The sponsor is Brilliant: The first 200 people to sign up at brilliant.org/stevemould will get 20% off an annual subscription. The alternative explanation goes something like this (I'm simplifying!) - Lift is generated when air is moving relative the sail. As the boat speeds up, the relative speed of the air should increase and so the lift should increase! This explanation doesn't work for when you're sailing somewhat with the wind though. In that scenario, as the boat begins to speed up, the relative speed of the wind actually goes down.
This isn't really correct. The term you are looking for is "apparent wind." As you speed up the angle that you feel the wind coming at you from shifts to in front of you, similar to how it always feels like the wind is coming from straight ahead when you stick your hand out a car window on the highway. This means that if you are sailing faster than the wind, you are also always sailing into the wind. When you sailing into the wind the relative wind speed goes UP, not down. When you are sailing away from the wind, you are moving with it, and the relative wind speed goes down. This is what the streamer on the front of the car in the veritasium video was showing.
Not sure if I missed this in the video, but need to also consider that Derek was using a wind turbine as a sail. A turbine can act like a flywheel, storing energy. A good question to ask is “what happens when the wind stops?”. A sail boat will no longer generate lift, but the inertia of the boat will keep it going. A wind turbine however will continue rotating and continue providing lift, so it’s possible to build more speed thanks to the energy storage element. At least, that’s my assumption, haven’t thought all that hard about it.
@@eyytee You are right, but the point here isn't that it will speed up when the wind stops. The point is that the turbine can store energy from past wind, which is added on top of the wind in the present. It's essentially a mechanical battery.
@@RealEngineering My point was that the cart in Derek's video goes faster than the wind in steady state. It stays above windspeed, as long there is true wind. It doesn't rely on stored energy that would eventually run out.
When the wind stops, from the frame of reference of the rickety turbine machine, there's still wind as it continues moving for a bit. But now it's moving into the wind. Wouldn't this negate any gains made from the flywheel effect?
I'd like to point out that unfortunately this video doesn't demonstrate how a sailboat can travel faster than the wind in the downwind direction. That being said, the model used can explain it perfectly! You just need to angle the hull away from the direction of the wind more than the sail. A turbine is analogous to a screw in the same way a sail is analogous to a wedge, so if you treat the sail car as a mechanical advantage problem it all checks out.
I think about it like gearing the difference in velocity between the wind and the ground. Like gearing between a pair of pinions attached to a pair of racks Imagine the wind and ground are racks and the sail and wheels are pinions. The two pinions are geared so that the wheel pinions move faster along the ground rack than the turbine pinion is moving along the wind rack. This seemed to work when I modeled it in on shape
Yeah also because when the wind pushing the boat in a reach will also rotate it a little it will carve up winward negating the force of wind pushing it leeward
Just as an aside, in practice sailors can rely on tactile and visual feedback to "feel" their way to approximately optimal angles. It quickly becomes largely intuitive, like learning to riding a bike. Forms of this feedback include the relative direction of small weather vanes, boat tilt or the sail floppiness.
We had a family boat when I was young that was not what would be called handy and even though a sloop was a pain to tack and just wanted to sit in irons and go nowhere. The sails and hull were not well balanced and apparently the hull was also used to produce a power boat version! We had to go off the wind in to a broad reach to accelerate the boat and then slam the always heavy feeling tiller over and hold the windward jib sheet to pull the bow round. This lazy boat really made you think of the relative speeds at angles to the wind. In some ways it made it more fun to sail. Happy memories.
@@alexjband yes, and we see these on aircraft too with yaw strings. Gliders typically have them though so too did the AV-8B, the U-2, and the F-14. Such string was the only instrument on the Wright Flyer though theirs was both Beta and Alpha as it was not over a windscreen and was next to an aft aligned peg so as to be able to see the alpha relative to peg while seeing beta relative to self.
_It is _*_impossible!_*_ In order to prove that you can sail faster than the wind, you have to tell me first how fast the wind is (thru an anemometer), and at the same time determine the speed of the sailboat, and compare both velocities._
7:08 this is why in sailing, changing the angle of the sail is similar to changing to a higher gear in a car. you start at a steep angle because that gives the most perpendicular force, but after accellerating for a bit you reach the maximum speed for that angle and have to pull the sail into a shallower angle to get any more speed. until you reach the maximum speed the boat is capable of when the sail is almost perpendicular to the wind. so the best angle for the sail depends on where the boat is pointing, where the wind is coming from, the speed of the wind AND the speed of the boat.
Not true, the true wind angle stays the same. The relative wind angle shift forward due to the speed of the boat. That is why the sails need adjustments.
As a semi pro sailor we have gears in the sense of different mast angles for different breezes and different sail depth and camber to affect the CL. the pulling sail in bit is more like a rocket thruster in space.
Bernoulli's Principle and the Coanda Effect are two sides of the same coin as I understand it. The Coanda Effect describes how flow clings to a convex surface resulting in a change in the flow's direction of travel, and Bernoulli's Principle describes how the force required to change that direction of travel is reacted against the curved surface via a change in pressure. You don't get one without the other.
@@SteveMould Good stuff! If you use my mini sandblaster design and find it shreds right through electrical tape it's probably because the sandblaster barrel is too long. It's a balance between cutting the glass quickly without destroying the stencil.
I more or less agree until you say "You don't get one without the other." For example, Bernoulli's equation can be used to describe the flow in a pipe that has a reduction in diameter (no increase). With no increase in diameter (as one travels downstream), I don't think the Coanda Effect applies anywhere.
@@andrewsnow7386 I think the coanda effect is still present in that situation unless the reduction never levels out (a closed cone shape, which would have no flow anyway), as is the reacted force on the wall of the pipe. Because of the coanda effect you can assume the fluid will fill the volume of the pipe and follow the curves of the wall (because bernoulli's principle tells you that a vacuum would form otherwise) so it's not necessary to think about both principles simultaneously.
For anyone wondering, there is also the really fun phenomenon of generating your own wind. Which occurs because as you gain speed, you are now experiencing wind equal to your speed(essentially) in the opposite direction of your travel. So as you speed up, you start having more wind, in a more bow(front of boat) position. So you can then capitalize on that and go faster, which is why many sailboats nowadays are optimized for more upwind sailing. The most dramatic example I have seen was America's Cup World series boats(which has all sorts of optimizations like wings and foils) and traveling downwind, they had their sails in close as if they were going upwind, and their windex's read that the wind was about 4x faster than we experienced elsewhere. Really good video, thank you for making. I did not know about the whole missing thing with the wind, and you could certainly make a hundred videos about the physics of sailing.
4:27 The blue/sideways force does have an affect! Because it and the ‚resisting force on the hull‘ are offset, the boat gets tilted. Thats why big boats have weights in the keel and small boats relie on the bodyweight of the sailors to counteract it.
Yes, but "tilting against the natural vertical" is just a change in _potential_ energy, and once the tilt is achieved, no more _work_ is done, at least as far as tilting is concerned. Also, it's effect, not affect.
I don't say this lightly, but this might be my favourite video of yours. Something complicated and counter-intuitive explained with such elegance and ease that I'm half convinced that its entirely obvious and I always knew it. Worthy of being the first one after the million barrier
One thing I'd really like to see, a plot where the velocity of the ship is one axis, the angle of the sail relative to the wind on the other, and coloured according to the magnitude of the force on the ship. My new found intuition is that, the sharper angle the lower the force (wind gets deflected less) up to when you approach the "maximum speed" for that angle. But that maximum speed itself increases with that angle. Would be good to see how that would look graphed out, if there's a clear optimum trade off for a given speed, and what that optimum looks like.
@@QuantumHistorian You might be interested in explanations of the tip speed ratio of a wind turbine. It covers this concept. Blades angled close to the wind have a high speed but as you say the lift force going in the direction you want is low so low torque. Used on rotors with 1 or 2 blades. What complicates things and wasn't covered in this video is that when something moves through air it has it's own headwind. This adds to the existing wind and changes it speed and direction as experienced by the moving object.
@@Ed.R Actually, while it's not discussed, the model presented covers these forces. It can thus explain how a boat can travel in the downwind direction faster than the wind, which unfortunately was not demonstrated because that is the true analog to Veritasium's video.
Solid collaboration. Funny that I sign up for a sailing class this summer, and boom, Steve Mould makes a video about sailing. The universe is calling mate.
Solid or non newtonian fluid? You may have tapped it, and it felt solid, now you need to wait to see if it oozes all over the floor. In a temperature controlled environment, to rule out melting of course
Friggin awesome explanation and congrats on 1 million subscribers! I can tell which parts you filmed before and after lunch from the stain on your shirt :P
Sad to see how quick internet fame got to poor old Steve… The moment he hits a million subscribers out goes the unnecessary detail of wearing clean shirts for video shoots. Next he'll grow some ridiculous face-beast like some crazed stand-up mathematician. Or worse, move somewhere is doesn't rain all the time.
I watched the whole video again to see any stainless shot but the stain was there during the whole video, can you help me see where his shirt was clean?
Very nice explanation, I’ve done a couple years of sailing and this is pretty accurate. Only thing is for the perpendicular trajectory, on a sailboat when you go perpendicular you will bring your sail near completely in and counter balance your boat with your own weight on a small boat like a laser.
In no way do you have your sail completely sheeted in on a beam reach, that is incredibly inefficient, especially on a laser. The only possible situation in which you should be sheeting in all the way when on a beam reach is when you are sailing significantly faster than the wind and your apparent wind is coming from a close hauled heading. On a beam reach the sail should be roughly half way out. Source: I'm a sailing instructor, have been sailing for 7 years, and am campaigning for the waszp world championships.
It helps that normally there is a LOT of stuff going on at once and reducing it down to a narrative bite size chunk leaves plenty behind for further discussion
Great explanation of how to sail faster than the wind but what I spent a while trying to work out after the Veritasium video was how you can sail such that the component of your velocity in the direction of the wind is faster than the wind. With this explanation that requires angling your sail in the opposite direction to the conventional way so I’m not sure how you do it in practice.
The angling of the sail shouldn't be important. It's the fact that the wind pushes the machine, which allows the wheels to turn the propeller. It seems odd that the wind can be slower, but the slower wind does reduce drag, which makes it easier for the machine to overcome friction and maintain its momentum.
I think a explanation could be: (its my explanation) When the wind speeds up the vehicle it doesnt speed it up due to it turning the blade, but due to pushing on the vehicle. Then the wheels will turn also and this causes the blade to spin. Now when the vehicle is at the speed of the wind it will get faster, cause actually if you imagine a horizontal line through the rotors blade there will be a crossing point between the imaginary line and the blade. This dot actually moves backwards while the blade is spinning, because of the blade is tilted. Now you have a point on the vehicle that is moving slower than the boat, cause this point is moving backwards relative to the boat (it could even really move backwards, but lets assume it doesnt) So then the air can push on this point, since its slower than the air and thus push on the whole boat. Of course this backwards moving point doesnt really exist. But you can also think about it this way: The rotor is spinning, and thus it will blow air against the actual wind. This will cause some swirls and this will cause the vehicle to kind if push itsselve from the wind. Now you could argue that pushing from the wind takes at least as much energy as it takes to turn the wheels. But thats not true, since the vehicle is moving faster relative to the ground than to the air. And thus its easier to push from the moving air than to turn the wheels to be able to push the air backwards. (Have you ever been in a pool with circle motion and just floated in the water while pushing yourselve activly from the fast water jet at the edge tonbe faster than the others? did you notice that gaining speed by this was easier than gaining the same amount of speed difference due to pushing off the non moving water? ) this is because the kinetic energy increases quadratic with speed. So lets say you want to gain a ∆v of 1m/s relative to non moving ground while you've got no speed in the first place. The energy reqiered would be 0.5(m^2/s^2)*M with M being your mass. But if you try to gain 1m/s when you are at 20m/s to get to 21m/s you will need a energy of 20.5(m^2/s^2)*M. So much more. So if you push from a object that isnt moving to gain 1m/s while you are at 20m/s you will have ro use a energy of 20.5(m^2/s^2)*M But if you are pushing from a object being as fast as you, you will have to use only 0.5(m^2/s^2)*M. This is because you will push the other object backwards by doing this and thus you will decreas its veilosity and thus its energy and thus you will gain energy without having to do that much of a work. (of course this 0.5(m^2/s^2)* M does only hold, if you assume that the mass of the object you are pushing from is infinity, cause else it will get slower while you are pushing from it like i already said, and this will make calculations complicated) So you can actually divide this process into steps: Step one: Pushing from the wind using a energy of 0.5(m^2/s^2)*M and increasing with speed of 1m/s Step two: using your energy relative to the ground to push from the air. So if you calculate that you will loose 0.024m/s. (cause you will get a energy of 0.5(m^2/s^2)*M if speeding down from 21m/s to 20.976m/s) . So over all you are gaining 0.976m/s without blaming the law of thermodynamics.
Steve only shows a beam reach which is 90 degrees to the wind so on the direction of the wind you do not travel any distance. the veritasium video shows a broad reach (about 45 degrees away from the direction of the wind) going faster in the down wind direction than the wind itself. on the broad reach you will travel downwind. I would like to see the Steve's model on this broad reach and see if it can out run the air molecule in the down wind direction. I think the boat will still go faster than the wind on the 45 degree course but will it go faster in the down wind direction ? my head can not picture it doing this I need to see the model doing it.
Your graphics actually are very good. No need for a bunch of visual noise for gratuitous reasons. Simple shapes to explain the concept in a simple manner is exactly what is called for in a video like this. Good job.
Steve, to me you are like the mid life dad who started documenting random experiments in his back yard out of curiosity for how things work. Really enjoy watching you explore and explain stuff you learned.
I'd like to add that sailing is only possible when you've got two mediums with different velocities (different direction and/or magnitude), that's what lets you continuously extract energy from the medium. Edited for clarity.
