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Vojta

Does somebody have a footage of what happens when kiteline tears?

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The title says it all. I would like to watch a video where a kite line is broken and see what is happening to the kite. Mainly to see how far it is going to travel* and how safe/ dangerous it is.

There is a video where the camera is filming from the falling kite: YT link but I would like to see it from my (kite operator or how we call ourselves) perspective.

 

*I have the knowledge to calculate hit, but you know I'd rather look. And I hesitate to do such an experiment.

 

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I've released a quad freely many times (to demonstrate glide and field recovery),... would that count?

the kite, properly tuned doesn't even need you to flyit  downwind under control!  the point is: don't say you can't get back to your starting area as you've backed-up all over the field.

it should be done with the leading edge facing down, as high as possible in the window and centered. 120 feet of string might get 80 feet of elevation, utterly releasing should net 240 feet of field recovery (glide down wind).  If it does this all by itself~ imagine what you can add by holding the handles and accompanying the kite!!!~

Feel that float, use the glide

 

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Quad line or dual line won't go anywhere if one line breaks. If it's a single line kite or if all of the lines break the kite will travel downwind. How far it goes depends on the strength of the wind, the altitude from which the kite is released, whether the kite is framed or not, where the lines break and if there's enough line dangling to create drag or possibly snag on objects, and probably a few other factors that I haven't thought of. I've had two dual line kites break both lines. Both were parafoils -- a 1.4 and a 2.2 meter. The 1.4 snapped near the handles at an altitude of about 50 feet in a medium-high wind, and traveled about 100 yards before the lines snagged on a bush. The 2.2 lines snapped near the kite in a 35-mph gust at an altitude of about 80 feet and the kite traveled 300 yards and ended up about 50 feet up at the top of a tree.

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Variables that goes into account are known to me. Was just curious on seeing it :)

Hope you managed to safe your kite from the tree somehow.

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Hi There,

Not sure if this is of use. I remembered seeing this video several years ago and was surprised at the speed that the loose kites went away over the sea and the skill of the recovery team.

A flock of Crow kites had their line cut and flew out to sea, only to be rescued by the skillful action nearby fighter kite team.

Kite Rescue 2016 Dieppe

 

An explanation of what happened by Andrew Beattie

"This is fairly cool but I need to explain. The guy in the red jacket was flying a"flock" of bird kites.
A single main line with many smaller lines tied along it, each one of which was connecter to a single bird,
giving the appearance of a flock. The main line was cut and the whole lot went off into the drink in the off-shore wind.
A couple of the kites at the bottom caught in the water, providing enough drag to keep the rest of the kites flying.
Quickly, the flier dashed to the Columbian tent where he recruited some fighter kite fliers for assistance.
Before they had even reached the water, the fighter flyer had manoeuvred his kite out amongst the flock.
By repeatedly spinning the fighter round one of the birds, he snared it and was able to bring the entire flock back to the beach."

 

Comments by the crows' owner.

"Yes the crows were unfortunately cut from the sky about ten foot from their anchor. I was chatting to a fellow kiter when an Indian fighter drifted by us only feet from the ground when my colleague said I think that !*"^! cut your line. At that instant I noticed my line marker tumbling to the ground and the crows floating away towards the sea. I immediately gave chase but they were already in the water five in the water and five flying high dragging the rest out to sea.
Having the fighter competition guys behind us around the arena I ran back up the beach while Sandra stayed at the waters edge I hoped that the Indian guy's I had been talking to earlier were still there and could help. They were not but the Brazilian team were, so I approached one of them for help to retrieve my crows which were now well away from the shore, we had a language problem but that was soon resolved as others in the team were fluent in English and the rescue was on its way.

While the one flying retrieved his head stick Brazilian fighter another ran for some stronger line while another changed the line. With all six in tow one feeding the line off the drum for the flyer by the time we got back to the beach the rescue kite was already 2-3 hundred metre's away and almost on to the crows. At that point I knew my beloved crows were coming back and the rescue kite was manoeuvred into position wrapping around the lines The team then slowly pulled the kites back to shore and very kindly untangled the birds nest of lines and sea weed. After 30 mins all ten crows were aloft. I will always be grateful to my new found friends of the Brazilian fighter competition team they were magnificent and took the top 2 positions in the competition the existing world champ finishing second on the day."

