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Changing Mixer Line Length

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foilholio
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Re: Changing Mixer Line Length

Postby foilholio » Fri Jul 12, 2019 7:37 pm

PugetSoundKiter wrote: I was going to try and take the higher AR Aurora2 and make it more stable. Hoping to have a better upwind angle kite than the A15, in a smaller size, and easy riding for hydrofoil use.
Making it more stable is as simple as extending Z. You can get more involved and say extend more of the tip area of Z. Which will improve upwind even more. My mod improves upwind on the A15 too and involves extending Z at the tip. An 18m has quite limited range with a hydrofoil, low end is very good though.
PugetSoundKiter wrote: when I would sheet out with my long throw bar, the kite would recover from the back stall and shoot too far forward, I suspect due to the high camber/lift.
That is what high camber does. It causes the kite to rotate LE forward/down and reduce AoA and so fly forward. Doesn't help the rotation will cause a collapse too, as it is towards the lines and not away like low or negative camber.
PugetSoundKiter wrote: I’m going to follow your suggestion and go back the original A length and lengthen Z instead and then then make an adjustment to C as needed
Good you will find it works well. When you want to increase the depower and keep the ratio between ABCZ the same you will need to lengthen all BCZ together in ratio.
PugetSoundKiter wrote: So I’ve updated the diagrams:
- Changing Z line
- Changing A line
- Shrinking B pulley line
- Shrinking C pulley line
Only error is still in Z diagram. It doesn't change depower, well unless changed extremely.
kitexpert wrote: main reason for mixer tweaking is to correct changes which have happened because lines (pulley lines, bridle) have shrunk.
It should be to alter the kites behavior. Correcting for pulley length with say a level mixer like Flysurfer advise will usually make a kite fly wrong because of other bridle changes.
kitexpert wrote: Original factory settings are carefully designed and adjusted for the best general behavior of the kite (stability, performance).
The problem with original bridle lengths is they were designed for original canopy condition, which on an aged kites is not exact anymore.
kitexpert wrote: Then all line rows are level, canopy is clean and well supported. Kite air foil shape is kept original while kite changes AoA when kiter sheets in/out (with the possible small effect of line row locations).
I think there is many potential possibilities, some of them good to have the canopy distort for some of the sheet range. With this you have a mixed airfoil. Trick is how much and when. It seriously complicates foil kite design. Flysurfer seems to have explored it the most and given up on the more extreme implementations. Performance in a regard is certainly hindered by not keeping the skin smooth, but performance is not 1 dimensional.

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Re: Changing Mixer Line Length

Postby kitexpert » Sat Jul 13, 2019 11:31 am

foilholio wrote: I think there is many potential possibilities, some of them good to have the canopy distort for some of the sheet range. With this you have a mixed airfoil. Trick is how much and when. It seriously complicates foil kite design. Flysurfer seems to have explored it the most and given up on the more extreme implementations. Performance in a regard is certainly hindered by not keeping the skin smooth, but performance is not 1 dimensional.
That is correct. But it is a bit weird approach to distort canopy when great work has been done to design airfoil, cell shapes (incl. billowing), bridle, inner structures, LE stiffeners etc. to match precisely each other to keep canopy as clean as possible.

Most used and appropriate method to distort canopy is to increase camber when powered up. Then kite sits deep in the WW and maximum lift and resistance to backstall is needed, increased drag doesn't matter then much if at all.

To have to decrease camber by having more pull on B-C suggests there is stability issues with the design itself, usually meaning kite has too much camber in its airfoil.

It should be remembered that airfoils with different cambers do have quite different shapes, and comparable difference exist in every part of finished kites. For example if you had a high camber kite and you would like to convert it to stable depowerable kite by replacing profiles (ribs), you would find out that new low camber profiles (with same chord and thickness and other parameters) don't fit to old skins at all: lower skin appears to be too short, upper skin is too long and also both have wrong shapes by the chord. Also D-ribs and straps are of different lengths and shapes.

So it is not possible to adjust a stable depower kite to a high lift kite or vice versa. Fine tuning of bridle and mixer is possible and also necessary.
foilholio wrote: The problem with original bridle lengths is they were designed for original canopy condition, which on an aged kites is not exact anymore.
Main problem is that lines don't keep their lengths. If canopy has lost its shape kite is too far gone, and before that it very probably has lost its air tightness.

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Re: Changing Mixer Line Length

Postby foilholio » Sun Jul 14, 2019 2:27 am

I have seen some foil kites with some unbelievable amount of use. In one case the canopy had lost maybe 90% of it's color. It's a testament to truly how durable foil kites are. Having recoated porous kites and tuned many kites many times for many reasons, I can say a worn canopy is far from the end of the possible life of a foil kite.

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Re: Changing Mixer Line Length

Postby HALF » Sun Jul 14, 2019 10:12 am

foilholio wrote:
Fri Jul 12, 2019 7:37 pm
Correcting for pulley length with say a level mixer like Flysurfer advise will usually make a kite fly wrong because of other bridle changes.
Does the long mixer test introduced in the soul account for these changes?