Probably the most important point for understanding how the car in the Veritasium video works. I think very few people appreciate this and it's the reason so many people call hoax.
Specifically, you need to have much higher resistance, at least to lateral motion, in one medium than in the other. "Sailing" on a water-oil interface likely would not work.
Sure you can, but not in any other direction than the one where said medium is going - you've got no "leverage" to pull/push in any other direction. Imagine yourself floating in a vacuum, if someone pokes you with a stick you will extract energy off that stick but then flailing away you go.
This is much more intuitive in the boat case than the car from veritasiums video. In the boat case the water simply provides the resistance you need to hold at the right angle
Matt's been on UA-cam for so long, done so many things, and I can't believe his channel doesn't have 1 million subscribers 🤔 that's the definition of underrated
I teach swimming lessons, and use a similar hand trick to show that 'laying' (floating flat)on the water will help you go faster and easier through the water than if you are in a standing position.
"you can explain lift using Newton _or_ Bernoulli" an aerodynamicist is about to tell you all about how _neither_ actually explain the full mechanics of a wing
It wasn't explained well in this video. Maybe a more appropriate explanation with apparent wind will feel more intuitive (it definitely is to me): ua-cam.com/video/NI39O6t4gPI/v-deo.html
I don't know how many times I've explained this now but in Veritasium's video it can go faster than the wind as once the craft is up to speed, and the propeller is producing thrust, (remember the propeller is not a windmill on that craft) the thrust from the propeller is increased because of the tail wind. It aerodynamically increases the propellers thrust close to its' maximum which is "static thrust". An easy way to think about this is a light aircraft produces maximum thrust when it is not moving. As it accelerates down the runway the thrust drops off significantly. As it accelerates down the runway if you were to introduce a tail wind to the propeller its thrust would increase. (However detrimental to lift over the wings)
In the model, the board is acting as a wedge. In a real sailboat, that's not quite the case, since as he says, the direction of the force is not the same as the direction of the wind.
You have your flat sail acting like a wedge with the “sail” being pushed and not like a curved wing, which would be creating lift from the low pressure created by the air passing more quickly across the front rather than the way you are representing it... a common misconception made by non-sailors...
Aerofoil or not, I agree that a wedge is a good enough approximation to describe how to sail faster than the wind. This video doesn't explain how to beat the wind however. I just made a video with graphics explaining how you can do so: ua-cam.com/video/CbNCz0_iO7c/v-deo.html
Pretty spot on video. I’ve been sailing most of my life and this gives a pretty good intro to what’s happening above the water. Obviously, one can’t squeeze the entire theory of sailing into one 12 min video. I hope someday you’ll look into the hydrodynamic effects of the hull/keel as they’re as, if not more, important than the sails when it comes to speed.
What’s even more interesting is dinghy’s below the waterline, because they don’t need standard elements like a keel you get way more variance, from displacement to semi planing, skiffs, cats, foilers, planing cats, foiling cats, etc you see way more variance than in keelboats
As a sailor myself, I can confirm that this video is amazingly well done and explained. Congrats on 1 million subscribers! I'm glad I am part of those! Would have been nice to also mention True Wind, Boat Wind, and Apparent Wind too though.
Mentioning tw bw and aw has no real place in this video because they’re technically incorrect they’re just tools we as coaches use to give the people we teach an intuitive understanding quickly. It’s not really an accurate description of the physics at play
For real. I'm a fairly decent sailor and it's always felt intuitive to me, but I could never really give a rigorously worded description of how it actually worked till I sat down and thought about it for a while. This was after like 6 years of sailing.
@@lmva you can see a sail working by looking at it, wind blows boat moves, there's logic to it. You know how a computer works just by looking at it? or how about a modern automobile?
@@ivortragedi2787 Depends on the desired level of understanding. There's some fascinating stuff going on inside the engine, that the electronics only provide timing for.
As a sailor I find it funny that this is even a topic of discussion, as we know we can go faster than the wind and we've known it for thousands of years.
I guess it's just a different source of learning. I grew up inland so I'm not familiar with sailing intuition but this video helped. Ironically I used to think some sailing games had bugs and now I realise they were realistic.
Its different in this case because sailboats can sail against wind but travel at a certain angle relative to it. Whats trying to be proven here is going faster but, in the exact same direction that the wind is going, which sailboats can’t do.
Of course we know that from experience, but this video is about how it does it, which will be counter-intuitive to many people. I'm going to bet there are other things we know work from experience, but you don't know how. That's quite normal.
I first heard about this years ago when someone claimed that his unpowered cart with a big fan on the back could travel directly downwind faster than the wind. Someone mentioned sailboats traveling faster than the wind but most people assumed this meant traveling with the wind but diagonally. Some guy who did ice sailing showed that he could arrive at a point directly downwind much earlier than a balloon floating with the wind. To me, this proved it could be done. Just left the question of explaining the physics. I was surprised that many people continued to deny it was possible based on their theoretical calculations.
The reason the sailboat isn't pushed sideways is not just due to the thin hull shape. There will also be some rudder input to correct the course of the boat.
It is good to mention that if we speak of Bermuda type rig (Genoa/Jin and main sail) that there is a possibility to not use rudder at all if we find so-called balance of the sails. Wind rotates the boat in different direction around the mast/keel depending on what sail you tighten and ease. So, if you find balance of sails, boat can go upwind with no rudder input.
@@whatswrongwithyarik4835 Yep, we sailed a couple weekends back and found ourselves with perfectly balanced sails close hauled (with a slight inclination to a close reach) and I showed my son how we could adjust our course just but adjusting the Jib or Mainsail having the rudder locked amidship. I would be curious the efficacy if we could remove the rudder from the boat/equation.
A good sailor balace the boat, so the rudder is straigh forward without breaking. I sail on a 3 mast schooner gaff rigg. If you put up sails in the front, you have to put up sails in the back. The jib in the very front is in pair with the top sail on the mizzen mast. Whith good riggers, you never have to fight the boat and the wind at the helm.
Thanks ! That is indeed missing from this video. The Bernoulli effect is completely overlooked here, after the initial comparison with airplane wings. America's cup boat would be a great exemple of what Dererk was providing a handwaiving explanation for in his video. (that's the first time I have disliked a Steve Mould video)
I think a explanation could be: (its my explanation) When the wind speeds up the vehicle it doesnt speed it up due to it turning the blade, but due to pushing on the vehicle. Then the wheels will turn also and this causes the blade to spin. Now when the vehicle is at the speed of the wind it will get faster, cause actually if you imagine a horizontal line through the rotors blade there will be a crossing point between the imaginary line and the blade. This dot actually moves backwards while the blade is spinning, because of the blade is tilted. Now you have a point on the vehicle that is moving slower than the boat, cause this point is moving backwards relative to the boat (it could even really move backwards, but lets assume it doesnt) So then the air can push on this point, since its slower than the air and thus push on the whole boat. Of course this backwards moving point doesnt really exist. But you can also think about it this way: The rotor is spinning, and thus it will blow air against the actual wind. This will cause some swirls and this will cause the vehicle to kind if push itsselve from the wind. Now you could argue that pushing from the wind takes at least as much energy as it takes to turn the wheels. But thats not true, since the vehicle is moving faster relative to the ground than to the air. And thus its easier to push from the moving air than to turn the wheels to be able to push the air backwards. (Have you ever been in a pool with circle motion and just floated in the water while pushing yourselve activly from the fast water jet at the edge tonbe faster than the others? did you notice that gaining speed by this was easier than gaining the same amount of speed difference due to pushing off the non moving water? ) this is because the kinetic energy increases quadratic with speed. So lets say you want to gain a ∆v of 1m/s relative to non moving ground while you've got no speed in the first place. The energy reqiered would be 0.5(m^2/s^2)*M with M being your mass. But if you try to gain 1m/s when you are at 20m/s to get to 21m/s you will need a energy of 20.5(m^2/s^2)*M. So much more. So if you push from a object that isnt moving to gain 1m/s while you are at 20m/s you will have ro use a energy of 20.5(m^2/s^2)*M But if you are pushing from a object being as fast as you, you will have to use only 0.5(m^2/s^2)*M. This is because you will push the other object backwards by doing this and thus you will decreas its veilosity and thus its energy and thus you will gain energy without having to do that much of a work. (of course this 0.5(m^2/s^2)* M does only hold, if you assume that the mass of the object you are pushing from is infinity, cause else it will get slower while you are pushing from it like i already said, and this will make calculations complicated) So you can actually divide this process into steps: Step one: Pushing from the wind using a energy of 0.5(m^2/s^2)*M and increasing with speed of 1m/s Step two: using your energy relative to the ground to push from the air. So if you calculate that you will loose 0.024m/s. (cause you will get a energy of 0.5(m^2/s^2)*M if speeding down from 21m/s to 20.976m/s) . So over all you are gaining 0.976m/s without blaming the law of thermodynamics.
Uniformed guess on how this is possible : Watching the the Americas cup we see there is a lot of 'dirty' air coming off the back of the boats. This would match the explanation of how the device the the veritasium works, robbing velocity from the air. Given that the velocity in the direction of travel can be >3x windspeed the boat will meet a lot of air to steal velocity from. The second part is Steve pinns, from the point of view of the boat the speed and direction of the wind are radically different. And complex physics stuff happens
Agreed, this is completely missing and very relevant. It is all to do with 'apparent wind' . Google will provide ample reading on the matter, but here is my attempt at a very simplified explanation: Imagine Steve's sailing trolley boat thing moving at 10m/s without any wind. It will feel like there is 10m/s of wind coming from straight in front of it. This is 'induced wind'. Now imagine there is a 10m/s wind blowing at 90 deg to the direction it is traveling in. This is 'true wind'. Someone on board the trolley (and the sail) will experience the combination of these two coming from 45 deg at 14m/s (ish). This is 'apparent wind'. The trolley can now adjust its direction of travel to be at 90 deg to the 'apparent wind' (135 deg from 'true wind') and accelerate up to 14m/s (ish). The trolley sail will now experience the combination of the 14m/s 'apparent wind' and the new 14m/s 'induced wind', resulting in an apparent wind of 20m/s (ish). This process repeats with the trolley getting faster and faster while turning away from the 'true wind', resulting in a trolley having a 'speed made good' greater than the true wind. Obviously pesky things like friction, drag, and other physics get in the way to some extent but hopefully you get the underlying principles.
Thank you. I think I sort of understand it now. Still wish Steve would do a follow up as the most counterintuitive aspect from the Veritasium video is missing from his explanation ✌️🤓
I sail competitively for my university, and this is spot on. Always delighted to see sailing content on here, I would love to see more of it. Well done Steve!
@@Spakianor At 8:50? Yeah, it's not perfect because his model is still kind of using a board instead of sails, but it gets the idea of tacking across. Good point though
Uhoh, Matt is going to go talk to his topology friends. Those people are uber-nerds. They're going to have a very maths based explanation of that power cord knot, and I will enjoy every second of it!
@@nathanrocks2562 lolol at first I read your comment and didn't look very close, so I thought that your "rock on" emoji was actually an electrical plug on a power cord (see it? the fingers are the prongs!). Weirdly enough, in this case it works both ways! I think you may have created the first ever emoji pun + regular pun double-pun combo move, so congratulations!
@8:51 I could be mistaken about this, but my understanding of "tacking" is that it's the maneuver of bringing the bow of the ship across the wind, i.e., one turn in your zig-zag pattern, whereas the process of tacking repeatedly as to maintain a coarse that is overall directly into the wind is called "beating." This may be archaic usage, however, as all my sailing knowledge comes from Patrick O'Brian's book series.
4:05 indeed, the slight sideways drift away from the wind, or to leeward (the opposite of windward) is why you should always leave yourself some _leeway_ when trying to clear an obstacle. Especially if for some reason you don't make very good _headway_ I'm always amazed by how deeply sailing has worked its way into our language!
Modern day boats can actually generate net zero leeway by canting their foils to windward as to generate windward lift as well as vertical lift which is why most moths and foiling boats cant to windward
Fun fact you’re minorly incorrect. It’s true that you can have net 0 leeway or even positive leeway but rigorous testing, a very small part of which I’ve been involved with as part of my uni program and sailing team, has shown that while it’s possible to achieve 0 or positive leeway it’s optimal to have between 1-2 degrees of leeway angle because the drag required to generate the extra hydrodynamic lift and resulting speed penalty is greater than the vmg improvements from better point, outside of niche tactical situations like pinching an opponent off a start line in a sailboat race
Exactly, my vector diagrams and wikipedia says that. I was thinking maybe I am wrong. Your comment verifies my calculation and diagram ok wikipedia too.
i think his explanation was waaay too convoluted, albeit clever. It took me a while to understand what's going on, i've invented a good explanation for myself.
I'll try. In Deric's machine the propeller blades are acting as sails. If the machine is going slower than the theoretical max speed, the "packets of air" will hit the blades/sails transferring some of their kinetic (velocity) energy to the propeller. This energy is then transferred to the wheels allowing the machine to accelerate further. This is why the air behind the propeller slows down.