Cheers

Stephen

 

 

 


 

 


 

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37 minutes ago, Caller Stephen said:

Cheers

Stephen

I thought it's pretty crazy that a flock of birds got tangled into kite line and you were pulling them to the shore to help them...

Glad you all teamed up to rescue your kite birds. They look awesome! Did you make them by your own, any chance for a template? :)

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On 5/8/2020 at 7:54 AM, Vojta said:

Mainly to see how far it is going to travel* and how safe/ dangerous it is.

Paul gave a video of one way of intentionally doing it.  

In some orientations the kite falls somewhat slowly in place.  You can do this easily with a quad by trying to reverse too hard (see about 3:55 of this video of one of my practices), or performing an axel with too much of a tug (see about 1:59 of this video of a more recent practice), and the kite tumbles out of the air. Both clips have a few other examples. The kite is basically stationary, or may even come back toward the pilot by a few feet, so travel distance is basically zero. The impact speed is moderately light, unlikely to damage anything or anyone unless there is torque from the tumble.  

In some orientations the kite can travel a LONG way.  The wing is naturally balanced as a glider, and at a guess it probably glides close to 3:1 or even 10:1 in whatever direction was forward.  Heading fully downwind in a proper glide, on 120' lines at the top of the wind window I can imagine it gliding downwind 800 feet in a long, slow glide. The impact at the end would be almost nothing, like any glider. Imagine the landing of a perfectly balanced paper airplane after gliding a long, long way.  Dual line example video showing how to do it.

And that exact glide is leveraged when doing a catch maneuver, forcing the kite to glide directly back to you with a well-timed tug. Again it can potentially travel a long way, all depending on the angle. The impact forces there are usually minor, easily caught with one hand. This time, not me, but clearly demonstrating it repeatedly through the clip.

Perhaps the most dangerous condition from a small kite losing control is a kite slamming directly down.  No videos I can find of an impact but a full-on dive can go quite fast. Kites like the Supersonic can hit 70+ MPH no problem. Revolution advertises the Supersonic as able to reach 0-60 in 1 second. Multiply out the mass times the speed and you've got a substantial impact. While normally they crash into the ground, break some spars, and rip some fabric, if they hit a spectator it could mean some bruises, maybe a broken bone, or possibly losing an eye. 

 

But be aware that the kites in the clip are small, weighing less than a pound, have flexible frames that absorb energy then break, and generally flying in controlled positions.

While those are relatively safe, there are also dangers.

 

Large show kites are much larger and heavier, and more dangerous.  Quickly looking up a few, a 10 meter design weighing 9 kg (20 pounds), a 5 meter kite weighting 6 kg (13 lbs), a large ray design weighing 16 kg (35 lbs). Very large show kites can reach several hundred kg.  In addition to having considerable surface area that can trap and ensnare, they have lines where people can become tangled. Blowing downwind they can even catch the wind again potentially re-launching using a snagged person as the anchor. These kites are potentially dangerous both for falling on people and them becoming trapped, and becoming tangled in the lines as they lose and regain tension, potentially amputating body parts or throwing people into the air.   Sadly there are a few reports of deaths from these every year if you search the news.

Every year there are around 20 or so deaths reported globally from kiteboarding accidents, many involving an accidental or intentional pilot launching followed by a fall. While kiteboarding encourages jumping and dangerous tricks, it's not the only danger. There are plenty of amputated fingertips, fingers, and worse from a kite unexpectedly catching the wind and lines going tight while someone was handling the line. 

I've met several people who have survived major accidents, and known one who died. Others were notable that left memorials were created. It's been a decades but Steve Edeiken's death, a major figure in the kiting world who died at a kite festival during a mishap, serves as an oft-repeated warning. The AKA has an annual award named after him. A sudden gust and getting an ankle caught in the lines lifted him before he fell to his death. Another I know about from decades past, Dean Jordan who organized man-lifting anchored kites and ran some AKA events, nearly died after an accident despite having a safety rig, helmet (which likely saved his life) after a mishap lifted him and violently threw him to the ground. 

