Variable area sail for sail board etc. - has hinged boom with double area sail whose fold abuts mast loosely

摘要

The sail is trapezoidal with its outer corners secured at the ends of the double boom (15) and with its upper and lower corners secured on the mast. For normal use the boom is hinged in the middle to fold about the mast and link the free ends. The sail can fold double and operate as a normal triangular sail. With the boom folded outwards the full area of the sail is available making full use of a following wind. No change of rigging is required to change the mode of sailing and the whole operation is single-handed.