Turbosail

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The turbosail or French turbovoile is a marine propulsion system using a sail-like vertical surface and a powered boundary layer control system to improve lift across a wide angle of attack. This allows the sail to power the boat in any direction simply by moving a single flap at the back of the sail, unlike conventional sails which have to be continually adjusted to react to changes in the relative wind.

The turbosail was first developed in a large scale application by Jacques-Yves Cousteau who commissioned the Alcyone to test the concept in production. The larger Calypso II was also designed to use a turbosail, but that design was not built.