First I have a few questions; does this boat have canvas on the outside or is the outside glassed? Are any of the ribs cracked?

I cracked my canoe (no ribs) a few years ago, under some fairly harsh conditions (a lot of shallow rapids). It was glassed inside and out. The crack was on the inside about the same in length. I sanded the area about 4 inches on all sides of the crack and placed a fiberglass patch over the area. It seems to have worked just fine.

If any of the ribs are cracked, you could remove them (grind them out) smooth out the area and patch the crack. Then take similar material that the ribs are made of and steam bend new ribs using the outside of the boat as a form. You will need to make a jib (2x4) to hold the center of the new rib down to help the wood take shape.

After the ribs are made, slide them into place and attach them just like the old ones were.

Good luck.

Jason