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Illustration of the problem: http://www.youtube.com/watch?v=OWRixptJaRo

The non physics solution: http://www.youtube.com/watch?v=FRwHcJjfCR4

My first approach to learn this was to follow youtube tutorials. After getting the beating of a lifetime hitting the water over and over again I don't want to try it anymore until I see some vectors instead of words like flick the board.

A ------------- B is a steel cable 10 m above the water surface moving at 30 km/u. I am holding a 18.25 m tow line attached to the cable.

How do I get in the air using a 1.43 m wakeboard?

Note that in the middle of A and B the steel cable has too much sideways slack, and the trick needs to be performed close to point A where there is more tension holding the rope coming out of a corner.

I can't explain why but when you steer away from the cable in a more or less 45 degree angle at some point the conditions for getting out of the water are better then when you try it underneath the cable.

My personal experience is that it feels like, speed and making some sort of wave to launch form it, has more to do with getting in the air then the tension of the rope but I can't prove it. And I don't know how to make a wave and at what angle I should direct my board during take off.

I will edit this question if more information is required.

A vector instruction representation would be awesome, or a calculation how much pull is required by the cable at that angle with my body weight to figure out how much jumping force is still needed to get upward from the wakeboard itself instead of the cable. Then I know if I need to work on my pull or jump out of the water or both :D I can compare calculated pull tension I need in the gym by lifting weights so I know if I need to increase cable tension on the water.

EDIT:

  • 70 kg body weight + 5 kg wakeboard

  • estimate distance 300 m between A and B see picture

  • cable turning clockwise

distance

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It seems to me that the key to this trick is to build up enough elastic energy in the rope - which requires you to "build tension" by riding the edge hard, as explained in this video. If you do the trick too close to point A, there is limited lateral motion needed to build tension - but as you take off, the force you are looking for will disappear as the angle in the rope becomes smaller. On the other hand if you start the trick towards the middle of AB, then as you approach B the tension (which pulls you out of the water and gives you air) will actually increase.

So I would say - start at the middle, or after. That way the tension will increase as you fly up, and this will permit you to perform the trick.

No time to make a drawing right now... does this make sense?

Incidentally, whether a particular cable setup (length, tension) will allow you to perform the trick is not certain, in my mind. It will depend on the tension, and the distance AB.

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  • $\begingroup$ I agree with the elastic tension but it's not clear how to release it. For example if I would jump straight up at the moment where I feel maximum tension I smack down like a pancake transferring all the elastic tension into forward momentum and very little into height. I think there is a physical aspect of this trick where I need to redirect speed into height. I was hoping numbers could confirm this that rope tension is not enough. $\endgroup$ – Gert Cuykens Jun 26 '16 at 3:36
  • $\begingroup$ In other words I think my 70kg body weight is much higher than the upward angle tension from the rope alone. The elastic tension only assist with the air time I think. $\endgroup$ – Gert Cuykens Jun 26 '16 at 3:45
  • $\begingroup$ The tension is only enough if it is maintained as you move - in other words, you need to "store elastic energy" in the cable. This will only happen if it has the right amount of "give" and the angle is sufficiently vertical. There is no guarantee that your cable is set up right for this trick. I agree that the tension can only "help" - you need to jump. But if you have 80% of your weight carried by the rope, it is like decreasing gravity by 80% - so you can be a lot more air time... $\endgroup$ – Floris Jun 26 '16 at 3:49
  • $\begingroup$ You are probably correct :) But I can confirm it's not the cable because my friends are doing it at the same cable. Anyway I will accept this answer, until somebody can disprove it. Thank you $\endgroup$ – Gert Cuykens Jun 26 '16 at 3:55
  • $\begingroup$ Are you taking off at the same point as your friends? That is probably the most important variable. $\endgroup$ – Floris Jun 26 '16 at 3:58
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You need to redirect the energy. Building tension in the rope, by riding the edge hard, is great for building the speed you need; but once you simply leave the water to perform your trick, very little of that momentum is maintained, and you are nothing more than the cable's B#@tc& as you become dead weight falling back in line with the tail end of the source velocity.

How do you maintain Momentum from the tension of your edge, or even generate it upward for height, airtime? Essentially you need to generate the force and direction of outside variables to rival the force and direction of the cable pulling you. One way of doing this has already been discussed: riding the edge of your board to build tension.

Riding the edge builds tension why? Because you are on a board designed give you just the ability needed to manage the flow of water under your feet -- placing the full weight - of unreliable and turbulence provoking variables that make every crease, bulge, pit, and orifice - of your 70 kg body on that of a 5 kg - laminar accommodating - board against the pressure of a relative flow; generating a relatively stable application of force that is the function of gravity anchoring 75 kg on a 18.25m radius, to a plane that is around -10m of the source velocity fixed at 30 km/u.

