LIBEL is very promising, it would be interesting to use the fock sail, headsail, principle to improve efficiency on the second foil with the first one (A catamaran has only one main sail, the Americans cub catamarans use a jib which improve the efficiency of the main sail).
Americans cub catamarans (fock)
www.pinterest.ch/pin/americas-cup-2017-bermuda-f18-acat-ac45-world-series-f16-foiling-gc32-racing-tour-nacra-17olympics--818740407230016613/
A-Cat (no fock)
www.saca.ch/gallery3/index.php/2014/Crit-rium-Versoix/DSC_1601
At a good setup the efficiency double decker must be better and generate more lift at a more tiny surface.
This makes the biplane very interesting for Lake Pump Foil long distance records. Here you have to increase the area of the foils more and more, so that top fit 100 kg athletes can foil for a long time at low heart rates. It would be very nice if there were foil adapters for the biplane, e.g. to make an SAB 1550 even more efficient (then the matching "jib" is probably very thin and long).
Stay tuned...
