The Gaff Rig recognizes that boat building will involve inherently dangerous activities, and each builder must be responsible for his own safety. The Gaff Rig encourages all builders to read manufacturer’s instructions, follow all safety precautions, and be pro-active in seeking out more information on reducing the risk of injury or illness. Information presented here is general in nature and not intended to replace the safety instructions provided with products or tools.
     You’ve glassed, sanded, glassed, and sanded again, and the hull looks pretty good. You are in the home stretch now, and you can almost hear the water lapping at the sides of the hull. One of the major "final steps" awaits: painting the boat. But you’ve heard the horror stories of paint coming off in sheets on launch day, blisters and flaking starting while its still on the trailer. How can you be sure you are using the right paint?
     There are many choices of paint for the boat builder. Some builders swear by hardware store enamel, while others sing the praises of two part linear polyurethane applied with commercial grade sprayers. While there may be dozens of choices, there are just a few basic categories of paint used by builders.
     Anti-fouling, or bottom paint, is widely advertised in the chandlery ads, but is only appropriate if your boat is stored in the water. They are intended to prevent marine growth from making its home on the bottom of your boat. For boats which are "day sailed," as most Pocket Yachts are, anti-fouling paint is not needed. Anti-fouling paint is expensive, and some formulations may not be available in your local area due to environmental regulations as they may contain one or more dangerous chemicals to kill marine growth. Most are "ablative" paints, which depend on "sloughing off" to repel marine growth, which makes for an ugly finish. For most of us, this one can be scratched off the list.
      For a "day sailer", the least expensive choice of paint is alkyd, or oil based, exterior enamel, found nearly everywhere (except for areas with "low VOC" regulations, such as California.) The alternatives are water based latex paints and usually, they are not recommended for use below the waterline. Two part epoxy paints, such as garage floor epoxy, are sometimes used, but care must be used since all epoxy products are subject to chalking in UV. They are more expensive than regular exterior alkyd enamels, and may have adhesion problems with some resins.
     Next up the cost scale are the "topside" paints sold in marine supply stores. These oil based enamels may contain other additives such as Teflon, and are generally thinner than the regular exterior enamels found in hardware stores. After applying several coats, a hard, glossy film is left on the hull. These paints are sometimes called "one part polyurethane." Two part linear polyurethane paint (LPU) is still more expensive, and the most difficult to apply. When sprayed, the paint is considered hazardous, and respirators should be worn (the danger is when the sprayed particles are breathed in and absorb quickly into the blood stream or dry on the surfaces of the lung.) The labels on most brands have much less stringent precautions if you are brushing or rolling the paint on. The difficulty in applying the paint by roller or brush remains, as the paint dries quickly. Don Casey in his book This Old Boat, advises using both a roller and a brush, rolling on the paint and "tipping it out" with the brush. Its usually a job for two people to keep ahead of the fast drying paint. But the reward is a hard shell, high gloss finish.
     In making a paint choice, the builder has to be careful to ensure that the paint will adhere to the type of resin he has used. Even with proper preparation, some paints may react with some resins, causing the paint to not cure completely, or to flake off. Recently, System Three Resins started selling their own paint after seeing so many failures related to a reaction between resin and paint. By providing their own paint formulation, they ensure that there is no reaction between the ingredients of the resin and paint. But they make no guarantee with other resins.
     So your hull is ready, and you’ve made a paint choice. There’s a lot of work invested in fairing the hull. How will you know if the paint will react with the resin on your boat, causing blisters, peeling or flaking off?
     Prepare a "test patch," using the same plywood used in the boat, covered with the same fiberglass cloth and resin. Prepare it just as you have the hull, following the recommendations for washing and sanding the cured resin. Then apply the primer and finish coats of your paint choice, just as you would when painting your boat. Let the paint dry. Now for the testing. Sometimes, the paint will dry on the surface, but be gooey underneath, even if you have prepared the surface perfectly. A chemical reaction between the paint and epoxy is the culprit here. Luckily, you can easily test for this with your fingernail. The paint film should be tough and dry all the way through, and you should not be able to dislodge it with your fingernail.
     The paint has dried, and it isn’t gooey underneath. How do you know that it really "sticks" to the resin surface? Perform a cross hatch adhesion test: using an X-Acto knife or razor blade and a metal ruler, make 8 parallel cuts through the paint on the test patch, about 1/8^th inch apart. Then, make 8 more at 90 degrees to the first cuts. The result is a "grid" or section of 1/8" squares scratched into the paint surface. Take a 2" length of cellophane tape and press one inch of it across the grid, burnish it down with your fingernail, and jerk the tape off the grid quickly like you are removing a bandage from a hairy arm. If the paint has adhered well, you won’t have any 1/8^th squares of paint on the tape (although you will see the lines formed by the scratches in the paint surface.) Once your paint passes this test, you know it dries well and adheres. Time for painting!
     As when using any chemical, the builder should be careful to follow the safety instructions provided by the manufacturer. The purpose of these instructions is usually to prevent the chemicals in the paint, or the solvent used in clean up, from entering your bloodstream. They usually advise to paint in a "well ventilated area" to reduce exposure to the fumes, which prevents the chemicals from entering your bloodstream through your lungs. Even though that seems at odds with preventing dust from settling in your new paint job, the only safe alternative is to use a respirator rated for use with paints (the standard "dust mask" is not sufficient.) The use of gloves, to prevent the chemicals from entering your system through your skin (especially when using chemicals such as paint thinner or acetone), has the same goal. Care must be taken to find the proper type of gloves for the chemicals used. For instance, if acetone is used, latex gloves do not provide an effective barrier, and the chemical soaks into the skin readily.
     Just as with every step of the building process, the builder is faced with making his own decisions on how to finish his boat. The Gaff Rig wishes to remind the builder to take care choosing the proper safety precautions to take as well.