As an engineering student who want to learn how to surf, I came here for some tips of pumping but end up re-learning kinematics - one of the toughest course in college. lollllll
Thats quite an explanation....I always thought of it as make yourself "heavy" on the way down by throwing yourself low and compressing, make yourself "light" on the way up by extending and throwing yourself up.
It's not necessarily a bad way to see it. By compressing your body down and forward over your front knee as you go down the wave, you bring your centre of mass forward & lower, so that helps to go down & forward on the wave. A bit like leaning down a quarter pipe on a skateboard. As for making yourself "light" while going up on a wave, this mental image will also help because you will bring your centre of mass closer to your axis of rotation as you pump back up. Just to be clear though, Conservation of Angular Momentum does not explain every aspect of speed generation on a wave. There are other aspects to consider such as the surfboard's rail engagement & water flow hitting on the bottom, the type of board you use, gravity, positioning, etc. Explaining all of these in one video would be too long but there's a lot more information to be found on our online coaching platform: tutorials.barefootsurftravel.com We don't presume to know every single aspect of speed generation, but we work very hard to get the most precise answers and explain them in the clearest way possible :)
@@barefoot_surf Just after commenting here i heard a kool way of thinking about pumping on a half pipe..Similar to the way you build up height swinging on a swing..always kool content, glad you are posting more regular..)
@@MsMesem Yea it came naturally on a half pipe and ramps but it doesnt often occur to do it on a wave...for most people on a wave and losing speed the natural thing to do is stomp the front foot like using a foot pump...)
As an engineer that is learning how to surf, this was WAY helpful then I thought. The physics, at least for me, made everything clearer. At least I am putting my knowledge to a much more fun use hehe
I was just coaching some girls this morning and trying to explain this to them. The physics and your visuals and comparisons helped me understand it EVEN MORE! Thanks!
Please do a part 2 where you talk about when to pump and when to bottom turn. It has to do with the slope of the wave in relation to the horizon. Most shortboard beginners I see fall in love with pumping as soon as they learn it. They pump themselves right off waves. I prefer to position better and surf better peeling waves so i don't have to pump 3-4 times before doing a maneuver.
I'm quite sure that the real reason why pumping works is because you can use your muscle chain to generate upward thrust on the contact surface between the board and the water (or the board and the wall) when you're going upwards, and use it to push down against the surface when going down,so that's what's increasing your momentum. You are using your body as a motor/propeller that adds momentum. When you're on a swing, you're adding momentum with your body, which is applied onto the chains of the swing. You can also pump on a carver-type skateboard when rolling on a flat surface, and it's not just about changing moments of inertia, it's about exerting yourself to get momentum.
Yeah, i think that plays a bigger role than center of mass. It feels obvious on a skateboard that you're pushing off the ground upward to generate speed and adapt to the angle of a steepening ramp. It's like jumping without going so far as to come off the ground- the energy still goes upward and the weight that's lifted from the board allows it to rise with less resistance. This seems like a more intuitive, and accurate, less complicated, and therefore more useable understanding of pumping to me.
I thought of swings when I was learning to pump on a half-pipe, and kinda forgot to add those two ideas to how it relates to pumping on a wave. The physics just gets way more complicated for surfing though. A good practice for beginners is to hop on a swing. This will help them get a feel for the timing naturally and also let them relax by flying through the air. Happy surfing, skating, and swinging!
Amazing source of information with so much clear and simple examples. I often make those same errors and while viewing/hearing this video I can visualize what I might be doing wrong. Meanwhile I'm getting mentally ready (with some cues that I took from the video) for my next session. 😄 Thank you very much for this and keep up the good work!! 🤙🤙
I've seen the angular momentum explanation before and while it does make some sense, I think it makes more sense to use the velocity vector explanation. Pumping works just fine on angled, non-radiused ramps, and also works fine on flat ground by moving side to side, to give your self some rearward friction to push against.
