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Wingtip collapse, Cause and Fixes

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SpunMonkey
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Wingtip collapse, Cause and Fixes

Postby SpunMonkey » Mon Jul 18, 2016 1:52 am

Hey All,

Been down this road with the chrono before and managed to sort that out by correcting speed system . Now another kite and a new kite( three flys)...

-Wintips Collapse on the beach when landing or maneuvering the kite anywhere except when sheeted in fully or directly overhead. Almost always the bottom wingtip
-Upwind, No Problems but bar seems heavy(sometimes requiring oversteer to keep kite from flying down)and there is a distinctive crease between C and Z, especially on the top hand
-Downwind, No problems if lit and sheeted hard. Transitioning between puffs and lulls or fast mode 30+ to edging mode 25-29 and the wingtip usually the bottom one just like on the beach will collapse into the bridle.

What does easing Z do(there is a knot i can move 40mm)? Will this help? What else can I do without changing the wing profile?

Thanks of helps and tips. Tuning these things is my own personal nightmare..

SpunMonkey
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Re: Wingtip collapse, Cause and Fixes

Postby SpunMonkey » Mon Jul 18, 2016 2:00 am

And I really don't know what I'm doing when I do try and tune them..

foilholio
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Re: Wingtip collapse, Cause and Fixes

Postby foilholio » Mon Jul 18, 2016 3:31 am

The collapse is caused by the profile being too positively/high cambered, like your hand when it is cupped. This can be either caused by the bridles or how the kite is sewn/condition of the fabric. To fix it you need to make it more negatively/reduced/reflexed cambered, think flexing or pulling your hand back. You can do this by either shortening B and/or C, or lengthening Z and or C!. The simplest solution is to just lengthen Z as you already have the adjustment. One thing you have noticed, heavier bar pressure, is a symptom of Z being shorter/tighter. This is because of the pulley setup, all force on Z goes directly to the bar. Z being tighter also makes the kite higher camber which also moves the center of pressure further back while increasing it too, so generating more force further back , i.e. more on C and Z etc, i.e. heavier bar. The reason higher camber causes collapses is because it generates a moment of torque that causes the wing to flip forward. Think the rear of the wing deflecting air down, so newtons law, it wants to do the opposite. A negative camber will do the opposite, wanting to flip backwards ,but because of the towpoint or bridle the kite can't do anything really, except be more stable and perhaps lose some efficiency. You can go into a myriad of ways to alter the kites camber from playing with individual bridles to sewing pleats on the canopy. Best to play with mixer first as it is simple and easy, as I said lengthen Z. You could also look at restretching your bridles. One other thing is the final tension B has when you depower can affect the stability of the kite depowered, you can play with that by either just adjusting B, but that will also change the camber/profile or you can adjust all of BCZ or change the length or put a stopper in the pulley line. Moving that knot attaching Z would eventually affect this. But yes complicated :-), just adjust Z and your problem should be fixed.

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Re: Wingtip collapse, Cause and Fixes

Postby Adventure Logs » Mon Jul 18, 2016 5:20 am

Have this problem on my Sonic 11m out of the bag. Messed with the bridle some and will see hopefully on Tuesday if I fix it. Which kite is doing this to you? I want to see if this is a regular occurring thing on certain kite models.

Mossy 757
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Re: Wingtip collapse, Cause and Fixes

Postby Mossy 757 » Mon Jul 18, 2016 3:12 pm

What kite and in what size? You said it's new, as in brand new from the manufacturer? This is important as the age/hours on the kite will rule out certain possible problems like bridle stretch above the mixer.

Assuming it's a brand new kite and that you've done the mixer test to verify your B and C lengths relative to A, you could loosen Z 40mm and it shouldn't make anything worse - if it makes it better, cool you can probably live with it like that. Like Foilholio said, if you're getting collapse where the leading edge curls inward from the tips, could be that your B and C are too loose and causing too much camber.

If it's an Elf, it shouldn't have heavy bar pressure like you described, so that would also point to Z being tighter than ideal. The new Joker's have the "turbo line" on Z now like the Diablo's do, so if you're used to foil kites without "turbo Z" lines, that might also account for the added pressure you feel.

