Sharing Trade Secrets — The Bottom Line

These tips from the pros on how to handle preparation for and application of bottom paint will help you do a first-rate job and launch on time

August 7, 2002

In the days when I managed a boatyard, I often advised clients that, even though they painted their boat’s bottom every year, they needed to have a 10-year outlook on the overall antifouling process. I meant that those looking for a bargain job needed to consider paint buildup, as well as the chipping, flaking and serious adhesion problems that go hand-in-hand with a slap-dab approach and inferior material. Their up-front savings would disappear in the long run as their bottom paint fouled early in the season and in just a couple of years, needed stripping. Higher quality, self-polishing paint with better antifouling characteristics reduces the need for bottom cleaning and greatly extends, and in some cases even eliminates, the need for costly bottom stripping.

Apply an even coat of paint — avoiding drips and sags — around jack-stand pads. If time allows before launching, ask the yard foreman to move stands once the paint is cured, then prep and coat the unpainted areas under the pads. The small charge will result in a more uniform paint skin.

Modern ablative coatings gradually hydrolyze like a slow-motion Alka Seltzer tablet. Self-polishing provides dual advantages for boat owners; an ongoing renewal of exposed biocide and, at the end of its working life, the lack of a thick binder ready to flake off the surface. Prep work prior to recoating can be kept to a minimum, often just a good pressure wash-down and a light, scuff sanding.


Environmental Update
A variety of innovative new products and methods to use older technology minimize the impact from materials that can have an adverse effect upon marine ecosystems and human health. Some regulatory agencies mandate that bottom paint residue, wash-down water and leftover paint and solvents be collected. Do-it-yourselfers are prohibited from handling bottom paint in some yards.

Several revolutionary paints hold great promise. Non-toxic, ultra-slippery coatings such as Interlux’s Veridian, alternatives to conventional copper-based biocides, turn a boat’s bottom into a greased flagpole that prevents benthic organisms from getting a grip. In high-growth areas, the coating must be sponge-wiped on a regular basis. When a vessel sits idle for lengthy periods, such paints do not perform as well as conventional antifouling products. However, as the boat population density in important estuaries (such as those where shellfisheries exist) increases, the interest in alternatives to copper-based toxic antifoulants also grows.

Active biocide antifoulants remain the most popular, and copper-based coatings arguably work best for sailors today. Some manufacturers have introduced yet another twist by making water-based versions, which simplify clean-up, minimize the exposure to “user-friendly” chemicals and lessen the volatile organic compounds (VOC) evaporating into the atmosphere.


Survey The Bottom
Before you pull out the sandpaper, paintbrushes and antifouling paint, take a few minutes to inspect everything below the boot top carefully. Check key points where trouble arises — hot spots like the rudder and hull/keel interfaces — and look for signs of any previous grounding damage. If stress cracks, delamination or leaks are apparent, get an expert to diagnose exactly what’s going on. It takes an experienced do-it-yourselfer to cope with bigger problems. For major structural work, it’s usually best to bring in the pros.

Clean, Sand And Prep
Let’s assume that the bottom is in good condition, the paint is well adhered and the surface is fair and smooth enough to suit your requirements. Then all that’s needed is a light scuff sand and a good wipe down with clean cotton rags and you’ll almost be ready to start painting.

Pro Tip: A new breed of random orbital electric sander attaches to a shop-vacuum suction hose to make bottom sanding quicker, cleaner, more environmentally friendly and almost fun! These units usually can be rented at boatyards that allow do-it-yourself work, or they are available from many tool supply rental companies (companies such as Porter Cable sell such units for about $250 to $300). If you do much sanding at all, it’s a good investment.


Reading The Paper
Sanding is half energy exertion and half abrasive technology. Bargain basement sandpaper seldom works well. An abrasive’s ability to stay clog free and its tenacity for retaining a “toothy” cutting surface define the quality of sandpaper.

Pro Tip: Soft pad sanders such as the random orbital mentioned above work well with products such as 3M Stikit Disks. Most pros use rolls of 80-grit self-sticking paper to make bottom prep work quicker and more efficient.

The Big Cover-Up
Ideally, you’ll end up with little paint on the ground, in the atmosphere or on you. Many boatyards carpet the area surrounding each boat to capture debris from preparation and painting. Chandleries and catalog discounters feature full sets of protective apparel that are ideal for do-it-yourselfers. This year’s fashion statement leaves you incognito: The head-to-toe protection begins with a charcoal mask, goggles and a light cotton balaclavalike hood. Disposable paper suits shroud the body and with plastic or rubber gloves protect your skin.


Pro Tip: Don’t skimp on good-quality Playtex dishwashing gloves or a similar product that are much more durable than disposable gloves and, most importantly, are significantly more resistant to solvents. Solvents and clean-up chemicals, not the paint, destroy gloves. When bottom painting, much of the hull surface remains above shoulder height, so paint drips down one’s hands. Painters must be ready to change disposable gloves repeatedly or wear a pair that can be wiped clean with aggressive solvents. The harsh chemicals used to clean brushes and roller frames also mandate more rugged hand protection.

A Tape For All Seasons
Today, a wide array of tape products suit very specific jobs. Companies such as 3M make an assortment of excellent paper and plastic tapes with different adhesive characteristics. You can choose a tape such as “Fine Line” that can cut a crisp knife-edge border for boot-top painting. At the other end of the spectrum, rugged weatherproof products can shake off a rainy day and cope with several coats of bottom paint.