I think a much simpler way to look at it is like you are jumping up the wave and then sliding down. but when you put them together you are jumping up while your slidnig down the wave, and then you are psudo 'landing' higher on the wave, then sliding back down again
One of my problems si that I get to much speed. I would like to have more control and don't go like a motorcycle and finish my wave so fast. I don't know if I explain it correctly. thanks
Great video! So well made! Sadly, it’s not right. Happily, pumping is easier to understand than made out here. (The skate video in a comment is excellent). Pumping simply adds potential energy as you go from a crouch at the bottom of the bottom turn and extend to lift your body higher. Then when you come back down the wave gravity and the ramp make forward speed from the potential (height) energy your legs created. Letting the board rise up high to the top of the wave under you as crouch also gets you ready to pump with leg force on the way back down again, and due to the angle of the ramp this energy also adds to forward speed.
Good video, but I wonder what amount of potential energy is also added just by using your body extension to unweight and get your skateboard/ surfboard/ snowboard higher up the ramp / wave / ski-slope or whatever your hill of choice is. Each little unweight, climb then descent converts potential energy your legs created into kinetic energy. If I had roller skates on and frog jumped up a flight of stairs, then rolled back down I guess that’s the same equation. Could be totally wrong, but it makes sense to me that potential energy created by me becomes kinetic energy coming back down. Could also explain why I surf so badly! 🤓
As a skater, all the pumping happens on the way down. Compress and fall and stand up against the ramp. Ride up the ramp standing tall. The cartoon compressed into the ramp which would kill speed(trust me, I made this mistake for an entire decade or more)
When surfing and doing smaller turns like the ones in pumping are you changing weight from heels to toes and vice versa like a skate board or even surfskate, or are you using the fins as a pivot point and then sort of force the board into the small turn with your body? what are the steps of turning in pumping?
I was watching your channel on youtube and thought that it would be really great to introduce your video to Korean surfers We have lots of people here in Korea that are interested in surfers around the world. The market is growing rapidly, but we lack in information since surfing is quite new here. could I translate your video into Korean and introduce it on my RU-vid?
Awesome video! One point - at 5:19 you said “weight” but meant mass. In physics, those words aren’t interchangeable. It’s really great to see how physics applies in the real world so thanks for taking the time to put together such a great video!
at 10:07, isn't the problem that he's not compressed enough while going down the wave, in combination with not extending enough while going up? In other words the difference between compression and extension is too small, making the effect of getting the center of mass closer to the axis of ratotion smaller than when he would exegerate both his compression and extension more?
First of all,I absolutely love your videos! I'm afraid the explanation is wrong. The acceleration is due to different normal forces that are caused by pumping, nevertheless you can use the explanation on angular momentum in another surfing phenomenon.(turning around faster when sitting low on the board as opposed to being positioned in the middle of the surfboard) In your explanation there is no torque involved whatsoever so it would be impossible to elevate more than in the first jump to the air... a link to an intuitive video explaining pumping in skateboarding: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-8AJKN3QTfoE.html
I have to say, the explanation in that video makes more sense to me. Credit to him for correcting his own video from 5 years prior (he didn't stop improving.)
Hi there, Thanks for reaching out and sharing your thoughts! We've taken the time to look at the video you refer to. We have also asked a few experts in different fields such as physics & mechanical engineering for their opinion. Additionally, we reached out to Justin from Never Stop Improving (the creator of the video you refer to). He told us that a few people had reached out to him about angular momentum and admitted that "he had an incomplete understanding of the variables at play when he created the video". This being said, we don't think that Justin's video is "wrong" and that ours is "right". Neither of us claims to have found the "one and only" formula that explains how pumping works on a skateboard or surfboard. On our online coaching platform, we see many more elements contributing to speed generation, such as rail engagement, gravity, surf equipment, positioning, etc. This being said, we thought we would share some of the feedback that we received in part from Nick D. (PhD in Physics & author of the article we refer to in the video), who was kind enough to answer some of our questions. #1 Clarifying "forces", "energy conservation," and angular momentum When Newton first described his laws of motion in the late 1600s, including the famous law that every force has an equal and opposite reaction force, there wasn't yet a solid understanding of momentum, angular momentum or energy conservation. Newton's laws are very powerful, but it's sometimes much easier to describe physical systems by considering things like energy and momentum rather than just force. You can describe pumping just by considering the forces being applied at every point along a ramp like Justin's video does. We just don't think that's a particularly useful way of thinking about it and would make doing calculations tedious. At least for the case of quarterpipes (and probably ocean waves too), it's much simpler to think about pumping in terms of angular momentum. #2 The Problem with the "Normal Force" explanation In Justin's explanation, he talks about how the normal force has some component in the direction you "want to go." The laws of physics have no idea what direction you want to go. They only care about what direction you are going at that specific instant in time. And a normal force is