Topside Paint:
A New Look for Older Boats

By BoatUS Editorial Staff

As fiberglass gelcoats age they tend to oxidize and show the wear and tear of scuffs and scrapes accumulated over the years. Even the best of boat handlers will find that a time comes when gelcoat finishes succumb to the unrelenting attack from the marine environment.

There are several types of coating systems that vary dramatically in both cost and what they deliver. These range from traditional single-part enamels that are easy to apply, to sophisticated two-part systems. Decades ago resin manufacturers saw that urethane and epoxy based coatings had applications as marine paints. Epoxy topcoats had great adhesive qualities but little resistance to UV degradation. The solution came in the form of multi-coat systems that use an epoxy primer and linear polyurethane for the finish, as well as other systems. The two-part process has been greatly simplified but still remains predominantly a professionally sprayed product.

The good news is that do-it-yourselfers can now choose from both single and two-part systems that deliver near professional-quality finishes and are easy to apply by brush and roller. Here's a quick run-down of what to expect. You’ll need to think of the job as a ladder that must be climbed one step at a time. Each rung is inscribed with words such as clean, sand, spot fill, sand, prime, sand, paint, sand, and paint once again. Notice the repetition of the word sand, more than a casual hint toward what lies ahead. In the plus column for ardent do-it-yourselfers there's money to be saved and a very real sense of accomplishment. The following step-by-step approach works for any area of your boat, but remember that now products are developed regularly and you should always follow the instructions and recommendations of the product you use. For a good example of what types of products are available see Interlux Yacht Paint.

Prep Work

Cleaning the area to be painted may seem superfluous since the surface is to be sanded, but the actual sanding process can drive contamination deeper into the gelcoat. To prevent this, wash and wax the hull with soap and water and finally do a solvent wipe. It's important to wear gloves and cover any skin exposed to chemicals. During the solvent wipe down, regularly turn the rag used and change to a new one often to prevent smearing surface waxes and other contaminants. Make note of surface imperfections as you are cleaning.

First Sanding

If the surface is in good shape, a sanding with 80- or 100-grit sandpaper may be all that's needed prior to an epoxy primer coat. If there are one or more areas where the gelcoat has been badly gouged, carry out a spot repair using epoxy products or premixed epoxy filler. Epoxy resin based fillers are slower to set and a little harder to sand than polyester or vinylester fillers, but their long-term adhesive quality and reluctance to absorb water make them the preferred repair putty. Once the filler has been sanded flush, and reprime the filled areas.

Primer Application

Primers are usually important and it’s also important to use the primer and application method recommended by the paint manufacturer. The primer application is similar to how the finish coat will be handled and it can act as a dress rehearsal, helping an applicator to get the feel of roll and tip process.

Second Sanding

Use a much lighter grade of sandpaper (220-320 grit) to smooth the surface and take out as many surface imperfections as possible. If an orbital disk sander with a thick soft foam pad is used, keep it flat and avoid scalloping the primer. A do-it-yourselfer who is careful with primer application will see less drudgery in the sanding process. In areas where you sand through the primer, spot touch up and when cured, lightly scuff-sand the area.

The slogan "what you see is what you get", underscores how smooth the surface must be. The shiny topcoat will cause shortfalls in your prep work to stand out. Remember that most of the time, admirers are yards, not inches, away when admiring your boat.

Finish Prep

Blow the dust away and do a fresh water hose down of the boat. Once everything is dry, carefully mask off the essential lines. Fine Line tape from 3M™ allows you to cut a sharper edge. Use conventional solvent-resistant masking tape to widen the area for greater protection. Just prior to application of the first finish coat, wipe the surface with a clean rag and solvent product recommended for this purpose. If you spray with air, it's important to use a compressor that does not allow oil to mix with the air.

Paint Application

Regardless of how the paint is to be applied the goal remains the same, an even thickness of film that flows out to provide a smooth, glossy surface. It's a process that sounds easy, but few really master. In truth, it's part chemistry, part good housekeeping, and part the skill of the wrist. The first challenge is to mix part A and B according to directions and stir long enough to ensure good dispersion. Next is the art of mixing the right amount and type of reducer into the mixed paint.

Mix solvent into the paint to get the proper viscosity for application. This will vary with temperature and humidity and is an essential part of making brush and roller marks disappear. Do a test spot on the hull and watch it for a few minutes to see how the paint flows, look for sags and brush marks, and when satisfied with the mix, wipe area the clean with a solvent-soaked rag and start the job from the stern or bow.

As with much of life, too much of a good thing can cause a problem. This is especially true when it comes to using reducers in paint. Your best bet is to start with the manufacturer's recommendation and gradually fine tune the mix to what works best for you. Remember that slow reducers stay in the paint longer, and can be trapped in a paint film if it is prematurely overcoated. When brushing and rolling allow the work to completely cure and sand lightly between coats.

When it's time to actually start painting, the roll and tip process has a lot to offer. The roller wielding member of the duo applies an even coat of paint to a rectangular area using vertical strokes as the brush member immediately follows up brushing out the roller pattern with horizontal brush strokes. Keep the volume of paint applied consistent along the entire hull. Don't try for full coverage with just one coat, for best results it's usually takes three coats.


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