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Funalex ,Why Kites are Unstable and Autozenith

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foilholio
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Funalex ,Why Kites are Unstable and Autozenith

Postby foilholio » Sun Dec 06, 2015 1:25 pm

I just spent a good part of the day reading through 3 years of Funalex's posts on tubelesskite forum. His epic adjustments to the Pansh Aurora lead me to do it. And it seems it was well worth it. I uncovered a treasure trove of information and was lead to places I had interest in but never fathomed to uncover an understanding.

I was collating some of the posts but shortly stopped as I became engrossed. I will summarize what I discovered and then post them.

Stability. It's a function of the airfoil, either how it is sewn into the kite, or induced by the bridles.

The more cambered or hollow, as funalex likes to call it, the more torque is created for the wing to collapse. I look at it with modern aerodynamic theory that the strong curvature in the back of the wing down creates a strong upward force on the back of the wing, which acts around the center of gravity to flip the wing forwards.

With a reflex profile you have the opposite. The upward curve at the rear of the wing pushes it down. Causing the front to raise increasing AOA and stability. All seems a bit obvious now. That is how aeroplanes work after all. Elevator up wing goes up, elevator down wing goes down.

The other thing is the AOA, the more AOA the more deep the kite sits with more force to hold it open.

He did also get into discussing the curvature of the wing and how that reduces the amount of AOA the tips need to stay open.

all lead into


http://www.tubelesskite.net/t6767-comme ... nith#81719

http://arcusers.net/viewtopic.php?f=4&t ... nith#p4911

Which is a discussion of how Autozenith works. Basically if the kite has its center of lift infront and above of it's center of gravity it'll autozenith. Peterlynn himself is the source of this info. He goes into length discussing other methods to autozenith. Even discusses dihedral. All very interesting. I may try modifying a kite to have it.

foilholio
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Re: Funalex ,Why Kites are Unstable and Autozenith

Postby foilholio » Sun Dec 06, 2015 1:25 pm

Re: Speed ??3 - 12 and turbulence
Message funalex Thurs, October 17 2013 - 2:25 p.m.

3cm !! I find it just as huge difference !! especially if it is a 12m! but good even if there are gaps that are created, usually you pull the B and C more than standard mixer, and everything works out ...

Re: Speed ??3 - 12 and turbulence
Message funalex Thurs, October 17 2013 - 6:53 p.m.

another way of seeing the setting of a blender ... ABC test must always be aligned, and then what are the barriers that regulate everything, it would also be much simpler than Flysurfer proposes that the brake adjustment .. .car when C are shooting, B also follow, it is rare that ABC no longer aligned, and it would go a lot faster to solve ... and like that in 99% of cases, you loose the brakes to find a stable wing.

Re: Speed ??3 - 12 and turbulence
Message funalex Thurs, October 17 2013 - 8:22 p.m.

which creates a closing torque (jitter), the hollow in the back of the wing, near the trailing edge ... so the length of the brake is the most important of all, but as they can not change it, we play on B and C without understanding why it makes it more stable. If, for example, on an unstable wing, you untie the brakes, you always find a stable wing (and "on" even without B) ... all that to say that the alignment of ABC is not as important as the length of the brakes from the rest of the wing.

Re: Aurora Chez PANSH
Message funalex Thurs, December 12, 2013 - 11:12

you will not be able ... maneuverability and cap are incompatible, it is easy to understand, a handy profile is a hollow profile = bad cape ... and a manageable wing is a wing that remains behind in the window (where she still has enough support on the wind to spin fast), so that less bine cape, since falls short in the window. but in fact if you want to earn course, these are the C to be drawn, and a hair B.