always going to be, by definition, normal (i.e. perpendicular) to the surface you are pushing against, so it cannot provide an acceleration up or down a ramp, just perpendicular to its surface. Justin seems to confirm that at this part of the video. There's practically no difference in speed when going down with a straight body VS in a bent position. The real speed gain happens when he extends the body at the bottom during his 3rd test. We think that you might have written this comment because we don't really focus on the "force" or "energy" added by the skater by "pushing" on the ramp in our video. Please see point #3 below for more about that. We don't focus on the "push" because we don't think that it brings valuable understanding to skaters/surfers on "why" pumping actually works and what it means for their technique. As a surfing coaching company, we see a lot of surfers struggling with pumping, even though they "push" and extend the body. "Pushing hard" on the water can disrupt water flow under the board, slowing the surfer down. Most importantly, it's about pushing and extending at a very precise time to benefit from the center of mass getting closer to the axis of rotation. That is why we focus on this point in the video. #3 The "How" versus the "Why" of acceleration through Pumping - With both explanations, the "how" is the same: energy is added in the system with the skater's "pushing & extending" on the ramp. - The why seems to be where the theories are different. In our video, the energy of "pushing & extending" is the "how". The result of this is that the skater's center of mass gets closer to the axis of rotation, which is our "why" of the acceleration. If we understand correctly, in Justin's video, the why is the "equal and opposite reaction" of the "pushing down" on the ramp, which helps the skater accelerate in the direction where he "wants to go". We think that both Justin's and our explanations are quite similar and end up with the same "practical conclusion" that you need to push and extend the body at the transition point. The one difference is the "why" and in our opinion, it is best explained with angular momentum. If you find more documentation showing that our "theory is wrong", please send it through, and we will watch/read it carefully. The problem with commenting that the "theory is wrong" is that thousands of viewers might start doubting if this whole video is completely wrong. If angular momentum indeed has nothing to do with pumping and provided enough proof, we will certainly remove this video. The last thing we want is to mislead thousands of surfers! Thanks for mentioning Justin’s video, it allowed us to confirm and solidify our knowledge and will result in helping surfers better. Ps. If you've just read all this, that is awesome! Cheers :) The Barefoot Surf team
@@barefoot_surf Hi barefoot surf! You're applications of angular momentum are incorrect and unintuitive for learning about speed generation. While yes, a lower radius will increase angular velocity on paper (i.e. in a simple system), it isn't at all the 'why' or 'how' speed is created. Angular velocity isn't the same as forwards velocity, I would consider the forces and energy of surfers to figure out how it works. Firstly, a surfer isn't quite using a circular motion on the wave. While reducing radius WILL get you to the top of a wave faster, yes, it will reduce your speed as per the normal forces acting against your forward velocity. The pumping motion is less circular, therefore, and more compression and decompression to allow your board to get pushed up the wave. The speed is actually caused by fluid dynamics and normal forces. Consider this: Why do surfers gain speed without pumping, while surfing in the pocket? Look at this video, it's a far nicer explanation and the crux of what I'm saying: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LIX8PF9OfOk.html To summarise it for any viewers, water is pushed up by the wave. You can use normal forces to direct that water pushed by the wave behind you, using your surfboard. This is a normal force created, which causes forwards acceleration. Newton's laws aren't at all inaccurate or incomplete (at least classically, ie far from light speed)! Funnily, while you say Newton came up with his laws pre rotational physics, i think you would be humored to learn Newton FOUND the laws of rotational physics! en.wikipedia.org/wiki/Newton%27s_laws_of_motion
Hi there, Thanks for reaching out. Just to clarify, our last comment was focused on the skateboard pumping comparisons with Never Stop Improving's video, because that was what David's initial comment was about. As we said in the previous message, this video does not cover every aspect of speed generation for surfing. We see many more elements contributing to speed generation on our online coaching platform, such as rail engagement, gravity, surf equipment, positioning, etc. What you are referring to is definitely a big part of speed generation, and we focus on it a lot in the rail engagement tutorial on the Speed Generation course: tutorials.barefootsurftravel.com/courses/speed-generation/ To make things easier for our students, we divide tutorials in specific subjects. The way surfers generate speed by using their rails & redirecting water flow towards their tail isn't specifically related to "pumping". It can be done by trimming on the face of the wave and doing practically nothing apart from a bit of toe/heel pressure. In your explanation, are you certain that "water is pushed up by the wave"? When you say: "Angular velocity isn't the same as forwards velocity". We understand, of course, but do you mean that you are certain surfers or skaters don't use "curvy" lines to generate speed "forward"? If it was just about fluid dynamics, why would professional surfers bother "extending" the body so much towards the wave? And also, why would it be possible to gain speed on a surf skate by pumping in "circles", on a completely straight road? Take a look at this interesting video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-YgUmAwq1WG4.html As for the comments on Newton, we only copy/pasted the responses from the people that work in physics that voluntarily sent their feedback. Again we appreciate the comments and we're stoked to see that so many people care about this stuff. All the best!
