Just saw this;
I note the ongoing discussion about patents. This article says that KTH invented them in 2008.
What propulsion are they using? Appears to be a very ducted prop which would be inefficient?
are you asking about eFoil boards…or just foil boards in general? There were foiling waterskis as early as 1956 and a patent exists for a foiling surfboard in 1973. The Aqua Lift hydrofoil kneeboard came out in 1985. There were other iterations between 1985 and 1988 that adopted a single mast with a front and rear foil that look very much like what we ride today.