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Foil Kite folding in half when going upwind!?

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foilholio
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Re: Foil Kite folding in half when going upwind!?

Postby foilholio » Mon Jul 09, 2018 11:18 am

evan-expert :-)

kitexpert
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Re: Foil Kite folding in half when going upwind!?

Postby kitexpert » Mon Jul 09, 2018 11:24 pm

Good points from evan and foilholio. However also A can shrink and especially in the wingtip area where loads in the lines are smaller and where problems quite often exist. To stretch A may not be elementary fix but it works for front collapse because it relatively decreases B-C length reducing camber.

For sure Z can be too tight, because then B-C are respectively too loose, meaning those areas are pulled too little. I've always adjusted Z for feel and look, and some prefer tighter Z, some looser. I know what I want and there is no problem there.
foilholio wrote: Situation in foil kites exist where bar is pulled in but AoA is reduced.
Really? :roll: :) Single skins can fly further in the WW when slightly sheeted in. This is because when fully depowered there is so much drag from the unsupported and flapping part of the kite.
foilholio wrote: The kite designer has spent much effort finding the correct limit for B
? When depowered kite seeks the AoA in which it wants to settle. If kite is stable enough, it will then fly mostly or fully on A lines, all other line rows are slacking.

The work of designer is to design kite so stable it can be depowered enough. I don't know what "limits" there should be, usually there is no "arbitrary" way to restrict kite AoA range.

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Re: Foil Kite folding in half when going upwind!?

Postby foilholio » Tue Jul 10, 2018 1:03 am

kitexpert wrote:Good points from evan and foilholio.
I mean really? You switch positions just like that?
kitexpert wrote: However also A can shrink and especially in the wingtip area where loads in the lines are smaller and where problems quite often exist.
Yes but you will also find Z will shrink more still in those areas. Effect of A shrink there does though amplify the problem of a shrunken Z. The problem of shrink exists on all lines to kite. It is biggest on the rear of the kite being rear lines and rear bridles. The order of most shrink to least goes simply Z,C,B,A . The shrink would most likely be caused by either lower forces there or less time with force or both. Bridle shrink tends to stay in ratio except for Z. Span wise shrink is an issue, like you mentioned with A.
kitexpert wrote:I've always adjusted Z for feel and look
I mean very LEI there, everything is about looks. Z has a large effect on the performance of a kite, I adjust for this. Biggest change is power and upwind.
kitexpert wrote: Really? :roll: :) Single skins can fly further in the WW when slightly sheeted in. This is because when fully depowered there is so much drag from the unsupported and flapping part of the kite.
I am not talking just about just window change but an AoA reduction where the kite collapses. You are correct that drag changes window position, but I am talking about a kite with Z shorten more than what the designer intended. Like this with bar in kite then collapses. It makes me doubt your experience with foil kites you have not experimented with a very short Z.
kitexpert wrote: I don't know what "limits" there should be, usually there is no "arbitrary" way to restrict kite AoA range.
Airfoil shape, A position, if solely on A and then also B position and then AB length if on A and B ,define AoA minimum. But also Z could be used but not very practical and also drag as you mentioned.

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Re: Foil Kite folding in half when going upwind!?

Postby kitexpert » Tue Jul 10, 2018 8:02 pm

foilholio wrote:I mean really? You switch positions just like that?
I'm not switching anything these things are not black and white. Reasons for problems and cures are quite often complex. However if kite collapses in a situation OP described reducing camber/increasing AoA (limiting lowest AoA) is the fix. There is no harm to do it by stretching A's, and like I wrote effect of it is bigger on wingtips where it is needed usually more.

