Abstract: A sail assembly for attachment to a bicycle having a frame, a rear wheel and a seat mounted on the frame forwardly of the rear wheel. The sail assembly includes a fork for bridging the rear wheel to mount on the frame and extend upwardly therefrom rearwardly of the seat. A boom is carried on the upper end of the fork to be generally horizontal and to pivot in a horizontal plane. A mast is mounted on the boom to extend upwardly generally in line with the fork, and a sail is attached at a leading edge thereof to the mast and at a lower edge to the boom. The fork is pivotally attached to the frame to enable pivoting rearwardly if the mast strikes an object while riding the bicycle. A flexure device restores the fork and mast to the generally upright position after the force which caused pivoting of the mast is removed. A flexure device also allows the boom to pivot laterally, but then restores the boom to a position generally in line with the bicycle after the force which caused the pivoting is removed.