I think a explanation could be: (its my explanation) When the wind speeds up the vehicle it doesnt speed it up due to it turning the blade, but due to pushing on the vehicle. Then the wheels will turn also and this causes the blade to spin. Now when the vehicle is at the speed of the wind it will get faster, cause actually if you imagine a horizontal line through the rotors blade there will be a crossing point between the imaginary line and the blade. This dot actually moves backwards while the blade is spinning, because of the blade is tilted. Now you have a point on the vehicle that is moving slower than the boat, cause this point is moving backwards relative to the boat (it could even really move backwards, but lets assume it doesnt) So then the air can push on this point, since its slower than the air and thus push on the whole boat. Of course this backwards moving point doesnt really exist. But you can also think about it this way: The rotor is spinning, and thus it will blow air against the actual wind. This will cause some swirls and this will cause the vehicle to kind if push itsselve from the wind. Now you could argue that pushing from the wind takes at least as much energy as it takes to turn the wheels. But thats not true, since the vehicle is moving faster relative to the ground than to the air. And thus its easier to push from the moving air than to turn the wheels to be able to push the air backwards. (Have you ever been in a pool with circle motion and just floated in the water while pushing yourselve activly from the fast water jet at the edge tonbe faster than the others? did you notice that gaining speed by this was easier than gaining the same amount of speed difference due to pushing off the non moving water? ) this is because the kinetic energy increases quadratic with speed. So lets say you want to gain a ∆v of 1m/s relative to non moving ground while you've got no speed in the first place. The energy reqiered would be 0.5(m^2/s^2)*M with M being your mass. But if you try to gain 1m/s when you are at 20m/s to get to 21m/s you will need a energy of 20.5(m^2/s^2)*M. So much more. So if you push from a object that isnt moving to gain 1m/s while you are at 20m/s you will have ro use a energy of 20.5(m^2/s^2)*M But if you are pushing from a object being as fast as you, you will have to use only 0.5(m^2/s^2)*M. This is because you will push the other object backwards by doing this and thus you will decreas its veilosity and thus its energy and thus you will gain energy without having to do that much of a work. (of course this 0.5(m^2/s^2)* M does only hold, if you assume that the mass of the object you are pushing from is infinity, cause else it will get slower while you are pushing from it like i already said, and this will make calculations complicated) So you can actually divide this process into steps: Step one: Pushing from the wind using a energy of 0.5(m^2/s^2)*M and increasing with speed of 1m/s Step two: using your energy relative to the ground to push from the air. So if you calculate that you will loose 0.024m/s. (cause you will get a energy of 0.5(m^2/s^2)*M if speeding down from 21m/s to 20.976m/s) . So over all you are gaining 0.976m/s without blaming the law of thermodynamics.
This is the first Brilliant-sponsored video I've seen that actually made me go "wow, I want that". Countless other "sponsored" videos talk about brilliant and what it does, but *seeing* that little graphic of the interactive coding lessons... that sold me. I wish child me had access to this kind of stuff.
Steve Mould´s videos are always beautiful. I look forward to each one. Once again it is obvious that a lot of work has gone into this one. There are a number of very nice concepts and explanations presented and packed into just 9 minutes! I wish it could have been longer. Here are a couple things that I noticed that might be of general interest, or perhaps I will be corrected on and thus learn more about the subject. And though this video provides some wonderful intuition on sailing mechanics, I explain in detail here as to why it does not give us an intuition about faster than wind travel. At the end of this post I suggest something that might be a missing piece that I think would complete the explanation. Steve did not mention, but as a boat travels faster, the wind appears to change direction. Say we start sailing downwind at an angle. Initially the wind will be at our backs. As the boat speeds up we will notice that the wind appears to come more and more from the front, even though the true wind has never changed. People on motor boats and motorcycles just expect wind from the front no matter which way things are really blowing without even thinking about it. Consequently, the 'sailing upwind' part of this video also applies to fast downwind sailing. Consider sailing downwind at a 45 degrees angle when the boat is traveling equally down wind and perpendicular to it. At this angle the wind will appear to be coming over the starboard bow. (x, y) a vector (0, 1) velocity of wind blowing in the y direction (1, 1) velocity of boat at 45 degree angle traveling the same speed as the wind (-1, 0) velocity of the apparent wind (over starboard bow due to boat traveling at an angle) Thus the upwind sailing scenario that Steve shows at time 8:24 is also the downwind at the speed of the air scenario. Hence, this little demonstration is key for this video. Steve makes use of a stick and cart model for sailing. The stick has a wheel attached to the end of it. An interesting aspect of having the wheel there is that force will always be perpendicular to the surface of the board being used as a sail. This would be the case for real if air reflected upon striking a sail and had equal incident and reflection angles. Because the force is always perpendicular to the surface of the board acting as the sail, the stick may be rotated around so the shaft is perpendicular with the surface of the sail. When this is done no sideways force need be applied to hold the stick when pushing. The travel would then be scaled by cos(theta) of the angle of rotation. Hence the actual angle that we see for the stick in the video is only symbolic of wind direction. He pretty much could have used any stick angle. A sailboat has a keel, so it travels in local straight lines. Sail powered land vehicles and those with ice skates also travel on local straight lines. So we can think about these vehicles as though they are on a fixed track. With the stick and cart model, the little cart will always move on its track in such a way as to create a gap between it and the wheel attached to the stick. In other words the vehicle will always move on the track so that the wheel on the stick will roll down hill. Given a stick perpendicular to the surface of the sail, the travel of the vehicle on its track will be greater than the travel of the stick when the sail is at less than a 45 degree angle to the track. Steve shows this at 6:25. If the stick was also rotated, then another cos(theta) must be overcome to cause the cart to travel faster than the travel of the wind. For the upwind case given at time 8:24 this calls for a small angle between the sail and the track. Just look how far the stick would have to be rotated to make it perpendicular to the sail. That will make for a very small cos(theta) also. Steve himself discusses the problem with such small angles between the sail and the track at 6:47 while showing the stick rotated around. The stick and cart model is of course an approximation of what happens when sailing, so this model loses its predictive power just when it is needed, when we approach the speed of the wind. Steve presents another model, that of air displacement, at 2:51. With this model he shows the air clinging to the sail and then turning and following its surface. This is a different assumption about air behavior than that built into the stick and cart model. In the example at 2:51 the angles are not quite right for the faster than the downwind case we are interested in, and for this model we do need correct angles. The correct angles are given in the 8:24 example. However if air clings to a sail, then it takes some effort to remove it. This removal effort is known as drag and it pulls the vehicle backwards. When we use the correct angles we find that the displacement is small so the drag component question becomes critical. So like the stick and cart model, the displacement model stops being predictive just when we reach the point of interest, when the vehicle reaches the speed of the wind. I am not sure why, but Steve avoided discussing the Bernoulli Effect. Due to the Bernoulli Effect a shaped wing, such as presented at 7:56 can generate high lift force with little drag force when wind flows over it. This will cause air flow to be of a bigger concern than other variables, so the angles we see in the faster than wind travel cases actually become an advantage instead of a difficulty. With the Bernoulli Effect lift appears at about 90 degrees to the flow, without large drag. It is kind of magical. I wish the video had been longer. I would be happy to listen to Mould go on for hours. Steve, how about making a second video including the Bernoulli Effect?
"Thus the upwind sailing scenario that Steve shows at time 8:24 is equivalent to traveling downwind at about the speed of the wind." The scenarios are symmetrical, not identical: the roles of sail and keel are swapped.
@@eyytee Interesting observation about the keel physics, which was not touched on in the video other than to say that the keel provides a conservative force that is just big enough to cancel off track forces. Which it is doing in both cases. In both the fast down wind case and the upwind case the sail provides the same lift, so the keel is providing the same lift. In both cases the water travels over the keel from fore to aft. However, I do see a difference in that the speed of water over the keel (or the speed of the land vehicles wheels are turning) will be higher in the downwind case because the boat will be moving over the water faster. So I don't see a symmetry, I see a difference in speed of the water over the keel, or the speed the wheels are turning. The sailing mechanics are identical. eyytee, did you not like the comment? It is well done no?
@@ep5acg By symmetry I mean the forces vs. motion parallel and orthogonal to the wind: TACKING UPWIND: - sail drives the boat across the wind - keel drives the boat upwind TACKING DOWNWIND WITH VMG > WINDSPEED: - keel drives the boat across the wind - sail drives the boat downwind This also explains why to go directly upwind, the rotor cart would have to reverse the transmission, and turn the wheels with the propeller.
@@ep5acg It's true that you could hold he stick anyway you want, and push sideways with it. But the convention in the demo is that you move the stick only parallel to the stick, which indicates the true wind direction. In that sense I don't think the demo as shown applies to both scenarios. In a more general sense, there are similarities/symmetries, but it would haven been better if he had explicitly shown the downwind case.
Hmm, I already found it intuitive that the sail boat can move faster than the wind in Veritasiums video. What I still do not find intuitive is the claim that the *component* of the velocity of the boat *downwind* can be faster than the wind speed (ua-cam.com/video/jyQwgBAaBag/v-deo.html ). When starting this video I was kinda hoping for a n answer to *that* question.
I would have liked for this video to talk about apparent wind: ua-cam.com/video/NI39O6t4gPI/v-deo.html As it is, the video does not explain well and intuitive how a sailboat works.
@@Дістатижовтімаюнаметі The only explaination I found so far why a tacking boat would be faster than the wind in the direction of the wind (ie overtake the balloon) is that each time you change direction you still have your momentum so around the turning point you go faster than the wind for a short while. This, however, does not work if the boat never changes direction, as implied by the two boats "taking" on the "water tube" that turns into the propellor....
It's simply because the "apparent wind" seen by the sail is not the same as the ground wind. Both direction and speed will change as the boat speed changes. As the boat speeds up the wind will first seem to come from behind, then it will seem to shift to from the side (abeam) and so from on the boat it will feel like an abeam wind would feel at standstill. An abeam wind at standstill will accelerate the boat forward. This then takes you beyond( faster than) the true wind forward component because now you are sailing "into" the apparent wind, slightly. Which means you have the downwind component PLUS the "into the wind" component and these combined can be faster than the true downwind speed.
@@imd12c4advice Well, what do you know, it was rich sailing wizards all along ( ua-cam.com/video/uylpjlz8SjY/v-deo.html ). I think your comment + that video finally gave me an epiphany. Thank you
As BSc graduate and a competitive sailor (Canadian Championship), I'd like to point out that this is HIGHLY simplified. The curvature of the sail is like 90% of what makes one sailboat sail faster than the next. We spend a lot of time and brain power tweaking the sail's curvature. Championship sailing is truly the battle of the brains.
Damn you guys. This video was EXCELLENT. The graphics were fantastic. I too was suffering from a lack of explanation in that other video, despite it also being very inspiring. Good combination here. That was honestly some of the best explaining of anything ever I've seen, and I watch a ton of these videos. Great job! I'd also like to posit that this phenomenon is FAR MORE important than we realize. It's not just lift in wings and sails I think but a whole host of other similar things in the universe and future technologies for space travel, or even as an alternative to the failed vacuum tube idea for hyperloops.
And now not any more? Note that Veritasium's boat-prop explanation is based on the fact that a boat can beat a balloon drifting with the wind! I.e. not just that boat can go faster than wind in an expertly chosen angle, but that the boat can summarily go faster than the wind in the direction of the wind, too. Steve only explained the initial part.
@@u1zha Yeah, I made a separate comment requesting a part 2. I kind of understood Derrick's explanation, but I'd understand it a LOT better if Matt and Steve did it.
@@dykam It's possible to use the speed difference between the ground and the air, this difference exists even if the vehicle is the same speed as the wind, and you can get enegy out of this difference if you decrease it, however this is only a very general explanation and doesn't adress the mechanical aspects.
@@dykam this video wasn't about that vehicle, it was about what Veritasium hand waved as being true. which is fine as his video wasn't on how sails go faster. this video gave a more complete answer for how sails can move at an angle to the wind faster than the wind, and since the two blades on the vehicle are effectively just 2 sails move at an angle into the wind more completely explained that specific portion. it would be nice to see more of that vehicle though it was cool
I think a explanation could be: (its my explanation) When the wind speeds up the vehicle it doesnt speed it up due to it turning the blade, but due to pushing on the vehicle. Then the wheels will turn also and this causes the blade to spin. Now when the vehicle is at the speed of the wind it will get faster, cause actually if you imagine a horizontal line through the rotors blade there will be a crossing point between the imaginary line and the blade. This dot actually moves backwards while the blade is spinning, because of the blade is tilted. Now you have a point on the vehicle that is moving slower than the boat, cause this point is moving backwards relative to the boat (it could even really move backwards, but lets assume it doesnt) So then the air can push on this point, since its slower than the air and thus push on the whole boat. Of course this backwards moving point doesnt really exist. But you can also think about it this way: The rotor is spinning, and thus it will blow air against the actual wind. This will cause some swirls and this will cause the vehicle to kind if push itsselve from the wind. Now you could argue that pushing from the wind takes at least as much energy as it takes to turn the wheels. But thats not true, since the vehicle is moving faster relative to the ground than to the air. And thus its easier to push from the moving air than to turn the wheels to be able to push the air backwards. (Have you ever been in a pool with circle motion and just floated in the water while pushing yourselve activly from the fast water jet at the edge tonbe faster than the others? did you notice that gaining speed by this was easier than gaining the same amount of speed difference due to pushing off the non moving water? ) this is because the kinetic energy increases quadratic with speed. So lets say you want to gain a ∆v of 1m/s relative to non moving ground while you've got no speed in the first place. The energy reqiered would be 0.5(m^2/s^2)*M with M being your mass. But if you try to gain 1m/s when you are at 20m/s to get to 21m/s you will need a energy of 20.5(m^2/s^2)*M. So much more. So if you push from a object that isnt moving to gain 1m/s while you are at 20m/s you will have ro use a energy of 20.5(m^2/s^2)*M But if you are pushing from a object being as fast as you, you will have to use only 0.5(m^2/s^2)*M. This is because you will push the other object backwards by doing this and thus you will decreas its veilosity and thus its energy and thus you will gain energy without having to do that much of a work. (of course this 0.5(m^2/s^2)* M does only hold, if you assume that the mass of the object you are pushing from is infinity, cause else it will get slower while you are pushing from it like i already said, and this will make calculations complicated) So you can actually divide this process into steps: Step one: Pushing from the wind using a energy of 0.5(m^2/s^2)*M and increasing with speed of 1m/s Step two: using your energy relative to the ground to push from the air. So if you calculate that you will loose 0.024m/s. (cause you will get a energy of 0.5(m^2/s^2)*M if speeding down from 21m/s to 20.976m/s) . So over all you are gaining 0.976m/s without blaming the law of thermodynamics.
