This inflatable sail was already realized for a small boat:
Laurent de Kalbermatten was a co-inventor of this sail. Previously he was the designer of Woopy, an inflatable wing according to the same concept, using also a small blower to stabilize the pressure, and a spar who became a telescopic mast for the sail. SALSA / KALBERMATTEN LAURENT (Fabricant de deltaplane) :
According to Laurent de Kalbermatten, the fabric of the sail (or the wing?) is much less stressed thanks to the inflation.
A lead for AWES for more durable and scalable flexible kites?