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Re: Changing Mixer Line Length

Postby foilholio » Sun Jul 14, 2019 11:34 am

Yes a long mixer test should somewhat account for them, except for spanwise changes and changes to the B limit. A long mixer test is certainly a good way to go at trying to resolve some issues. Personally my go to is always Z, correct for B limit at a level mixer then adjust Z. Playing with B and C is too complicated.

Also the long mixer test is not new, but been around since a long time now. I have till now never done it :-) I would suggest my full mixer test if all other things fail you which they shouldn't, but you will only address some things completely by mostly correcting all the bridles. Secret I think to that was reducing the measuring force to as little as possible.

Also "Playing with B and C is too complicated." just reminded of something PugetSoundKiter said.
PugetSoundKiter wrote: I’m going to follow your suggestion and go back the original A length and lengthen Z instead and then then make an adjustment to C as needed.
Making sole adjustments to C on flysurfer mixers is a PAIN. You adjust C and then you need to adjust B back. B is super sensitive, 2.5mm on B is like 1cm on Z. You can get 2.5mm from the loops in the rings tightening. Honestly I am no longer a fan of the flysurfer mixer. They could do much better.

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PugetSoundKiter
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Re: Changing Mixer Line Length

Postby PugetSoundKiter » Thu Sep 05, 2019 7:56 pm

I haven’t tamed my 10m Aurora2 yet, still trying tho. Still hopeful as I’ve seen posts and videos of others having success with it [<link1>]. With the 8m Aurora2 I was able to make it useable for landboarding in light winds by lengthen A about 3in [<link2>]. Useable meaning power is on/off with little depower, but at full throw the kite does not overfly. In light winds I can handle/direct the kite out of other situations, but the overfly luff is dangerous landboarding and irritating in the water.

I returned the kite to the original lines and lengths and then extended the Z-Line with very closely knotted pigtails. For each knot Z was extended, C was shortened 0.5in and B was shortened about 0.25in. I flew it at a knot that had C shortened an 1.5in and B 0.75in and noticed eliminating the overfly was not solved, the center row of C-bridles were pulling the canopy hard enough to distort the fabric, and the trailing edge middle of the kite from C-to-Z was hardly inflated, maybe due to Z being longer and C being shorter. Quick turning would fold the wingtip too. Anyway, I decided that this was probably going in the wrong direction for trying to improve stability/performance.

I returned it to original lines/settings, removing the Z extension pigtails. Out of curiosity I tied one knot in the Z line where it is sewn/doubled to see how this flies with slightly shorter Zs. I have been flying my tests in winds under 15mph, I’m going to wait for an over 15mph day to do the next tests. It may be the case that the smaller size Aurora2s work best in higher winds and avoiding the zenith position especially if depowered (but in <link1> above it looked ok). I had a 5m Montana1 that was like this, useable but not user friendly…

Rereading the earlier posts I see kitexpert’s point that adjusting the mixer and/or bridle lines can only do so much. If the kite bridles are too different than the original design then distortion to the skins, ribs, and wing-shape will lead to diminishing returns in performance, stability, and load distributions which may cause tearing.

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Re: Changing Mixer Line Length

Postby foilholio » Fri Sep 06, 2019 12:43 am

PugetSoundKiter wrote: With the 8m Aurora2 I was able to make it useable for landboarding in light winds by lengthen A about 3in
PugetSoundKiter wrote: Useable meaning power is on/off with little depower, but at full throw the kite does not overfly
When you lengthen A other than profile change you are largely limiting the depower. 3 inch lengthen of A = 3inch shorter B = 4x3inch less depower so 12inches of lost depower. Foil kites go upwind and jump float so well because of their efficient good lift to drag ratio, they also overfly for the same reason. It is very very difficult to have a kite that is both very efficient and doesn't over fly. Some kites mainly LEIs seem to achieve less overflying through allowing part of the kite to flap when full depower, or having a wide tube or thick airfoil to slow them down or just having more AoA when depowered. Rarer kites will become more C shaped depowered. Seemingly though anything that reduces overly increases drag and reduces performance. The compromise with foil kites is to manually increase the AoA with the bar or trimmer so to prevent overflying.
PugetSoundKiter wrote: For each knot Z was extended, C was shortened 0.5in and B was shortened about 0.25in.
Are you adjusting just Z or C and B as well?
PugetSoundKiter wrote: I flew it at a knot that had C shortened an 1.5in and B 0.75in and noticed eliminating the overfly was not solved,
To get the same effect as extending A 3in without altering it you would need to EXTEND BOTH, Z 12in(!!!) and C 6in(!!!), and then limit your depower throw by 12in(!!!) ( this would need to be 12inch measured at the kite not necessarily the bar). These are crazy numbers and widely different to what you had adjusted.
PugetSoundKiter wrote: the center row of C-bridles were pulling the canopy hard enough to distort the fabric
That will happen with some adjustments. There is a period of play on most foil kites where just B is pulled, this will distort the canopy a bit. The sole engagement of B is how a foil kite can have good control and stability with less pull, i.e. when depowered. This is partially why your setting of extending A 3inch is so effective, because it will engage B 3inches shorter, giving more stability. The rest is the limit on the depower but you could just do that at the bar or trimmer.
PugetSoundKiter wrote: the trailing edge middle of the kite from C-to-Z was hardly inflated
That is not right, maybe give a vid of that. You may have a tear or other hole somewhere.
PugetSoundKiter wrote:see how this flies with slightly shorter Zs
More power, usually less efficient if tuned from a good efficiency and always less stable. Good to get a feel for things.
PugetSoundKiter wrote: avoiding the zenith position especially if depowered
Zenith is the most stable place to put a foil kite especially when depowered. And not just overhead but DIRECTLY overhead. In this position the kite is evenly balanced and has the best chance to hold it's shape with no line tension, I use it all the time surfing with the kite. Now it may not be the safest all the time, so use digression, and I will put a kite low if I think I might get lofted but in general 95-98% of the time it is overhead. Your weight is more effective against it overhead too, there is some very bad situations to get dragged sideways, rocks etc and then you can easily lose control of the kite. Having a kite low is not as safe as it is made out to be. You can with skill fly easily through a loft. Oh and you can get lofted with a kite low, with no hope of landing softly. Many people have been hurt like this.

