Ok you Boffins, how come water based yachts and aeroplanes have had winglets on rudders and wings for years and nobody has thought of fitting them on Landyacht sails? Looking at proven advantages there is up to 20% efficiency to be gained without much pain. 20% also can be gained by increasing the aspect ratio and length of a wing but has the disadvantage of tipping you over easier.

So why not make those high aspect sails shorter and add a winglet?. Put on the thinking caps and create something new so we can pinch your ideas after you have sorted all the structural problems out!!