloth. Protect your optics with goggles and your lungs with a good dust mask. Long sleeves will reduce skin irritation. Tilt the sander and so that only i side of the disk is touching the surface and the grit is thrown abroad from you lot. After you lot brush away the dust and wipe the surface area with an acetone-dampened rag, the sanded surface should have a uniform dull look.

Mask and Mold

To preclude whatsoever resin runs from adhering, give the exterior surface of the pare around the hole a heavy coat of paste wax, taking intendance not to get any on the edge or within the pigsty. Mask the surface area beneath the hole.

Cut a scrap of smooth plastic laminate (Formica) or thin clear acrylic (Plexiglas) a pes 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 merely one direction in the damage expanse, the backer will presume the correct bend. If the hull is spherical, i.eastward. curving in two directions, acrylic screwed to the hull tin sometimes exist coaxed into the right shape if warmed with a rut gun (before applying the mold release).

Fabric

Cut sufficient fiberglass fabric to fit the hole. Unless you accept reason to follow a unlike schedule, begin with 2 layers of 1 i/2-ounce mat, then alternate mat and 6-ounce cloth. The number of laminates will exist determined past the thickness of the hull; you will roughly need one layer for every one/32 inch. Cut the first layer of mat the full size of the ground depression, then cutting subsequent pieces about an inch smaller. This order of largest slice commencement, so progressively smaller pieces is how you are going to use the new fabric. We do information technology this counterintuitive way, particularly with polyester resin, considering information technology maximizes the expanse of the secondary bond, the adhesion of the new fabric to the one-time laminate.

Using Polyester or Vinylester Resin

For above-the-waterline repairs you can use either polyester or vinylester resin. Of form, for an even stronger repair you can also use epoxy, simply not if the surface of the repair volition be gelcoat. (You should use epoxy for underwater repairs.)

If you are doing your repair with polyester or vinylester resin, you demand laminating resin. Laminating resin does not fully cure while exposed to air, which allows yous to get a chemical bail between the multiple laminates y'all will exist applying. To get the concluding laminate to cure, y'all just seal information technology from the air, either with a plastic or by blanket information technology with polyvinyl booze (PVA) mold release.

Catalyst

The goad for both polyester and vinylester resin is methyl ethyl ketone peroxide, or MEKP. Do not misfile MEKP with the common solvent MEK; they are not the same.

Polyester resin usually requires 1 to 2 percent of hardener past volume (follow the manufacturer'southward instructions). Every bit a rule of thumb, 4 drops of hardener volition catalyze ane ounce of resin at 1 per centum. Be certain to stir the catalyst in thoroughly or part of the resin will exist undercured, weakening the lay-up.

You tin adjust the cure fourth dimension by adding more than or less catalyst. Temperature, weather condition, and the thickness of the laminate all bear on curing times. Some experimentation is more often than not required. The mix shouldn't kick (starting time to harden) in less than 30 minutes. Hardening in about two hours is probably ideal, only overnight is simply every bit adept unless the wait volition concord you lot up. Always err on the side of too little goad; if you add together as well much, the resin will "melt," resulting in a weak lamination.

Gelcoat

Gelcoat is essentially pigmented polyester resin. Start the repair by spraying or brushing about twenty 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 offset 2 layers of mat and one layer of textile, compressing them against the gelcoat and working out all voids and bubbles with a resin roller and/or a squeegee.

Allow the first 3 plies kick, and then lay upward four boosted plies. Never lay up more than four plies at a time or the generated oestrus may "cook" the resin and weaken it. Go on the lay-up four plies at a time until the repair is flush with the interior surface.

End

For a finished look, cutting a rectangular piece of mat and one slightly larger of fabric and apply these over the patch, smoothing them with a squeegee. Seal this top layer with plastic or PVA to permit 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, so sand, if necessary, and shine the repair expanse.

Author

Don Casey

Correspondent, BoatUS Magazine

Don Casey has been ane of the most consulted experts on boat care and upgrades for 30 years, and is i of the BoatUS Magazine's console of experts. He and his wife cruise aboard their 30-footer part of the yr in the eastern Caribbean area. His books include Don Casey'south Complete Illustrated Sailboat Maintenance Manual, and the recently updated This Old Boat, the bible for practise-it-yourself boaters.

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Source: https://www.boatus.com/expert-advice/expert-advice-archive/2012/july/how-to-repair-a-fiberglass-boat

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