One problem I have seen with tryin these flex type designs is its easyer to load and unload all that flex at a LOW center of gravity , kneeboarding is best, Ryan that parabolic Jaws board at the show is what Brian and I are tryin for the same thing , I will try and post a pic later, Im off to the pools, oh boy .
It seems to me that CF might not be the ticket for any kind of flex operation. Skaters use ply to get both resilience and flex. The pawlonia alaias get some flex going without any layering at all. Maybe some layering of bamboo veneer could be used in your lamination in place of some of the CF. I would think that 2-3 layers of bamboo wrapped or sandwiched in 4oz would be a lot less brittle than a 6oz CF +9oz S glass combo.
In following the bamboo veneer thread and in light of how the compsands handle flex with balsa veneers by limiting core thickness, I was wondering if your application could use a little different approach.
I wonder how it would go if you built the hull part of the board using a 1/2" or 1" core of 1lb foam with 1 layer of the bamboo on both sides for the flex, and then added the rails and floatation on the deck side in 2lb foam and glass as normal? Or maybe do the rails in 2lb or 3lb and add a layer of 1lb up the center with a deck patch in bamboo.
Wow, I never thought of the wooden rail or perimeter as a solution to the pliability problem, but it's kind of a neat possibility when you think about it. A perimeter structure, built with the right characteristics, could concievably offer the right kind of torsional flexibility that surferguy80 has got in mind, and still allow for a good level of storage/recovery of elastic energy. It could wind up being just a matter of rolling his rails to create a kind of tube, possibly strategically adjusting the cavity size, or by strategically filling portions of the cavity with materials of different stiffness, like on a variable-cheese-stuffed pizza crust. Sort of a spoon approach but with a twist (... lame pun*).
If you or anybody knows if such an approach has been taken, it would be interesting to read about it. Memory fails me, but my guess would be that it has, I just don't recall by who or when.
small beside...
Also, Roy Stewart (a.k.a TomBloke) seemed to incorporate, via his unique construction techniques, a lot of flex, both longitudinal and torsional into his crafts, and he attributed great benefit to it. It would be interesting to know if his build technique scaled, that is could a sufficient degree of pliability be built into a much smaller craft? (His usually builds tended to be relatively big. The analogy is one of a spring again - for a given force and two springs having the same stiffness, the longer spring will undergo a greater deformation or extension, than the shorter one.) I'd ask Roy, but ... well, after our last exchange, he'd probably have little incentive to respond.)
kc
*… , probably a lame notion too…I think I should start napping more. Good luck with your project, surferguy80.
Gotta get this up by the resonance thread since they're so closely related...
I built a paulownia-railed hull with a glass flextail last summer and it did very very well on my search for twist, i think that is the most ‘viable’ way to go, but i wanted to explore this avenue to keep my mind busy!
I can only repeat the obvious
is there an obvious?
by the by, the board buckled under a sand sucky lip one stormy day, it’s hanging out in my shop but I don’t think i’ll fix it; didn’t go quite the way i had hoped but the build was more than half the fun of it!
if i were to do it again, i would use less glass in the tail (take out the s-glass patches), glass a fin on, and leave more volume through the end of the tail, t he way the board sat in the water was a bit funky (as predicted!) maybe it’ll come back to life one day when im bored…that’s how it started at least 
Ryan, congrats on starting down this path.
Control. How are you going to control the twist? This will be the big issue.
I must use both arms to control it on my carbon flexspoon. One hand is always on the outside rail and the other is amost always grabbing the wave face for balance and to increase my leverage. A real wrestling match that takes all my strength.
Maybe one like this, similar to Greenough windsurf board.
