Great stuff! That's what I learnt on back when I was 8. Still got two of those sails at the back of the house.
Those guys must get the sorest arms.
Thanks Choco - haven't seen that for a long time. It's also a shame catapulting isn't as soft on the body as it once was.
Yes, that kinda equipment was real sport. Not recommended anymore (not kidding), but real hard to hold on to.
I was sailing one just last week in zero wind - old Dacron all baggy, just screwing around.
Then the wind picked up to some 20 knots, all of a sudden. Was impossible to hold - too floppy and baggy.
So I have even more respect for those early pioneers in the video...
True boardcrazy.. and I'm wondering is 'stuffed up in some way' the technical reason?
I have to admit, I sometimes feel a strong sense of nostalgia and longing for those early days of windsurfing; an era I missed out on.
But a good session on modern gear soon cures me of that! 