A bit surprised I don’t see lots of comments calling this out as an incorrect description of how sails work (and also how aircraft aerofoils work). In both cases the lifting (or boat pushing) force is not at all because the sail or wing is on an angle to wind. It’s because both the wing and sail form an aero foil, shape. As one side of the sail/wing is longer than the other, air must travel faster over that surface in order to meet with the air on the other side (if it didn’t, there would be a spectacular and dangerous vacuum at the trailing edge of the wing/sail). The effect of the faster travelling air on that surface is to reduce the air pressure compared to that of the other side. The result is a force in the direction of the upper/longer surface of the wing/sail. This is called Bernoulli’s Principle. The one exception to this is when a sailboat is sailing down wind and has the sail set out perpendicular to the motion of the boat. In that case it is just moving by pushing from the wind on the sail. For those who will point out a sail has the same length on either side - yes, but if you understand how air flows smoothly over a curved surface but turbulently over a suddenly break in a surface (the mast and trailing cavity of the curved sail behind it) the overall effect is still a pressure differential.
"As one side of the sail/wing is longer than the other, air must travel faster over that surface in order to meet with the air on the other side (if it didn’t, there would be a spectacular and dangerous vacuum at the trailing edge of the wing/sail)." This is the equal transit time thoery, and it was debunked decades ago. That said it still appears in text books and Neil Degrasse Tyson used it to explain how a wing generates lift very recently. *sigh*
Great video as always Steve. Myself and some friends recently started sailing and spent a fair bit of time pondering the physics as well. It might be worth noting that as the boat speeds up it's advantageous to reduce the angle between the sail and the direction of travel, I think this is because the 'resultant' angle of wind on the sail changes with the speed of the boat.
Sailors use what's known as an apparent wind to sail their boat and say your heading angle is 090 @ 20 knts and the wind comes from 000 @ 30 knts your apparent would be 030 at 37 knots which would be a close hauled course when you are actually on a reaching course
As a sailor, I love to see this kind of stuff. Another addition to this is that when a sailboat is moving at a certain speed, let's say five knots in 10 knots of wind then the sailboat is experiencing another 5 knots of wind against it because of the speed it's going. This is called apparent wind. So now that boat has 15knots of wind against it. When a sailboat does this and it happens on every sail on a boat if the boat is moving, then you have to pull the sail in to counter the apparent wind. This is because the apparent wind is coming from the direction that your boat is moving or the front of the boat while the real wind on a boat's preferred angle is usually about 120 degrees from the wind. Now your boat has its sail pulled in its wind angle is around 80 degrees even though the boat is pointing in the same direction. This can be repeated for a long while when you have the right sea conditions. This is also why you don't see the GP boats or the AC75s letting their sails out very far. They are trying to capture the apparent wind.
The "power cord knot" 12:10 is called HMS (Halbmastwurfsicherung), Munter hitch in English, or half clove hitch. Used commonly in rock climbing as a belay knot on a carabiner (the carabiner is also called HMS, name from this knot). It is great to see how the knot "flips" the other way when you pull the other strand. Try it! It seemed like magic for me first time I learned how to belay using HMS, and then you start to understand how it works. Try it with a rope on a carbiner!
Derek made a video about clickbaity titles/thumbnails (years ago), and why he will start using them. While still maintaining the same quality as before.
everything i know about the dynamics of sailing, i learned from zelda (or rather, link) in the windwaker. you could get the boat to go into the wind by building up speed and turning into it, back and forth, alternating left and right so you don't veer off to one side.
Its called tacking! It's a lot of fun in reality. Which Zelda title is this? I might have to give it a try, that sounds like a blast! I've never heard of a game with realistic sailing physics.
You totally forgot about true windspeed and apparent wind. More boat speed, that more influence it have to the apparent windspeed. It have influence on the boat speed as well in the angle to the true wind. For example the ac75 always have the same sail trim, doesn’t matter if they are on a up wind or down wind course, because of the high speed they use more the apparent wind as the true wind.
Those ridiculous models actually really made this explanation really easy to understand. I hope you guys decide that now that you're at 1 million the next goal is just 10 million and you keep challenging each other.
At the section about sailing against the wind, there's a discrepancy between the physical model (around 8:30) and the drawing of the zig-zag motion of the sailboat (near 8:48) as on the model the front of the sail is on the side the wind is coming from, and on the drawing the front of the sail is away from the wind. I think the drawing is the most likely to be incorrect...?
3:05 shouldn't it be a parallelogram of vector forces, not a triangle. So instead of the resultant pointing a little back, it's a longer arrow halfway between the first two?
The force, impulse, or change of momentum is the difference of the two momentum vectors, not the sum. Parallelogram is for summation (addition), and here we need difference. Edit: so, horizontal (before) plus red (change) equals the resultant slanted white vector ( after)
3:06, shouldn't the red arrow only point in that direction (the direction shown) with that magnitude when the horizontal arrow is pointed left (with the 45° arrow remaining as is)? Is my fundamental understanding of vectors incorrect?
CONGRATS STEVE! Been watching you for years and always felt that you were an undiscovered or hidden gem. I was always shocked that more people hadn’t found you and subscribed…..well, now they have and it’s well deserved! Looking forward to seeing how long it takes to get you to 2 million subs! And worry not Matt Parker…we’ll get you to that magic 1 million soon (here’s an idea….just plaster more images of Steve’s face on your video thumbnails and you’ll reach a million subs in no time at all!)
As a sailor of 30 years I love to watch You explain simple things. In general they are considerend simple, but when you ask yourself "but why tho?", there comes Steve with his clever and simple explanations. Always with a smile on the face. Thanks Steve, have a great one.
Sails and sailing vessels come in countless variations and different configurations, of course. The most common sails these days - seen on that Bermuda-styled pleasure boat at 8:12 - are actually shaped more like wings than like triangles. They look like triangles curved out of shape by the wind but they are more like three-point _pockets_ carefully designed to catch more wind.
At 8:34 your sails are on the wrong side of the boat, you would be backwinding and actually end up traveling backwards not upwind. You would just need to switch the sides that the sail is on.
@1:42 “How often is it that the place you want to go happens to also be the direction that the wind is blowing?” As a paraglider pilot who is trying to get into XC (cross country) flying, I really felt this. 😂
@@Rick_Cavallaro, I live in the Salt Lake area so I primarily fly The Point, but I actually just had my first real thermal mountain flight this past week at The V. Taking baby steps so I can join the big boy XC crew in due time. :)
@@Andyg2g you know Dingo Dave? He was one of our locals, but now a POTM guy. He hang glides, paraglides, skydives, wingsuit... And a great guy. Thermalling can be great. But I would caution you to take a very deliberate approach as you move into thermalling and XC. Give yourself wider safety margins, and try (at least at first) to avoid falling into the "I've gotta go further than the last pilot" mindset. If you haven't done an SIV clinic, I highly recommend it.
@@Rick_Cavallaro, the name doesn’t ring any bells, but it’s entirely possible that we have crossed paths at some point if he is a POTM regular. And thank you for the advice! I have been flying for nearly a year and have two SIVs under my belt as well as a maneuvers course with Cody Mittanck scheduled for later this year, so I’m still very much a fledgling pilot, but am taking steps learn as much as possible from the local experts in my area. Slow and steady McGee is the way for me. :) All things in due time! If you’re ever in the area let me know! Would love to come out to San Francisco sometime as well!
Dunno if anybody else has pointed this out, but the overall net force of the wind on the sail is not called "lift". Only the component of the force that is perpendicular to the wind is called "lift", and the component that is parallel to the wind is called "drag". Also worth remembering that in this context "wind" is always measured relative to the motion of the vehicle, so a plane travelling 150kts through still air is experiencing 150kts of wind, and once the boat starts moving, the wind direction relative to the boat will change. This is confusingly different to how sailors talk about wind direction which is almost always relative to the water. Also there was no mention of a broad reach, which was surprising because that was the first example given with the model sailboat. That's a great way to get faster than the wind, and Derek also briefly showed it in his video. Basically you've got a sail angled so it's flat on to the wind, and the boat goes downwind, but angled off by about 45 degrees. Then you end up travelling with the wind but because your path is longer than the wind's path, you go further. Also you start to get relative wind effects and you can start to angle the sail a bit more and get an extra boost, in fact because of the curved sail, in this configuration you do end up throwing some wind back, just like the turbine car did. Hitting a broad reach just right in a strong wind with a dinghy is an incredible feeling, it's like you're getting lifted up out of the water almost.
Great video. Awesome explanation. No hand waving at all. I would argue that Your presentation was infinitely clearer than the similar video by the other author.
I'd love to see the energy balance on this. I think people (myself included) see something traveling directly into the wind at a speed faster than the wind and initially think "perpetual motion!" but obviously that isn't true. Great video.
6:02 a very similar effect is happening in asynchronous induction motors (squirrel cage motors) when operated without a load. The rotating magnetic field around the rotor accelerates the rotor until it matches speed and phase with the magnetic field. By that point, no more force is generated and it slows down. The motor reaches an equillibrium state where there is just enough force generated to overcome friction and air resistance inside the motor.
The sponsor is Brilliant: The first 200 people to sign up at brilliant.org/stevemould will get 20% off an annual subscription.
The alternative explanation goes something like this (I'm simplifying!) - Lift is generated when air is moving relative the sail. As the boat speeds up, the relative speed of the air should increase and so the lift should increase! This explanation doesn't work for when you're sailing somewhat with the wind though. In that scenario, as the boat begins to speed up, the relative speed of the wind actually goes down.
I love you, Mr Mould 🌈
If you are sailing into the wind, and speed up, doesn't the relative wind speed increase?
I though the sponsor was brilliant as they might have done something brilliant in this video. But it was only Brilliant.
This isn't really correct. The term you are looking for is "apparent wind." As you speed up the angle that you feel the wind coming at you from shifts to in front of you, similar to how it always feels like the wind is coming from straight ahead when you stick your hand out a car window on the highway. This means that if you are sailing faster than the wind, you are also always sailing into the wind. When you sailing into the wind the relative wind speed goes UP, not down. When you are sailing away from the wind, you are moving with it, and the relative wind speed goes down. This is what the streamer on the front of the car in the veritasium video was showing.
Isn't it the other way around? Relative wind should increase with the speed of the boat when sailing into the wind and vice versa.
Delighted that I can wave my hands and a Steve Mould video appears
It's so cool when the same topic is explained by my two favourite science communicators.
Can you make a hand-propeller to improve this process?
A Wild Steve Appears!
In my experience: the novelty wears off after a while.
@@standupmaths kinda feels like christmas ❤️
Not sure if I missed this in the video, but need to also consider that Derek was using a wind turbine as a sail. A turbine can act like a flywheel, storing energy. A good question to ask is “what happens when the wind stops?”. A sail boat will no longer generate lift, but the inertia of the boat will keep it going. A wind turbine however will continue rotating and continue providing lift, so it’s possible to build more speed thanks to the energy storage element. At least, that’s my assumption, haven’t thought all that hard about it.
@@eyytee You are right, but the point here isn't that it will speed up when the wind stops. The point is that the turbine can store energy from past wind, which is added on top of the wind in the present. It's essentially a mechanical battery.
@@RealEngineering My point was that the cart in Derek's video goes faster than the wind in steady state. It stays above windspeed, as long there is true wind. It doesn't rely on stored energy that would eventually run out.
When the wind stops, from the frame of reference of the rickety turbine machine, there's still wind as it continues moving for a bit. But now it's moving into the wind. Wouldn't this negate any gains made from the flywheel effect?
I'd like to point out that unfortunately this video doesn't demonstrate how a sailboat can travel faster than the wind in the downwind direction. That being said, the model used can explain it perfectly! You just need to angle the hull away from the direction of the wind more than the sail.
A turbine is analogous to a screw in the same way a sail is analogous to a wedge, so if you treat the sail car as a mechanical advantage problem it all checks out.
I think about it like gearing the difference in velocity between the wind and the ground. Like gearing between a pair of pinions attached to a pair of racks
Imagine the wind and ground are racks and the sail and wheels are pinions. The two pinions are geared so that the wheel pinions move faster along the ground rack than the turbine pinion is moving along the wind rack.
This seemed to work when I modeled it in on shape
”I am the wind” -Steve Mould 2021
Someone tell Kvothe
Someone please make a Tshirt of that.
@@cillianwilliamson16 why don’t u
omg the best C++ programmer in the world!
@@avw5kt I C what you did there...
"Let's assume it worked perfectly"
- Oh, yes, physics
Assume resistance is 0
Assume that a spherical cow in a vacuum...
@@stevenkelby2169fuck lol
Assume I did.
Assumptions are free to take; just like mistakes! 🤷
Yeah also because when the wind pushing the boat in a reach will also rotate it a little it will carve up winward negating the force of wind pushing it leeward
Just as an aside, in practice sailors can rely on tactile and visual feedback to "feel" their way to approximately optimal angles. It quickly becomes largely intuitive, like learning to riding a bike.
Forms of this feedback include the relative direction of small weather vanes, boat tilt or the sail floppiness.
Don't forget the telltails, they're little bits of yarn taped to the sail in various locations to help visualize airflow over the sail.
@@alexjband Aye And don't forget the nose. A good sailor can smell a fart and tell you exactly whence it came, and who the likely culprit.
