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Not windsurfing but these guys are going super good at the moment in high wind.

It's real time so if you click on it later when they are at the equator it might not be so fast

That Gitana is amazing! Sooo fast! First 8 mins of this video! What fascinated me is the emphasis on aerodynamics of the hull structure to gain Knots of speed. Fantastic!

If we wanted to be efficient we would be making smaller sails not bigger with flappy leaches

If you could do similar achievement on windsurfing board then also nice distance record will be recorded.+1300 km in one day !!
I could imagine the well designed windsurfing gear rig could be made self adjusting and self balancing, so you could even replace sailor with bag of potato, to get this same result.
Our hero could then sleep most of the time, as long as there is enough water in the front to sail straight.