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How Does A Sailboat Actually Work?

How Does A Sailboat Actually Work?


so my question to you is a let’s say the wind is coming from over there I want you to position the boat in whatever direction you think will make go the fastest and how would you set it up and then you can you can set the sail how you want something like that take this load which you want to point the boat this way what would you want to do so how do most people think a sailboat works where would you say most people think a sailboat get some wind and manages to move they don’t really know or maybe that like gets pushed from behind yeah they’re pushing by behind is is somewhat easy to visualize your fastest direction would be straight forward will be going with the wind yeah with wind I want you to talk to me about what the wind is doing to the boat here to make it go forwards well with the wind behind push into the sail push against sue and it pushes the self important so the slowest way to position your boat is well the slowest is straight into the winds because you’re not generating any lift and the second slowest like the slowest actually sailing that would probably be close to dead away because you’re very limited to so the wind’s coming from the back and you just got your sails full yeah because when you’re going directly away from the wind your boat wind cancels out the actual wind so yours you can actually never exceed it you would only be able to match and you would have nothing no force in your sails without any wind but that would be frictionless too which couldn’t happen could you say up up up wind probably with difficulty very slowly that’s doing this in little six egg how does it go forwards if the wind is coming from here how do you get agile you’d have to bring it right round like that to bring it to the side and then flick it right back round to bring it in against the wind as you go but that’s how I’ve seen the boats go so I’m trying to figure out what could make the boat go forwards if the wind’s coming from that side generally mean engine Shh yes where is the force on these sails what do you think I think it tends to be a little Little Italy little bit aside words so nurses back inside words yeah how does the boat go forwards yes okay but that dude Oh again well I know I know it does but again I don’t have all the answers so how does the sailboat move the sails actually act like wings generating high and low pressure on each side you generate high pressure on the inside of your sail and low pressure on the outside so you’re going faster around it right it has a longer way to travel in a sense right okay and then you generate a bit of lift so the lift will actually end up being in kind of this direction towards me which is mostly sideways and will be mostly sideways in a little bit forwards but and that’s why we need to have the center board and rudder and they do they kind of counteract that force because they generate high and low pressure as well as the boats trying to be pushed sideways and kind of balances it out so the boat goes forwards give it it seems like I mean if the there’s a force pushing that way on the sail and the opposite way on the center board it seems like the whole thing would tend to it would absolutely try and turn over which is why the body weight in the leverage of the people is so important how can a sail boat go faster than the wind because it can generate it can generate more pressure by its motion okay right like it’s there’s only it can actually happen quite easily in light wind because let’s say you only have three knots going this way and then you generate an odd of motion all of a sudden you’re sailing with more than three knots of breeze over your sails and then I can build and compound on itself the limiting factor is the drag on the hull okay yeah yeah so and the drag on the sails actually that’s actually very large as well so in fact the fastest way to sail a boat is not downwind it’s actually kind of like 90 degrees or 45 degrees something like that that makes about go faster okay thank you very much you’re very welcome I hope you enjoyed this video on the physics of sailing if you want to see more with Hunter click the first link if you want to see more about how a wing generates lift click the second link and if you haven’t subscribed to veritasium yet then click the third link and i’ll see you next time Oh

100 comments on “How Does A Sailboat Actually Work?

  1. I am an amateur windsurfer and even after watching this i don't completely get how it works haha but it does so whatever i guess.

  2. The fastest position is called close hauled; it is the closest you can face toward the wind without going into irons. However if it is a rather windy day, there's a very big chance that you'll capsize.

  3. I don't click on this channel to hear amateurs give opinion. I click on it to learn something, and I learned nothing in this video. 🙁

  4. @veritasium Here's on for you: How about other "sail like" devices – can we make one that goes directly into the wind, or can we make one that goes directly down-wind faster than the wind speed? Thinking windmills driving wheels here. It can cause quite an argument (answer is yes and yes BTW)

    About faster than the wind sailing – you kind of hinted at the forces involved, but it's quite simple. Terminal velocity is where all forces balance out, and that can happen at higher than wind speed if drag is low. The new AC foiling cats are doing about 3x windspeed in 15 knots in Bermuda right now, but at about 120deg off the true wind. Ice boats can do more than that, at much deeper angles again (apparent wind is quite forward at those speeds)

  5. is much simpler than that…. action reaction, the air expelled by the trailing edge of the sail if i might call it so, is propelling the boat, as for why it can move faster than wind im not sure, but i guess the change in direction of the wind caused by the sail lowers the pressure of the air and increases its velocity as in a venturi.

  6. 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.

  7. This video is pretty inaccurate, even though the explanations are the accepted ones. Anyone can see that sails aren't shaped like wings, and there's no significant difference in distance the air needs to go on each side (they're just sheets of canvas!). The sails work simply because the wind hitting them is deflected by a certain amount. This means the wind experiences a force, and so the sails get the same force by Newton's third law. Because the sail is effectively a 'reflector' of wind, the net force on the sail is normal to the sail (ignoring drag; drag brings the direction of the net force backwards a bit). The normal to the sail always points at least slightly forwards so there is always a component of force from the sails that points forwards. The keel and rudder are there to react to as much of the sideways component as possible. The difference in pressure is an equivalent explanation, but it makes no attempt to explain the origin of the pressure difference.

