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How much tension really is on the lines?

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kite_hh
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How much tension really is on the lines?

Postby kite_hh » Thu Feb 07, 2019 12:00 am

I have been looking at line strength, breaking load and alike. It has all been tested and results are available.

However, I have yet to read about someone measuring the actual tension on lines.

E.g. tension on steering lines and power lines
while holding the kite at 12,
while landing,
when taking off,
when landing,
riding a wave,
going unhooked,
etc.

I know the latter ones (dynamic) may not be easy to get, but the first two are static and can be obtained fairly easy with the right equipment.

It goes without saying that these values depend on wind speed, kite, kite lines, etc. Also the peaks may be way above the average load. Which makes it even more interesting to find out about.

Do you know of a source where I could start to look or maybe even look up those numbers?

Thanks!

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Re: How much tension really is on the lines?

Postby edt » Thu Feb 07, 2019 12:18 am

The last time I saw someone try to measure some of those numbers they had a scale attached to the top of a van and were racing around the parking lot trying to measure this stuff. Suffice to say there's no scientific measurement of those numbers, you'll have to do it yourself if you want them.

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Re: How much tension really is on the lines?

Postby kite_hh » Thu Feb 07, 2019 1:49 am

Well, no scientific measurement is not quite correct.

There is some research going on at the Technical University in Berlin, Germany. ( https://www.mpm.tu-berlin.de/menue/fors ... ruefstand/ )

I found this (short):
https://repository.tudelft.nl/islandora ... J/download

And this paper:
https://www.researchgate.net/publicatio ... rane_Wings

However, it is probably aimed at industrial uses for kites, hence I doubt they will actually test with a person. But maybe elsewhere this idea was or will be taken up?

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Re: How much tension really is on the lines?

Postby downunder » Thu Feb 07, 2019 2:54 am

This was discussed...

Here:

viewtopic.php?f=1&t=2399369

I am riding ultra thin race lines all the time for the last 3.5 years. Same lines, and always wash them after. Sure, I'm 60kg, but I'm also averaging 6-10m jumps, 30-60 per sesh, 100-150 seshs/year, 11m Edge 99% of time. Yesterday scored double front rolls, so 720, imagine that line twisting, plus looping. Doing at least 10 front rolls per sesh, plus loops.

Works for me.

And that forces are not presented in the above article. Hence, doesn't mean much in my books.
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Re: How much tension really is on the lines?

Postby rynhardt » Thu Feb 07, 2019 8:43 am

The dynamics of the system can vary a great deal.
Worst case scenario is all the load being on one line, when hooked in and constrained. And by constrained I mean the rider is edging hard, or his board is submerged, or for some reason he can't be lifted clear).
Under a completely constrained scenario, the loads can keep increasing until the weakest link fails, which may be the lines, harness, kite, bar, etc.

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Re: How much tension really is on the lines?

Postby Peter_Frank » Thu Feb 07, 2019 10:37 am

There was a similar thread earlier, and a post where one had mounted gauges on the lines, and a video when riding and jumping on a TT, while showing the load on the lines simultaneously :thumb:

I am at work now, but if anyone can find a link to that, would be great :rollgrin:

8) Peter
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Re: How much tension really is on the lines?

Postby downunder » Thu Feb 07, 2019 11:35 am

I think I did?!

Or missing something :) There was no jump tho.

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Re: How much tension really is on the lines?

Postby kite_hh » Thu Feb 07, 2019 12:10 pm

Thanks a lot!!

This is the video. Great start!


I will need to look into this and see if they have done more. (Edit: Sadly it seems they have gone out of business. I couldn't find any other information. Their setup seems so simple yet effective.) Also I would be interested how the riders weight, wind strength, kite size, etc. influence the results.

It confirms my impression that the power on the bar needed to pull is not that high. (Whatever that means. :-) )

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Re: How much tension really is on the lines?

Postby alunj » Thu Feb 07, 2019 12:41 pm

Ralf Grosel (Duotone) Seems to be working on measuring this. He is working with TU Berlin and there is a video on his FB page https://www.facebook.com/ralfgroeseldesign
in the video you can see the outputs from the strain gauges
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kite_hh
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Re: How much tension really is on the lines?

Postby kite_hh » Thu Feb 07, 2019 12:47 pm

Great! This seems to confirm the values dimensions of the other video.
Screenshot_20190207-124449.png
Green line probably is the combined tension on the power lines and the lower two lines are the measurements on the steering lines.

I wish they would make the data publicly available.


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