The potential energy lies in the force generated by these constant variables: energy only realized in the effort of pulling some sick tricks when applied to the conflicting forces of the water. So the only way to act independently of a dead weight dragging behind the cable kind of nature, is to change the interaction your 75kg can have with the steady surface plane of water. And redirecting the pressure of your weight among different leading points in the wakeboard manages this interaction.

Press into an edge hard and you disrupt that laminate flow of the water's plane, shaping the water around the board in shapes of friction that directly conflicts the ideal nature of the constant variables, and builds tension along the rope as a result. That tension needs to be resolved, but on an 18.25m radius the only give is not in the direction of relative water flow because that distance is limited (unless the force generated is so great and sudden your little gwabby hans can't hold on), the only give becomes the angles out to the side --- along the perimeter of this radius. In so Creating a vector across the relative flow of water, and generating more potential energy and momentum along the edge of this radius.

With enough lead time, i.e. relative distance at 30km/u, you can even build enough energy by managing these force interactions, utilizing the course momentum of a pendulum as you use your edges to crisscross the cable's axis of travel, to even out "run" your cable. Enough speed and momentum to overcome the radial deficit of a rope's length at 30km/u. But once you're ahead of your tether to the cable, you have nothing left but left-over-momentum to carry you across the water (until the cable catches up). You're caught in between the two engines of a system that gives you the control and freedom to chart your course. Outrunning the Cable negates one of those engines - like the chain of a bicycle popping off the track - and how graceful you can manage that flailing momentum back onto that track will determine weather you can stay up as the engine hits.

Now. At any moment can you reshape the water's relative flow under your feet, and depending on the new vectors and how the variables of that new course of travel interact with your constants; you can build more and more energy and momentum -------- OR LESS.

You lift the board off the water, and just like the needle of a record player, all that music comes to an abrupt stop. There is no longer any pressure under your feet to redirect and anchor your inherent momentum. So you effectively negate the second engine that powers your ability to control the energy of this system. So you're then dead weight waiting for the forces of least resistance to pull you back in line toward the tail end of the cable's axis. The trick then becomes to avoid scratching the needle of the record and (just like outrunning the cable) manage the momentum that takes you out of the system with enough grace to fall back into track after you pop your trick.

Creating an edge against the water understandably kicks you out to the side, but how do you go UP (instead of out) with control and power? Once you leave the water you're without the second engine of this system, and the overwhelming source of momentum naturally becomes that of the source velocity of the tethered cable. Disrupting that natural outcome requires one to therefore generate momentum as they jump to catch enough air to keep the independent momentum of the jump in direct conflict with the momentum sourced at the cable. Just as hitting an edge hard will create tension across the surface plane of water along the 18.25 radial perimeter; the momentum riding up off the jump creates the tension to ride along the vertical range of that radial perimeter, in the air, to generate whatever height the force inputs create.

Now this is how you jump with enough air to carry out your trick: you shape the relative flow of water under your feet in such a way as to leave significant upward momentum as the least resistant path for the generated tension to resolve. Digging your board into the water as if a loaded slingshot drawing back. Without a pocket for the board to rest, there is no pocket for the slingshot to aim up. So what is this pocket? It's an edge carved down under the board using the leading front foot -- in so creating a low pressure cavity. The jump then becomes the relative laminar flow of the water suddenly dropping into the face of high pressure turbulence, securing the board's position on all horizontal sides as the force of your carved edge sinks below the -10m surface plane of the water. You literally shape a "jump", or graduated incline into the surface of the water. Shaping this edge with the front foot, filling the low pressure cavity of this edge with the weight of your 75kg position centering through the back foot as to pin the length of the board against this graduated incline; at which point the momentum force of our constants are redirected along a vertical vector where your trick can be performed with enough height and radial tension to control your effort.

---- You can Jump incredibly easily by using only the back foot --- punch through the back foot to create the cavity that provides you with the graduated incline; and that creates both the pocket and the tension needed to get air. In fact the back foot is most important in distributing the weight anytime you jump, otherwise you punch through the front, and the turbulence collapses the cavity around the top of the board, and you faceplant. But on a 1.43m wakeboard, you are dramatically decreasing the amount of surface area that shapes and grips the water when the top half is ignored, thereby the area applying work in the equation is limited to the space below the tail end. To pop off the water and do shove-its on a wakeskate, or simply ollies on either wakeskates or wakeboards, use back foot as the equating variables allow for more stable "sweet spot" for the jump. From there you learn to shape a larger and more aggressive gradient by artfully lending more and more surface area to apply a working force against the relative flow of water.

Weather or not you can do it depends on your ability to maintain any potential energy you've generated, long enough to shape the cavity that allows you to realize that energy into height and control.

Certainly, I mean - I feel like this is a fairly comprehensive analysis of what variables to consider and how they interact. BUTTTTTTTT - I would love to see someone apply numbers to the relevant variables and calculate the limits of these interactions.

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