As long as you can see it...
I've been using VC17 for almost 10 years now, in warm fresh water and high-fouling salt water. The paint is effective as long as you can see it. In my case it's lasted anywhere from six months to four years, depending on where and how long the boat was in the water. I would also agree that painting in the fall is better for all the reasons stated earlier. VC17 dries so fast that you can get two coats on a 30 ft hull in an afternoon. The paint does not lose its effectiveness out of the water. It may change color but it's still good.Ideally, the hull should be primed with VC Tar before applying VC17. It's not mandatory but I've found that VC Tar helps the paint adhere better and last longer. As the name suggestes, VC Tar is black, so as soon as the VC17 wears through you'll know. As mentioned, high wear areas include the three to four inch wide band around the waterline, also the leading edge of the rudder and keel and around the bow area.The best way to apply VC17 is to mix it in one of those large clear plastic ketchup bottles with the flip cap. Shaking it is easy. Squeeze the paint onto your roller or brush as you need it. The small opening keeps the paint in the bottle from drying.Close the cap and shake the paint occasionally to keep the copper powder in suspension. You can stop painting at any time, again by just flipping the cap closed. I've kept VC17 liquid for more than a year in the ketchup bottle.As long as the VC17 doesn't wear completely off (allowing bottom growth to start) you should not have to sand the hull in preparation for recoating. Pressure washing and a light wipe with paper towels or rags dampened with denatured alcohol should be enough. Good luck.PeterH23 "Raven"