Depends on lots!
The bottom painting schedule depends on many things (the type of paint, where the boat is kept and sailed, how heavy the fouling is in that area, whether the water is fresh or salty), but typically will be done every year or (at most) two. As for sanding, that also depends. If you use a soft ablative paint, Yes! sanding is required before every repaint. On the other hand, if you are in fresh water and are using VC-17, the only prep that is required is to wash the bottom with soap and water, and possibly, wipe the bottom with an acetone soaked rag to remove oil. (We really like VC-17 on Lake Michigan). Find out what paint is used by the sailors in your area and what type of paint is on the bottom of your boat, read the directions on the can. Following the directions will usually work, and give you an adequate paint job. As with all painting, everything depends on a good prep job. Make sure that the paint that you are applying is compatible with the existing paint, prep the bottom as recommended, and have fun.
