A Flettner rotor can be used to provide propulsion for ship from the wind.
Would it make sense to fit a Flettner rotor to a full displacement expedition trawler in the 55-70 foot class like a Nordhavn or Bering? These vessels are deep draft ships that move slow, about 8 knots typically, and are designed for stable ocean travel over long distances. The idea is that the rotor would augment the diesel propulsion to make the ship faster and more fuel efficient.
Below is a photo of a 65-foot Bering with a rectangle showing the imaginary location of a Flettner rotor. A 4 inch drive shaft would go through the decks to the engine room and be coupled to the engine or main drive shaft via a gear box.
The drawbacks I can see are that it could potentially decrease the stability of the ship and would be added weight. Also there would be a 6 inch column going through the center of the lounge and a loss of space on the top deck.
The question would be how much benefit would the rotor bring?
For example, if the rotor could increase cruising speed by 20% and decrease fuel usage by 30% on a transoceanic crossing, that would be significant benefit.
Another question would be how would the rotor affect the roll stability of the ship? Would it tend to dampen roll or increase it?