Last summer I made a long board from 5/32" milled redwood. I used the same redwood for ribs that I used for the skin. Not a good idea! The first time out, the first wave, the first turn, I could hear and feel the ribs cracking under my feet as I stepped on the rail for a bottom turn. No!! The board is really pretty and looked undamaged, so I hung it up at a friends office as a decoration. After about 6 months, I retreived the board and decided to repair it. I cut the deck out, shook out all the wood debris from the broken ribs and installed 7 new 3/8" ply ribs with two top stringers for support of the rather thin 5/32" deck. Lesson: use plywood for the ribs. With the bi-directional laminations, it is far stronger than solid wood and won't crack along the grain. Duh.
Routing the deck
Three broken ribs.
All cleaned up and ready for the new ribs.
New 3/8" ribs spaced at 7" on center. 8" is my normal spacing.Next step...fit and glue the planks in and glass her up!