There was a huge string last year on this in SA with allsorts of technical stuff.
I remember asking Bill Roberts about it a very long time ago when the came back after all he was a rocket scientist at Pratt Whitney. It is not new but old technology that was re-born again in the late 70's early 80's or there about for beach cats.

He said some simple things to me:
A sail is a wing.
Ever see pointy wings on modern airplanes?
Also a bunch of scientific stuff about the way the wind leaves the sail, and the vortex of wind not going down the face of the sail.
Bill made fast boats and knows more about airplanes and rockets then me I took his word for it.
When I went flat head my boat sailed faster.