Re: Aurora Chez PANSH
Message funalex Fri, December 13, 2013 - 9:11 p.m.

imotep33 wrote:
I wonder a little how I can optimize my wing over B and C for the rise in pres. if exememple by releasing the B ca not do something like move the center of lift of the wing and wind up better?

making it the best upwind is a flat profile (underside) / convex http://aerodynamique.chez.com/profil1.jpg for it is he who has the best power / drag, so in effect releasing B may seem to be what to do to better caper, but in practice it is too unstable. So you still have a nose round rather to overcome the instability. So you can releasing the B and C draw, it should in theory caper better than the reverse, except it's not run very well. after all that is theoretical, must be seen in the field, each wing is different. (ps: do not take offense, but I hope you do not have a pansh because it is still very limited in when the perf compared with a speed 3 for example). I hope they will eventually evolve, there is not much to do to make a good wing, good not to mention the poor quality of materials anyway.)http: // aerodynamics. in. com / profil1. jpg

Re: Flysurfer Speed ??4 "Lotus" (large) ... here we go :)
Message funalex Fri, December 13, 2013 - 9:33 p.m.

imotep33 wrote:
-the pitiful thing I find is that the video is voi wings that sail callées. there is not an ounce of ammorce of occilation for or how it will run, no person view in the command bar for even that it makes to ride this wing ...

actually me, it suits me well she sails firmly seated in wakestyle less wing moves, the better. good after we see anyway a rider make a kiteloop unhooked 1:20 to dare this is that the wing must run a minimum. but not see the wing. While it is indeed hard to see the differences with S3, for having tested a wing package with different shapes, while generally returns to S3, so if the basic shape is good, so keep it. Then, there are improvements that can be invisible, for example the fact that they have changed the profile can give a lot of surprises, it can bring in stiffness (for the depower) of power, responsiveness ... well, the distribution of B and C on the wing may cm close to some radically change the behavior of the wing, let alone the bridle, which is carément invisible, change a few cm of your flanges to your speed, you quickly understand the impact that can have. I defend ... because I think it's a little early to draw conclusions. images I feel that the twist is not quite the same, but it's so hard to see ... if they already are 25% lighter, it should already be feeling. then for who are eager to see the arrival of two lines, be aware that the paraglider wings fly much faster, and therefore the rigidity is higher, kite, it is difficult to obtain the same pressure and thus the same rigidity with much lower speed.


FLYSURFER SPEED ??4 "LOTUS" (LARGE) ... HERE WE GO :)
standelac wrote:
I just compare the description of the clamping Speed ??3 and 4 speed, c is the same.


false, you have not compared well ... at least for the 12m is not the same, or when you compare that A. there are important differences of more than 3cm negatively on one side and positively on the other side, either 6cm difference, and when we see a small cm mixer setting on the 12m makes it completely unstable, it confirms that this simple can bring many different clamping. in assuming the shape is the same (it is probable, but not certain there too, because the clamping of the drawing does not represent the same as and flat), so what I notice is that: for Whom have not moved ... -they have flattened shape of the arch of B ie they get more central than before, and less on the sides -idem for C -idem for brakes that means a wing with a different twist (less important, much like my mod of pansh) in theory it frees ears to better recharge, while stabilizing the center. depower is doing more by the ears (there will increasingly anyway), it is conceivable that the internal pressure gain lotus tissues allowed to lower the angle of attack of the ears. In theory once lined we dig faster ears that the center, which again is in line with a depower / power by the ears, the effect is significant on power, trust me based on my testing, if hollow ears of a wing it deviates more and pulls harder, but it loses stability, hence the fact that the center is more drawn than before to stabilize it. other details, less hollow wing center with less twisting, it's normally a better ratio power / dragged, so best perfs head to see in high jump, and if once lined it offsets to flatten more than before, so it might want ie less than surbordage also unhooked (which would not displease me). verifying that this observation is true for other sizes in short, all that to say, it's not the same wing, and the lotus fabrics allowed more things than just additional sealing, to say the profile they say they have changed, which is likely, it is very difficult to see, and that all assumptions, including that will be probably false and far from the truth! strongly tested.

Re: How to calculate a complete clamp from scratch?
Message funalex Sat., Feb. 8, 2014 - 12:54

Once you know where the stall fronts and rear assembly points, the rest is rather ... Scientific clamping consists of bisectors bisectors bisectors ... etc more clamping is long and without waterfall, plus c is rigid ... the 'cascades' are there to simplify and reduce the cost. Unfortunately, to determine the timing, determine the 3D pressure center of the wing ... that is where should point bisecting the first, one from which all others depend ... And a few cm near, it Fair! values ??may be known for experienced paraglider designers, who have proven software ... but if your wing is different from what is done, you'll have surprises anyway. generally, the clamping wedge to 30% of the rope, Front groupings is the space of 50% of the projected scale and the clamping length is about 70% of the scale. but in small nuances that recognizes the good wings ... so I know what is too much project, but must not dream, make a good wing on the first try, I think that apart from copying, c ' is not possible.

