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- https://en.m.wikipedia.org/wiki/Tacking_(sailing)
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.
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”.
They do it by turning the sail so that it is more along the length of the boat rather than across it. Say, the forward end of the sail is slightly to the left of the boat, and the back end of the sail is slightly to the right of it. If the wind comes up from the front but slightly to the left of the sail, then it pushes the sail and the boat to the right. But since the boat is headed slightly to the right of the sail, it means it also gets pushed forward. And the boat’s keel keeps it from falling on the right.
Note: It’s an ELI5, I know there’s way more to it.
The sail is at an angle to the wind. The wind pushes against the sail and the keel of the boat (or the fins on a sailboard) prevents the boat from being pushed sideways in the case if it wasn’t present. Therefore, the force exerted on the sail is redirected towards the rear of the boat and pushes the boat forward.
The important thing to understand is that a wing generates a force (which we call lift) at right angles to the flow of air past it. An aircraft is moving forward through the air, so the wing sees the air moving backward, and the force generated is upwards.
If a boat is at right angles to the wind then the force generated by the sail will be at right angles to that which is forward.
If a boat is pointing 45 degrees into the wind (so halfway between across the wind and straight into it) then the sail will generate a force at right angles to that, which is forward and sideways (45 degrees off the bow).
So why doesn’t the boat go forward and sideways? Well there is another wing underwater called the keel, and it generates another force which is sideways *in the other direction*. This cancels out the sideways force from the sail and all that is left is a forward force.
The closer you point the boat into the wind the more the resulting force from the sail is pointing sideways, and the less it is pointing forwards. At some point the forwards force won’t be big enough to counteract all the drag acting on the boat, the sail and the keel, and you will stop moving forward.
https://i.pinimg.com/originals/40/a1/5a/40a15a4ed22b2fb753feef17db950177.jpg
I’ll try to post a longer answer later, but the shape of the sail when angled at wind can be shaped a bit like a wing. The wind moving over the sail or wing basically created a sucking force It’s that force which sucks the boat towards the wind for lack of a better word.
Edit – Actually this video is way better, ignore above
It’s a well known, documented fact that sailboats release ground salocine proteins into the water to draw fish. Fish swim up and eat the food and repay the sailers by pushing the boat to their destination. The stronger the wind you are against, the more fish food you need in order to draw greater numbers of fish.
This is why sailboats are bad for the environment: the production of this fish food releases octane bitroxide into the atmosphere and the consumption of the product causes fish to urinate roughly 9.6 times more than they should. It is estimated that by the year 2046, the oceans will be 83% fish piss.
Source: I saw a guy in a mental institution eating dead flies from the windowsill with his left hand, and with his right hand he was writing the above facts on the wall in his own shit.
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