The German engineer Anton Flettner was the first to build a ship which attempted to use the Magnus effect for propulsion.[3][4] Assisted by Albert Betz, Jakob Ackeret, and Ludwig Prandtl, Flettner constructed an experimental rotor vessel; October 1924 the Germaniawerft finished construction of a large two-rotor ship named Buckau.[5] The vessel was a refitted schooner which carried two cylinders (or rotors) approximately 15 metres (50 ft) high, and 3 metres (10 ft) in diameter, driven by an electric propulsion system of 50 hp (37 kW) power.[citation needed]