http://foilivier.free.fr/fr/3d007.htm

http://www.tubelesskite.net/t6484-faire ... sson#77434

Jamie-NYC
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Re: Funalex ,Why Kites are Unstable and Autozenith

Postby Jamie-NYC » Mon Dec 07, 2015 2:20 am

Thanks for posting on this topic - of interest to me since I have just ordered a Pansh a15 18m to compliment an LEI quiver (I want to learn what foil kites are about, and have never seen one in my area, let alone had a chance to fly one). I have done many searches, but cannot find a single source for tuning information - what information there is comes from forums, uncompiled. I can see that there are useful data points in what you have posted, but they are single points on a map, with no path to connect them. Have I missed something - is there a good starting point for basic tuning information?

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Re: Funalex ,Why Kites are Unstable and Autozenith

Postby plummet » Mon Dec 07, 2015 2:32 am

But do you actually want an auto zenith kite?

As convenient as it is.... if you become overpowered and get lofted. There is a chance that the autozenth feature can keep teabagging you to your death.

foilholio
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Re: Funalex ,Why Kites are Unstable and Autozenith

Postby foilholio » Mon Dec 07, 2015 3:31 am

I am getting the 18meter too, we can join a club lol. It's a bit of a worry getting a new pansh model so soon released. But the reviews are good, videos too. The price even better considering I payed full price for my Aurora. Flysurfer would be a much easier foil to start with, but they are much more expensive especially considering you must buy their bar and all and through a distribution chain.

Tuning I have just a little experience ;-) Just ask me anything to explain it further.

There are 2 Strategies with multiple paths. Return the kite to original or modify the kite.

To return the kite to original it is perhaps easiest although not always as possible. The easiest way is to use things like adjustable mixers, to return things to there correct lengths or ratios. The other is to stretch out things that have shrunk, this being more applicable to thin bridles which can be restretched easy. Another way is the measure things and adjust them back to original, very difficult and time consuming. Another way is to adjust the kite in such a way as you think it was original. The last 2 lead more to the next bit.

Modifing the kite. See something your kite is doing that it didn't before or that you don't like? How about we change it. Perhaps the fastest way to get results, and the most permanent, but it requires the most knowledge / intuition. My first post was really about this, understanding it deeper. There is certain behaviors a foil can have and it's causes. The causes can be because of the bridles, the profile of the airfoil, the state of the fabric. The bridles change, they shrink. The airfoil changes too, because of the bridles and the fabric. The fabric stretches/ shrinks get holes in it from damage or age of the water/air tight coating degrading.

We can modify the kite to be original or different. We can change the lengths of the bridle mains ABCZ, length of pulley lines, position of pulley lines. We can change the length of individual bridle lines. We can sew modifications into the kite. We can recoat the kites fabric so it's more air and water tight. The question is do we really want to do all or any of this, or just buy a new kite LOL.

Well the changes all offer different fixes for different or similar problems. With different levels of effort required to implement and levels of change. But by far the easiest is to play with the Main bridle lengths ABCZ. And of them Z is the most important with the greatest effect on the Kite. A tight Z will cause more instability, bar pressure and lift/drag. And a loose one the opposite.

As I was reading from Funalex. Flysurfer has BC adjustments. But what you are really adjusting is the length of Z when you move these outside of normal.

The reasons for Z being so important. One It hardly ever gets used and as such shrinks like crazy. Two it controls the very back of the kite where the very slightest of forces can act easily as a lever on the airfoil.

Then we get into adjusting B. B can be used to restrain the kite making it more stable depowered, but reducing depower.... Which I am now learning about.


I'll leave it at that for now. I don't consider myself an expert and am still learning. But do ask me and I will try to answer. My head is now filled with a fresh understanding.

foilholio
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Re: Funalex ,Why Kites are Unstable and Autozenith

Postby foilholio » Mon Dec 07, 2015 4:07 am

Autozenith is awesome.

Only those who don't have extensive experience with it are scared of it.

There seems to be some extensive false information about safety in this sport for which people still die today.