We had a family boat when I was young that was not what would be called handy and even though a sloop was a pain to tack and just wanted to sit in irons and go nowhere. The sails and hull were not well balanced and apparently the hull was also used to produce a power boat version! We had to go off the wind in to a broad reach to accelerate the boat and then slam the always heavy feeling tiller over and hold the windward jib sheet to pull the bow round. This lazy boat really made you think of the relative speeds at angles to the wind. In some ways it made it more fun to sail. Happy memories.
@@alexjband yes, and we see these on aircraft too with yaw strings. Gliders typically have them though so too did the AV-8B, the U-2, and the F-14. Such string was the only instrument on the Wright Flyer though theirs was both Beta and Alpha as it was not over a windscreen and was next to an aft aligned peg so as to be able to see the alpha relative to peg while seeing beta relative to self.
_It is _*_impossible!_*_ In order to prove that you can sail faster than the wind, you have to tell me first how fast the wind is (thru an anemometer), and at the same time determine the speed of the sailboat, and compare both velocities._
7:08 this is why in sailing, changing the angle of the sail is similar to changing to a higher gear in a car. you start at a steep angle because that gives the most perpendicular force, but after accellerating for a bit you reach the maximum speed for that angle and have to pull the sail into a shallower angle to get any more speed. until you reach the maximum speed the boat is capable of when the sail is almost perpendicular to the wind.
so the best angle for the sail depends on where the boat is pointing, where the wind is coming from, the speed of the wind AND the speed of the boat.
Not true, the true wind angle stays the same. The relative wind angle shift forward due to the speed of the boat. That is why the sails need adjustments.
As a semi pro sailor we have gears in the sense of different mast angles for different breezes and different sail depth and camber to affect the CL. the pulling sail in bit is more like a rocket thruster in space.
@@judem8028 you've never trimmed the sails?
Rockets don't work in a vacuum
It's retarded
I feel like that’s not the only framed photo of Steve he owns
The day a stumbled on his shrine was an awkward day
@@SteveMould Yeah, that’s it. “Shrine.”
@@standupmaths Isn't a voodoo work station a type of shrine?
@@standupmaths could temple be more accurate?
You THINK, you don't "feel like", you muppet. Stop talking like a woman.
Bernoulli's Principle and the Coanda Effect are two sides of the same coin as I understand it. The Coanda Effect describes how flow clings to a convex surface resulting in a change in the flow's direction of travel, and Bernoulli's Principle describes how the force required to change that direction of travel is reacted against the curved surface via a change in pressure. You don't get one without the other.
Good insight. I think I might end up using your glass cutting techniques for an upcoming video by the way!
@@SteveMould Good stuff! If you use my mini sandblaster design and find it shreds right through electrical tape it's probably because the sandblaster barrel is too long. It's a balance between cutting the glass quickly without destroying the stencil.
Thanks for the tip!
I more or less agree until you say "You don't get one without the other." For example, Bernoulli's equation can be used to describe the flow in a pipe that has a reduction in diameter (no increase). With no increase in diameter (as one travels downstream), I don't think the Coanda Effect applies anywhere.
@@andrewsnow7386 I think the coanda effect is still present in that situation unless the reduction never levels out (a closed cone shape, which would have no flow anyway), as is the reacted force on the wall of the pipe. Because of the coanda effect you can assume the fluid will fill the volume of the pipe and follow the curves of the wall (because bernoulli's principle tells you that a vacuum would form otherwise) so it's not necessary to think about both principles simultaneously.
For anyone wondering, there is also the really fun phenomenon of generating your own wind. Which occurs because as you gain speed, you are now experiencing wind equal to your speed(essentially) in the opposite direction of your travel. So as you speed up, you start having more wind, in a more bow(front of boat) position. So you can then capitalize on that and go faster, which is why many sailboats nowadays are optimized for more upwind sailing. The most dramatic example I have seen was America's Cup World series boats(which has all sorts of optimizations like wings and foils) and traveling downwind, they had their sails in close as if they were going upwind, and their windex's read that the wind was about 4x faster than we experienced elsewhere. Really good video, thank you for making. I did not know about the whole missing thing with the wind, and you could certainly make a hundred videos about the physics of sailing.
4:27 The blue/sideways force does have an affect! Because it and the ‚resisting force on the hull‘ are offset, the boat gets tilted. Thats why big boats have weights in the keel and small boats relie on the bodyweight of the sailors to counteract it.
Yes, but "tilting against the natural vertical" is just a change in _potential_ energy, and once the tilt is achieved, no more _work_ is done, at least as far as tilting is concerned. Also, it's effect, not affect.
I don't say this lightly, but this might be my favourite video of yours. Something complicated and counter-intuitive explained with such elegance and ease that I'm half convinced that its entirely obvious and I always knew it. Worthy of being the first one after the million barrier
One thing I'd really like to see, a plot where the velocity of the ship is one axis, the angle of the sail relative to the wind on the other, and coloured according to the magnitude of the force on the ship. My new found intuition is that, the sharper angle the lower the force (wind gets deflected less) up to when you approach the "maximum speed" for that angle. But that maximum speed itself increases with that angle. Would be good to see how that would look graphed out, if there's a clear optimum trade off for a given speed, and what that optimum looks like.
@@QuantumHistorian You might be interested in explanations of the tip speed ratio of a wind turbine. It covers this concept.
Blades angled close to the wind have a high speed but as you say the lift force going in the direction you want is low so low torque. Used on rotors with 1 or 2 blades.
What complicates things and wasn't covered in this video is that when something moves through air it has it's own headwind. This adds to the existing wind and changes it speed and direction as experienced by the moving object.
@@Ed.R Actually, while it's not discussed, the model presented covers these forces. It can thus explain how a boat can travel in the downwind direction faster than the wind, which unfortunately was not demonstrated because that is the true analog to Veritasium's video.
Solid collaboration. Funny that I sign up for a sailing class this summer, and boom, Steve Mould makes a video about sailing. The universe is calling mate.
good decision
Algorithm*
Solid or non newtonian fluid? You may have tapped it, and it felt solid, now you need to wait to see if it oozes all over the floor. In a temperature controlled environment, to rule out melting of course
what are the chances, you must be THE ONE and the rest of us are nothing but npcs! you should buy a gun and start cleaning us up!
The universe is always calling. We only need to tap in and listen 🤙
Friggin awesome explanation and congrats on 1 million subscribers! I can tell which parts you filmed before and after lunch from the stain on your shirt :P
I was hoping no one would notice! It was worth it for the ethiopian injera
Cool vid
@@SteveMould Ooh... now I want Ethiopian. There's a good place near my house but I'm at uni. :(
Sad to see how quick internet fame got to poor old Steve…
The moment he hits a million subscribers out goes the unnecessary detail of wearing clean shirts for video shoots.
Next he'll grow some ridiculous face-beast like some crazed stand-up mathematician.
Or worse, move somewhere is doesn't rain all the time.
I watched the whole video again to see any stainless shot but the stain was there during the whole video, can you help me see where his shirt was clean?
Very nice explanation, I’ve done a couple years of sailing and this is pretty accurate. Only thing is for the perpendicular trajectory, on a sailboat when you go perpendicular you will bring your sail near completely in and counter balance your boat with your own weight on a small boat like a laser.
In no way do you have your sail completely sheeted in on a beam reach, that is incredibly inefficient, especially on a laser. The only possible situation in which you should be sheeting in all the way when on a beam reach is when you are sailing significantly faster than the wind and your apparent wind is coming from a close hauled heading. On a beam reach the sail should be roughly half way out.
Source: I'm a sailing instructor, have been sailing for 7 years, and am campaigning for the waszp world championships.
Me: "Why do you even own a framed picture of Steve, Matt?"
*Looks at the picture"
Also me: "Holy shit, that is one handsome Steve"
I love watching 3 or 4 of my favorite UA-camrs all give their "take" on a physics project/thought experiment. I learn something new from each
It helps that normally there is a LOT of stuff going on at once and reducing it down to a narrative bite size chunk leaves plenty behind for further discussion
Actually, the boat moves away from Steve Mould due to the awkward encounter they had at the Christmas party last year.
Great explanation of how to sail faster than the wind but what I spent a while trying to work out after the Veritasium video was how you can sail such that the component of your velocity in the direction of the wind is faster than the wind. With this explanation that requires angling your sail in the opposite direction to the conventional way so I’m not sure how you do it in practice.
^^This^^
This is the part that is actually confusing, and the part that Steve seemed to totally skip over...
The angling of the sail shouldn't be important. It's the fact that the wind pushes the machine, which allows the wheels to turn the propeller.
It seems odd that the wind can be slower, but the slower wind does reduce drag, which makes it easier for the machine to overcome friction and maintain its momentum.
I think a explanation could be: (its my explanation)
When the wind speeds up the vehicle it doesnt speed it up due to it turning the blade, but due to pushing on the vehicle. Then the wheels will turn also and this causes the blade to spin. Now when the vehicle is at the speed of the wind it will get faster, cause actually if you imagine a horizontal line through the rotors blade there will be a crossing point between the imaginary line and the blade. This dot actually moves backwards while the blade is spinning, because of the blade is tilted. Now you have a point on the vehicle that is moving slower than the boat, cause this point is moving backwards relative to the boat (it could even really move backwards, but lets assume it doesnt)
So then the air can push on this point, since its slower than the air and thus push on the whole boat.
Of course this backwards moving point doesnt really exist. But you can also think about it this way:
The rotor is spinning, and thus it will blow air against the actual wind. This will cause some swirls and this will cause the vehicle to kind if push itsselve from the wind. Now you could argue that pushing from the wind takes at least as much energy as it takes to turn the wheels. But thats not true, since the vehicle is moving faster relative to the ground than to the air. And thus its easier to push from the moving air than to turn the wheels to be able to push the air backwards. (Have you ever been in a pool with circle motion and just floated in the water while pushing yourselve activly from the fast water jet at the edge tonbe faster than the others? did you notice that gaining speed by this was easier than gaining the same amount of speed difference due to pushing off the non moving water? ) this is because the kinetic energy increases quadratic with speed. So lets say you want to gain a ∆v of 1m/s relative to non moving ground while you've got no speed in the first place. The energy reqiered would be 0.5(m^2/s^2)*M with M being your mass. But if you try to gain 1m/s when you are at 20m/s to get to 21m/s you will need a energy of 20.5(m^2/s^2)*M. So much more. So if you push from a object that isnt moving to gain 1m/s while you are at 20m/s you will have ro use a energy of 20.5(m^2/s^2)*M
But if you are pushing from a object being as fast as you, you will have to use only 0.5(m^2/s^2)*M. This is because you will push the other object backwards by doing this and thus you will decreas its veilosity and thus its energy and thus you will gain energy without having to do that much of a work. (of course this 0.5(m^2/s^2)* M does only hold, if you assume that the mass of the object you are pushing from is infinity, cause else it will get slower while you are pushing from it like i already said, and this will make calculations complicated)
So you can actually divide this process into steps:
Step one: Pushing from the wind using a energy of 0.5(m^2/s^2)*M and increasing with speed of 1m/s
Step two: using your energy relative to the ground to push from the air.
So if you calculate that you will loose 0.024m/s. (cause you will get a energy of 0.5(m^2/s^2)*M if speeding down from 21m/s to 20.976m/s) .
So over all you are gaining 0.976m/s without blaming the law of thermodynamics.
Steve only shows a beam reach which is 90 degrees to the wind so on the direction of the wind you do not travel any distance. the veritasium video shows a broad reach (about 45 degrees away from the direction of the wind) going faster in the down wind direction than the wind itself. on the broad reach you will travel downwind. I would like to see the Steve's model on this broad reach and see if it can out run the air molecule in the down wind direction. I think the boat will still go faster than the wind on the 45 degree course but will it go faster in the down wind direction ? my head can not picture it doing this I need to see the model doing it.
Your graphics actually are very good. No need for a bunch of visual noise for gratuitous reasons. Simple shapes to explain the concept in a simple manner is exactly what is called for in a video like this. Good job.
Steve, to me you are like the mid life dad who started documenting random experiments in his back yard out of curiosity for how things work. Really enjoy watching you explore and explain stuff you learned.
I'd like to add that sailing is only possible when you've got two mediums with different velocities (different direction and/or magnitude), that's what lets you continuously extract energy from the medium.
Edited for clarity.
Probably the most important point for understanding how the car in the Veritasium video works. I think very few people appreciate this and it's the reason so many people call hoax.
Specifically, you need to have much higher resistance, at least to lateral motion, in one medium than in the other. "Sailing" on a water-oil interface likely would not work.
Is there any reason you can't extract energy from the medium you're travelling in?
Sure you can, but not in any other direction than the one where said medium is going - you've got no "leverage" to pull/push in any other direction. Imagine yourself floating in a vacuum, if someone pokes you with a stick you will extract energy off that stick but then flailing away you go.
This is much more intuitive in the boat case than the car from veritasiums video. In the boat case the water simply provides the resistance you need to hold at the right angle
someone: how do you know all this?
me: i watched a man push a toy boat with wheels with a stick that also has a wheel
Matt's been on UA-cam for so long, done so many things, and I can't believe his channel doesn't have 1 million subscribers 🤔 that's the definition of underrated
Everyone gets there, eventually. 2.18 millions when I left this comment.
@@Supremax67 I was talking about the guest on the video, Matt, whose channel did finally get to a million 🥳
@@gutobernardo7457 because most people flock to easy to watch content...
One is experiencing the same when inline/ice skating. You are moving much faster forward than your foot moves outwards.
I teach swimming lessons, and use a similar hand trick to show that 'laying' (floating flat)on the water will help you go faster and easier through the water than if you are in a standing position.
"you can explain lift using Newton _or_ Bernoulli"
an aerodynamicist is about to tell you all about how _neither_ actually explain the full mechanics of a wing
As a chemist, we should just stick to ab initio calculations for everything. Hrmf!
You need differential equations to explain lift
@@kellymoses8566 Differential equations are a description, but definitely not an explanation.
