[alex_duf]

Edit: I'm wrong, see responses bellow for correction

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

[LeifCarrotson]

You are, unfortunately, incorrect. The Magnus effect doesn't gain you anything other than the helpful drag of a tall cylinder when going in the same direction as the wind. Rotating it only pulls you sideways, which doesn't help.

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.

[jacquesm]

> You are, unfortunately, incorrect.

No, you are, unfortunately, incorrect.

> Without tacking, no wind power systems will help when going straight upwind.

https://en.wikipedia.org/wiki/Windmill_ship

[danaos]

He was right that "The Magnus effect doesn't gain you anything other than the helpful drag of a tall cylinder when going in the same direction as the wind."

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_...

[ars]

> In fact, the Magnus rotors will not provide any usefull thrust is both upwind and downwind scenarios.

If the wind is coming from behind won't it simply push the stationary cylinder, adding some thrust?

[jacquesm]

That was not the part of the comment that I referenced.

[sjbase]

It seems like Magnus sails work best when the wind is coming from the side (port or starboard), since the direction of force is perpendicular to the wind [0]. Doesn't matter which side, since you can just reverse the rotation of the cylinder.

With a headwind or tailwind, tacking could be used but the increased distance traveled may offset the gains from the Magnus sail.

0: https://en.wikipedia.org/wiki/Magnus_effect

[jtuente]

Rotor ships still need to tack for headwinds, but not to the same degree as conventional sails.

https://en.wikipedia.org/wiki/Tacking_(sailing)