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
North Sails the 3DL line of upwind sails in 1992. In the 3DL manufacturing process, aramid or carbon fiber yarns and layers of polyester (PET) film are laid over a computer-controlled mold that is configured to assume the airfoil shape of the sail, and then thermo-formed to produce a laminated sail with the intended three-dimensional shape. North Sails manufactures 3DL sails in facilities in Minden, Nevada, and Sri Lanka. In 2009, North Sails began using pre-impregnated tapes of carbon and UHMPE fibers on its full-sized articulating molds. When thermomolded, the layers of reinforcing material consolidate to form a seamless composite sail membrane,