NotWal said...
No its not a ducted fan. There's a fan of some sort in the base that pressurises the ring. This air passes through long skinny ports all around the leading edge and directed over the foil. Have a look at the video.
I was especially impressed that it blows far more air than it sucks in, even if it is not the 15x stated it is likely more than double, and if it is 15x... wow.
There's a little bit of hover-craft design in there.
Maybe food for thought regarding somewhat stagnating board, fin and sail design?