Eric and Wouter,

Thanks for your comments.

Yes Eric, I know flat is fast, especially in high winds, but I still think that too flat is slow. On my monohull dinghy I added a 4:1 outhaul because I thought that would make it easy to fine tune the OH under load while hiking if I needed to and the result of that much purchase is that it's all to easy to make the foot of the sail flat as a pancake (ie, flat with horizontal creases). Now what I was saying is that when the foot of the sail was drum tight, I felt it was too flat and the boat felt slow. By adding some draft (ie, an inch or so from the boom) the boat seemed to heel less and accellerate. I'm not sure but I doubt when you say you want a flat sail you really mean having the foot of the sail drum tight (or do you)?

Wouter - interesting that Goodall's comments included having twist 1/3-1/2 down the sail with narrow draft in overpowered conditions. As I said earlier that is exactly how windsurfing sails are designed. You get a flat sail with twist at the top. The twist does dramatically reduce drag, but I think it has to do with more than tip vortex drag. There's lots of info on that in the windsurfing literature. The ability to get that shape does result both from a combination of the mast stiffnes/bend profile, how the sail is rigged (tensioned), as well as from how the sail is cut. Each person's experience on the best way to trim their boat may vary significantly not only if they have a different mast section but also becuase the cut of their sail will effect how it flattens and what it's drag/lift characteristics are as the mast bends. In windsufing, the stiffness and bend profile of the mast massively effects sail shape as the rig is tensioned and that's obviously true of catamarns as well. Interestingly, whereas windsurfing masts have a fixed stiffness and bend profile one of the things that's so great about the super wing mast is that the stiffness and bend profile are dynamically configurable. I used to think of the super wing mast as softer (in comparison to Hobie or Nacra masts) but after reading your posts Wouter I've concluded that the super wing mast can be stiff or bendy depending on how you rotate it in relation to the apparent wind (spreader rake and diamond wire tension notwithstanding). No need for on the fly adjustable diamond wire tensioners!

Jerry