When I work speedfins between 18 to 28cm i work they very stiff so they cannot produce a lot of
twist and flex. When,than a little flex for lift and not 2 things ,flex and twist at the same time ,one works against the other. A twisting fin need more power for flexing. That reduce the speed. I worked a fin with
20cm for one way. The idea is, to work flex in the fin,for a little lift of the end of the board.The fin stay
in an angle of 10° to the left or right side.So you need only the half power for to get flex and later the lift.
The power you need for flex ,reduce the speed a little. I work only 100% carbon fins,the reaction of
carbon is the shortest,I know,( bending and back). I worked a fin inside only with rowings.I lay the rowings
in epoxy and do powder of ceramic around the rowings. that makes the fin stiffer than all the other things.
So I try and try. Wolfgang