Painting the bottom of the hull with antifouling paint is mandatory for any boat that is stationary in the water. And the best time is now, in winter, when the weather gets drier. Check out 10 questions about the subject:

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1. Does every boat need background painting?

No. Only those stored in wet spaces, therefore in permanent contact with water. That is, sailboats and bigger boats. This is because the gelcoat that coats the fiberglass must not be submerged for more than five days in a row, which is why it requires antifouling paint on the bottom.

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2. Is all antifouling paint poisonous?

No. There are already paints of this kind free of copper and other heavy metals, such as cuprous oxide, which repel marine organisms with the same efficiency and also have the capacity for self-polishing, that is, they gradually wear out due to friction with water, reactivating thus its efficiency, without losing its antifouling capacity or harming the environment.

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3. How do you know if it's time to paint the bottom of the hull?

When slime starts to appear, which will then harbor a colony of algae, which in turn will attract barnacles, which need to be eliminated because they quickly infest the entire hull. The right time is when fouling is starting to settle in, not when the boat is already infested.

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4. Do you need to call a specialized painter or can you paint on your own?

The ideal is to hire a professional, because the application (as well as the previous cleaning of the hull, which is fundamental for the efficiency, fixation and durability of the paint) requires care, even for health. In addition, there is a sequence of primers and drying times that need to be followed. But if there is no painter with good recommendations, it is better to do it yourself, although it is a tiring and time-consuming job.

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5. What does it take to paint the bottom of a hull?

In addition to adequate space and protective equipment, such as overalls, goggles, filter mask, gloves and boots, adhesive tape for painting, sander, water sanders number 60 to 120, solvent, spatula, paint trays, medium hair rollers , half- to four-inch brushes (for the toughest corners), canvas for the splashes, burlap and — of course — the paints. Namely, adhesion primer, intermediate primer and the antifouling paint itself.

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6. Roller, brush or gun? What is better to use?

The ideal is to hire a professional, because the application (as well as the previous cleaning of the hull, which is fundamental for the efficiency, fixation and durability of the paint) requires care, even for health. In addition, there is a sequence of primers and drying times that need to be followed. But if there is no painter with good recommendations, it is better to do it yourself, although it is a tiring and time-consuming job.

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7. How to calculate the amount of ink needed?

There are formulas to calculate the exact area to be painted and, consequently, the amount of paint needed. The most common are: beam + draft x length of the waterline (for boats), and beam + draft x 0.75 x length of the waterline (for sailboats). Both indicate the area to be painted in m2.

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8. Does it matter if the hull is made of metal, wood or fiberglass?

No. Antifouling paints are suitable for any type of hull. What changes is the primer that will be applied before and that, this one, must be specific. It should be applied with two or three coats, in this case with an intermediate layer, the tie-coat, which, in addition to providing extra protection, promotes adhesion between the first primer and the antifouling paint, which is applied only at the end of the process.

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9. What is the best time of year to redo the background painting?

The drier and less moisture there is in the air, the better. In other words, the best time is now, in winter, when it rains little. As a reference, choose days with air humidity around 65%, so as not to compromise the quality of the painting.

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10. Do I need to completely remove the old paint?

Not always. If it's not too thick or peeling, just clean it well and apply (as long as it's the same paint) over the top. But there is a limit to repaints: no more than four. After that, it is necessary to eliminate all of them, until reaching the primer, preserving, however, the gelcoat of the hull.