I've never liked very tight brakes because it makes kite twitchy and increases bar pressure. With tight brakes turning becomes pivotal and even backstally, I like it round and powerful.
foilholio wrote:Like this with bar in kite then collapses.
If this happens there is something very wrong with the kite. Never happened to me. And why on earth kite wouldn't have collapsed earlier, bar sheeted out? Or is kite so bad bar should be sheeted in all the time?
foilholio wrote: doubt your experience with foil kites you have not experimented with a very short Z.
No reason to do that. I have not experimented many other nonsense things.
foilholio wrote: Airfoil shape, A position, if solely on A and then also B position and then AB length if on A and B ,define AoA minimum.
Basic kite design parameters. One of them is by far most important, most crucial, others just more or less fine tuning (within sane values). This defined minimum is not a design goal, but a result of chosen parameters (which should be of course in harmony with general type and intended use of kite).

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Re: Foil Kite folding in half when going upwind!?

Postby PullStrings » Tue Jul 10, 2018 9:22 pm

Hey Cornholio
Foil easily folds in half.........get yourself a good LEI........no more Z this and Z that

Image

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Re: Foil Kite folding in half when going upwind!?

Postby Nash556 » Wed Jul 11, 2018 12:40 pm

Ok guys thanks again. What I've decided to do seeing as the kite is only a couple of months old. I am going to revert back to the original knot settings, which I am assuming is the factory default. (Luckily I took photos prior to changes made). It was only when I changed from the factory settings to those recommended on the card that this issue started to occur. See attached pics
Attachments
IMG_20180524_190913872.jpg
IMG_20180524_190356873.jpg

foilholio
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Re: Foil Kite folding in half when going upwind!?

Postby foilholio » Wed Jul 11, 2018 11:50 pm

Makes sense, if that is what caused the problem. A bit of explanation for you is mixers shrink to reduce camber and be more stable. When you level them kite increases camber and becomes more unstable. Mixer shrink actually works to counter the Z shrink at the kite.

Also you really need to compare with Z to work out what is going on.

The photo you show looks like B is about -1.5cm and C -3cm, which means less camber and more stable. You could level them and lengthen Z 6cm to get the same effect, but better AB limit. As is your AB limit will be reduced and most likely reducing range and low end. For that you will need to lengthen beyond level and Z even more.

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Re: Foil Kite folding in half when going upwind!?

Postby kitexpert » Thu Jul 12, 2018 6:06 pm

foilholio wrote:
Wed Jul 11, 2018 11:50 pm
You could level them and lengthen Z 6cm to get the same effect,...
No. Lenghtening Z can't affect A - BC relation. If you want to adjust A-B relation you must do it between A and B. If you take Z completely away A-B-C are still pulled like before and also presets they had (mixer adjustment positions/designed bridle lengths) of course remain the same.

If you do like foilholio suggest kite will have higher camber A-B-C area and looser brakes - not sensible and not at all same situation like it is in the picture.

Mixer setup in the picture is a good starting point to try to fix front stalling.
foilholio wrote:
Wed Jul 11, 2018 11:50 pm
...but better AB limit. As is your AB limit will be reduced and most likely reducing range and low end. For that you will need to lengthen beyond level and Z even more.
It makes no sense to worry about some lost depower if kite is so unstable it collapses during the normal use. Some acceptable setup for stability must be found, then depower is what it is for that kite.

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Re: Foil Kite folding in half when going upwind!?

Postby PullStrings » Thu Jul 12, 2018 8:05 pm

Smart readers should only trust kitexpert on this forum

foilholio
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Re: Foil Kite folding in half when going upwind!?

Postby foilholio » Fri Jul 13, 2018 2:05 am

Well then you are both idiots.

What kit"not"expert wrote in that post is complete nonsense.
kit expert wrote:No. Lenghtening Z can't affect A - BC relation.
Of course it does. How can you be so stupid.
kit expert wrote:It makes no sense to worry about some lost depower
Everyone should worry about lost depower, it is not just lost depower but lost range. The kite will stall in the window at higher wind(at lowend) with B not slack enough. It's also the reason users like Pullstrings can't understand how foils fly in 1-2knots. If kite is not tuned correctly this is not going to happen. Because of companies like Flysurfer and stupid people like you giving out this advice no one actually fixes the AB relationship correctly.


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