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Re: Wingtip collapse, Cause and Fixes

Postby SpunMonkey » Mon Jul 18, 2016 3:23 pm

foilholio wrote:The collapse is caused by the profile being too positively/high cambered, like your hand when it is cupped. This can be either caused by the bridles or how the kite is sewn/condition of the fabric. To fix it you need to make it more negatively/reduced/reflexed cambered, think flexing or pulling your hand back. You can do this by either shortening B and/or C, or lengthening Z and or C!. The simplest solution is to just lengthen Z as you already have the adjustment. One thing you have noticed, heavier bar pressure, is a symptom of Z being shorter/tighter. This is because of the pulley setup, all force on Z goes directly to the bar. Z being tighter also makes the kite higher camber which also moves the center of pressure further back while increasing it too, so generating more force further back , i.e. more on C and Z etc, i.e. heavier bar. The reason higher camber causes collapses is because it generates a moment of torque that causes the wing to flip forward. Think the rear of the wing deflecting air down, so newtons law, it wants to do the opposite. A negative camber will do the opposite, wanting to flip backwards ,but because of the towpoint or bridle the kite can't do anything really, except be more stable and perhaps lose some efficiency. You can go into a myriad of ways to alter the kites camber from playing with individual bridles to sewing pleats on the canopy. Best to play with mixer first as it is simple and easy, as I said lengthen Z. You could also look at restretching your bridles. One other thing is the final tension B has when you depower can affect the stability of the kite depowered, you can play with that by either just adjusting B, but that will also change the camber/profile or you can adjust all of BCZ or change the length or put a stopper in the pulley line. Moving that knot attaching Z would eventually affect this. But yes complicated :-), just adjust Z and your problem should be fixed.
Thanks tons for the education!!!

Going to go ahead and ease the Z line, hoping this will correct the issues.

Don't want to say what kind of kite this is as I'm looking to learn how these thing work in general and not get into brand specific tuning and characteristics.

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Re: Wingtip collapse, Cause and Fixes

Postby borist » Thu Jul 21, 2016 9:58 pm

My FS sonic 11 started to collapse wing tips more and more, probably due to wear. I shortened B by about 1 cm. Noticeable improvement :thumb:

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Re: Wingtip collapse, Cause and Fixes

Postby windrider1 » Fri Jul 22, 2016 12:14 am

All the high aspect ratio kites have tip tuck some more than others its just part of having a thin profiled kite. now if this happens every session then may be something needs to be adjusted. but dont expect to completely get rid of it.

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Re: Wingtip collapse, Cause and Fixes

Postby Jzh_perth » Fri Jul 22, 2016 3:53 am

logsdon wrote:Have this problem on my Sonic 11m out of the bag. Messed with the bridle some and will see hopefully on Tuesday if I fix it. Which kite is doing this to you? I want to see if this is a regular occurring thing on certain kite models.
I've had many customers with Sonic's now and it's critical that you have the correct front / rear line lengths. Sounds like you have a brand new kite - I assume a new bar aswell ? After about 10 flying hours your rear lines will have shrunk and you'll need to lengthen by a knot or so under the bar floats. This is normal.

If your mixer is not ABCZ all equal, then reset to that. We had a couple delivered slightly out of whack.

Sonic should fly well with neutral mixer, but as others have mentioned you can shorten B / C 1cm at a time to reduce camber and increase stability.

Occasional Lower Wingtip folding when riding deep downwind ( ie foiling) is common, and required careful technique to avoid. Rear line tension here helps.

SpunMonkey
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Re: Wingtip collapse, Cause and Fixes

Postby SpunMonkey » Sat Jul 23, 2016 5:22 pm

Jzh_perth wrote:
Occasional Lower Wingtip folding when riding deep downwind ( ie foiling) is common, and required careful technique to avoid. Rear line tension here helps.

Got out on the kite I was having problems with yesterday, after easing the Z lines 40mm.

Amazing what a difference that made!!! Seldom did the wing tips collapse either standing on the beach and diving the kite to the edge of window or flying downwind. It did happen as you mention above but only slightly. Technique and body posture seem to correct the issue.

Thanks everybody for the help!!


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