eswanson
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Hi there,
I just bought some slacklining equipment from a local outdoor shop and am wondering if it is going to be strong enough. I don't plan on highlining or anything, but I really don't want it to snap and whip me in the face. It's a 60-foot stretch of 1-inch tubular webbing, which is what I've used before, so I'm not too worried about that. However, the oval biners I got are only rated to 18 kN, which seems low for climbing grade equipment (even if it is still massively strong). Should I return these biners ASAP, or will I probably be alright?
Thanks!
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marks
 | Posted: June 16th, 2010 Edited: June 16th, 2010 | Quote, Reply |
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eswanson said:
Hi there,
I just bought some slacklining equipment from a local outdoor shop and am wondering if it is going to be strong enough. I don't plan on highlining or anything, but I really don't want it to snap and whip me in the face. It's a 60-foot stretch of 1-inch tubular webbing, which is what I've used before, so I'm not too worried about that. However, the oval biners I got are only rated to 18 kN, which seems low for climbing grade equipment (even if it is still massively strong). Should I return these biners ASAP, or will I probably be alright?
Thanks! |
18 kN is more than you could ever realistically create so I wouldn't worry about it at all. Chances are this is far from the limiting factor (i.e. abrasion on the webbing around the tree will fail well below this). That being said it won't happen. 18 kN is a lot.
Life dependent carabiners (designed to take much more force from big falls etc. are also 18 kN).
Example:
and that's best case scenario. They rarely ever fail when loaded on their minor axes (7 kN).
Now that being said, if you get into high lining: be paranoid and double it all up / equalize.
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eswanson
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Thanks, Mark! That is what I had figured, I was just wondering if I should upgrade for some steel biners, but I think these BD aluminum ones will hold up at least until I get good enough to need an upgrade. After that, three carabiners for my keys!
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NP ya it's not going to be a problem. Most climbing carabiners are listed at a much lower strength than they actually are capable of anyways. - Mark
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kiloyrinim
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I disagree. I could be wrong here, but there is a reason many slacklining kits are sold w/ the 50-60 kN steel biners.
The forces created during slacklining are extremely large because of the extreme angles involved (you are pushing down on the line, it is pulling sideways).This is why 2 bolt anchors should always be built with small (<60 degree) angles above the master point. I didn't run any numbers on this, and they would be simplified and low assuming a static situation, but I think stronger carabiners would be a good idea...
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justinadmin
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I'd use this link as a reference on slackline forces to put it in perspective:
Slackline physics
For shorter lines and simple pulley systems you can get away with lighter gear as the leverage rate changes quickly and the initial tension doesn't need to be as high. With longer lines, you need lots of initial tension to make them usable plus the angles don't change as quickly, so you have a lot of leverage for a longer period of time. Also, with a long high line, you are planning on taking leader falls onto your tether, so the forces generated are higher as well.
18 KN is a little more than 4000 lbs. In the tests they performed in the article, they measured forces at about half of that while performing jump and flip tricks.
The initial tension is somewhere between 3 and 5 KN with a pretty impressive 15:1 and 10kn with a 45:1 pulley system. Assuming you could pull 100 lbs with a 12:1 pulley system (totally ignoring friction in the system) you could get to that number. Most simple short lines are set up with a much simpler system.
Assuming we want our safety margin at 2X our expected load, the ovals are sufficient for short lines and modest tension, but you should plan on upgrading when you get a nicer pulley system.
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