Embodiments of the invention relate to blades for turbines, such as wind turbines, comprising a structural frame with a sail mounted thereon. In certain embodiments, a portion of the frame contributes to the buoyancy of the blade. In further embodiments, the frame comprises strengthening cords. In further embodiments, the frame comprises a reinforced tip. In further embodiments, the blade has a tip arranged to articulate relative to a body portion to alter the aerodynamic profile of the blade as the blade rotates to thereby assist up-strokes of the blade.