Flettner

Flettner refers to Anton Flettner, a German aviation engineer and inventor best known for developing the Flettner rotor, or rotor sail. The term Flettner is also used to describe the family of devices and concepts associated with his work on wind-assisted propulsion. The most prominent application is the vertical, rotating cylindrical sail that uses the Magnus effect to generate thrust to help propel a vessel.

Flettner rotors are tall, vertical cylinders mounted on a ship’s deck or superstructure. Each rotor is mounted on bearings and can be spun by a drive system. When wind flows past a rotating cylinder, the interaction between the moving air and the rotating surface creates a lift force perpendicular to the wind direction. By orienting the rotors and controlling their rotation, part of this force can be transformed into forward propulsion or added thrust, reducing the ship’s reliance on conventional engines and lowering fuel consumption.

Historical context and modern use: The concept was introduced in the 1920s by Anton Flettner and saw experimental and commercial use on some German merchant ships in the interwar period. After limited activity for several decades, rotor sails experienced renewed interest in the late 20th and early 21st centuries as a way to reduce emissions and fuel use. Modern implementations often feature computer-controlled control of rotor speed and orientation, with various sizes and configurations deployed on different vessel types, particularly in energy- and cost-conscious shipping programs.

See also: Magnus effect, rotor sail, wind-assisted propulsion.

---