Flettner ship
A Flettner ship is a ship designed according to the ideas of German engineer Anton Flettner. The underlying principle is the Magnus effect, where a spinning body in a moving airstream experiences a force perpendicular to the direction of the airstream.
Flettner's spinning bodies were vertical cylinders; the basic idea was that thanks to the Magnus effect, small motors powering a ship via rotating cylinders could propel it more efficiently than if they had driven a conventional propeller. These types of propulsion cylinders are now commonly called Flettner rotors.
His first idea was to produce the propulsion force by using a belt running round two cylinders, but after further thought he abandoned this idea and decided that the cylinders would be better rotated by individual motors. Flettner applied for a German patent for the rotor ship on 16 September 1922.
Assisted by Albert Betz, Jacob Ackeret and Ludwig Prandtl, Flettner constructed an experimental rotor vessel, and in October 1924 the Germaniawerft finished construction of a large two-rotor ship named Buckau. The vessel was a refitted schooner which carried two cylinders (or rotors) about 15 metres high and 3 metres in diameter, driven by an electric propulsion system of 50 hp power.
Following completion of its trials, the Buckau set out on her first voyage in February 1925, from Danzig to Scotland across the North Sea. It was discovered that the rotors did not give the slightest cause for concern in even the stormiest weather, and that the rotor ship could tack (sail into the wind) at 20-30 degrees, while the vessel with its original sail rig could not tack closer than 45 degrees to the wind.
On 31 March 1926, the Buckau, now renamed Baden Baden after the German spa town, sailed to New York via South America, arriving in New York harbor on 9 May.
The rotor system was less efficient than conventional engines. Flettner turned his attention to other projects and the rotors were dismantled. Baden Baden was destroyed in a Caribbean storm in 1931.
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