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Author Topic:   Antifouling Paint Coverage

Jefecinco posted 03-14-2012 09:24 AM ET (US)
I need some advice on buying bottom paint. I've selected Petit Ultima SR 40 paint. The boat is a 1981 Boston Whaler Sport. West Marine's calculator says to use Length x Beam x .75 to calculate the square feet to be painted. I've rounded up to 100 square feet. Petit says a gallon will cover 750 square feet. I can buy a gallon for $177 or two quarts for $162 or one quart for $81. Clearly a gallon is the better value but only if it has at least three years of shelf life after opening.
Is 100 square feet accurate for the boats bottom?
Is one quart sufficient to apply two coats of the paint?
Is it realistic to expect the paint to have a three year or greater life once the can has been opened and paint has been removed?
Butch

PFSQUAN posted 03-14-2012 02:42 PM ET (US)
Butch: the best way to keep anti-foulant paints from thickening into a gel when a portion has been used is to thoroughly clean the rim so you can seal the lid tightly. Then, pour a tablespoon or two, or more of the recommended thinner, (I think in your case it might #120, but I am not positive, so check your can to be certain)to create a thin layer of the thinner over the paint. Make sure the entire surface is thoroughly covered about 1/4 inch. Don't stir it. This will prevent air in the can from reaching the paint and keep it in good shape. Gently tap the lid tight with a hammer and it will last at least a year. This trick works with all oil-based, one part paints.Be sure to store the can upright so the thinner remains on top.
An alternative would be to buy a clean, empty quart can from the paint store, fill it to the brim and seal it tight.
On my Tashmoo and Montauk I never needed more than one quart for one coat when I used Interlux Fiberglass Bottomkote. I have also used Pettit Unipoxy, Pettit Hydrocoat (water base), Interlux Micron will excellent results. This year I had the bottom of my Montauk soda blasted and after I patch a few blisters I will be applying Interprotect 2000 and top coat with Interlux Pacifica,a non copper paint, which I also will use on the lower unit and motor bracket. Peter
Jefecinco posted 03-15-2012 07:57 PM ET (US)
Thanks Peter. I guess it was a stretch to hope to put two coats on the bottom of a 13 Sport with one quart of paint.
I need to get with this project so I'll have to explore some options. I will probably buy two quarts even though they are just a few dollars less than a gallon. With my 13 spending much of the time at the slip or on the trailer I would expect two coats to last for at least a couple of years. I don't want to chance ruining a good part of a gallon of paint and having to add it to the Earth's pollution.
Butch
Theron1033 posted 03-17-2012 07:27 PM ET (US)
one quart of unthinned antifouling bottom paint will produce one full coat on the bottom of a 13ft sport, applied by a roller

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Author	Topic: Antifouling Paint Coverage
Jefecinco	posted 03-14-2012 09:24 AM ET (US) I need some advice on buying bottom paint. I've selected Petit Ultima SR 40 paint. The boat is a 1981 Boston Whaler Sport. West Marine's calculator says to use Length x Beam x .75 to calculate the square feet to be painted. I've rounded up to 100 square feet. Petit says a gallon will cover 750 square feet. I can buy a gallon for $177 or two quarts for $162 or one quart for $81. Clearly a gallon is the better value but only if it has at least three years of shelf life after opening. Is 100 square feet accurate for the boats bottom? Is one quart sufficient to apply two coats of the paint? Is it realistic to expect the paint to have a three year or greater life once the can has been opened and paint has been removed? Butch
PFSQUAN	posted 03-14-2012 02:42 PM ET (US) Butch: the best way to keep anti-foulant paints from thickening into a gel when a portion has been used is to thoroughly clean the rim so you can seal the lid tightly. Then, pour a tablespoon or two, or more of the recommended thinner, (I think in your case it might #120, but I am not positive, so check your can to be certain)to create a thin layer of the thinner over the paint. Make sure the entire surface is thoroughly covered about 1/4 inch. Don't stir it. This will prevent air in the can from reaching the paint and keep it in good shape. Gently tap the lid tight with a hammer and it will last at least a year. This trick works with all oil-based, one part paints.Be sure to store the can upright so the thinner remains on top. An alternative would be to buy a clean, empty quart can from the paint store, fill it to the brim and seal it tight. On my Tashmoo and Montauk I never needed more than one quart for one coat when I used Interlux Fiberglass Bottomkote. I have also used Pettit Unipoxy, Pettit Hydrocoat (water base), Interlux Micron will excellent results. This year I had the bottom of my Montauk soda blasted and after I patch a few blisters I will be applying Interprotect 2000 and top coat with Interlux Pacifica,a non copper paint, which I also will use on the lower unit and motor bracket. Peter
Jefecinco	posted 03-15-2012 07:57 PM ET (US) Thanks Peter. I guess it was a stretch to hope to put two coats on the bottom of a 13 Sport with one quart of paint. I need to get with this project so I'll have to explore some options. I will probably buy two quarts even though they are just a few dollars less than a gallon. With my 13 spending much of the time at the slip or on the trailer I would expect two coats to last for at least a couple of years. I don't want to chance ruining a good part of a gallon of paint and having to add it to the Earth's pollution. Butch
Theron1033	posted 03-17-2012 07:27 PM ET (US) one quart of unthinned antifouling bottom paint will produce one full coat on the bottom of a 13ft sport, applied by a roller