@Barefoot Surf I don't have any problem with this video not covering every single aspect of speed generation for surfing. I think the problem is I (and others) disagree with Nicholas Drachman's theory - or at least I think it's incomplete and unintuitive - and I think it applies even less to surfing than skateboarding. When talking about speed generation, the question is how can we increase average kinetic energy of "the system" over time. The explanation of increasing angular velocity by decreasing the radius of rotation does nothing to address this question, as the increase in radius of rotation must be met with an equal and opposite decrease in radius of rotation (because a body can only extend so much). I guess an argument can be made that this decrease in radius of rotation must happen while angular velocity is 0 (for example, while in the air or at the bottom of the ramp). Then I could maybe see this resulting in more and more speed. Except I'm still not convinced that any skaters actually do this. And there's some disconnect between "increasing the radius of rotation" and "increasing the average kinetic energy over time" - mainly what exactly is happening when the radius of rotation is changed? Some work needs to be done here - ie forces are exerted. How do these forces act on the skater/surfer in a way that results in more speed? Someone else in the comments gave an example using rollerblades, which I'll adapt: Let's say you have a very wide ramp with a linear incline. Your goal is to ride parallel to the entrance of this ramp (the way surfskaters do to emulate a wave face) and gain as much speed as possible. You could do this by repeatedly jumping up the ramp and rolling down. Rolling up the ramp results in a loss of kinetic energy, but jumping up the ramp avoids most of this - basically increasing gravitational energy without losing much kinetic energy. Now how would you explain this using conservation of angular momentum? Maybe you could, but I would be surprised if anyone considered it an intuitive explanation. From my understanding, pumping while surfing is very similar to the rollerblading example. You throw your body up the wave, unweighting the board and reducing the loss of kinetic energy due drag. I think radius of rotation has very little to do with anything here. I commented similar ideas on Nicholas Drachman's blog post, but it seems he deleted my comment... Anyway, if I'm wrong I'd love for someone to convince me because I'm just trying to become a better surfer, and I think having correct intuition about these things is crucial.
07:52 I = mr^2 so Inertia depends even more of the value of r (distance between your center of gravity and the center of rotation) :) fr.wikipedia.org/wiki/Moment_cin%C3%A9tique
I think that technical explanation of the physics behind pumping, though interesting, misses some key points. When you bend down low and then decompress rapidly (pump up), a few things are happening. The center of mass is one that never occurred to me and seems tertiary. More effective i think is the severe reduction of weight on the ground- if you pump hard enough, you can easily jump off your board and effectively weigh nothing momentarily. This is coupled with the force and extra momentum you get from pushing off the ground, and therefore at an upward angle to better match the steepening surface. That seems to me more central to generating speed than center of mass. Another small thing that happens when pumping is that you smooth the transition between steep and flat by extending your legs (going up or down a transition), and this smooths your body's path. So you don't drive all that mass down into the ground, for instance.
Hey there- thanks for your feedback! Some great points to note for sure. These are all great explanations and key points you have contributed. Cheers! 🙌🏽
Proper nonsense physics explanation. Claiming that energy isn't conserved? The energy put in by the skater extending and compressing is the reason they are able to reach the same height
Nope. Pumping only works in the transitions. Due to the conservation of angular momentum. If you pump on the flat bottom of a half pipe absolutely nothing happens.