@@jorehir Tell that to a physicist lol.
@@jorehir go away monster, Newton was a god.
I hate it when a concept doesn't feel intuitive.
It's like having an itch in your hand that you can't scratch.
This is why I've never got on with physics.
Just like if you had only one hand.
It wasn't explained well in this video. Maybe a more appropriate explanation with apparent wind will feel more intuitive (it definitely is to me): ua-cam.com/video/NI39O6t4gPI/v-deo.html
I don't know how many times I've explained this now but in Veritasium's video it can go faster than the wind as once the craft is up to speed, and the propeller is producing thrust, (remember the propeller is not a windmill on that craft) the thrust from the propeller is increased because of the tail wind. It aerodynamically increases the propellers thrust close to its' maximum which is "static thrust". An easy way to think about this is a light aircraft produces maximum thrust when it is not moving. As it accelerates down the runway the thrust drops off significantly. As it accelerates down the runway if you were to introduce a tail wind to the propeller its thrust would increase. (However detrimental to lift over the wings)
Congrats on the 1 million subs Steve. I love this channel, I hope it continues to grow.
Turns out it’s a mechanical advantage problem. The sail is a wedge.
Lol
In the model, the board is acting as a wedge. In a real sailboat, that's not quite the case, since as he says, the direction of the force is not the same as the direction of the wind.
@@EebstertheGreat that is correct, with a wedge the input and output forces are perpendicular, so the sail is acting as a wedge.
You have your flat sail acting like a wedge with the “sail” being pushed and not like a curved wing, which would be creating lift from the low pressure created by the air passing more quickly across the front rather than the way you are representing it... a common misconception made by non-sailors...
Aerofoil or not, I agree that a wedge is a good enough approximation to describe how to sail faster than the wind. This video doesn't explain how to beat the wind however. I just made a video with graphics explaining how you can do so: ua-cam.com/video/CbNCz0_iO7c/v-deo.html
4:39 “Where you use wheels on land”.
What an interesting and novel concept, Stephen.
Pretty spot on video. I’ve been sailing most of my life and this gives a pretty good intro to what’s happening above the water. Obviously, one can’t squeeze the entire theory of sailing into one 12 min video. I hope someday you’ll look into the hydrodynamic effects of the hull/keel as they’re as, if not more, important than the sails when it comes to speed.
What’s even more interesting is dinghy’s below the waterline, because they don’t need standard elements like a keel you get way more variance, from displacement to semi planing, skiffs, cats, foilers, planing cats, foiling cats, etc you see way more variance than in keelboats
I was wondering how the NZ land yacht broke the land speed record recently by doing 222kmh with only 40.7kmh winds.
_It is only possible in Never Land_
As a sailor myself, I can confirm that this video is amazingly well done and explained. Congrats on 1 million subscribers! I'm glad I am part of those!
Would have been nice to also mention True Wind, Boat Wind, and Apparent Wind too though.
Indeed. Though I was busy being concerned with the terrible sail positioning and design.
Mentioning tw bw and aw has no real place in this video because they’re technically incorrect they’re just tools we as coaches use to give the people we teach an intuitive understanding quickly. It’s not really an accurate description of the physics at play
Well, congrats, Steve, you've made it!
Sailors: lol eZ.
Everyone, even mathematicians: Okay, so... It's like... Hold on.
For real. I'm a fairly decent sailor and it's always felt intuitive to me, but I could never really give a rigorously worded description of how it actually worked till I sat down and thought about it for a while. This was after like 6 years of sailing.
another lesson in how we dont need to understand something in order to utilise it
@@lmva you can see a sail working by looking at it, wind blows boat moves, there's logic to it.
You know how a computer works just by looking at it? or how about a modern automobile?
@@coreys2686 the only thing that makes modern cars confusing is their integrated computers tho.
@@ivortragedi2787 Depends on the desired level of understanding. There's some fascinating stuff going on inside the engine, that the electronics only provide timing for.
"resting sarcasm voice" is SUCH a mood lmao
As a sailor I find it funny that this is even a topic of discussion, as we know we can go faster than the wind and we've known it for thousands of years.
I guess it's just a different source of learning. I grew up inland so I'm not familiar with sailing intuition but this video helped. Ironically I used to think some sailing games had bugs and now I realise they were realistic.
Its different in this case because sailboats can sail against wind but travel at a certain angle relative to it. Whats trying to be proven here is going faster but, in the exact same direction that the wind is going, which sailboats can’t do.
Of course we know that from experience, but this video is about how it does it, which will be counter-intuitive to many people. I'm going to bet there are other things we know work from experience, but you don't know how. That's quite normal.
I first heard about this years ago when someone claimed that his unpowered cart with a big fan on the back could travel directly downwind faster than the wind. Someone mentioned sailboats traveling faster than the wind but most people assumed this meant traveling with the wind but diagonally. Some guy who did ice sailing showed that he could arrive at a point directly downwind much earlier than a balloon floating with the wind. To me, this proved it could be done. Just left the question of explaining the physics. I was surprised that many people continued to deny it was possible based on their theoretical calculations.
but different direction
The reason the sailboat isn't pushed sideways is not just due to the thin hull shape. There will also be some rudder input to correct the course of the boat.
also the "fin"/keel
Not if the boat is set up right, you can actually let go though most boats are designed to point up wind for stability reasons
It is good to mention that if we speak of Bermuda type rig (Genoa/Jin and main sail) that there is a possibility to not use rudder at all if we find so-called balance of the sails. Wind rotates the boat in different direction around the mast/keel depending on what sail you tighten and ease. So, if you find balance of sails, boat can go upwind with no rudder input.
@@whatswrongwithyarik4835 Yep, we sailed a couple weekends back and found ourselves with perfectly balanced sails close hauled (with a slight inclination to a close reach) and I showed my son how we could adjust our course just but adjusting the Jib or Mainsail having the rudder locked amidship. I would be curious the efficacy if we could remove the rudder from the boat/equation.
A good sailor balace the boat, so the rudder is straigh forward without breaking. I sail on a 3 mast schooner gaff rigg. If you put up sails in the front, you have to put up sails in the back. The jib in the very front is in pair with the top sail on the mizzen mast. Whith good riggers, you never have to fight the boat and the wind at the helm.
OK, but in the veritasium video they said "speed made good" can be faster than the wind. Down wind by tacking with the wind. can you explain that.
Thanks ! That is indeed missing from this video. The Bernoulli effect is completely overlooked here, after the initial comparison with airplane wings. America's cup boat would be a great exemple of what Dererk was providing a handwaiving explanation for in his video. (that's the first time I have disliked a Steve Mould video)
I think a explanation could be: (its my explanation)
When the wind speeds up the vehicle it doesnt speed it up due to it turning the blade, but due to pushing on the vehicle. Then the wheels will turn also and this causes the blade to spin. Now when the vehicle is at the speed of the wind it will get faster, cause actually if you imagine a horizontal line through the rotors blade there will be a crossing point between the imaginary line and the blade. This dot actually moves backwards while the blade is spinning, because of the blade is tilted. Now you have a point on the vehicle that is moving slower than the boat, cause this point is moving backwards relative to the boat (it could even really move backwards, but lets assume it doesnt)
So then the air can push on this point, since its slower than the air and thus push on the whole boat.
Of course this backwards moving point doesnt really exist. But you can also think about it this way:
The rotor is spinning, and thus it will blow air against the actual wind. This will cause some swirls and this will cause the vehicle to kind if push itsselve from the wind. Now you could argue that pushing from the wind takes at least as much energy as it takes to turn the wheels. But thats not true, since the vehicle is moving faster relative to the ground than to the air. And thus its easier to push from the moving air than to turn the wheels to be able to push the air backwards. (Have you ever been in a pool with circle motion and just floated in the water while pushing yourselve activly from the fast water jet at the edge tonbe faster than the others? did you notice that gaining speed by this was easier than gaining the same amount of speed difference due to pushing off the non moving water? ) this is because the kinetic energy increases quadratic with speed. So lets say you want to gain a ∆v of 1m/s relative to non moving ground while you've got no speed in the first place. The energy reqiered would be 0.5(m^2/s^2)*M with M being your mass. But if you try to gain 1m/s when you are at 20m/s to get to 21m/s you will need a energy of 20.5(m^2/s^2)*M. So much more. So if you push from a object that isnt moving to gain 1m/s while you are at 20m/s you will have ro use a energy of 20.5(m^2/s^2)*M
But if you are pushing from a object being as fast as you, you will have to use only 0.5(m^2/s^2)*M. This is because you will push the other object backwards by doing this and thus you will decreas its veilosity and thus its energy and thus you will gain energy without having to do that much of a work. (of course this 0.5(m^2/s^2)* M does only hold, if you assume that the mass of the object you are pushing from is infinity, cause else it will get slower while you are pushing from it like i already said, and this will make calculations complicated)
So you can actually divide this process into steps:
Step one: Pushing from the wind using a energy of 0.5(m^2/s^2)*M and increasing with speed of 1m/s
Step two: using your energy relative to the ground to push from the air.
So if you calculate that you will loose 0.024m/s. (cause you will get a energy of 0.5(m^2/s^2)*M if speeding down from 21m/s to 20.976m/s) .
So over all you are gaining 0.976m/s without blaming the law of thermodynamics.
Uniformed guess on how this is possible :
Watching the the Americas cup we see there is a lot of 'dirty' air coming off the back of the boats. This would match the explanation of how the device the the veritasium works, robbing velocity from the air.
Given that the velocity in the direction of travel can be >3x windspeed the boat will meet a lot of air to steal velocity from.
The second part is Steve pinns, from the point of view of the boat the speed and direction of the wind are radically different. And complex physics stuff happens
Agreed, this is completely missing and very relevant.
It is all to do with 'apparent wind' . Google will provide ample reading on the matter, but here is my attempt at a very simplified explanation:
Imagine Steve's sailing trolley boat thing moving at 10m/s without any wind. It will feel like there is 10m/s of wind coming from straight in front of it. This is 'induced wind'.
Now imagine there is a 10m/s wind blowing at 90 deg to the direction it is traveling in. This is 'true wind'.
Someone on board the trolley (and the sail) will experience the combination of these two coming from 45 deg at 14m/s (ish). This is 'apparent wind'.
The trolley can now adjust its direction of travel to be at 90 deg to the 'apparent wind' (135 deg from 'true wind') and accelerate up to 14m/s (ish).
The trolley sail will now experience the combination of the 14m/s 'apparent wind' and the new 14m/s 'induced wind', resulting in an apparent wind of 20m/s (ish).
This process repeats with the trolley getting faster and faster while turning away from the 'true wind', resulting in a trolley having a 'speed made good' greater than the true wind.
Obviously pesky things like friction, drag, and other physics get in the way to some extent but hopefully you get the underlying principles.
Thank you. I think I sort of understand it now. Still wish Steve would do a follow up as the most counterintuitive aspect from the Veritasium video is missing from his explanation ✌️🤓
I sail competitively for my university, and this is spot on. Always delighted to see sailing content on here, I would love to see more of it. Well done Steve!
Spot on? Look again at the tacking illustration 😉
@@Spakianor At 8:50? Yeah, it's not perfect because his model is still kind of using a board instead of sails, but it gets the idea of tacking across. Good point though
Uhoh, Matt is going to go talk to his topology friends. Those people are uber-nerds. They're going to have a very maths based explanation of that power cord knot, and I will enjoy every second of it!
Did someone say power chord? 🤘
@@nathanrocks2562 lolol at first I read your comment and didn't look very close, so I thought that your "rock on" emoji was actually an electrical plug on a power cord (see it? the fingers are the prongs!). Weirdly enough, in this case it works both ways!
I think you may have created the first ever emoji pun + regular pun double-pun combo move, so congratulations!
@@idontwantahandlethough that's because rock n roll is electrifying!!
@8:51 I could be mistaken about this, but my understanding of "tacking" is that it's the maneuver of bringing the bow of the ship across the wind, i.e., one turn in your zig-zag pattern, whereas the process of tacking repeatedly as to maintain a coarse that is overall directly into the wind is called "beating." This may be archaic usage, however, as all my sailing knowledge comes from Patrick O'Brian's book series.
4:05 indeed, the slight sideways drift away from the wind, or to leeward (the opposite of windward) is why you should always leave yourself some _leeway_ when trying to clear an obstacle. Especially if for some reason you don't make very good _headway_ I'm always amazed by how deeply sailing has worked its way into our language!
Modern day boats can actually generate net zero leeway by canting their foils to windward as to generate windward lift as well as vertical lift which is why most moths and foiling boats cant to windward
Fun fact you’re minorly incorrect. It’s true that you can have net 0 leeway or even positive leeway but rigorous testing, a very small part of which I’ve been involved with as part of my uni program and sailing team, has shown that while it’s possible to achieve 0 or positive leeway it’s optimal to have between 1-2 degrees of leeway angle because the drag required to generate the extra hydrodynamic lift and resulting speed penalty is greater than the vmg improvements from better point, outside of niche tactical situations like pinching an opponent off a start line in a sailboat race
0:11 I miss Steve even when he is in the video. Can we please have a picture of Steve all the time next to him?
I think the sails in the diagram at 8:50 must be oriented more horizontally than the boats, so that the lift actually creates a forward force
Exactly, my vector diagrams and wikipedia says that. I was thinking maybe I am wrong. Your comment verifies my calculation and diagram ok wikipedia too.
i would really appreciate you explaining how the mashine of deric works
@Boogie Baggins Either his explanation was bad or I'm too dumb, but it would be great anyway to have more intuitive explanation like in this video
i think his explanation was waaay too convoluted, albeit clever. It took me a while to understand what's going on, i've invented a good explanation for myself.
