David and All. >A more interesting version occurs when a rotating cylinder is placed >perpendicularly in a fluid flow. This generates lift too, at right angles >to the direction of flow and the axis of the cylinder. This theory was >used some time ago on German rotor ships,
-and very efficient they were too! - had it not been for corrosive sea spray and seagull droppings that upset the balance of the early metal rotors. Modern materials have overcome such problems. Flettner also experimented with cylindrical rotors spinning as the sails of high efficiency windmills and proposed an aerofoil with a moving surface. (New?) We made one about fifteen years ago in the Mech. Eng. Department but any increase in aerodynamic efficiency was offset by friction with the moving wing 'skin'. Tony Moss.