    Which direction is fastest is actually is far more nuanced than just a single number. For an average cruising boat, the best angle is probably around 110-130 degrees to the wind, but for a racing boat this angle is larger. For an ice yacht (these experience almost no forwards drag from the ground, but don't slip sideways like boats do on water), this angle will approach 180 degrees. This is because any wind the boat makes (called apparent wind) will tend to decrease the relative wind angle, because any apparent wind must come from 0 degrees. The most efficient relative wind angle (including apparent wind) is probably around 90 degrees, but the exact number is unimportant. If you start sailing from stationary with the wind at 90 degrees, you'll pick up speed, but now because of your apparent wind, the wind angle is probably closer to 70 degrees now, so you should turn away from the wind again to bring the apparent wind angle back to 90 degrees. But now because your efficiency has increased you'll accelerate, meaning the apparent wind will decrease the wind angle again, so you must turn away from the wind again. This is obviously a positive feedback loop that in principle will allow you to accelerate indefinitely. The limiting factor is obviously drag, but if drag is small enough, one can sail faster than the wind. Normal cruisers have a lot of drag so their most efficient angle is relatively low, whereas an ice yacht will have an ideal angle of around 170 degrees once they're up to speed.

  8. Too short video, too little explained, not enough diagrams, for a complex subject not a lot of people understand. need schemas for the both in all 4 directions.

  9. To explain this properly you should use velocity triangles for apparent/true wind and boat speed, and free body diagrams for the forces on the boat (sail, keel, rudder etc.). That gives a real appreciation for why boats can sail faster than the actual wind speed. This explaination doesn't actually teach you anything! There's a reason you learn these in physics/engineering. They actually mean something rather than this ambiguous approach!

  10. I got a certificate once for sailing little boats just like that one, I never thought it was so counter intuitive to other people how they actually move.

  11. I would disagree with 45-90 degrees for fastest point of sail. As an actual sailor, mathematically, 90 degrees is fastest,
    Warning, long explanation:
    but because of "vmg" or velocity made good, It is actually more like 95°. VMG is the speed that the boat is travelling in the direction the boat is pointing because all boats slip to the side a little because the centerboard can't be 100% efficient. The more downwind one turns, the less sideslip there is (because the sideslip is in the direction of travel). Anyways, turning 5° more downwind helps eliminate sideslip and therefore 92-98° is the fastest point of sail.

  12. This video would have been much more thorough if he had made visuals like he usually does, explaining the physics and including free body diagrams using vectors to represent the forces created from the zones of unequal pressure. This may help explain the reason you can travel faster than the actual speed of the wind with the vector addictions etc.

  13. Just like an airplane the shape of the sail will create low preasure on the convex side…. if th sail has an angle of 45 degrees in respect of the boat, you will have a force pushing 45 degrees foward… now the keel and the rudder will cancel de part of the force trying to move sideways, so you will only have a half of the original force only pushing foward…. so if you start moving foward at 2 knts and you had a true wind speed of 4 knts, this two will add up creating a relative wind speed of 6 knts, creating more force, and like that you can sail faster than true wind speed…. that is VERY basic to the point of being incorrect, but it is somehow like that

  14. 2:35 "It has a longer way to travel, in a sense." Spreading this stupid myth in an educational video. 🙁 Very disappointed.

  15. I've been wondering about this for a while now, ever since I found out about the center board from Top Gear. surprised I never saw this video, been subscribed for years

  16. Actually, the fastest a sailing boat can go is with a TRUE WIND coming around 45 degrees from the stern (rear). As the boat increases it's speed, the RELATIVE WIND comes forward, further from the stern and closer to the bow, until it ends up sailing about 40 to 45 degrees from the RELATIVE WIND (which feels like sailing upwind from the boat's perspective). True wind is much lighter and it's still coming offset from the stern. The exact angles obviously depend on boat and sail design, and wind speed.

  17. Something very weird just happened, I just saw Brady's sixty symbols video on Kelvin effect and this video came into recommendation. They are related but not obviously so, and they are years apart by different creators and don't even have nothing in the title in common.
    The algorithm is A LOT smarter than I thought if it can do this kind of connections.

  18. I hate this format of video, gives one hundred layman explanations that are probably wrong, for what? to show how people are stupid?
    sorry, I know you have your reasons, but there might be more effective ways to get to your goal.

  19. You spend 90% of the video trolling random people and then don't have enough time for the actual explenation which is too fast and not detailed enough. Very badly made.

  20. I wish people wouldnt use the word pressure at all when talking about this question. Pressure is force over an area. The real question is why is the force over the area of the sail greater on the one side when positioned in the unintuitive way that sailors position it. What exerts the force and how? And don't use conservation laws as an "explanation" either. Conservation of energy and momentum and whatever else are not fundamental laws (they are derived from more fundamental laws). Where is the freaking force coming from?

