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Zippy8
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Yoyos - the ways kites do them

Fri Oct 17, 2008 4:47 pm

Having recently snagged Andy Phelp's old Next Team Light (daylight robbery :-D ) I'd like to discuss the two paths that kites seem to be able to take in performing a Yoyo. Dunno if I actually have a point with this but it's been something that's been bothering me all week. :P

Exhibit A is the original Next, standard wind range:
Image
It rotates about a point close to the kite itself and the whole kite spins about. It's quick, tight and the lines hook up to the stoppers reliably.

Exhibit B is the Team version, for light winds:
Image
Try as I might (and I have been trying) all I get out of it is a wholly different experience. The centre of rotation is waaaaay distant from the kite and the trajectory is a wide arc that it glides around. It takes a good long time, takes plenty of room and is an absolute pig to reliably hit the stoppers as the lines have plenty of room and time to get lost.

The same sort of thing can be seen with the QPro - fitted with no weight it's solidly in Group B, slap in the (optional) weight kit and it joins in with the far preferable Group A. Of course other stuff gets messed up in the process but that's why it's an option. Is it merely a question of overall mass ? Mass distribution (the Team Light is tail weighted) ? Pixies ?

Mike.
 
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ObijuanKenobe
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Fri Oct 17, 2008 4:56 pm

I just notice that the indicated yoyo rotation is very difficult to pull off, and is something I haven't started practicing.

:P :lol:

obi
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Jest_of_EVE
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Fri Oct 17, 2008 5:04 pm

Try experimenting with tip weights. Their effect can be quite dramatic but due to being lower down, less actual weight is required.

I put them in the Talon UL and they really are small, but remove them and it's back to slooow-yo.

Using them in the vented too because I can't bear the feel of the kite with 30g's in the tail....awful.

Mark
 
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Zippy8
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Fri Oct 17, 2008 5:36 pm

Jest_of_EVE wrote:
Try experimenting with tip weights.

I realise that adding weights would almost certainly change the way the Yoyo took place on the Team Next LW but my Inner Engineer™ still screams at the very thought. :evil: I am also left wondering why a UL should be quite so different. It really is a whole heap o' sky that it takes up, and it is tail weighted already.

I have a few other modern ULs that don't behave quite this way.

Mike.
 
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Fri Oct 17, 2008 6:46 pm

Is the upper spreader the same length? Are the sails the same; is there more billow, tail width, inner standoff placement? What was the question again?
Rob
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Miles F
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Fri Oct 17, 2008 6:52 pm

Has the weight distribution on the UL changed markedly from the Stnd Next due to the sticks in it? To be the same you would need the same centre of gravity so sticks centre of mass versus tail weight must be in the same proportion.

Is the sail shape the same? The critical bit here is the angle of the leading edge panels (altered if the lighter sticks mean the wing tips are pulled in any), these decide the magnitude of the pitching movement at the deep pancake point. The early part of the yoyo gets its impetus from the curvature of the spine and the negative pitch transient of the tail weight.

It might also be that the negative pitch transient (tail looses height before the kite rise nose up) has more effect in the lighter winds in which a UL would fly.

Top of the head stuff this :oops: , I'll have a think about it.
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Zippy8
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Fri Oct 17, 2008 7:29 pm

One thing: I'm talking generics here. The Next and Team Next are quite different kites (which is something I may expand upon elsewhere). The shared name is a total red herring. You might as well call the Nirvana the "Opium Second Edition" as those kites have just as much in common as the two Nexts.

I don't think this is purely "it's a UL, that's what they do" sort of thing. Nor is a "slap more lead up its arse, she'll be right" solution what I'm looking for. It may be more along the lines of drive:carve that was used to describe the different way a kite turns depending on some aero-thingy. I must re-read Mark Cottrell's book on the subject.

Mike.
 
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Fri Oct 17, 2008 7:37 pm

...aren't your arrows pointing the wrong way?
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Fri Oct 17, 2008 7:39 pm

Fiction wrote:
...aren't your arrows pointing the wrong way?


I think that's why he's having so much trouble :lol:

obi
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Miles F
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Fri Oct 17, 2008 8:35 pm

Zippy8 wrote:
I must re-read Mark Cottrell's book on the subject.

Mike.


Very good book btw, accessible without being too lightweight.
A NOHD will be published for the DS in due course, till then wear sunnies.
 
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Sat Oct 18, 2008 2:53 am

Zippy8 wrote:
One thing: I'm talking generics here. The Next and Team Next are quite different kites (which is something I may expand upon elsewhere).


Please do. :)
 
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Zippy8
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Sat Oct 18, 2008 5:46 am

Fiction wrote:
...aren't your arrows pointing the wrong way?

My kites Yoyo in both directions.... :P

However 8-[ for the sake of clarity and the greater good I've redone the piccies. Happy now ?

Mike.
 
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Sat Oct 18, 2008 11:42 am

ah makes perfect sense now ;)


There's you're answer, right there
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Rob
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Zippy8
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Sat Oct 18, 2008 2:19 pm

I've actually just gone and videod the two kites doing a Yoyo Takeoff (Next; successful, Next Team; not so much). and I have overstated matters quite a bit. :oops: The Next does describe a loop but it is simply far tighter. I'm actually moderately gobsmacked that they are so close to each other given the win:fail discrepancy.

Back to mulling this one over.

Mike.
 
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Mark E Mark
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Sat Oct 18, 2008 2:32 pm

Is it perhaps not more related to the ammount of slack required in the two cases. As the kite rotates it also moves backward (well forward - then back) - some more than others. More slack gives more opportunity for too much slack (perhaps)?
Last edited by Mark E Mark on Sat Oct 18, 2008 4:39 pm, edited 2 times in total.