Abstract: A fluid-powered generator harvests the inherent energy in a flowing medium, such as wind or water, as it flows along a flexible sail, creating an undulating motion that causes rotation of a crankshaft. The generator comprises a plurality of ribs pivotably connected to a support shaft. Each rib is coupled to the sail and to a crank arm such that when the sail undulates, the ribs and crank arm pivot in the direction of the undulation, causing rotation of the crankshaft. The generator thus converts the linear motion of the fluid to circular motion to produce renewable energy.