How can sailboats go faster than the wind speed?


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

In: 315

The best analogy I’ve heard for this is ice skating. When you are ice skating and trying to accelerate, you push the skate at an outward angle with every stride – and you will end up going faster than the speed at which you are pushing out against the ice.

As another reply mentions, ice skating is an excellent analogy.

The keel/centerboard is like the skate planted on the ice. The sail is like a skate that constantly pushes sideways.

Minimise drag and maximize strength and sailfoil boats can attain nearly limitless (at least ridiculous) speeds.

Because the wind is not pushing against a sail that is perpendicular to it (with the wind coming from behind the boat) – if it were you would only be able to go as fast as the wind. Instead, the sail is angled (e.g. at say 30 degrees off perpendicular, with the wind coming from the side of the boat) so that you effectively create a horizontal and vertical component to the push which adds up to a speed greater than the wind itself

[Here]( is an explanation that made it click for me


The ice skating analogy makes a lot of sense. But to me that’s more like how a propeller moves a motor boat with stored energy. A sailboat passes energy between the wind and water.

Another way to think about it (at the risk of being more confusing): the boat is capturing energy from the difference in momentum between the wind and the water. Imagine the water and wind flowing in the same direction, at the same speed. From the boats frame of reference that is equivalent to being in still water with no wind. No sailing going to happen. Only a motor boat with stored energy could move.

Think of a windmill facing upwind. The windmill is on little wheels connected to the windmill drive shaft by a chain or belt. You can imagine that you could drive the windmill slowly upwind. From the frame of reference of the windmill that’s the same as going downwind faster than the wind.