$4.49, $4.99, HOW HIGH WILL FUEL PRICES GO?
by Robert Donat
Spending the time to choose, prep and apply the right bottom paint can have a major impact on the overall speed and fuel efficiency of any boat hull. Choosing the right bottom paint will make sure your boat bottom is free of slime and barnacles. Taking the time to properly prepare the bottom, and not just ‘slapping on’ a new coat of bottom paint, will pay off in the long run since a smooth, slime and barnacle free bottom will result in a fast and fuel efficient hull.
FACTS ABOUT THE FOULING AND FUEL USE
The images above show what effects the different types of fouling can have on drag and hence fuel penalty.
SURFACE PREPARATION
So let’s take a look at proper surface preparation. Have you ever seen a hull bottom that resembles craters on the moon or the mud flats of the Mojave Desert?
The roughness caused by chipping, cracking and loose paint increases drag, and slows down your boat. These conditions may be a direct result of poor preparation, or simply too much paint build-up on the bottom. The yearly re-application of hard anti-foulings results in the build-up of old spent coatings. As these coatings age the binders (a fancy term for resins) that hold the paint together become weakened as a result of the water moving in and out of the paint film. This causes the paint to detach from the hull. Paint buildup can be avoided by sanding hard anti-fouling paints before recoating each spring.
Power washing hard anti-foulings will remove the surface contaminants; and paint will adhere well to surfaces prepared this way. However power washing will not get rid of the underlying old porous coating, and the roughness of the surface will remain. Sanding the bottom with a good vacuum sander and 60 to 80 grit paper will remove the old porous coating and provide a smooth surface for the next coating of bottom paint. Smoothness deters fouling organisms, especially weed and slime fouling, since these organisms prefer to settle on rough, cracked and chipped surfaces. Fouling increases drag by creating “mini-eddies,” or turbulence, at the surface, and as this turbulence increases so do drag and fuel costs.
It is important to follow the paint manufacture’s recommendations on how much paint to apply. The performance of bottom paint is not only related to the surface prep and the type of paint being applied, but also to how much paint is applied. All bottom paints have a recommended coverage rate, to optimize performance, and as such should be applied at that rate. If applied too thinly, the paint will pick up fouling well before the end of the season.
FACTS ABOUT THE FOULING AND FUEL USE
The images above show what effects the different types of fouling can have on drag and hence fuel penalty.
SURFACE PREPARATION
So let’s take a look at proper surface preparation. Have you ever seen a hull bottom that resembles craters on the moon or the mud flats of the Mojave Desert?
The roughness caused by chipping, cracking and loose paint increases drag, and slows down your boat. These conditions may be a direct result of poor preparation, or simply too much paint build-up on the bottom. The yearly re-application of hard anti-foulings results in the build-up of old spent coatings. As these coatings age the binders (a fancy term for resins) that hold the paint together become weakened as a result of the water moving in and out of the paint film. This causes the paint to detach from the hull. Paint buildup can be avoided by sanding hard anti-fouling paints before recoating each spring.
Power washing hard anti-foulings will remove the surface contaminants; and paint will adhere well to surfaces prepared this way. However power washing will not get rid of the underlying old porous coating, and the roughness of the surface will remain. Sanding the bottom with a good vacuum sander and 60 to 80 grit paper will remove the old porous coating and provide a smooth surface for the next coating of bottom paint. Smoothness deters fouling organisms, especially weed and slime fouling, since these organisms prefer to settle on rough, cracked and chipped surfaces. Fouling increases drag by creating “mini-eddies,” or turbulence, at the surface, and as this turbulence increases so do drag and fuel costs.
It is important to follow the paint manufacture’s recommendations on how much paint to apply. The performance of bottom paint is not only related to the surface prep and the type of paint being applied, but also to how much paint is applied. All bottom paints have a recommended coverage rate, to optimize performance, and as such should be applied at that rate. If applied too thinly, the paint will pick up fouling well before the end of the season.
