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What causes jellyfishing?

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bragnouff
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Re: What causes jellyfishing?

Postby bragnouff » Mon Jul 19, 2021 9:57 pm

yeah, well... any severely underinflated kite will jellyfish.
Leading edge buckling is something that you can kind of control, avoid loading it too much and violently depowering it, whereas tips flaring in and out are more of a constant hassle, rocking back and forth in the window.

The GK Sonic, which the Waroos were inspired from, suffered from buckling/ kinks in the LE when overloaded. It was usually a sign that we should have been on a smaller size. Those kites offered a huge depower, that many people took as a free pass to use them in the top of that windrange, instead of using them in their sweetspot and just having some upper windrange safety margin. In the sweetspot, the buckling happened in very specific situations, like kitelooping yourself out of a sinking situation. Big traversal of the window and a sudden big load. I was the one having these troubles as I was riding quite aggressively, and being on the heavy side. None of the more intermediate riders had that, specially those who grew into kiting on those kites. They learnt finesse...
Most of the bow style kites from this era would be put in trouble in this scenario, the kinks and buckling were early warnings, and some models could easily invert once you hit their weakness. Turbo Diesel, Crossbow, to name a few.
Anyway, soon after, we evolved towards a bit more C-shape being re-injected into those designs, more connecting points on the bridles, and a much more stable profile overall. What didn't really change, is that people still ride too big of a kite...

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Re: What causes jellyfishing?

Postby Herman » Mon Jul 19, 2021 11:15 pm

Spork

I have an old 10.5m Flexi Ion 3, purchased second hand. Always was a bit of a buckler if not carefully flown. Buckling on that one, if anything seemed worse in light winds, probably being cranked hard though. It has got progressively worse, recoverable if only one side loaded, but if both sides evenly loaded in a big open loop both sides can kink and the kite will try to invert. Upto now I have been able to stop the full inversion by riding at the kite but it will hit the water. Interesting but unwanted experience.

Looking at the kite in smiley position and pulling on the front bridle pig it is fairly easy to replicate the kinking. The LE kinks at a seam and the Dacron there seems worn from the hinging effect even though the bridle looks OK. As luck would have it Flexi are selling off the pulley line section for this very kite. I will replace this section of the bridle and if that does not work I will try to stiffen the Dacron hinged area with a patch. If you like I will let you know the result.

Regards Herman

PS this kite was definitely not under inflated.

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spork
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Re: What causes jellyfishing?

Postby spork » Tue Jul 20, 2021 10:06 pm

Herman wrote:
Mon Jul 19, 2021 9:31 pm
Leading edge buckling is a totally different thing imho and the cures for the two are totally different.
Do you know what the cures for each are?

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Re: What causes jellyfishing?

Postby spork » Tue Jul 20, 2021 10:11 pm

bragnouff wrote:
Mon Jul 19, 2021 9:57 pm
Leading edge buckling is something that you can kind of control, avoid loading it too much and violently depowering it, whereas tips flaring in and out are more of a constant hassle, rocking back and forth in the window.
I'm not getting the L.E. buckling; just the tips flaring in and out and rocking back and forth in the window.

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Re: What causes jellyfishing?

Postby knyfe » Tue Jul 20, 2021 10:42 pm

I assume the kite flys as always and just your acceptance of a good kite changed ;-). Or it’s your incredible frankenbar attached to it LOL. G

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Re: What causes jellyfishing?

Postby Herman » Tue Jul 20, 2021 11:43 pm

I would not have the temerity to claim to have a cure for such things. Nor do I have the desire to rehearse all I know about, bridle design, pressurised tube bending and buckling or oscillating systems and, in any case, there are too many variables to be one cure for each. In truth I would need to see the kite in action to form a decent opinion on what is happening. Or at least that is my excuse for not being more helpful.

You say you are not getting any buckling it is just tip flaring. Is this tip flaring random or at a certain frequency and is it associated with a particular level of sheeting? Have you changed the Y/V level? Is it the same with all line lengths?

If it rhythmical you need to identify the excitation mechanism and remove it or change the natural frequency of the system.


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