Forces on sails apart, which generally prevents heeling. Each sailing craft is a system that mobilizes wind force through its sails—supported by spars and rigging—which provide motive power and reactive force from the underbody of a sailboat—including the keel, centerboard, rudder or other underwater foils—or the running gear of an ice boat or land craft, which allows it to be kept on a course. Without the ability to mobilize reactive forces in directions different from the wind direction, a craft would simply be adrift before the wind. Accordingly, motive and heeling forces on sailing craft are either "components of" or "reactions to" the
Forces on sails balance. Integrated over the sailing craft, the total aerodynamic force (F) is located at the centre of effort ("CE"), which is a function of the design and adjustment of the sails on a sailing craft. Similarly, the total hydrodynamic force (F) is located at the centre of lateral resistance ("CLR"), which is a function of the design of the hull and its underwater appendages (keel, rudder, foils, etc.). These two forces act in opposition to one another with F a reaction to F. Whereas ice boats and land-sailing craft resist lateral forces with their wide stance and high-friction contact with