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Comment by JamisonM | Hacker News Reader

Pretty sure you need a tail-wind to use a kite system, this works in any wind.

Pretty sure you don't need a tail-wind. Regular old sails as well as kites can be used at various angles to the wind. See e.g. https://en.wikipedia.org/wiki/Point_of_sail

[edit] P.S. from my understanding of the mechanism, I'm not so sure these Flettner rotors are useful in a headwind. They work by creating a pressure difference, but in a headwind, you could only create a pressure difference between the port and starbord sides, not the front and back. Unless there's some mechanism I'm missing?

If, by headwind, you mean sailing directly upwind, then no, they cannot do that, but they can beat to windward like a sailboat (the direction of the rotation must be reversed when tacking.) According to Wikipedia, the rotor ship Buckau could sail within 20-30 degrees of the wind, though I suspect that is a misreading of the supposed source of that data, and that 50-60 degrees is a more plausible figure. Similarly, I suspect the claim that they can sail closer to the wind than conventional sailing vessels is in comparison to square-rigged ships.

https://en.wikipedia.org/wiki/Rotor_ship#Pioneers

https://books.google.com/books?id=9lqwg3iZyH0C&pg=PA656#v=on...

I would be surprised if a kite system could get much closer than 90 degrees to the wind.

Aslong is the wire points forward of left and right the net force is forward right?

In practice you probably want the wire +-45 degrees from the bow or something. That is where you would use a gennaker or spinnaker.

I feel like this would be a worse version of a symmetric spinnaker, which you generally sail in 100-180

To second the others, "reaches" are the fastest. I forget why, but I suspect it's like gearing, less force, more distance, for the same amount of work.

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