Foldable kite sail "Manta" for small slender boats

In general, canoes, kayaks and faltboats are not suitable for rigging effective sails. Because of their inherent instability, use of sail is limited in small size, and in the tailwind direction. Authors have developed a foldable kite sail that has ample sail area, and can run against the wind. This sail rig consists of a pair of delta wings with a significant dihedral angle and a support strut. When in paddling, this folded rig is stowed compactly on the front deck of a canoe. To sail, the paddler fixes the lower end of strut into a socket attached to his harness belt, and grasps a crossbar handle fitted on the strut. By raising the folded sail rig and pulling a line in the following wind, the 2.5 m/sup 2/ sail unfolds to its shape like a parasol. Folding is also done easily by pulling another line. When he turns the sail head to the wind, sail flies stably like a kite, and the provided lift force pulls him (and the boat) up along the strut. By rotating the strut tactfully with the handle, he can control the kite sail (and the boat) to his desired direction not only with the wind but also against it. The sail rig assembly weighs about 2 kg when made with aluminum tube framework, but it can be halved if unidirectional CFRP tubes are used. Although very lightweight, the rig is usable even in the strong wind of 13 m/s. As the strut is supported by the paddler, not by the hull, the boat is free from heeling under sail regardless of the wind direction. Also, paddlers can practice all the sail control on land safely. Authors believe that this kite sail is useful for wide variety of small slender boats and others.