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 Post subject: What force gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 6:01 am 
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Just had crazy argument with my friend about it, so need some advice from you, folks :)

When you pop with kite steady at 45°, you have different forces, that give you height. I think they are:

1. Pull from your kite
2. Pull from stretched lines
3. Push from your legs
4. Small kicker from wake under your board
5. Your body as spring, that contracts and extends

These forces all together give you height. Question is which one is biggest? Specially when you jump like 2x body height.


Last edited by dandaka on Wed Apr 03, 2013 10:31 am, edited 1 time in total.

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 Post subject: Re: What force make gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 6:53 am 
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2-4: try to jump 10m high with one of them.
Only 1 brings you higher.
But all together will be max height!


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 Post subject: Re: What force make gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 6:58 am 
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If its pull from kite, why its so important to get a good pop with board?
Why edging and going upwind before jump makes pull bigger and jump much higher?


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 Post subject: Re: What force make gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 9:58 am 
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dandaka wrote:
Just had crazy argument with my friend about it, so need some advice from you, folks :)

When you pop with kite steady at 45°, you have different forces, that give you height. I think they are:

1. Pull from your kite
2. Pull from stretched lines
3. Push from your legs
4. Small kicker from wake under your board
5. Your body as spring, that contracts and extends

These forces all together give you height. Question is which one is biggest? Specially when you jump like 2x body height.


Aaaah - interesting 8)

1. Definitely.
2. Nope - they will most likely stretch less than 5-10cm, which would be the max benefit in height then.
3. Yes, although quite limited as humans are not able to jump more than around 1m up.
4. This is the "pop" (the wake gives nothing IMO), will describe below.
5. To a small extent, yes. Would not call it a spring, but you can lift your bodyweight with muscle work.


Of course redirecting the kite will give by far the most amount of jump height :thumb:


But if there is no "spring effect" in the lines, how come you can pop with kite parked ?

Three reasons - the obvious is the body work as you can make a (very) little jump, even without the kite.
But the primary is, that when you pop, you actually change direction and head upwind, you and your board.
When you do this, you slow your forward/halfwind speed down and upwind instead, and you also change direction so your speed is higher to the wind.

BOTH of these factors will increase the AOA on the kite, thus the kite will lift more :D

For those curious: Try to draw the vectors wind speed and rider speed, and see what happens to the AOA if you change direction :naughty:

So it is not the same as a stiff wire cable park jump, as when you pop with a kite, you actually increase the lift just like if you had pulled the bar in.

Third and last, you get a little pendulum effect too, just like you do on a cable park.

:D Peter


Last edited by Peter_Frank on Wed Apr 03, 2013 11:21 am, edited 1 time in total.

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 Post subject: Re: What force make gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 10:04 am 
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Peter, thank you for detailed explanation :thumb:

What about jump on flat water on a wakeboard in a cable park? There is no AOA to change, but you edge and release to get pop. Does it have different mechanism?


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 Post subject: Re: What force gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 10:53 am 
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Another thing to consider is that a lot of the height in a raley based trick comes from rotation of the rider about the bar. If you look at the bar itself you'll notice that it doesn't move up that much at all in comparison.

What does move massively is the board... it goes from sea level to a foot or two above the rider - this is 7-8ft in itself. If you couple this with some pull and lift from the kite and some upward force from pop you get the big unhooked airs that we see.
Slims for example look high because the rider pulls himself upside down, before flopping over the other side.

To get big height you need to have a big kite - as you can see on the PKRA comps, where the riders are much more powered than us mere mortals would want to hold down. You can only pop so high/so hard - to get higher you need more kite power.


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 Post subject: Re: What force make gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 11:09 am 
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dandaka wrote:
Peter, thank you for detailed explanation :thumb:

What about jump on flat water on a wakeboard in a cable park? There is no AOA to change, but you edge and release to get pop. Does it have different mechanism?


That comes from pop AND from the tension in the line.


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 Post subject: Re: What force gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 11:12 am 
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capitan nemo, you mean line stretches when you edge and contract when you release? Why don't we have same effect on kites?

Also "pop" doesn't explain anything, its a result. What forces make this pop?


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 Post subject: Re: What force make gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 12:21 pm 
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dandaka wrote:
Peter, thank you for detailed explanation :thumb:

What about jump on flat water on a wakeboard in a cable park? There is no AOA to change, but you edge and release to get pop. Does it have different mechanism?


I think it is very different, yes.

No expert in this, as I am used to aerodynamics and sailing, but not a cable park specialist, so correct me if I am wrong, but my immediate thoughts would be :


1. Pull from your kite
Not present by means of AOA changes.
But you got a wire that constantly are able to deliver energy and force horizontally, even when airborne.

2. Pull from stretched lines
There COULD be a considerable amount of "spring" effect when you load a long cable wire perpendicular by edging max (not the short wire you hold on to, no spring effect here), so indeed this could be some factor - I dont know...

3. Push from your legs.
Yes, it might be a considerable amount of the typical height you can get in a cable park - but maybe not used as I think step 4 means almost everything.

4. Small kicker from wake under your board.
The "pop" in wakeboarding (not really a "kicker here either", is in contrast to kitesurfing IMO the most contributing factor to height in cable park jumps.
As you can change your kinetic energy to height.
First you increase the kinetic energy by going faster and faster by edging and going from the center towards the side, and the cable will supply sufficient force giving you the extra energy.
And then you can convert this higher kinetic energy to height, by means of the pendulum effect you get when you leave the water in a motion "away" from the cable.
(this is just like when you ride on a swing or hold on to a rope fixed in a tree, so easy to understand)

5. Your body as spring, that contracts and extends
As said before - not acting like a spring, but you can supply a lot of energy/height with your body movements too, especially at these lower heights we are talking about.


So here the edging and direction change/release is the most important IMO, whereas with a kite you got both this effect, but also the major effect by redirecting the kite (or changing AOA by means of "pop", if a parked kite) - thus extremely different 8)


:D Peter


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 Post subject: Re: What force gives you maximum height after pop?
PostPosted: Wed Apr 03, 2013 12:37 pm 
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peet wrote:
Snip...

To get big height you need to have a big kite - as you can see on the PKRA comps, where the riders are much more powered than us mere mortals would want to hold down. You can only pop so high/so hard - to get higher you need more kite power.


Not true...

You need better technique, not necessarily a bigger kite 8)

And more wind, by far the (almost the only factor when high level riders) determining factor regarding jump height :thumb:

:D Peter


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