A wingsail is an aerodynamic structure that is fitted to a boat in place of conventional sails.

A wingsail is used to provide thrust on a boat.

Wingsails are analogous to airplane wings, except that they are designed to provide lift on either side to accommodate being on either tack.

Wingsails are more complex and expensive than conventional sails.

(from Wikipedia)

The structure:

- The are 2 parts in the wing: the forward element and the trailing element. The forward element is linked to the mast. It's possible to control the angle between the 2 parts. It's called the camber. This camber generates the power.

- The height of the AC72 wing is 40 meters.

- The wing is made of carbon fibers, kevlar and lightweight composite shells.

- The angle is controlled with a sophisticated system of pulley and lines, connected to a big great plate at the bottom of the wing.