The sails are so pivoted as to present their edges in returning toward the wind, but to present their faces to the action of the wind when they are on other side. The arrows show the wind direction.
The sails are automatically flipped under the wind action.
Mass center of each sail must lay on its rotary axis by adding counter weight to eliminate the influence of centrifugal forces.
This mechanism is numbered as 486 in the book “507 mechanical movements”, 1868.