Kiteboard Theory - Thread 7: The Biggest Jumps

[James]

... I remain however a bit frustrated with #7 which doesn't put so much emphasis on edging nor on moving the kite quickly in the window.

In deed the boat experience would work without (edging so much nor) moving the kite quickly in the window. That doesn't fit with what I see in kite jump movies nor with what I feel from my first jumps.

Hi Bruno,

Edging causes you to "head up", altering course toward the direction of the (true) wind, which increases your apparent wind speed. That gives you more kinetic energy to convert into potential energy, which makes it possible to jump higher.

If you edge too much though, you'll slow down enough to diminish your apparent wind speed, so you won't be able to jump as high.

Best regards,
James

[Nobben]

Than you James for your quick answer

I had understood the going upwind and increasing your apparent wind speed aspect of edging. And that is consistent with the boat image (that I find very pedagogic) and my feeling.

I keep however the feeling that :

- moving your kite quickly in the window is of paramount importance (as a beginner I began moving it too slowly and could not go high) and I doubt that it si only a matter of not losing time and not "slowing down your boat" ;

- edging is key above and beyond moving upwind even when you keep your direction. Why ? It could be not only to "remain on the boat" but also to anchor your feet (avoid the roller skates) to get the L/D kite speed and lift (like for waterstart).

I am sure that it helps to create lifting force (F). I remain uncertain that this force can create so much energy (F.dx) in such a short move (from releasing the edge to leaving water). But the waterstart comparison strengthens my belief.

Also inspired by those people jumping with their wakeboard under a teleski. They do it in corners. Edging hard. Creating tension in the their line (as they move away from the cable flow). And jumping high after they stopped edging. How ?

Not want to seem stubborn. Just curious and intellectually demanding when it comes to physics.

Bruno

[Slappy]

Also inspired by those people jumping with their wakeboard under a teleski. They do it in corners. Edging hard. Creating tension in the their line (as they move away from the cable flow). And jumping high after they stopped edging. How ?

Cable wakeboarding uses pure edging to load up the cable and then pop off the edge to slingshot towards the cable.

Wakestyle kiteboarding also uses mostly pure edging to do the exact same thing.

When boosting for max air you can load line tension to create that pop off the water using just your edging. Sure whipping the kite up will force some line tension but instead you should try and control the line tension through edging as you can get more tension and better timing that way. Once you get the optimal timing for when to send the kite and when to edge hard and release then you can achieve the maximum air.

[James]

- moving your kite quickly in the window is of paramount importance (as a beginner I began moving it too slowly and could not go high)...

Not want to seem stubborn. Just curious and intellectually demanding when it comes to physics.

Okay then...

If you successfully break down all of the dynamics at play (three dimensional aerodynamic and inertial force vectors, and near-universally misunderstood energy transfers), you'll discover that the "pendulum" motion made possible by long kite lines is the secret to high jumps. When you redirect your kite at an opportune instant, thereby achieving the dynamics outlined in this 2007 thread, the substantial distance between you and your kite allows you to transform most of your (scalar) airspeed-dependent kinetic energy into height-resulting potential energy, even though your kite maintains its own tension-and-trim-dependent airspeed.

Consider this example: a kiteboarder and a windsurfer are riding side-by-side on flat water with equal velocities (which can be represented by vectors but are often confused with speed, which can't be represented by vector ). It's pretty windy. Both jump simultaneously, each exploiting their respective 6m aerofoils to the best of their abilities. The windsurfer's jump height is pitiful compared to the kiteboarder's. The reason is that the windsurfer can't significantly trade airspeed-dependent kinetic energy for potential without also reducing airspeed over the sail, leading to failure, whereas the kiteboarder's redirected kite will maintain efficient airspeed even while the rider is swinging far below, ideally matching the true wind velocity during the apex of the jump (resulting in rider airspeed of zero).

[Nobben]

Thank you James and Slappy for your explanations and time.

I understand that the transformation of kinetic energy into potential is optimal if you reach a zero speed at the apex.

I must admit modestly in passing that I loved windsurf as well but could never jump without a good wave

I also theoretically understand what you say about pendulum... as in real life the kite doesn't "station just above" the boat.

I now have to experiment that pendulum in the coming weeks as my skills are not there yet. Painful landing still.

