I think ifthere is any curve to the sides of the boat, that you'll almost certainly want to create a template. If the curve is the same both port and starboard, you can flip it over for the second one. You can trace the pattern onto the wood you're using, then rough cut it and so some hand work to get the shape and size just right on the template. Once the pattern is smooth as a baby's behind, you can use it to outline the shape on your final material, then use a jig or band saw to cut the shape, leaving a little proud. You can then use a trim bit with a bottom mounted bearing riding on your perfected pattern to do a nice, clean final work piece. If you have a boat that requires it, you can cut a groove on the underside to match the top edge of the boat. I'd clamp that thing down and mark the groove carefully. This is a general process, but I think it's what you're looking for. I don't think you can hand shape the final wood piece so it matches exactly. That's why you make and perfect the pattern. I'd probably use a strip of half inch MDF for the pattern. You can hold the pattern in place with double stick tape.