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Bars with PU tubing

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andrewjohn
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Re: Bars with PU tubing

Postby andrewjohn » Sun Nov 03, 2019 11:57 pm

Yep, had depower rope snap on me inside pu tubing. No sign of wear, no sand or anything in there, and it snapped halfway up, nowhere near any area that might promote wear. So I have now changed to a standard, 2 line, no tubing bar.

matth
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Re: Bars with PU tubing

Postby matth » Mon Nov 04, 2019 12:02 am

Is it possible that the rope is rotting inside the tube because it gets little air and never drys out??? and why not use clear tubing so you can see the line??

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GregK
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Re: Bars with PU tubing

Postby GregK » Mon Nov 04, 2019 12:19 am

While sand inside the PU tubing is a sure cause of line wear, I'd like to suggest an additional cause :

Salt ( sodium chloride ) crystals forming from the salt water trapped inside the PU tubing after a session.

I expect most riders wrap the PU tubing around their bar ends and store them wrapped, and few make any effort to flush out salt water from inside that tubing.

I don't like the bends in the PU tubing created by storing it wrapped, so before winding my lines, I'll slide the bar all the way up the tubing, then wrap my lines. When not in use, I hang my bars from the chicken loop, keeping the PU tubing relatively straight.

Wrapping my PU-ccoated-depower-line bars this way also allows me to easily flush the salt water out when I get home, and the hanging allows them to drain fully.

I've had a Ocean Rodeo Shift bar ( big long PU coated centre line ) and several OR Control bars ( typical length PU tubing ) for over two years now of fairly frequent use, both by me and rider demos. Never had a main or safety line inside the PU tubing break. Safety line, which can be drawn in or out looks great, and can only inspect either ends of the main/power line by temporarily shifting the tubing up or down, no significant wear visible their either.

Meanwhile I've repaired loads of PU-coated line breakages for others, many different brands, riders all wrapping the PU tubing.

Something maybe to consider.

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GregK
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Re: Bars with PU tubing

Postby GregK » Mon Nov 04, 2019 12:21 am

matth wrote:
Mon Nov 04, 2019 12:02 am
why not use clear tubing so you can see the line??
UV-resistance, PU doesn't have great UV, the dark, usually black, is likely there to improve UV resistance.

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Re: Bars with PU tubing

Postby Matteo V » Mon Nov 04, 2019 1:24 am

Trent hink wrote:
Sat Nov 02, 2019 5:59 pm
1/8" dyneema has a breaking strength of around 2500 lbs. so it should be adequate.

The extra diameter in unsheathed depower lines is to account for wear.
Every line we use in kiting is oversized mostly for wear, and sometimes for handling (not cutting you as easily).

When normal sized or over sized (300kg to 360kg) front lines get just a bit of wear or get some strands poking out at the splice, you need to replace those lines.

When undersized (less than 300kg) front lines get even extremely difficult to see wear, you may experience a wear break with no prior indication of that wear. So smaller lines that can handle the load brand new, have a shorter wear life, and may break without any warning.


Given that the PU tubing is there to prevent the wear on the depower line, smaller lines can be used safely for a given service life in a given environment.

Unsheathed lines are so big because the wear life in harsh conditions needs to be reasonable. And indicators like a completely broken strand of fibers is not detrimental, but rather an indicator that the safe use life of the lines is over and replacement is needed. So while your depower line may look pretty ratty, it is not going to give out on you immediately. If that same single strand of fibers was broken on a smaller diameter line, the reduction in capacity may be enough to cause unexpected breakage.


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