I had to look this one up, I didn’t realize how old the technology was
https://en.wikipedia.org/wiki/Flettner_rotor
A Flettner rotor is a smooth cylinder with disc end plates which is spun along its long axis and, as air passes at right angles across it, the Magnus effect causes an aerodynamic force to be generated in the direction perpendicular to both the long axis and the direction of airflow.[1] The rotor sail is named after the German aviation engineer and inventor Anton Flettner, who started developing the rotor sail in the 1920s.
The Buckau, the Flettner Rotor Ship, photographed in 1924
if you have two fletner rotors, you can attach two lights and and a giant face statue to it and make people really regret that bottle of rum.
Master Control Program!
I thought a lot about these things, and apparently, a less elegant way to tackle this problem is decoupling power harvesting and propulsion. Like, put your best suitable power plant on a boat, then conduct power to best propulsion (probably submerged turbine or something)
https://en.m.wikipedia.org/wiki/Blackbird_(wind-powered_vehicle)
Can go directly upwind (no tacking required). Can also be applied to boats.
