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I need convincing too:) Bar back lines!

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downunder
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I need convincing too:) Bar back lines!

Postby downunder » Sun Apr 22, 2018 1:21 pm

Ok gents,

what is your opinion on back lines strength? I think, the less bar pressure, the less weight we pulling! But how much really?

Which means, why would anyone test the bar strength with 150-200 KG weight on the back lines? When can this weight happen, ie when looping?

Thoughts?

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Re: I need convincing too:) Bar back lines!

Postby edt » Sun Apr 22, 2018 2:32 pm

rears take between 5% foil kites just riding and 50% unhooked tricks. there are ways to load up the rears in a crash that will snap them or the bar.

There's no point in over engineering a control bar because if you do that just means something else fails, either a line snaps, attachment rips off the kite, pulley fails. You engineer it up to just strong enough.

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Re: I need convincing too:) Bar back lines!

Postby downunder » Sun Apr 22, 2018 2:56 pm

Ok,

Fair enough, 5% of what? :)

A lot of it depends on rider weight right? So, atm we have 'one size fits all'...

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Re: I need convincing too:) Bar back lines!

Postby Matteo V » Sun Apr 22, 2018 3:31 pm

downunder wrote:
Sun Apr 22, 2018 2:56 pm
Fair enough, 5% of what? :)

A lot of it depends on rider weight right? So, atm we have 'one size fits all'...
5% of total pull of the system - 5kg goes to the back lines (what you feel in your arms) and 95kg goes to your harness through the front lines. The exceptions noted by edt are very much valid. I rarely unhook, but have unevenly stretched a rear line when it loaded up in a botched unassisted launch. So you do need the strength there.

But why you really want some stronger lines in the back is not for strength, but rather thickness. Thickness can increase longevity via better (point) wear characteristics. Thickness also gives you something to hold on to by reducing the likelihood of getting cut. 100kg Dyneema will slice you at a lower pull than 300kg Dyneema. Think cheese cutter.

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Re: I need convincing too:) Bar back lines!

Postby BWD » Sun Apr 22, 2018 3:36 pm

With 12 strand braids of sk75, sk99 used normally, keep in mind all the strands are exposed so wear and is a key factor in the apparent over specification of 300-400kg lines. If you could find a lighter sleeved line with core protected maybe you could go weaker strength with less durability loss. But would such a line actually be lighter and thinner? Or just weaker?
Just as a reference point though I recently found after a session an older, lighter back line (150-200kg?) I have had been abraded/cut to only three strands out of the original eight! It was a light wind, no jumps session! 8-10 knots, surfboard, 80kg rider.
I’ll be retiring that line...

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Re: I need convincing too:) Bar back lines!

Postby jakemoore » Sun Apr 22, 2018 3:59 pm

I'm using 300 lb q-power on the rears and 600 lb on the fronts. This is for light wind hydrofoiling with 30m lines. Its quite thin.

I have used 200 lb (90 kg) on a bar set up for my then 60 lb kid to buggy with. I broke a line buggying with it myself. I can't remember if it was 200 x 4 or 200 rear 300 front and I can't remember if it was a front or rear line I broke.

Here are the key questions:

What kite and how is the bar pressure?
How many pull ups can you do?
How many one armed pull ups?
How bad would it be to break a rear line?

If you are at risk for falling from a dangerous height, a long swim, or twisting deathloop kite-mare or tangling somebody else who is riding in close proximity then the need to over-engineer increases.

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Re: I need convincing too:) Bar back lines!

Postby ShaveTheWhales » Sun Apr 22, 2018 11:07 pm

This is what your after, most lines are over hyped as proven when put under industry standard tests by rope manufacturers.
I agree that sudden load pressure has the potential to snap or weaken a line, only to Fail some other time. Don't forget- every time you loop or downloop your kite, the lines twist and cause abrasion..
I let mine wear to a point, then reverse them to the kite end for some longevity..

I feel safe if I have a very strong bar and lines - things get a little scary when in big storms going very high and looping. It really hurts if you drop wrong.

https://youtu.be/5w-fyN7wjN4

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Re: I need convincing too:) Bar back lines!

Postby downunder » Mon Apr 23, 2018 2:41 am

Matteo V wrote:
Sun Apr 22, 2018 3:31 pm
downunder wrote:
Sun Apr 22, 2018 2:56 pm
Fair enough, 5% of what? :)

A lot of it depends on rider weight right? So, atm we have 'one size fits all'...
5% of total pull of the system - 5kg goes to the back lines (what you feel in your arms) and 95kg goes to your harness through the front lines. The exceptions noted by edt are very much valid. I rarely unhook, but have unevenly stretched a rear line when it loaded up in a botched unassisted launch. So you do need the strength there.

But why you really want some stronger lines in the back is not for strength, but rather thickness. Thickness can increase longevity via better (point) wear characteristics. Thickness also gives you something to hold on to by reducing the likelihood of getting cut. 100kg Dyneema will slice you at a lower pull than 300kg Dyneema. Think cheese cutter.
95kg is the rider weight?

This means he's pulling ~5kg. Same percentage, the 60kg rider is puling what? 3kg? Yep, sounds ok with low bar pressure.

Now, the foil kite has even less pressure. I would say 1-2kg. Light foiling on a HF with a foil? Same token, 0.5-1kg?

Depending on the location, one might never need thick lines. Also, the back lines are quite thick near the bar for holding, so not a problem for the rider.

Sure, a super thin lines can do a lot of damages but we need to put this into perspective of the sport.

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Re: I need convincing too:) Bar back lines!

Postby downunder » Mon Apr 23, 2018 2:54 am

jakemoore wrote:
Sun Apr 22, 2018 3:59 pm

Here are the key questions:

What kite and how is the bar pressure?
How many pull ups can you do?
How many one armed pull ups?
How bad would it be to break a rear line?

If you are at risk for falling from a dangerous height, a long swim, or twisting deathloop kite-mare or tangling somebody else who is riding in close proximity then the need to over-engineer increases.
Don't really see relevance in questions? :) The bar pressure is irrelevant coz at this stage we have no clue what bar pressure is translating to. It's just a 'guesstimate', no real data exist. Or does it.

We have no idea what line thickness does as a 'parasitic' drag either. It's just a guesstimate. That's another topic anyway.

The bladder can explode, and drop you like a rock from a sky. No inspection can prevent this and can be a brand new kite.

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Re: I need convincing too:) Bar back lines!

Postby downunder » Mon Apr 23, 2018 3:06 am

ShaveTheWhales wrote:
Sun Apr 22, 2018 11:07 pm
This is what your after, most lines are over hyped as proven when put under industry standard tests by rope manufacturers.
I agree that sudden load pressure has the potential to snap or weaken a line, only to Fail some other time. Don't forget- every time you loop or downloop your kite, the lines twist and cause abrasion..
I let mine wear to a point, then reverse them to the kite end for some longevity..

I feel safe if I have a very strong bar and lines - things get a little scary when in big storms going very high and looping. It really hurts if you drop wrong.

https://youtu.be/5w-fyN7wjN4
STW, yes, me to using lines max two seasons. But that's not the point. The back lines will slightly abrade only if the bar is not rotated immediately.

The question is why we have 'one size fits all'? Sure, I understand the industry, proven concepts at.al but that's not the answer and still need convincing. If the lines stretch, sure enough, replace it every now and than (providing they are cheap).

For me, after me LE bladder explosion, I question putting a lot of faith into the back lines or the bar itself. It's a false security.


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