that's it.
Yes, Gil. I think that's how I'll do it. I feel better now.
Norm, I've only taken lines off one time, but here's how i did it.
I started with a good sized 3/4 sheet of plywood. I think 3 1/2 or four foot wide. I then cut a C shape into its side. I left enough plywood at the openings of the C so that it was still solid. That's the main part. It has to pass over the canoe you are copying and the area you are copying. Because the canoe I did was symetrical i only needed one quarter of a hull that was fair. I then used screws to fasten 8 or 10 pointer sticks to the open part of the C. You'll need alot more pointers I think for doing the entire cross section, I only did half, from keel to shear. The center line is the refernce point to morror image the line to the other side. They were about 1/4" by 1" by 12" or so. They need to be long enough to touch the hull everywhere when the copying frame is in place. the pointer sticks were slotted so they would slide in/out. A washer on the screw helps with the sliding/adjusting. Then, with everything square and set up on a good solid working surface I set the frame over the canoe. I used a strongback to hold the canoe. Every twelve inches along the canoe, (or one quarter of it in my case) I put the pointer stick points touching the canoe and tightened the screws so the pointers can remember their place in the world when I move the whole thing to the paper. Once all pointers were right I then took the frame from there and layed it on a large piece of paper and made a dot at every point onto the paper. Connect the dots with a fairing stick to make it a smooth curve. and it is the exact outside of the hull. You'll need to now allow for the thickness of the hull AND the thickness of the solid form either move the dots in or what I did was to draw the line and move that in using a compass, (If I remember correctly) I make it seem harder than it is. Probably way more by way of explanation than you asked for, but perhaps some of it is useful.