Abstract: A fluid-activatable vane is defined by a thin vane body having opposed narrow leading and trailing side edges and opposed substantially smooth large top and bottom surfaces. The body has a central longitudinal axis and is substantially symmetrical on opposed sides of the axis. An attachment shaft is aligned with the central axis at a near end edge of the vane to secure two diametrically opposed vanes through a coupling wherein the vane will tilt along a 90.degree. arc from a horizontal plane to a vertical plane when exposed to a fluid flow. The two vanes form a propeller and are fixed to a respective end of the attachment shaft in a respective plane and offset 90.degree. from one another. A fluid actuatable torquing curved outer end edge portion is formed integral with the vane body in an outer end edge portion thereof and on a respective side of a central longitudinal axis.