How can sailboats move forward into the direction of the wind by using their sail?


I don’t get how this is physically possible if the direction you want to go is literally the opposite direction of the way the wind is blowing. How can it ‘push’ them the opposite way it is going?

In: 20

They can’t and don’t. Sailboats use the sail *and the water*. Say the wind blows left. A good sail can use this to push down, and a downward force can become movement down and to the right by pushing off of the water.

It’s never moving directly into the wind, it’s always at an angle. It uses its sail literally on the same principle as an airplane wing, being propelled by the same pressure difference force that creates lift.

It’s called ‘tacking’.
Basically the ship will zigzag forward, using the wind to blow it at an angle, by adjusting the position of the sails. Have a look at this link-

They “cross against the wind”. This means they don’t sail straight against the wind but the boat gets set at an angle to the wind. Because the sails can also be turned, they are also set to an additional angle to the wind which allows them to “catch” a bit of the wind which pulls the boat diagonally forward to one side. Then boat and sail are moved to the opposite direction and the process starts again.

Imagine climbing up a hill. Going straight forward is impossible because it’s to steep. But if there’s a serpentine you can walk up by going a few steps up/ left, then up/right and so on. That’s how it looks when a boat is “crossing against the wind”.

Ultimately, you’re extracting energy from the difference in speed between the air and the water. Imagine a wind turbine that drives an underwater propeller. It’s the same principle in a sailboat except the blade of the wind turbine is the sail, the blade of the propeller is the keel, and the boat is moving diagonally to the wind instead of spinning in a spiral.