The ribs, as originally built were contructed of half tubes of some fiberous material (picture a paper towel roll cut in half lengthwise). they were about one inch in diameter. These tubes were laid down on the interior of the hull, diameter down. They were then glassed over with strips of non woven fiberlass matting, around 8 inches wide. These ribs were placed longitudinally for a keel, and abeam in 4 places for rigidity.

The matting/hull interface gave way eventually and the whole structure weakened. I ripped out what I could and plan to replace the ribs, and add a couple more, where I cut hatches. I could probably fashion cardboard tubes and laminate over them, but that seemed like too much work, so I plan on cutting some 1/2" x 1" by whatever strips of pink foam, chamfering the edges with a utility knife and sticking them down (they will conform to the hull nicely) in place, then covering them with 8 inch strips of cloth. I am pretty sure this will be both strong and light.