Join Date: Feb 2012
Location: New Orleans Louisiana
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Re: Don Casey: Paint Waterline Stripe with Bottom Paint
Leaving hard bottom paint exposed to air too long causes it to work, but it becomes less effective the longer it is allowed to dry out. If it isn't wet, it won't foul anyway, so no harm done. If it is wet then the paint will last just like the stuff on your keel.
Part of the problem is that manufacturers stripe a boat based upon its loaded waterline in salt water. Most boats though are moored in either brackish or mostly fresh water, so your boat actually floats deeper. Basically the fresher the water the deeper your boat sits, and the higher your bottom paint should come. Even a creek emptying into a cove can significantly reduce the local salinity of the water.
In addition if you happen to carry more weight than the designer calculated for the loaded water line, of course you sit deeper. So if the bottom paint stops right at the line... Well you get stuff growing.
Finally a boat with a little bottom paint showing is an indication she is being kept light (even when not true).