Mike,

   We already had a big discussion on the multihulls list about this but I’ll recap.  I did a frame by frame view of the video on my big monitor.  They are very careful not to show much of the top inside of the sail.  If you look at the still pictures on the site you’ll notice there are four halyards going up to the crossbar.  One goes to the front of the sail, one to the back to raise and lower it.  The other two go from the deck, to just aft of the mast on the crossbar.  From there they run down to the top of the sail, to what I think are blocks on either side of the top of the sail.  Those are the dark areas in the video.  From the blocks it looks as if they go to the front of the sail where there is probably a prod that moves right or left to adjust the leading edge of the sail.  On the bottom of the sail the bottom most rib is a set of two half sections, one from the mast aft and the other from the mast forward.  Just below the forward section is another prod that moves the leading edge.  So they have control of the leading edge of both the top and bottom of the wing.  Then you’ll notice that the intermediate ribs have a pivot point/hinge where the battens are attached.  It looks to me that to adjust the camber they move the nose and with the flexible battens the whole sail takes the right shape.  Things I wonder about is if it is better to rotate the whole mast as they did, or to make just the crossbar at the top rotate?  How high is the stack when the sail is fully down? 

Jerry Barth