Personally I have survived with a 16meter venom in 40knot+ squall. Most power I have every experienced with a kite. I left the thing above my head auto zenithing and got tea bagged a lot, up 2 meters and down. Lasted about 5 to 10 minutes. After I rode in. Got within 100meters of land, released packed up on the water and walked in. When I started I quickly worked out that land will kill you much quicker than water, though water can really hurt too nearly been knocked out a couple times. Staying mostly away from land has kept me alive so far. One person who I personally had a disagreement with over this is now dead. I will head out to ocean when the shit hits the fan. I'll release my kite at the slightest hint of being pulled into something solid or near something solid and losing control. ARCs are great kites for flagging, any line will flag the kite. Bridle foils are great too, anything goes wrong they get stuck to the water and or all the air eventually goes out of them. I know foils are unstable in smaller sizes especially, but I have come home from every 40knots outing, most solo kiting. I have seen some absolutely horrific stuff with inflatables. But at the end of the day I am sure you can kill yourself quite easily with a foil. Being aware of the conditions is the most important thing, followed closely by your gear. Your brains are the thing that keeps you going.

I'll add I have land kiting a lot too. I have mostly givin it up as I consider it too dangerous. I don't have may good spots for it too and I enjoy waves much more. I have had some god fun with a nasa wing and a skateboard.

As for autozenith it really makes kiting a lot easier. I really miss it from flying arcs. You can take your hands off relax, hook your kite on your towball and have lunch. Learning to ride in surf, just let go of the bar when your dumped, Kite flies itself ,haha so easy! ARC, bridled foil, inflatables all have different skills/quirks. What I don't miss about ARCs, is needing a kite 50%+ bigger, poor upwind, more difficult relaunch and those sticks my god did I hate them what a nightmare.

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Re: Funalex ,Why Kites are Unstable and Autozenith

Postby Jamie-NYC » Mon Dec 07, 2015 4:36 am

Plummet- "Teabagging you to your death" is one of the great phrases I have read on KiteForum, will be hard to top. I know I don't want the death part. Actually, my reply was much more general, no necessarily about auto-zenith - I know what that is, don't know enough to know if I want it (since it sounds like it might come with some downsides).

Foilholio- Glad to hear there is another intrepid kiter willing to take on the Pansh a15, but you are obviously in a different league than I am, since you already have a Pansh kite, and since you easily thrown around terms like "adjustable mixers" and ABCZ. I have an idea about what these mean (not Z though), but again no reference point. Where did you start? What do I read?

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Re: Funalex ,Why Kites are Unstable and Autozenith

Postby foilholio » Mon Dec 07, 2015 6:32 am

Good start , as I did, is to just play around with the kite. Pansh unfortunately dont have any adjustability built in and youll need to cut things and or tie knots. But hopefully out of the bag the A15 will be fine, fingers crossed.One problem with big kites is having low enough wind to mess around safely.

One thing I will be doing straight away to the A15 is removing the 5th line bridle. If I was riding on land or a beginner I would leave it for some security, easy landing.

Flysurfer has some great videos explaining things, like https://vimeo.com/9488886. http://www.foilzone.com/phpbb3/ is a great forum to search through. There is also http://www.tubelesskite.net/ and http://lesfoilz.com/phpBB3/, chrome with auto translate will help with them.

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Re: Funalex ,Why Kites are Unstable and Autozenith

Postby kitexpert » Tue Dec 08, 2015 11:21 pm

If you Pansh owners want, I can design a new bridle one of those kites. It might be interesting to see what it should look like when properly done. 8)

But I need some measurements to make a model in Surfplan. Area, wingspan, (AR), cell count, A-B-C-D lines positions (% chord), chord lenghts (middle, tip), cell width difference at LE and TE, both center and tip (how much, if any).

Canopy curve, plan view, towpoint, towpoint separation and airfoil shape I can approximate good enough, and check from the pictures.

So a kind of lesson how the bridle is designed. Foilholio?


.

foilholio
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Re: Funalex ,Why Kites are Unstable and Autozenith

Postby foilholio » Wed Dec 09, 2015 12:45 am

Thanks for the offer, I may take it up when I have some time. I am more interested in understanding them better so I can make modifications, much like funalex did to the aurora. If you have any links to material to read like http://foilivier.free.fr/fr/3d007.htm that would be appreciated.


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