I tried to google it and it left me very confused.
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If Google didn’t help, all these explanations likely won’t either.
Next time you’re out for a drive stick your arm out the window. Ta-da! Your body is the sailboat and your arm is the sail. Now experiment with turning the direction of your hand and feel the pressure differences and how your arm is pushed around.
This is an interesting yt film related to this question. Watch and learn.
A lot of people have answered the question, but I think that it should be emphasized that the wind isn’t “pushing” on the sail to propel the boat forward. The wind is blowing *past* the sail. The sail is a wing. That wing generates “lift”. That lift *pulls* the boat in the direction of lift (something less than 90 degrees away from the direction the sail is pointing, just like in an airplane the wing doesn’t point up. It points forward. The wind going over that wing provides lift in the up direction.) and the keel/dagger boards keep the boat from skidding over the surface of the water so that you can maintain direction.
You *can* arrange your sail such that the wind is straight-up pushing on the sail from behind the boat, but that will just cause a bunch of turbulence and very very little actual ‘lift’. It also causes a HUGE risk that a *very* small change in wind direction can cause your sail to come screaming across the boat to slam onto the other side. The problem is that along with the sail, there’s this long-assed pipe holding the bottom of the sail and when it hits you or the crew in the head at 20 knots, it makes the sound “BOOM” which is, coincidentally, it’s name.
Imagine that you have a big, heavy box that you want to move across the floor. If you push it straight ahead, it will move in that direction, but if you want to move it in a different direction, you can use a tool like a broom to push it from the side. This is how sailships can sail upwind – they use a big, fluffy blanket called a sail to catch the wind, which pushes the ship in the direction that the wind is blowing.
Because the sail is attached to the ship at an angle, the wind can push the ship in a different direction than the wind is blowing. It’s a little bit like using a broom to push the box, but instead of using your own strength, you’re using the wind to do the work for you!
Lots of great explanations but some are pretty elevated for this forum. Try this:
Let’s say the wind is coming from the north and blowing straight south. You want to go north in your boat. You can’t. Not exactly. But if you angle your sails just right, you can deflect the wind at a sharp angle and go North, North-east instead. Then, after a while, you can switch to deflecting the opposite and go north, north-west instead. So you might be going north a little each time you go east or west.
Sail boats have a keel underwater that prevents the boat from sliding sideways. The sail is shaped and adjusted such that a breeze coming directly from the side gives a bit of forward push along with the force that causes it to tip.
The keel also helps. Imagine a watermelon seed on the table. If you press on it with your finger, it’s shape causes it to slip out in a predictable way.
Although they can’t sail directly into the wind, they can move when the apparent wind direction. Is slightly forward. By zig-zagging, the boat can make slow progress toward the destination even if the wind is coming from exactly that place
(And yes bystanders, I do know all the proper nautical terms for this stuff)
My junior school headmaster told us to imagine squeezing an orange pip between our fingers. The forces are sideways but the pip goes forwards. I think the equivalent is the wind against the sail and the keel against the water.
And pop !
Yes, I don’t sail.
The main way sails work, at least modern sails, is not by catching the wind the way a parachute does. Instead they work more like an airplanes wing. They create “lift” that pulls the ship along. Due to this you can sail at an angle to the wind pretty easily, actually 99% of ships are faster sailing at a slight angle to the wind than sail directly with it.
Same way an airplane can fly against gravity.
If you angle a sail into the wind you create a “wing” shape (aerofoil) that provides a force that is perpendicular to the flow of air.
This video explains it really well:
A sail is not a cloth catching wind. Its a vertical wing. Sailers can angle the sail to best cut through the wind to create “lift” moving the ship forward.
The real mind blower is that a ship can theoretically travel faster than the wind speed.
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