Wingsail

From SpottingWorld, the Hub for the SpottingWorld network...

A wingsail is a form of marine propulsion similar to conventional sails. However, a wingsail is a built-up structure with airfoil cross-section, like an airplane wing, which shape can provide a much better lift-to-drag ratio than conventional sails.

There are numerous rigid as well as soft sail designs which achieve this purpose.

Other types of sails

References