Whether you haul your boat for the entire winter or just for occasional maintenance, the most common job done while out of the water is new bottom paint. For the seasonal and year round boaters alike, the goal is a long lasting finish that will deter marine growth and protect the hull. On boats like ours the bottom paint extends above the true waterline by several inches so a new coat of bottom paint can really improve the topside aesthetics as well. Prepping and painting the hull can be a daunting task, and some choose to hire the yard. Yet with the right tools, a discerning eye, and a little bit of patience you can save a lot of money by doing the work yourself. I’ve seen prices ranging from $40-60 per foot, which would have tacked on another $2k – $3k for our boat. With the help of family we were able to sand the hull in one full day, then clean, tape, and paint it in another.
I’m sure some of you are thinking, “I’ve done this for years, what’s the big deal?” Well, just stay with me for a minute as there are a few things to look for each time you do this. Depending on your hull material there will be tell tale signs of the condition of your bottom. For the purpose of addressing the majority I will focus on fiberglass in this post. Chances are, if you own a wood, steel, or aluminum boat you know that these materials have an entirely different set of preparation requirements and inspection standards.
Fiberglass is a long-lasting and relatively low maintenance material but it can degrade over the years, particularly on boats built during the 1970’s and 1980’s. The most common issue is blistering, a small pocket of fluid between the layers caused by an improperly or incompletely cured resin, or by the osmotic pressure of water on the gelcoat.
Resins during these years were of a lesser quality due to chemical shortages, resulting in inferior curing from some manufacturers. If you see small bumps or irregularities appearing on your hull over the years, this is probably what you are seeing. Occasionally, if left alone long enough, the blister will actually pop on its own leaving a nasty looking crater and exposing your hull to slow penetration of water. I plan to write more about the process of repairing blisters in the future, but for now I just want to alert you to be on the lookout. If you decide to open one up wear eye protection and gloves, at a minimum, as the fluid inside will be under pressure and is often acidic.
Fortunately we do not have any blisters on Polynya. The previous owners, during a refit in New Zealand, stripped the hull down three millimeters, re-laminated with vinlylester resin and layers of 450 gram matt fiberglass, then coated with an epoxy barrier coat. This was absolutely a factor that we weighed heavily when considering the purchase of Polynya.
So assuming you do not have issues with blisters, the first step is to sand the entire hull. Most yards will require a vacuum sander to contain the dust, and some will even have them available for rent. If the yard does not require it, you should use one anyway as containment is the responsible thing to do. When sanding you are not looking to remove more than one layer of paint. Fair the old paint, remove loose flakes, and rough up the surface to help the paint adhere. Here’s another chance to closely inspect your hull. Most of the time this part of the boat is inaccessible, so really take your time and inspect every section thoroughly.
A few flakes and chips is normal, just smooth the edges for a seamless final result. But large scale flaking down to the barrier coat can be an indication of a bigger problem. Eventually the paint buildup can become too thick, and the barrier coat can weaken causing a loss of adhesion to the hull. If you find large sections that peel off in sheets it may be time to strip the hull. Generally speaking this will entail removing all of the paint, sanding, reapplying barrier coat, and subsequently new bottom paint. It’s a much bigger job, but certainly not insurmountable. Thankfully we did not have to strip our hull this year either as the barrier coat is not very old.
With the hull sanded and inspected, clean the hull throughly. A good supply of rags, gloves, and acetone will make fairly quick work of it, contain the dust, and dry quickly. If you are not working in a well ventilated area, a respirator is a good idea. The last step of preparation before painting is to neatly tape your water line to keep bottom paint off of the topside paint. It’s a good investment to use quality tape, ask the paint salesman which is best.
Skye took charge of the paint research and selection, ultimately choosing Sea Hawk Cukote with a BioCop additive. She spent a lot of time with the Sea Hawk rep discussing the various products and choosing a paint for our specific needs. The Cukote product is a harder ablative that should last us a few years at a time. The BioCop additive, which is mixed in right before applying, excels at reducing slime and plant growth. They have plenty of colors to choose from and we decided to change from red to a brilliant blue. A combination of rollers and brushes is needed for maximum efficiency and for larger boats an extension handle can be very helpful. A minimum of two coats its recommended but if you find yourself with some leftover paint at the end, use it up. Once the BioCop additive is mixed in the paint must be used. We took advantage of leftover paint to thicken up high flow areas such as the stem, front of the keel, waterline and so on. Painting the bottom, on a cruising boat at least, does not have to be perfectly executed. Brush strokes and other small imperfections will not hinder your performance and will never be seen. Once the paint is tacky, remove the tape. If you have worked carefully you will be rewarded with a beautiful, crisp line. When the paint is totally dry ask the yard to move the stands so that you can paint the resulting squares from their previous position. Do not move the stands yourself, ask for help.
After a weekend of work you will be tired, dusty, and dotted with bottom paint. Your arms, shoulders and back will likely ache, but the transformation will certainly make you smile. Enjoy the sight of your hard work, and money saved, soon it will disappear until your next haulout.