How can sailboats go faster than the wind speed?

Question

Is it the apparent wind created by forward momentum? Is it possible to go downwind faster than the wind speed?

In: 315

Answer 1

Ultimately, they extract energy from the difference in speed between the air and the water, and how fast you go is determined by how fast you can extract that energy, balanced against drag. Sailboats can do this most effectively moving sideways relative to the wind. Basically the wind hits you from the side, and you direct it backwards, you’re pushed sideways away from the wind(which is balanced by the keel), and also forward. If the wind is pushing you with more force than is needed to maintain speed, you can accelerate, sort of like going faster than you’re pedaling when in a high gear on a bicycle.

You can outrun the wind going downwind, but not with a simple sail(because that would stop extracting energy once you reach the wind speed): https://en.wikipedia.org/wiki/Blackbird_(wind-powered_vehicle) The way that makes sense to me is that the gearing shifts the frame of reference such that the wind sees the turbine not moving downwind, so it can still push against it.