Pro Tip: To make straight lines even straighter, pull longer lengths of masking tape away from the roll and guide it onto the surface with a smooth, even motion. Sight along the length of tape as you pull it, aligning it with the tape that’s already in place. A second person, standing amidship but far enough away from the boat to see the entire waterline, can point out any hill- or valleylike diversions as you bend each length onto the hull.

The Paint Goes On
There’s nothing anticlimactic about applying bottom paint. It’s one of those grand finales that’s familiar to most sailors, like entering a good harbor at the end of a long day. As the capstone of the spring ritual, paint application needs all the finesse at one’s command. Unfortunately, it’s much easier to describe a perfect paint job than to achieve one.

In theory, all it takes is an even application of material matching the manufacturer’s recommendations for volume of paint per square foot and viscosity. In reality, the means of spreading the material is imprecise. Also, Mr. Newton’s law of gravity can’t be suspended while the paint goes on. Surface tension, adhesion, cohesion and textbooks-worth of chemistry and fluid dynamics are all out to dry-gulch the unsuspecting painter.

Regardless of whether you spray, brush or roll the product, you first must become a mix-master. A painter must be able to determine how much thinner (pros call it reducer), if any, needs to be added to the paint. You may wonder why the stuff isn’t ready to go right from the can. At certain temperatures it is, but variables such as painting technique and everything from sunlight to humidity affect paint flow. Consequently, a means of changing its behavior is essential.

In short, the painter must thin the paint enough so that brush strokes and roller dapple flow out and the paint skin stays open long enough to allow a smooth overlap as one set of roller/brush strokes or spray passes over the previous. If too much reducer is added, coverage will be poor and the paint may run. If the reducer is too slow (takes too much time to evaporate), the paint skin will remain open — will not skin cure — rapidly enough, resulting in sags, hangers and other painters’ nightmares. The best advice for those working with new materials is to follow the manufacturer’s recommendations initially and err on the side of being a little too thick rather than a little too thin. If, as you begin to apply the paint and find it hard to blend one brushed out area into the next, stir in a bit more reducer.

Pro Tip: The best spray painters and brush/roll painters have one thing in common — a methodical approach. They do everything possible to standardize their technique and apply a uniform film of paint using a smooth, gridlike approach to the surface. Many take a roll-and-tip approach, using a foam-pad roller and a good-quality bristle brush. Starting at the starboard stern quarter and working from the boot top down, I prefer to spread paint vertically using an evenly saturated roller and overlapping each vertical row by about one inch. Immediately, I follow up with horizontal strokes using a five- or six-inch, good-quality bristle brush.

The size of the square- or rectangular-shaped segment that is wet out in the roller phase varies from painter to painter. The larger the square footage of the roller application, the longer the paint has to set up, and the harder it will be to brush smooth and cut new work. With a team of two, one person can roll while the other tips the coat smooth with the brush.

Decisions such as whether to add more reducer or simply paint smaller patterns are affected by one’s technique; every painter has idiosyncrasies. Most manufacturers offer both a fast-spray reducer and a slow reducer that is meant for brush work and is much less volatile. Many veterans blend them to come up with the best flow and “skin-over” time for their particular style of painting. If you decide to thin the paint you’re about to apply, be sure to follow the manufacturer’s recommendations and never use one brand of paint with a different brand of reducer.

Those Hard-To-Get Spots
If you’re an avid do-it-yourselfer, be sure to check with the yard manager about existing protocol. I recall an enthusiastic new owner of a 40-footer taking on his first bottom paint job…and jeopardizing the lives of the people working next to him. In an effort to do the best job he could and eliminate as many jack-stand pad spots as possible, he loosened four of the seven supports holding up his boat. The paint went on and he and his helpers went off to lunch. His sloop had been stored with the mast stepped, and as an early spring southerly began to build, the three jack stands that supported the boat started to oscillate. By the time an attentive yard worker noticed what was going on, the boat had twisted one of the three remaining stands loose and all that kept the boat standing on its keel were a V-stand at the bow, a flat pad stand aft and a lot of luck. Within squashing distance another couple labored, unaware of the potential disaster just a few feet away.

Most boatyards forbid customers to touch boat stands. If you want to paint under-the-pad spots before your boat is hoisted into the Travelift slings, ask the yard foreman to have his crew move the stands several days after your initial paint work is dry. Moving the stands too soon will cause paint that is only skin dry to slide and deform — creating more problems than it solves. I prefer to paint the bottom one weekend and have the yard crew move the stands later in the week, allowing me to do the pad spots the next weekend.

Pro Tip: If you store your boat in your own backyard, heed the advice of jack-stand innovator Tom Brownell: “Always chain stands to each other athwartship and if they are set up on anything other than concrete or blacktop, make up six-inch by six-inch (minimum) plywood foot pads for each leg. These can be cut from a sheet of 3/4-inch exterior-grade plywood.”

By planning your projects ahead of time, including realistic time and dollar constraints, you’ll be able to get the jobs done on schedule and, most important of all, youÕll hit the water with a boat that’s ready to go cruising.

Ralph Naranjo is technical editor of Cruising World.


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