  21. someone experienced should make a circle to show how fast you can travel in any direction relative to the wind, showing how fast the boat would go and where you'd have to put the sails.

  22. 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.

  23. How does a sailboat actually work? You won't find out here, nor will you hear any physics of sailing.

  24. I tried to tell a PhD in physics that the boat I sail on sails faster than the true wind speed and he said it was impossible….scientific illiteracy is a very very serious problem in our culture, sometimes even among the well-educated.

  25. You are perpetuating the "equal transit time" fallacy in your explanation of lift. The air does not move faster on the back side because it has a longer way to go. NASA has a website debunking this https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html . The sail generates lift because it turns the wind. Result of that is a reaction force on the sail.

  26. This video actually doesn't explain anything. For the physics behind sailing watch this video https://www.youtube.com/watch?v=jJtvGF8vZbE it is clearer and more accurate

  27. 2:40 "the air has a longer way to travel". This is utterly false. The sail has effectively zero thickness, so the high velocity path is the same length as the the low velocity path. The longer distance argument is a fallacy that assumes that the two fluid streams must meet at the same time at the trailing edge of the foil. There is no such requirement. The fluid on the high velocity side of the foil arrives at the trailing edge much earlier than the air on the low velocity side, as can be clearly seen in wind tunnel tests. If foils relied on the fluid traveling faster on the high velocity side simply because of the "longer distance, equal time" argument, then foils with zero camber, such as rudders, keels, etc, or foils with zero thickness, like sails, would not be capable of producing lift. This would also mean that aerobatic aircraft with zero-camber wings would be incapable of flight, and aircraft with cambered wings would be incapable of inverted flight, yet both of these feats are manifestly possible.

  28. So why you didn't give the 2nd half of the video on the correct version of how sail boat work yourself cause im all confuse from everybody version and it was a waist of my time watching this ! You should NOT be waisting peoples time is the reason they are here to learn .

  29. Millenia have sailed, but even into the 16th century, European tall ships could not sail upwind, until after learning of triangular sails and principles from the far east. Who were the dummies?

  30. Lol I love this a new sailor for an rc boat this is funny as I know what it Acauly means everyone thinks a dead run is faster

  31. Hmm. Are we talking about apparent wind or true wind? I'm not sure it's useful to talk to people that don't understand the difference, other than to understand that they don't understand the difference.

  32. It’s called ‘lift’. A sailboat is not pushed by the wind it is lifted by the foil of the sail on the backside of the sail. Except on a run(straight downwind). The fastest is just off a reach(90%)to the wind.

  33. Although a sail could be considered to generate lift, a simpler explanation is that similar to a wing that diverts the relative air flow (relative to the wing) downwards (when in level flight), a sail diverts the relative air flow. (relative to the sail). A sailboat takes advantage of the difference in the speed of the wind versus the speed of the water, which assuming a steady wind, is independent of the sail boat's speed.

    The key component of the sails diversion of flow is that it diverts a relative crosswind (relative to the sail boat) backwards, which coexists with a forwards force exerted onto the sail (which in turn exerts a forward force to the sail boat). For a given true wind speed relative to the water, then the crosswind relative to a sail boat is the sin of the angle between the path of the sail boat and the path of the true wind, and this crosswind is independent of the sailboats speed.

    For sailing upwind, the more efficient the sail boat, the smaller the angle between the boats path and the wind's path, and the smallest angle for a specific sail boat is called "beta". The fastest speed (with respect to the water) occurs when the sail boat travels at 90 degrees across the wind and "beta" degrees downwind. Remember the crosswind (relative to the boat) is independent of the sail boats speed and only depends on the sail boat's heading with respect to the wind.

    Very efficient sail boats like catamarans can "outrun" the wind, meaning their net downwind component of speed can be faster than the true wind speed. The Americas cup catamarans can achieve net downwind speed faster than 1.5 x true wind speed both downwind and upwind. Although the sail boat "outruns" the wind it's currently in, the wind ahead of the boat has a head start and the boat continues to sail into a continuous supply of crosswind, again regardless of the sail boats speed.

    Somewhat related, what is known as a directly downwind faster than the wind (DDWFTTW) land craft, drives a propeller with it's wheels and can go faster than the wind that propels it. In the case of the "Blackbird", it could go directly downwind about 2.5 times the speed of the true wind.

    https://en.wikipedia.org/wiki/Blackbird_(land_yacht)

    https://www.youtube.com/watch?v=5CcgmpBGSCI

  34. Maybe spend more time explaining how it works and less time dunking on people for not knowing how it works.

  35. I'm loling at all the idiots that disliked the video and are bitching about how He doesn't actually explain how It actually works. Just check the damn description ffs

  36. 😂 I love how dumb they are
    Like seriously the guy "that's how I've seen they do it" 😂🤦‍♀️

  37. sailboats are really just airplanes but on water, the pressure, and lift components are very very similar

  38. We have now proved that if you can reduce the apparent wind drag to 0 you can go the speed of light (or very close)

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