Gel coat is a polyester resin or plastic that cures rapidly and is normally sprayed inside a highly-polished female mold but, with proper preparation and a few tools, it can also be applied externally. Anyone with reasonable skills is capable of refinishing a boat.
Preparation
Step 1
Remove all stainless or aluminum fittings and trim in order to sand and gel coat under those items.
Step 2
Wash the total surface area to be prepared with acetone. Use clean rags to remove all contaminants, oil, grease, wax or silicone.
Step 3
Cover the areas you want to protect from gel coat over-spray and damage while sanding by using masking tape.
Step 4
Grind, sand and fill or level any damaged areas with fiberglass or fairing compound. The area should be smooth and made to blend into the original contours of the boat.
Step 5
Sand the entire area to be gel coated with 180-grade sandpaper. Pay particular attention to sanding edges where adhesion problems occur. Feather out deep scratches, gradually tapering into larger areas that won't be visible after the new gel coat is applied.
Step 6
Wash the entire prepared surface once more with acetone, using clean rags to remove any dirt, grease or oils that have accumulated during your prep work. Wipe the entire project with a "tack cloth." This can be purchased at any paint store and is used to remove dust or lint.
Gel Coat Application
Step 1
Mix the gel coat and catalyst. The normal ratio is 40 cc hardener MEKP per one gallon of gel coat. Stir well for at least a minute. Do not catalyze more than you can apply in a 10-minute period. If you need to thin the gel coat, acetone may be used but never more than a maximum of 15 percent. To avoid lumps and clogs, pour the mixed gel coat through a paint stainer before it enters the spray gun.
Step 2
Spray the gel coat onto the surface from a distance of 15 inches using 40 to 50 pounds of air pressure. Using steady sweeping motions, spray at a speed that will create a wet shine and an even overlap of product. Two coats are fine. Remember you have a limited time window before the product gels and begins to cure. The desired thickness of gel coat needs to be roughly the same thickness as 20 sheets of paper. Continue this process again, covering the entire area. If you are doing a large boat, have an assistant to prepare the next batch of gel coat while you spray, timing it with your use of product.
Step 3
Clean the spray gun and equipment immediately upon completion of spraying the gel coat. Once gel coat has cured its is difficult to remove.
Step 4
Let the gel coat cure for at least 24 hours, then wet sand with a hand block and 320-grit sand paper. The intention is to knock off the orange peel finish left from spraying. Use 400-grit sand paper, 600-grit sand until you reach 1,200-grit sand paper. You will begin to see a dull but smooth finish that can be polished with first medium, then finer grades of compound and a power buffer.
Tips and Warnings
- Be sure that your boat has not been painted. Gel coat will not adhere to paint. Put all tools in a bath of acetone in order to keep them clean. Gel coat is extremely sticky and impossible to remove once it has cured.
- Wear protective clothing, eye-wear, latex gloves and a proper respirator or mask to reduce exposure to contaminants. You will need a well-lit and well-ventilated area. Remember that all of these chemicals are highly flammable and toxic.
Things You'll Need
- Screwdrivers and wrenches specific to the fasteners on your boat
- Acetone
- Masking tape
- Sand paper
- MEKP catalyst
- Polishing compound
- Electric or air powered power buffer
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