Numerous attempts have been made to attach sail assemblies to bicycles for the purpose of achieving a useful vehicle generating propulsion from the wind as well as from pedal power. The difficulties commonly encountered by such designs include the inherent lateral instability of a bicycle as well as the need to control the sail assembly while also controlling the direction of the vehicle, i.e. by steering. It is necessary to control the angular rotation of the sail relative to the longitudinal axis of the vehicle for maximum drive from the sail, a process known as trimming the sail. In a conventional sailboard both hands are commonly used to control the sail and steering is done by the manipulation of the position of the sail in relation to the underwater foils. In the case of a one person sailboat, steering requires one hand on a tiller and occasionally both hands are required to participate in the control of the sail which is ordinarily controlled by means of a rope sheeting arrangement. An example of prior attempt at a sail-powered bicycle is shown in U.S. Pat. No. 4,738,460 to Alexander which describes a means for mounting a sail on the rider of a bicycle; the sail angle being controlled by a sail lever requiring the operator to devote one hand to the constant operation of the sail and attempt to steer solely with the other hand. Similarly, U.S. Pat. No. 3,986,722 to Patterson and U.S. Pat. No. 4,557,495 to Kindermann both require the operator to use one hand to constantly attend to the trim of the sail. Another attempt to solve this problem is shown in U.S. Pat. No. 4,735,429 to Beck which shows a sail mounted behind the seat of a conventional bicycle which allows no manual control of the sail, the sail being basically controlled by a spring loaded mechanism constantly urging the sail back to a central position with respect to the boom. Similarly, U.S. Pat. No. 3,994,508 to Danner describes a method of controlling the sail for mounting on a bicycle which is essentially a flexible but rigidly positioned boom relying on the flexibility and resilience of the boom to control the sail trim. All of these inventions require the operator to substantially constantly attempt to steer with one hand which is difficult, frequently dangerous and prevents the operator from operating two hand brakes when necessary. In addition, none of the designs provide any righting moment which is necessary to counteract the lateral force of the wind on the sail.