|A windsurfing board has no rudder, it is turned by varying the relationship between the center of effort (force of the wind on the sail) with the center of resistance (force of the water on the center fin or centerboard). Thus, when the sail is leaned backward and positioned behind the center fin, the board turns into the wind. When the sail is leaned forward in front of the center fin the board turns away from the wind.
The focal point of the sideways resistance generated by the centerboard and skeg is called the center of lateral resistance or CLR. The focal point of the forces generated by the sail is called the center of effort or CE.