Finally I wonder if you could complete your (boat) theory by adding extra vertical speed and kinetic energy before take off.

Where would this vertical speed (and kinetic energy) come from ?

The same kind of lift that you get under the cable or during the water start or pop with vertical component before take off.

Happy to exchange on this again in the future. Will tell you if I get extra thoughts from practice.

Bruno

[Antonych]

Hi!
A real interesting thread! Thanks, James, agreed with lots of your statements, especially about lines tension and faster kite movement and as a result more lift. I would also emphasize the importance of board control skills to provide enough of grip for getting the lines really tensioned.
I think my work might be interesting for guys, who's reading this thread.

youtu.be/s7qR1Bvo-D4
Check out the page with comments and discussion about it here
http://vimeo.com/ondemand/learningtoflyepisodeone
I've put a lot of info from my teaching experience, hope you find it usefull!

[Chomps23]

Hi!
I've put a lot of info from my teaching experience, hope you find it usefull!

As someone who purchased Anton's video I can say it is excellent. The tips are great for those relatively new to the sport or find themselves stuck and not progressing. Great work Anton!

[BCKiter123]

As someone who purchased Anton's video I can say it is excellent. The tips are great for those relatively new to the sport or find themselves stuck and not progressing. Great work Anton!

Agreed, same here! Detailed and technical yet very practical. By following the tips, even my general riding has improved immensely, including edge control and staying upwind.

[James]

Thank you James and Slappy for your explanations and time.

I understand that the transformation of kinetic energy into potential is optimal if you reach a zero speed at the apex.

I must admit modestly in passing that I loved windsurf as well but could never jump without a good wave

I also theoretically understand what you say about pendulum... as in real life the kite doesn't "station just above" the boat.

I now have to experiment that pendulum in the coming weeks as my skills are not there yet. Painful landing still.

Finally I wonder if you could complete your (boat) theory by adding extra vertical speed and kinetic energy before take off.

Where would this vertical speed (and kinetic energy) come from ?

The same kind of lift that you get under the cable or during the water start or pop with vertical component before take off.

Happy to exchange on this again in the future. Will tell you if I get extra thoughts from practice.

Bruno

Oops, missed this post last year

Sure, some vertical speed at launch would help. A bunch of people on the boat could give you a boost before setting you free...Cirque-du-Soleil-style.

[luminary]

A couple of observations
. air at the speeds of kiting can be considered incompressible
. the notion that a jump is solely the conversion of kinetic to potential energy isnt realistic. That suggests that jump height is limited to the speed of the rider at takeoff - given the jumps I see on utube that simply isnt the case. However for argument, what is the kite doing as the rider is converting his/er kinetic to potential energy? It's continuing to add to the system as it is still flying/lifting. Hence jump height will/should exceed the nominal kinetic->potential height.
. All that being the case, real-world issues such as drag, the horrendous aero performance of kites, imperfect trim, orientation and terror act to reduce jump height. In most cases.

I think that the most effective way to get greater height in a jump is to launch into a gust with the most advantageous lifting trim on the kite. Lift is proportional to v^2 so getting the apparent wind at the kite will far overpower the human jumping idea. Secondly the boundary layer that exists in the air over the ocean surface means that the higher you are, the stronger the wind. So, if you can get up there, there might also be more windspeed.

up-up and away!!

Cheers
l.

[Antonych]

Hi!
I've put a lot of info from my teaching experience, hope you find it usefull!

As someone who purchased Anton's video I can say it is excellent. The tips are great for those relatively new to the sport or find themselves stuck and not progressing. Great work Anton!

Hey, so glad to read posts like this) Thank you! I've really put a lot into that movie. Really happy that it works)

[Antonych]

As someone who purchased Anton's video I can say it is excellent. The tips are great for those relatively new to the sport or find themselves stuck and not progressing. Great work Anton!

Agreed, same here! Detailed and technical yet very practical. By following the tips, even my general riding has improved immensely, including edge control and staying upwind.

Yeah, exactly! A lot of people improve their general riding techniques, when following the system, shown in the video. It means, that you get everything right. Even the lightwind riding skills improve also. That is the idea - to review the foundation and to grow further. In the Episdode II I'll bring you more interesting stuff, more specific for boosting really huge big airs, but again useful for dealing with high power, while you're riding on the surface.