Here is an interesting idea for sanding curve sailboat hulls. I did something like this once, but this is a better idea. I found this tip in a model airplane magazine on sanding curve airplane wings.

Either use self-sticking sandpaper or paint some adhesive to the sandpaper, and apply it to an abrasive pot-scrubber sponge. The sponge will conform to the curve of the boat's hull when you are sanding. This will eliminate the flat spots you can get when you sand with a hard sanding block. Using a sponge beats using just your hand because your fingers are not flat all across the sandpaper.

Another good thing about using a sponge is the soft, exposed side can be used to wipe away the sanding residue if you are wet sanding.

Just make sure you don't use the same sponge for finer grit sandpaper when you have used the same sponge for course grit sandpaper. Doing so may scratch your hull when you wipe away the sanding residue. So use a different sponge, and avoid any problems.