Join Date: May 2002
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It depends on how long maintenance on the bottom has been deferred, and your expectations for the boat in terms of performance. You really won't know whether it's in bad condition until the boat is out of the water. Start with a good pressure wash to clean all the loose dirt and slime off the bottom, so you can see what's beneath it. If you're lucky, the paint will be fairly smooth underneath, and you'll be able to get by with a light sanding and a couple coats of antifouling. If, however, you find that the old paint is peeling, or has peeled, like old house paint, leaving thick, uneven layers, then the question is, what are your expectations in terms of boat performance? If you plan to race your boat and want optimum performance, then you should strip off all the old paint down to the bare fiberglass. If you want to daysail your boat casually around a lake, you might be satisfied with sanding the old paint as smooth as you can, and putting on a couple of fresh coats of antifouling. The plain truth is, however, that you can't continue giving it a light sanding and applying additional layers of paint forever. If it already has a thick layer of accumulated paint, it will eventually begin to peel so badly that you'll need to strip it all off and start over.
It's always possible, too, that you'll find osmotic blisters or some other problem, but I wouldn't obsess over that. If you find them, they're repairable.
If you get two consecutive days of good weather, and, if the bottom is in very good condition, and if you're willing to put in two long days of work, then you might be able to get it done in two days. If it's in bad shape, I'd plan on more like 7-10 days, and it'll be hard work.
I'd think one gallon of antifouling would be nearly enough to put on two coats. I buy the best ablative paint available, based on my thinking that it'll pay for itself many times over by avoiding the need to strip it all off down the road. I have stripped three boats, and don't want to do it again.