I'll try. In Deric's machine the propeller blades are acting as sails. If the machine is going slower than the theoretical max speed, the "packets of air" will hit the blades/sails transferring some of their kinetic (velocity) energy to the propeller. This energy is then transferred to the wheels allowing the machine to accelerate further. This is why the air behind the propeller slows down.
Isn't it Derek ?
I think a explanation could be: (its my explanation)
When the wind speeds up the vehicle it doesnt speed it up due to it turning the blade, but due to pushing on the vehicle. Then the wheels will turn also and this causes the blade to spin. Now when the vehicle is at the speed of the wind it will get faster, cause actually if you imagine a horizontal line through the rotors blade there will be a crossing point between the imaginary line and the blade. This dot actually moves backwards while the blade is spinning, because of the blade is tilted. Now you have a point on the vehicle that is moving slower than the boat, cause this point is moving backwards relative to the boat (it could even really move backwards, but lets assume it doesnt)
So then the air can push on this point, since its slower than the air and thus push on the whole boat.
Of course this backwards moving point doesnt really exist. But you can also think about it this way:
The rotor is spinning, and thus it will blow air against the actual wind. This will cause some swirls and this will cause the vehicle to kind if push itsselve from the wind. Now you could argue that pushing from the wind takes at least as much energy as it takes to turn the wheels. But thats not true, since the vehicle is moving faster relative to the ground than to the air. And thus its easier to push from the moving air than to turn the wheels to be able to push the air backwards. (Have you ever been in a pool with circle motion and just floated in the water while pushing yourselve activly from the fast water jet at the edge tonbe faster than the others? did you notice that gaining speed by this was easier than gaining the same amount of speed difference due to pushing off the non moving water? ) this is because the kinetic energy increases quadratic with speed. So lets say you want to gain a ∆v of 1m/s relative to non moving ground while you've got no speed in the first place. The energy reqiered would be 0.5(m^2/s^2)*M with M being your mass. But if you try to gain 1m/s when you are at 20m/s to get to 21m/s you will need a energy of 20.5(m^2/s^2)*M. So much more. So if you push from a object that isnt moving to gain 1m/s while you are at 20m/s you will have ro use a energy of 20.5(m^2/s^2)*M
But if you are pushing from a object being as fast as you, you will have to use only 0.5(m^2/s^2)*M. This is because you will push the other object backwards by doing this and thus you will decreas its veilosity and thus its energy and thus you will gain energy without having to do that much of a work. (of course this 0.5(m^2/s^2)* M does only hold, if you assume that the mass of the object you are pushing from is infinity, cause else it will get slower while you are pushing from it like i already said, and this will make calculations complicated)
So you can actually divide this process into steps:
Step one: Pushing from the wind using a energy of 0.5(m^2/s^2)*M and increasing with speed of 1m/s
Step two: using your energy relative to the ground to push from the air.
So if you calculate that you will loose 0.024m/s. (cause you will get a energy of 0.5(m^2/s^2)*M if speeding down from 21m/s to 20.976m/s) .
So over all you are gaining 0.976m/s without blaming the law of thermodynamics.
That hand on the plank brought tears of joy to my eyes. So simple and yet explains so much.
This is the first Brilliant-sponsored video I've seen that actually made me go "wow, I want that". Countless other "sponsored" videos talk about brilliant and what it does, but *seeing* that little graphic of the interactive coding lessons... that sold me. I wish child me had access to this kind of stuff.
Steve Mould´s videos are always beautiful. I look forward to each one. Once again it is obvious that a lot of work has gone into this one. There are a number of very nice concepts and explanations presented and packed into just 9 minutes! I wish it could have been longer. Here are a couple things that I noticed that might be of general interest, or perhaps I will be corrected on and thus learn more about the subject. And though this video provides some wonderful intuition on sailing mechanics, I explain in detail here as to why it does not give us an intuition about faster than wind travel. At the end of this post I suggest something that might be a missing piece that I think would complete the explanation.
Steve did not mention, but as a boat travels faster, the wind appears to change direction. Say we start sailing downwind at an angle. Initially the wind will be at our backs. As the boat speeds up we will notice that the wind appears to come more and more from the front, even though the true wind has never changed. People on motor boats and motorcycles just expect wind from the front no matter which way things are really blowing without even thinking about it. Consequently, the 'sailing upwind' part of this video also applies to fast downwind sailing.
Consider sailing downwind at a 45 degrees angle when the boat is traveling equally down wind and perpendicular to it. At this angle the wind will appear to be coming over the starboard bow.
(x, y) a vector
(0, 1) velocity of wind blowing in the y direction
(1, 1) velocity of boat at 45 degree angle traveling the same speed as the wind
(-1, 0) velocity of the apparent wind (over starboard bow due to boat traveling at an angle)
Thus the upwind sailing scenario that Steve shows at time 8:24 is also the downwind at the speed of the air scenario. Hence, this little demonstration is key for this video.
Steve makes use of a stick and cart model for sailing. The stick has a wheel attached to the end of it. An interesting aspect of having the wheel there is that force will always be perpendicular to the surface of the board being used as a sail. This would be the case for real if air reflected upon striking a sail and had equal incident and reflection angles. Because the force is always perpendicular to the surface of the board acting as the sail, the stick may be rotated around so the shaft is perpendicular with the surface of the sail. When this is done no sideways force need be applied to hold the stick when pushing. The travel would then be scaled by cos(theta) of the angle of rotation. Hence the actual angle that we see for the stick in the video is only symbolic of wind direction. He pretty much could have used any stick angle.
A sailboat has a keel, so it travels in local straight lines. Sail powered land vehicles and those with ice skates also travel on local straight lines. So we can think about these vehicles as though they are on a fixed track. With the stick and cart model, the little cart will always move on its track in such a way as to create a gap between it and the wheel attached to the stick. In other words the vehicle will always move on the track so that the wheel on the stick will roll down hill.
Given a stick perpendicular to the surface of the sail, the travel of the vehicle on its track will be greater than the travel of the stick when the sail is at less than a 45 degree angle to the track. Steve shows this at 6:25. If the stick was also rotated, then another cos(theta) must be overcome to cause the cart to travel faster than the travel of the wind. For the upwind case given at time 8:24 this calls for a small angle between the sail and the track. Just look how far the stick would have to be rotated to make it perpendicular to the sail. That will make for a very small cos(theta) also.
Steve himself discusses the problem with such small angles between the sail and the track at 6:47 while showing the stick rotated around. The stick and cart model is of course an approximation of what happens when sailing, so this model loses its predictive power just when it is needed, when we approach the speed of the wind.
Steve presents another model, that of air displacement, at 2:51. With this model he shows the air clinging to the sail and then turning and following its surface. This is a different assumption about air behavior than that built into the stick and cart model. In the example at 2:51 the angles are not quite right for the faster than the downwind case we are interested in, and for this model we do need correct angles. The correct angles are given in the 8:24 example. However if air clings to a sail, then it takes some effort to remove it. This removal effort is known as drag and it pulls the vehicle backwards. When we use the correct angles we find that the displacement is small so the drag component question becomes critical. So like the stick and cart model, the displacement model stops being predictive just when we reach the point of interest, when the vehicle reaches the speed of the wind.
I am not sure why, but Steve avoided discussing the Bernoulli Effect. Due to the Bernoulli Effect a shaped wing, such as presented at 7:56 can generate high lift force with little drag force when wind flows over it. This will cause air flow to be of a bigger concern than other variables, so the angles we see in the faster than wind travel cases actually become an advantage instead of a difficulty. With the Bernoulli Effect lift appears at about 90 degrees to the flow, without large drag. It is kind of magical.
I wish the video had been longer. I would be happy to listen to Mould go on for hours. Steve, how about making a second video including the Bernoulli Effect?
"Thus the upwind sailing scenario that Steve shows at time 8:24 is equivalent to traveling downwind at about the speed of the wind."
The scenarios are symmetrical, not identical: the roles of sail and keel are swapped.
@@eyytee Interesting observation about the keel physics, which was not touched on in the video other than to say that the keel provides a conservative force that is just big enough to cancel off track forces. Which it is doing in both cases. In both the fast down wind case and the upwind case the sail provides the same lift, so the keel is providing the same lift. In both cases the water travels over the keel from fore to aft. However, I do see a difference in that the speed of water over the keel (or the speed of the land vehicles wheels are turning) will be higher in the downwind case because the boat will be moving over the water faster. So I don't see a symmetry, I see a difference in speed of the water over the keel, or the speed the wheels are turning. The sailing mechanics are identical. eyytee, did you not like the comment? It is well done no?
@@ep5acg By symmetry I mean the forces vs. motion parallel and orthogonal to the wind:
TACKING UPWIND:
- sail drives the boat across the wind
- keel drives the boat upwind
TACKING DOWNWIND WITH VMG > WINDSPEED:
- keel drives the boat across the wind
- sail drives the boat downwind
This also explains why to go directly upwind, the rotor cart would have to reverse the transmission, and turn the wheels with the propeller.
@@eyytee I reworded that to say that the demo applies to both scenarios. Did you not like my post? Is it not well done?
@@ep5acg It's true that you could hold he stick anyway you want, and push sideways with it. But the convention in the demo is that you move the stick only parallel to the stick, which indicates the true wind direction. In that sense I don't think the demo as shown applies to both scenarios. In a more general sense, there are similarities/symmetries, but it would haven been better if he had explicitly shown the downwind case.
I'm here at T+6 hours and Steve has passed 1M, so congrats Steve!
Hmm, I already found it intuitive that the sail boat can move faster than the wind in Veritasiums video. What I still do not find intuitive is the claim that the *component* of the velocity of the boat *downwind* can be faster than the wind speed (ua-cam.com/video/jyQwgBAaBag/v-deo.html ). When starting this video I was kinda hoping for a n answer to *that* question.
I would have liked for this video to talk about apparent wind: ua-cam.com/video/NI39O6t4gPI/v-deo.html
As it is, the video does not explain well and intuitive how a sailboat works.
Finally found the question i was the most curious about. Give this comment more likes to get it to the top
@@Дістатижовтімаюнаметі The only explaination I found so far why a tacking boat would be faster than the wind in the direction of the wind (ie overtake the balloon) is that each time you change direction you still have your momentum so around the turning point you go faster than the wind for a short while. This, however, does not work if the boat never changes direction, as implied by the two boats "taking" on the "water tube" that turns into the propellor....
It's simply because the "apparent wind" seen by the sail is not the same as the ground wind. Both direction and speed will change as the boat speed changes. As the boat speeds up the wind will first seem to come from behind, then it will seem to shift to from the side (abeam) and so from on the boat it will feel like an abeam wind would feel at standstill. An abeam wind at standstill will accelerate the boat forward. This then takes you beyond( faster than) the true wind forward component because now you are sailing "into" the apparent wind, slightly. Which means you have the downwind component PLUS the "into the wind" component and these combined can be faster than the true downwind speed.
@@imd12c4advice Well, what do you know, it was rich sailing wizards all along ( ua-cam.com/video/uylpjlz8SjY/v-deo.html ). I think your comment + that video finally gave me an epiphany. Thank you
As BSc graduate and a competitive sailor (Canadian Championship), I'd like to point out that this is HIGHLY simplified. The curvature of the sail is like 90% of what makes one sailboat sail faster than the next. We spend a lot of time and brain power tweaking the sail's curvature. Championship sailing is truly the battle of the brains.
Damn you guys. This video was EXCELLENT. The graphics were fantastic. I too was suffering from a lack of explanation in that other video, despite it also being very inspiring. Good combination here. That was honestly some of the best explaining of anything ever I've seen, and I watch a ton of these videos. Great job!
I'd also like to posit that this phenomenon is FAR MORE important than we realize. It's not just lift in wings and sails I think but a whole host of other similar things in the universe and future technologies for space travel, or even as an alternative to the failed vacuum tube idea for hyperloops.
Thank goodness. I was totally confused about how this works after the Veritasium video.
And now not any more?
Note that Veritasium's boat-prop explanation is based on the fact that a boat can beat a balloon drifting with the wind! I.e. not just that boat can go faster than wind in an expertly chosen angle, but that the boat can summarily go faster than the wind in the direction of the wind, too. Steve only explained the initial part.
@@u1zha Yeah, I made a separate comment requesting a part 2. I kind of understood Derrick's explanation, but I'd understand it a LOT better if Matt and Steve did it.
I was hoping for a more detailed explanation after the veritasium one!
Yes, I found Veritasium's explanation for the phenomenon of going faster than the wind way better than Steve's, his is just too much saling-related...
Same here, I'm missing an intuitive explanation of how to extract energy from the wind once your relative speed to the wind is zero.
@@dykam It's possible to use the speed difference between the ground and the air, this difference exists even if the vehicle is the same speed as the wind, and you can get enegy out of this difference if you decrease it, however this is only a very general explanation and doesn't adress the mechanical aspects.
@@dykam this video wasn't about that vehicle, it was about what Veritasium hand waved as being true. which is fine as his video wasn't on how sails go faster. this video gave a more complete answer for how sails can move at an angle to the wind faster than the wind, and since the two blades on the vehicle are effectively just 2 sails move at an angle into the wind more completely explained that specific portion. it would be nice to see more of that vehicle though it was cool
I think a explanation could be: (its my explanation)
When the wind speeds up the vehicle it doesnt speed it up due to it turning the blade, but due to pushing on the vehicle. Then the wheels will turn also and this causes the blade to spin. Now when the vehicle is at the speed of the wind it will get faster, cause actually if you imagine a horizontal line through the rotors blade there will be a crossing point between the imaginary line and the blade. This dot actually moves backwards while the blade is spinning, because of the blade is tilted. Now you have a point on the vehicle that is moving slower than the boat, cause this point is moving backwards relative to the boat (it could even really move backwards, but lets assume it doesnt)
So then the air can push on this point, since its slower than the air and thus push on the whole boat.
