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
Polytarp sails 14 or 14 x 14. Increasingly, white polytarp is used to construct mainsails, jibs, and mizzens, while the lightweight polytarp materials are reserved for making spinnakers. Polysail is the term given to any sail made of polytarp material and not just the white polytarp material. Polytarp is used to construct nearly every type of sail. However, the material is best for traditional sail types such as sprits, lugs, gaffs, gunters, lateens, junk sails, and jib-headed sprits. They are not suitable for sails that depend upon being highly tensioned, such as the marconi or Bermuda types of triangular sails. Polytarp sails