Does your boat’s topsides look shabby? Does polish and buffing do little to make the hull look good? Have you had the boat for five to seven years and never repainted it? If you answer yes to any of the above questions, it may be time to repaint the topsides.
“But that’s a five to ten thousand dollar job,” you say. Former president of Interlux and now with Quantum Paints, Steve Schultz says, “98% of painting is preparation and you can do all the prep work yourself.” In fact, the only part a professional spray operator needs to do is the actual topside spraying which usually takes less than one day in the spray booth and two or three days to thoroughly dry, depending on the ambient temperature. For a few hundred dollars and some dust under your fingernails you can increase the boat’s value by thousands of dollars.
The first step in any repaint job is to fill any cracks, dings and dents and get the hull absolutely smooth. If you are working on a fiberglass hull, first clean the entire hull using soap and water. Repair any dings and dents using a marine filler such as Interlux’s Interfill, Awlgrip’s professional Awlfair, or an equivalent product from any other manufacturer. If you cannot get any of these professional products, use a little polyester or epoxy resin and add micro-balloons until the mixture is the consistency of peanut butter. Mix the resin well before adding micro-balloons. Use a plastic spatula to apply the mixture after you have mixed it. Be sure to wear a dust mask.
Now buy yourself a sanding longboard and sandpaper from your local chandlery. If your hull is very rough or you need to remove a previous paint layer use 100 or 120-grit. For fairly smooth hulls use 220 or 300-grit. You will also need some 320 and 400-grit for the final sanding.
Sand the entire hull until it is perfectly smooth. This step can take up to a week if you do it carefully. Use a long flexible batten to check for smoothness. On a 12 meter boat the criteria for smoothness was that you could not get a piece of paper under the batten, but you do not need to go that far.
Only when the hull is smooth should you wipe it down with a solvent. This will get rid of any grease or wax on the surface. At this stage I would advise that you have a professional look at it. If you are changing color from a dark to light color, for example, the professional might recommend an undercoat to cover the dark color. A good professional will also tell you where the hull is unfair or has any other problems.
As soon as the hull is acceptable, it should be undercoated with a hi-build primer. Before undercoating, mask off at the boot-top, the underbody, and along the toerail to protect against overspray. Remember to cover the entire deck or you may get overspray on it. You can also roll-and-tip the primer layer to reduce the cost of having it sprayed. (See sidebar.)
The primer helps to smooth out minor imperfections and will need to be sanded thoroughly. Use 320 to 400-grit to sand the topsides smooth. Note: Some painters recommend no finer than 320 grit to give the topsides a rough enough finish for good paint adherence. Wipe the topsides down with a solvent to remove any dust residue and oil or grease. Be aware that oils from your hands can mar the final surface so keep your hands off.
After the primer has been sanded, many painters will use an undercoat the same color as the topcoat to ensure the primer color does not affect the finished top coat color. If an undercoat has been sprayed on, you will need to sand it with 320 to 400 grit. By priming and sanding you can spot any problems and fix them before the topcoat is applied. Only after the hull is perfectly smooth should the topcoat be sprayed.
Do not go into the spray booth without a respirator when the hull is being painted. Most topside paints contain isocyanates which are dangerous to your health. Leave the hull in the spray booth for at least 24 hours for the paint to harden, then carefully peel off the masking tape and paper. You should have a perfectly finished hull.
Paint is rolled onto the topsides using a marine grade sponge roller and then ‘tipped’ by using the tips of a dry brush. Do not put the brush in the paint, just use the brush to make the layer of freshly rolled wet paint smooth. You will find that working from the rail to the boot top gives you the smoothest finish.