And people in India created an entirely new set of dangers with Manja, glass-impregnated line for kite fighting.  Every year many people die from the stuff, many others lose body parts or have serious wounds due to the cutting line. It has spread to a few countries like Brasil. That's not so much danger from the kite itself, so probably not what you're looking for.

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On 5/9/2020 at 7:50 AM, Vojta said:

Variables that goes into account are known to me. Was just curious on seeing it :)

Hope you managed to safe your kite from the tree somehow.

Thanks. I got it out of the tree using a slingshot and a fishing weight attached to a long cord.

If you want to know what happens just disconnect line(s) while flying. Of course, make sure you have lots of open terrain when you do it.

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There's a story in the Spring 2020 issue of the AKA mag that includes a bit about an atmospheric research team flying very high altitude kites and having their 8 meter double conyne's line break at 4000 ft........!!!!

It goes on to say it kept gliding for about 15 min (with payload weight and tether helping to keep it stable) and they were driving around following the kites untethered flight. They were able to see the kite land and it was ok....

bt

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Yeah, the main danger tends to be what can damage, as opposed to what will happen.

The worst case on can happen is pretty severe. The line snaps back at the full breaking strength near a person, who is then hit with a fast velocity whipping cord. The whip puts out an eye, or causes a severe lash. The kite happens to be in a position where it divebombs directly to the ground, striking someone with its full weight at 100 MPH or so.  Or for a large kite, covers a crowd and gets them tangled up in many strings, like a fishing net over a crowd.

The safest that can happen is minimal.  The line snaps at a location far from the ground, and gently drifts to the ground. The kite itself is on a glide position and maintains it the entire time to a soft, gentle landing away from people, roads, or other obstructions. 

Most likely it will be on the safe end of the spectrum, but it cannot be guaranteed.  Mistakes happen, and every year around the globe there are deaths related to kites. Statistically they are safe, but there are real dangers.

The video links show a few of the ideal and mid-case scenarios. I think the harshest on those videos was depowering from inversion while doing a vertical hover, where the leading edge fell like a vertical spear directly to the ground.

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Thank you for commenting. I would never think of some dangers you mentioned. Fortunately I won't have a chance to be in the majority of scenarios mentioned.

Regarding the calm case of a kite just sliding down: I calculated a terminal velocity of a kite v = 3-5 m/s (the maximum falling speed). Meaning a kite in 5 m/s (11,2 mph) wind at height h = 100 m (328 ft) will travel 100-166 m (328-544 ft) downwind :)

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That may be a terminal velocity for one condition, but terminal velocity is could be anything on a huge spectrum. The sail can potentially be in many orientations and conditions. 

Since you discount a glider option -- and a glider orientation can maintain a near-flat gliding profile, not 3-5 m/s -- you're describing where it could act as a parachute. But it could have fabric flapping around, and could even have winds and turbulence lift it temporarily into the air. On the flip side, it could be oriented to have practically no drag from air, cutting through the air like a falling stone.

 

Why are you attempting all these calculations?  I've done some of the math myself a few years ago for a simulator program, and my brother-in-law went into aeronautics and we've talked about it, and this is an area where nearly every equation includes a "fudge factor" which is experimentally obtained. At any moment a kite has a mixture of both laminar flow and turbulent flow, can range from almost zero profile to having a full surface profile, can range from a completely rigid body to a completely soft body, with portions behaving anywhere in between.  And the conditions can change in an instant, a kite fully inflated behaving as a hard body with a narrow profile and laminar flow can depower and become a soft body tumbling with a variable profile and a highly turbulent flow, then it can catch the wind again and revert back to hard body, fixed profile, with a strong laminar flow.

There are formulas giving approximations under a wide range of conditions, but most functions and engineering principles say the only way to know for certain is to try it experimentally.

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5 hours ago, frob said:

Why are you attempting all these calculations? 

Because I don't want to do it experimentally. Or if I do I want to have a prediction first. But mostly I like physics.

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