I think given you are maybe uncomfortable with zenith and have trouble with controlling the kite you mainly need more experience with foil kites?
PugetSoundKiter wrote: Rereading the earlier posts I see kitexpert’s point that adjusting the mixer and/or bridle lines can only do so much.
Understanding him exactly can be difficult at times. When he says like that he assumes all kites are tuned to manufacture exactness and given the effort that the maker has put into coming up with those lengths then no one can do better. There is a few glaring holes in that position. First no kite is like the maker intended not even the makers kites. Bridles lines and fabric are such tricky things that they are constantly changing even just a little even as they fly. It is impossible for the maker to absolutely predict and account for everything. The makers have put effort to solve these but I think we will always to some degree be here. Secondly as much as with kitexperts head up his own ass, kite makers are not perfect. They do not in reality spend a lot of time on a single kite, given how many models and prototypes they have to make. It is much easier for the owner of a kite to spend exponentially more time testing and tweaking a single kite, exploring even the most minute things. Thirdly kite makes will design a kite to a specific use or even for maybe themselves but most likely a team rider or riders. It is likely you are similar to this design given your ownership of that particularly kite, but it is also possible your use is slightly different or even quite different from what they designed it for. So for you you could find changing the setup of the kite or even bar to be more suiting to your individual style. For me as an example I like high performance like high AR but also like to surf... leaves me with mid AR chasing more performance.
PugetSoundKiter wrote: If the kite bridles are too different than the original design then distortion
Even original design will distort the wing, particularly as the wing tapers and AoA increase more at the tip than center. There is is advantages to distorting the shape particularly for a kite that is more stable when depowered, or has more range. There is performance negatives to distortions sure, you can pull some of the makers designed distortions like at the tips out and get more performance. But then like with the A15 you can remove all the C bridles and you get slightly more distortions but performance actually increases, I guess from the reduction of drag from all that reduced bridle.

Kitexpert has a very myopic view (or at least his posts express it like that) of kites. It is that kites can only be used a certain way and they should only be designed a certain way. The designs should have internal structures a certain way and bridles a certain way. The bridles and kite structure should always maintain harmony never deviating at all from each other. Sounds great? sounds like something hilter or stalin or any of the famous society engineers. Well in practice things that sound great ain't always that great. Maybe bring those names in are too much but with kites some of the most advance and in my mind interesting and best ones have gone against that, and so too it is with societies .

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Re: Changing Mixer Line Length

Postby PugetSoundKiter » Fri Sep 06, 2019 11:59 pm

foilholio wrote:
Fri Sep 06, 2019 12:43 am
PugetSoundKiter wrote: For each knot Z was extended, C was shortened 0.5in and B was shortened about 0.25in.
Are you adjusting just Z or C and B as well?
No, only adjusting Z (from original design setting), and then measuring the change in C and B positions (from original design settings)
Z= Not lengthened, C=no change and B=no change (original design setting)
Z= lengthened 1 knot, C=length shortens 0.5” and B=length shortens 0.25”
Z= lengthened 2 knot, C=length shortens 1” and B=length shortens 0.5”
Z= lengthened 3 knot, C=length shortens 1.5” and B=length shortens 0.75”
Z-Pigtail.jpg
Z-Pigtail.jpg (36.25 KiB) Viewed 105 times
foilholio wrote:
Fri Sep 06, 2019 12:43 am
Zenith is the most stable place to put a foil kite especially when depowered.
Not this kite, it overflys. And that is what I hope to remedy.


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