Of course this backwards moving point doesnt really exist. But you can also think about it this way:
The rotor is spinning, and thus it will blow air against the actual wind. This will cause some swirls and this will cause the vehicle to kind if push itsselve from the wind. Now you could argue that pushing from the wind takes at least as much energy as it takes to turn the wheels. But thats not true, since the vehicle is moving faster relative to the ground than to the air. And thus its easier to push from the moving air than to turn the wheels to be able to push the air backwards. (Have you ever been in a pool with circle motion and just floated in the water while pushing yourselve activly from the fast water jet at the edge tonbe faster than the others? did you notice that gaining speed by this was easier than gaining the same amount of speed difference due to pushing off the non moving water? ) this is because the kinetic energy increases quadratic with speed. So lets say you want to gain a ∆v of 1m/s relative to non moving ground while you've got no speed in the first place. The energy reqiered would be 0.5(m^2/s^2)*M with M being your mass. But if you try to gain 1m/s when you are at 20m/s to get to 21m/s you will need a energy of 20.5(m^2/s^2)*M. So much more. So if you push from a object that isnt moving to gain 1m/s while you are at 20m/s you will have ro use a energy of 20.5(m^2/s^2)*M
But if you are pushing from a object being as fast as you, you will have to use only 0.5(m^2/s^2)*M. This is because you will push the other object backwards by doing this and thus you will decreas its veilosity and thus its energy and thus you will gain energy without having to do that much of a work. (of course this 0.5(m^2/s^2)* M does only hold, if you assume that the mass of the object you are pushing from is infinity, cause else it will get slower while you are pushing from it like i already said, and this will make calculations complicated)
So you can actually divide this process into steps:
Step one: Pushing from the wind using a energy of 0.5(m^2/s^2)*M and increasing with speed of 1m/s
Step two: using your energy relative to the ground to push from the air.
So if you calculate that you will loose 0.024m/s. (cause you will get a energy of 0.5(m^2/s^2)*M if speeding down from 21m/s to 20.976m/s) .
So over all you are gaining 0.976m/s without blaming the law of thermodynamics.
It has HAPPENED... Our boy is at 1000K💕
A bit surprised I don’t see lots of comments calling this out as an incorrect description of how sails work (and also how aircraft aerofoils work).
In both cases the lifting (or boat pushing) force is not at all because the sail or wing is on an angle to wind. It’s because both the wing and sail form an aero foil, shape. As one side of the sail/wing is longer than the other, air must travel faster over that surface in order to meet with the air on the other side (if it didn’t, there would be a spectacular and dangerous vacuum at the trailing edge of the wing/sail). The effect of the faster travelling air on that surface is to reduce the air pressure compared to that of the other side. The result is a force in the direction of the upper/longer surface of the wing/sail. This is called Bernoulli’s Principle.
The one exception to this is when a sailboat is sailing down wind and has the sail set out perpendicular to the motion of the boat. In that case it is just moving by pushing from the wind on the sail.
For those who will point out a sail has the same length on either side - yes, but if you understand how air flows smoothly over a curved surface but turbulently over a suddenly break in a surface (the mast and trailing cavity of the curved sail behind it) the overall effect is still a pressure differential.
Ouch!
"As one side of the sail/wing is longer than the other, air must travel faster over that surface in order to meet with the air on the other side (if it didn’t, there would be a spectacular and dangerous vacuum at the trailing edge of the wing/sail)."
This is the equal transit time thoery, and it was debunked decades ago. That said it still appears in text books and Neil Degrasse Tyson used it to explain how a wing generates lift very recently. *sigh*
Congrats on 1mil subs! I love seeing collaborations between favorite UA-camrs. :)
How weird that me and Matt have exactly the same picture framed 👀
This reminds me of those vector calculations we did for our mathematics exams... Pretty intriguing stuff.
Great video as always Steve. Myself and some friends recently started sailing and spent a fair bit of time pondering the physics as well. It might be worth noting that as the boat speeds up it's advantageous to reduce the angle between the sail and the direction of travel, I think this is because the 'resultant' angle of wind on the sail changes with the speed of the boat.
Sailors use what's known as an apparent wind to sail their boat and say your heading angle is 090 @ 20 knts and the wind comes from 000 @ 30 knts your apparent would be 030 at 37 knots which would be a close hauled course when you are actually on a reaching course
As a sailor, I love to see this kind of stuff.
Another addition to this is that when a sailboat is moving at a certain speed, let's say five knots in 10 knots of wind then the sailboat is experiencing another 5 knots of wind against it because of the speed it's going. This is called apparent wind. So now that boat has 15knots of wind against it. When a sailboat does this and it happens on every sail on a boat if the boat is moving, then you have to pull the sail in to counter the apparent wind. This is because the apparent wind is coming from the direction that your boat is moving or the front of the boat while the real wind on a boat's preferred angle is usually about 120 degrees from the wind. Now your boat has its sail pulled in its wind angle is around 80 degrees even though the boat is pointing in the same direction. This can be repeated for a long while when you have the right sea conditions. This is also why you don't see the GP boats or the AC75s letting their sails out very far. They are trying to capture the apparent wind.
The "power cord knot" 12:10 is called HMS (Halbmastwurfsicherung), Munter hitch in English, or half clove hitch. Used commonly in rock climbing as a belay knot on a carabiner (the carabiner is also called HMS, name from this knot). It is great to see how the knot "flips" the other way when you pull the other strand. Try it! It seemed like magic for me first time I learned how to belay using HMS, and then you start to understand how it works. Try it with a rope on a carbiner!
So... this is part 1 and part 2 is how that machine Derek used works?
was thinking the same
There are three (equivalent) ways to explain lift - Newton (deflection/reaction), Bernoulli (speed/pressure) and Biot-Savart (circulation/vorticity).
"Assume there's no resistance. So the air on the sail-"
the friction of the air on the sail isn’t powering it. it’s a detriment to the efficiency of the transfer of energy.
Congrats on a Million, Steve! It is well deserved and long overdue!
"The speed at which the sail exactly misses the packet of air"
That's such a clever way of putting it!
I haven't actually watched Derek's video yet, because the title was so offputtingly clickbaity.
Watching this one has made me reconsider.
Derek made a video about clickbaity titles/thumbnails (years ago), and why he will start using them. While still maintaining the same quality as before.
everything i know about the dynamics of sailing, i learned from zelda (or rather, link) in the windwaker. you could get the boat to go into the wind by building up speed and turning into it, back and forth, alternating left and right so you don't veer off to one side.
Its called tacking! It's a lot of fun in reality. Which Zelda title is this? I might have to give it a try, that sounds like a blast! I've never heard of a game with realistic sailing physics.
@@o_manam i was very simplistic physics, but it was called The Legend of Zelda: The Wind Waker, on GameCube.
You totally forgot about true windspeed and apparent wind.
More boat speed, that more influence it have to the apparent windspeed. It have influence on the boat speed as well in the angle to the true wind.
For example the ac75 always have the same sail trim, doesn’t matter if they are on a up wind or down wind course, because of the high speed they use more the apparent wind as the true wind.
Veritasium and Steve Mould channel are one of the best things in youtube. Tons of science which i love 😊👍
Those ridiculous models actually really made this explanation really easy to understand. I hope you guys decide that now that you're at 1 million the next goal is just 10 million and you keep challenging each other.
5:08 Only a sith would say that
Borg make this assumption on the regular.
31secs ago omg so early
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he's obviously the best invested 20,000USD with him and 9 I made a profit of 50,000USD
Trading on your own is very risky l've lost alot trading for my self
I lost £1200 carelessly trading on a platform then I was referred to Mr Charles Schwab he recovered the loss and made an extra profit of £10,000
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I got Charles Schwab info how good is he ?
At the section about sailing against the wind, there's a discrepancy between the physical model (around 8:30) and the drawing of the zig-zag motion of the sailboat (near 8:48) as on the model the front of the sail is on the side the wind is coming from, and on the drawing the front of the sail is away from the wind.
I think the drawing is the most likely to be incorrect...?
I think so too. My vector diagram shows that the sail should be between the boat and the wind, not the boat in the middle
3:05 shouldn't it be a parallelogram of vector forces, not a triangle. So instead of the resultant pointing a little back, it's a longer arrow halfway between the first two?
The force, impulse, or change of momentum is the difference of the two momentum vectors, not the sum. Parallelogram is for summation (addition), and here we need difference.
Edit: so, horizontal (before) plus red (change) equals the resultant slanted white vector ( after)
3:06, shouldn't the red arrow only point in that direction (the direction shown) with that magnitude when the horizontal arrow is pointed left (with the 45° arrow remaining as is)? Is my fundamental understanding of vectors incorrect?
Considering he's a smart guy you're either wrong or confused
CONGRATS STEVE! Been watching you for years and always felt that you were an undiscovered or hidden gem. I was always shocked that more people hadn’t found you and subscribed…..well, now they have and it’s well deserved! Looking forward to seeing how long it takes to get you to 2 million subs!
And worry not Matt Parker…we’ll get you to that magic 1 million soon (here’s an idea….just plaster more images of Steve’s face on your video thumbnails and you’ll reach a million subs in no time at all!)
0:53 and again, Matt Parker the hero saves us all
I love that all you guys are watching each other's videos and jumping off of the ideas. Its absolutely peak UA-cam.
Congrats on your 1mil! You deserve it, freaking love your videos, thanx!!!
As a sailor of 30 years I love to watch You explain simple things. In general they are considerend simple, but when you ask yourself "but why tho?", there comes Steve with his clever and simple explanations. Always with a smile on the face. Thanks Steve, have a great one.
Sails and sailing vessels come in countless variations and different configurations, of course.
The most common sails these days - seen on that Bermuda-styled pleasure boat at 8:12 - are actually shaped more like wings than like triangles. They look like triangles curved out of shape by the wind but they are more like three-point _pockets_ carefully designed to catch more wind.
At 8:34 your sails are on the wrong side of the boat, you would be backwinding and actually end up traveling backwards not upwind. You would just need to switch the sides that the sail is on.
This made me appreciate how great Wind Waker's sail mechanic was
@1:42 “How often is it that the place you want to go happens to also be the direction that the wind is blowing?”
As a paraglider pilot who is trying to get into XC (cross country) flying, I really felt this. 😂
What part of the country do you fly in? I fly PG in the S.F. bay area.
@@Rick_Cavallaro, I live in the Salt Lake area so I primarily fly The Point, but I actually just had my first real thermal mountain flight this past week at The V. Taking baby steps so I can join the big boy XC crew in due time. :)
@@Andyg2g you know Dingo Dave? He was one of our locals, but now a POTM guy. He hang glides, paraglides, skydives, wingsuit... And a great guy.
Thermalling can be great. But I would caution you to take a very deliberate approach as you move into thermalling and XC. Give yourself wider safety margins, and try (at least at first) to avoid falling into the "I've gotta go further than the last pilot" mindset. If you haven't done an SIV clinic, I highly recommend it.
@@Rick_Cavallaro, the name doesn’t ring any bells, but it’s entirely possible that we have crossed paths at some point if he is a POTM regular. And thank you for the advice! I have been flying for nearly a year and have two SIVs under my belt as well as a maneuvers course with Cody Mittanck scheduled for later this year, so I’m still very much a fledgling pilot, but am taking steps learn as much as possible from the local experts in my area. Slow and steady McGee is the way for me. :) All things in due time! If you’re ever in the area let me know! Would love to come out to San Francisco sometime as well!
Dunno if anybody else has pointed this out, but the overall net force of the wind on the sail is not called "lift". Only the component of the force that is perpendicular to the wind is called "lift", and the component that is parallel to the wind is called "drag". Also worth remembering that in this context "wind" is always measured relative to the motion of the vehicle, so a plane travelling 150kts through still air is experiencing 150kts of wind, and once the boat starts moving, the wind direction relative to the boat will change.
This is confusingly different to how sailors talk about wind direction which is almost always relative to the water.
Also there was no mention of a broad reach, which was surprising because that was the first example given with the model sailboat. That's a great way to get faster than the wind, and Derek also briefly showed it in his video. Basically you've got a sail angled so it's flat on to the wind, and the boat goes downwind, but angled off by about 45 degrees. Then you end up travelling with the wind but because your path is longer than the wind's path, you go further. Also you start to get relative wind effects and you can start to angle the sail a bit more and get an extra boost, in fact because of the curved sail, in this configuration you do end up throwing some wind back, just like the turbine car did. Hitting a broad reach just right in a strong wind with a dinghy is an incredible feeling, it's like you're getting lifted up out of the water almost.
Great video. Awesome explanation. No hand waving at all. I would argue that Your presentation was infinitely clearer than the similar video by the other author.
I'd love to see the energy balance on this. I think people (myself included) see something traveling directly into the wind at a speed faster than the wind and initially think "perpetual motion!" but obviously that isn't true. Great video.
That picture of Steve really helped me stay focused at the beginning.
I hope these vids dont stop, was both happy and sad to see 1M subs. You deserve every last sub and more, both of you.
Finally, an intuitive and visual explanation of tacking that actually makes sense to me!!!!!!!
I wanted this too! That was the part I wanted more of in the Veritasium video! I was so thrilled to see this come out.
I touch on that here, but not in as much detail as it deserves...
ua-cam.com/video/X6oJpnSJyV8/v-deo.html
6:02 a very similar effect is happening in asynchronous induction motors (squirrel cage motors) when operated without a load. The rotating magnetic field around the rotor accelerates the rotor until it matches speed and phase with the magnetic field. By that point, no more force is generated and it slows down. The motor reaches an equillibrium state where there is just enough force generated to overcome friction and air resistance inside the motor.
Wooo! Congrats on 1 MILLION, Steve!!
Proud to be one among 1 million. Congrats!