How Does A Sailboat Actually Work?

How does a sailboat work? The standard idea is that the wind pushes the sails from behind, causing the boat to move forward. Although this technique is used at times, it is not the most efficient way to sail a boat (and it means the boat can never go faster than the wind). Lift is the key mechanism driving a boat forwards. As air flows over the sails, it moves faster over the outer side, creating lower pressure than on the inner side. This produces a force which is mostly to the side and a bit forwards. Lift on the centerboard pushes to the opposite side, cancelling the sideways force and adding a forward component of force to the boat.

[OJsY]

"What could make a ship go forward if the wind's coming from the side?"
"An engine" clever.

[TheShoreman]

This is the first episode of Veritasium that I have watched where I feel like I did not really learn anything.  I love the channel and this is a great subject.  Lots of physics involved.  I wish that you would revisit this subject in the future some time.

[willgordge]

The modern sailboat is one of the purest most beautiful applications of mechanics. The video failed to describe this very well. As the wind provides a pressure gradient between both sides of the sail, the force exerted generated by the lift is somewhat parallel to the of the boats boom. Why does this not cause the boat to drift off in that direction? The center board that protrudes the bottom of the hull causes an opposite effect to take place. The force with the wind opposes the force in the water, which is stationary. The two forces can be visualized as vectors on a vector diagram. These two forces create a resultant vector, in the direction in which the boat moves, which is a single component representing the effect of all other present vectors. For those of you who know sailing, you might know now why a broad reach (135° from oncoming wind) is the fastest point of sail, not because of the wind behind generally behind the sail, but because the vectors point nearer to the direction of motion (increasing the value of the resultant) than at any other point of sail.

[shananagans]

My dad was an Air Force engineer when I was a kid & he fully explained how wings work etc. When we took up sailing, I was about 12. We took a beginning sailing course to learn all the knots & rules of the road etc. Anyways, my dad had already explained wings to me & he showed me how the sails work like wings. As far as that aspect of sailing, we were way ahead of the rest of the class. I thought it was really cool because the teacher would draw a boat on the board & indicate the direction of the wind & then ask the class who knew how to set your sails. I got up every time & drew the sails in & explained how the boat moved on the point of sail. lol I was 12 & up there explaining it to a class full of adults. I thought that was really cool. Once you understand the basics, it's not really complicated but it made me feel smart & was a big boost to my confidence.

[JulienNeel]

Very interesting and intriguing video! I love it when physics get counter-intuitive like this, yet with a little effort, you can understand what's really going on.

I think you could have spent a little more time in your video explaining how it all works. The segment was a little short and quick on that point.

[jean-alexandreamat]

It would be nice if you remade this video, you make them much better than you used to! Big fan, I look forward to all your new videos!

[JulienNeel]

I don't find the question obvious at all. I never learned the physics of sailing in school, and I have some background in math & physics.

[FlyntofRWBY]

4:03 That was the most uninterested response I've ever heard xD

[gingersteve]

I have a fluid dynamics exam next week and my lecturer is a sailing fanatic and explains nearly everything to do with lift through sailing. This helped, thanks!

[spacepirateivynova]

My father had me on a sailboat from an early age, and one thing i learned more than anything else is that you use the sails to push the keel against the water in different ways to create the pressure to 'go faster than the wind'. Water currents also come into play.

Moving into the wind requires 'tacking' back and forth sometimes depending on the wind conditions.

[keiyakins]

I hadn't internalized the physics, but it really doesn't take long to learn how to sail a small boat. Like, a week is enough if you have a good teacher.

And then for the rest of your life you curse at Nintendo for getting it wrong in The Wind Waker.

[exon]

Loved your last two videos explaining lift and how sailboats operate. Always learn something new from you Derek.
Love how you question people as to how things work and even when the answer is incorrect, you have this amazing way of encouraging further discussion without ever making them feel stupid. I know this formed a major part of your thesis.
Well done!

[blayman]

Usually when I watch these videos I can't believe people don't know the answers to what you're asking them, like in the "What makes a tree grow, " but in this one I was just as stumped as everyone else. Learned something, thank you!

[Bluemann]

DEREK!!! I love how you let people figure things out. You are the best and nicest guy EVER.

[tmrossello]

Hi Derek,
I think you got the last one wrong. The boat is fastest not at 45 or 90 degrees but somewhere around 135 degrees. Sailing in this direction and thanks to the position of your sails you still have a laminar flow of wind on both sides of the sail, which generates lift (which doesn't happen when sailing at 180°) and in addition more lift gets generated underneath the hull, which causes it to raise higher from under the water, grateful reducing drag on the hull. Therefore 135° would be the fastest direction to sail.

[miniberserker]

that guy actually did not explain anything at all... wtf.

[veritasium]

OK, I recognise the last vid may have been confusing. Bernoulli is fine if you don't make simplifications like 'air meets up at the trailing edge, ' and 'air does not need to be deflected by its interaction with the air foil.' This is what I was trying to say. And the reason I made that vid was so there would be backup for this vid because I knew we didn't have time to go into lift in detail in this vid.

[pickledavis]

four minutes of ignorant people and 30 seconds of information. fantastic!

[sachmophoclies]

Thank you for bringing in an expert, explaining the physics, and showing that your interviewees might learn something.

[scythedd]

As a sailor, I'd have to disagree with his conclusion of 90-45 degrees off the wind being the fastest point of sail, at least with most boats.  The fastest most boats goes is when they're broad reaching, or about 110-160 degrees or so off the wind.  I don't know the physics behind it, but I know it's enabled partially with a combination of using wave action, being able to put up large, parachute-like sails called spinnakers which can't be used sailing upwind, and the all important ability to plane, which greatly reduces drag.  Also, since the centerboard is less necessary when headed in that direction, some boats allow it to be retracted, thus reducing drag even more.  Some super high performance boats may act differently, but with most traditional boats, it simply isn't true.  For example, a boat I typically sail on, the Melges 24, can, in let's say 20 knots of breeze, go about 6-8 knots beating upwind, but can get up to speeds of 12-15 knots while reaching back down wind with it's chute up,