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Old 03-09-1999
Tom Wood Tom Wood is offline
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Paint the Bottom Yourself

Painting the boat's bottom with antifouling paint is 90 percent preparation and 10 percent application. The first step is to choose a antifoulant that is the best match to the water of your area. Consult with local dealers and sailors to find the most effective paint for your waters. But remember: Get numerous opinions before making your choice.

Antifouling paints are toxic to both you and the environment. While tributyl tin paints are banned nationally in most cases, even standard copper-based products should be handled with extreme care. When sanding or applying antifouling paint, cover your skin, hair and eyes completely, and wear an adequate respirator. Spread a plastic sheet under the boat to prevent toxic runoff that could reach the ground or adjacent water.

Inspection before beginning

Inspect closely for the following:

  • Thick accumulations of years of paint may need to be removed. A thorough sanding each year will prevent such a build-up. A professional sand-blasting eliminates heavy coats more easily and with less toxic dust than by sanding. Wet-blasting with a combination of sand and water is best.

  • Blisters run the gamut from minor cosmetic blemishes in the gelcoat to serious structural problems. If blisters appear to be deep and are weeping fluid of any kind, or if you're getting a high reading on the moisture meter, potentially major repairs may be in order first. If you don't have a moisture meter, test for retained water by taping (with duct tape on all four sides) a few square feet of plastic or Saran Wrap. Droplets of water condensing inside the plastic indicate excess moisture in the hull.

  • Nicks or deep scratches can be filled with a waterproof polyester filler such as America's Cup or with an epoxy filler such as Marinetex and then sanded smooth. Epoxies are more difficult to sand.

  • Inspect the keel-hull joint. If movement is evident, repairs will be necessary before painting. Simply stuffing a gap with caulking or filler is no fix for the problem.

    Hull preparation: cleaning, sanding and taping


    Most bottom antifouling paint can be rolled on. A properly rolled bottom should have an even color.

    Read the paint manufacturer's instructions carefully. All paints require the bottom to be clean--toothed or keyed by sanding--and free of peeling paint.

    Don't neglect to clean and sand the bottom of the keel and under jackstand pads. Most yards charge extra to lift the boat or rearrange the stands, so plan your work for the minimum moves.

    If your boat has a centerboard or swing keel, it will need to be cleaned and sanded as well. Gluing sandpaper to a long piece of 1/4-inch plywood makes cleaning inside the centerboard trunk easier. And while the boat is in the air, inspect the centerboard pin and lift cable.

    Once the prep work is complete, follow the paint manufacturer's directions in cleaning the bottom of sanding dust, yard grease and fingerprints. Some paints use water; others use alcohol or a proprietary solvent. Allow cleaner to evaporate before painting.

    Masking the hull or boottop paint gives both amateurs and professionals difficulty. Choose good quality tape such as 3M's Fine Line, since inexpensive paper tape causes many problems. Do not rush this job. Wavy or crooked paint lines detract surprisingly from the boat's appearance. Two pairs of eyes are best. One person pulls the tape and sighting down the hull, while the other stands amidships calling out the straightness of the line.

    Taping in short lengths usually results in a choppy, angled line. Try tacking the masking tape at the bow and peeling off an entire boat's length of tape. Wrap the tape around the curve of the hull in one smooth motion, adjusting the height of the tape by eye as you go. This may take numerous attempts and adjustments. View the tape line from all angles until you are satisfied that it is straight.

    The bottom of this boat will need a thorough cleaning and sanding before taping and painting begins. A good taping job is critical to bottom-painting success.

    Applying the antifouling paint

    Now it's time to paint. Methods include brushing and spraying, but most bottoms can be done by rolling on the paint. Remember to keep paint off yourself. Rubber gloves are a necessity, even to just open and stir the paint. Of course, if you are spraying, it is crucial to wear a professional-level respirator.

    This bottom has had blister and gelcoat removed by a peeler and is now ready for new laminate, then the antifouling.

    If rolling the paint, choose a roller cover that is made to withstand the solvents in the paint. Inexpensive paper rollers fall apart quickly. Use a thin foam roller on well-prepared racing bottoms for a smooth finish. Short-to-medium nap covers are better for rougher surfaces or for cruising boats where thicker coats of paint may be desirable.

    Keep a brush handy for areas around the rudder, strut and other protrusions too small to allow the roller to pass.

    Since the waterline receives the most wear, abuse and exposure to sunlight, apply extra paint to this area. Put one roller width horizontally around the masking tape before applying a full coat. With two full coats on the bottom, the waterline area now has four coats.

    Soon after the last coat is finished, pull the making tape off at a 4-degree angle and upward for a crisp, clean line.

    Don't forget to paint under the pads and keel bottom before launching.

    Consult the manufacturer's directions on drying time--some paints require immediate splash while others require drying time. Now let's go sailing.

    Photographs by Kathy Barron

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