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mystic stealth bar

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knotwindy
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Re: mystic stealth bar

Postby knotwindy » Mon Oct 28, 2019 4:53 pm

Curious, what problems have you had with two lines?

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Re: mystic stealth bar

Postby elguapo » Mon Oct 28, 2019 5:13 pm

oregonkiter wrote:
Mon Oct 28, 2019 5:22 am
Where did the line break? Center, or where it exists the bar holes, or...?

Thanks much
the center. just snapped right in the middle..
i'll try taking a photo

Two lines sucks. Insert normal thin flying line as core /think splicing/ into the slider line as last resort insurance go home without drama.
interesting.

why do you say 2 lines suck?

i really dont see how even one line that size could get fatigued and break under any type of 'human on a kite' type load.. maybe i could understand if i was on a 21m kite in hurricane winds while trying a tow an oil tanker.
but i was foiling underpowered on a 3m snow kite when the twintippers were rinding 15-17 meters.
i'm thinking of simply using an old sailing line...since i know those lines function and arent just there to look pretty



i actually *almost* was able to get the peak4 re-launched.. but the ozone loop barely fit into that small '2nd' fixed dyneema cord. (so..took a few seconds too long getting re-attached....and i had a nice little swim)

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Re: mystic stealth bar

Postby oregonkiter » Mon Oct 28, 2019 5:40 pm

IMG_3502.JPG
Thanks for information re line break location. My worry has been where they exit bar, because you really can't inspect there. I have about 2.5 months on mine, a lot of hours, foil only. Line looks slightly fuzzy, but noth9ng I would normally worry about.

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Re: mystic stealth bar

Postby tomtom » Mon Oct 28, 2019 5:43 pm

two line sucks because it wont slide as nice as one - two lines is like jam and skid. For sure it will be slider dependent. Im using just 5mm ring /5mm is wire diameter not ring/

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Re: mystic stealth bar

Postby knotwindy » Mon Oct 28, 2019 6:19 pm

tomtom wrote:
Mon Oct 28, 2019 5:43 pm
two line sucks because it wont slide as nice as one - two lines is like jam and skid. For sure it will be slider dependent. Im using just 5mm ring /5mm is wire diameter not ring/
Thanks for the reply. I used to use two lines with one slack so mostly riding on one line with the second line there just in case the tighter line broke, so we use them differently.

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Re: mystic stealth bar

Postby purdyd » Mon Oct 28, 2019 7:02 pm

I think the rope is just something you will have to replace often, I’ve seen far many broken ropes to mess around, I’m on my second rope and will probably change again this winter.

I don’t see anything special about the rope other than it is says it is black dyneema.
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iriejohn
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Re: mystic stealth bar

Postby iriejohn » Mon Oct 28, 2019 8:50 pm

tomtom wrote:
Mon Oct 28, 2019 5:43 pm
two line sucks because it wont slide as nice as one - two lines is like jam and skid. For sure it will be slider dependent. Im using just 5mm ring /5mm is wire diameter not ring/
Two lines will slide just as well as one 5mm line as long as you splice two full lengths of 3.5mm* Dyneema inside each other which gives almost exactly the same total diameter (4.95mm) as a single 5mm rope. Then if the outer breaks you still have the inner.

hth

* I use Marlow Ropes 3.5mm Dyneema.
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Re: mystic stealth bar

Postby purdyd » Tue Oct 29, 2019 5:24 pm

iriejohn wrote:
Mon Oct 28, 2019 8:50 pm
tomtom wrote:
Mon Oct 28, 2019 5:43 pm
two line sucks because it wont slide as nice as one - two lines is like jam and skid. For sure it will be slider dependent. Im using just 5mm ring /5mm is wire diameter not ring/
Two lines will slide just as well as one 5mm line as long as you splice two full lengths of 3.5mm* Dyneema inside each other which gives almost exactly the same total diameter (4.95mm) as a single 5mm rope. Then if the outer breaks you still have the inner.

hth

* I use Marlow Ropes 3.5mm Dyneema.
That is a really good idea.

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Re: mystic stealth bar

Postby Herman » Tue Oct 29, 2019 9:24 pm

With regard to line breaking on sliders you have to bear in mind that you are using what I call a rope lever. The tension in the runner line is considerably higher than that in the centre lines. Been a while since I did any real engineering but a quick look suggests to me that the tension in the runner will be T/2 X 1/sine ∆ where ∆ is the angle subtended by the runner and the line of the 2 attachment points.

For my Dynabar which is ~ 230mm long with a line reaching ~30mm from the line of the attachment 1/sine∆ is ~4. Therefore when my 200lbs is hanging on the harness the tension on the line, neglecting stretch etc, will be 400lbs. This is well within the breaking strain of the line I use, 5+3 dyneema. (Core insert makes it run in my pulley hook better as well as added strength. The outer is grey, core is bright yellow which may help assess or spot wear.)

However if you want to reduce the load use a longer rope to enlarge ∆. Please feel free to check this analysis!

When I do my next replacement I intend to go from 30 to 40mm of runner slack, but this will be for the sake of the way it feels rather than any load consideration.
Last edited by Herman on Wed Oct 30, 2019 5:56 pm, edited 5 times in total.
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Re: mystic stealth bar

Postby purdyd » Tue Oct 29, 2019 10:22 pm

Good point. Looks like tension on rope is force from kite divided by 2 x sine theta.

I hadn’t considered that. A really tight rope will have a fair amount of load.
67360BD3-225B-4C7E-A9BE-A9A06A2902C3.png
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