I'v told this forum already before of this spanish cat, but I like to tell you once again because I have owned (with joy) several years such a cat.
See me below in South France:
In Spanish it's called a "Patin A Vela" which means skate with sail.
They are made of wooden veneerplates around a wooden frame of bulkheads and stringers. Beams are also wooden plates (1.5m large).
These type of cats are invented by Spanish monks in a monastery in North Spain around 1920!!!!
Steering is done with the sail and the lateral point of the hulls. So moving forward on the hull means turning to the wind as does sheeting of the sail. The reverse means turning away from the wind; but the effect of moving the weight distribution on the hulls is by far the most.
Handling this type of cat seems impossible the first time when you sit on it, but everything get used to. At the end you can be very handy on it and even steer close around swimmers in the break.
One thing though: they are not racing cats as such. The speed is zero compared to a modern beachcat. (But ofcourse you can course race with fellow-users)