The world's fastest wind powered craft is still a windsurfer! Frenchman Antoine Albeau has edged the record closer to 50knots with an average speed over 500m of 49.09knots (approx 56mph) in about 40 knots of wind.
He was covering over 25 metres every second!
To put this into perspective, the fastest speed any of my guests recorded in Margarita for the fastest split second was 32 knots, not their average speed over 500m (which takes approx 20 seconds of sheer terror). 32 knots was set by an incredibly capable windsurfer of 95kgs who regularly planes out of carve gybes and sails large waves. His average speed over 500 metres would have only been around 26 knots.
The average speed of the average intermediate windsurfer very capable in the footstraps and making some of their gybes is around 22 knots, peaking at about 25 knots on a very good run.
So Antoine was sailing at least twice as fast as most of you have ever sailed. That must be scary, I take my hat off to who ever breaks the 50 knot barrier!
There's plenty of clips of the record at youtube, including a couple of severe wipe outs, and here's a French News TV report-
http://www.youtube.com/watch?v=NBXBhu-DRms&feature=related