Original message: I seem to remember (if I'm wrong please correct me) that the Magnus effect works regardless of the direction of the wind, whereas the sky sail needs the wind to be roughly in the same direction of travel.
They could be combined but as far as I understand these spinning columns are more generic
However, it can pull you forward when the wind is coming from the side. You change the direction of rotation based on which side the wind is coming from.
Without tacking, no (edit: solely) wind power systems will help when going straight upwind.
No, you are, unfortunately, incorrect.
> Without tacking, no wind power systems will help when going straight upwind.
In fact, the Magnus rotors will not provide any usefull thrust is both upwind and downwind scenarios.
https://en.wikipedia.org/wiki/Rotor_ship#/media/File:Points_...
If the wind is coming from behind won't it simply push the stationary cylinder, adding some thrust?
With a headwind or tailwind, tacking could be used but the increased distance traveled may offset the gains from the Magnus sail.