cleaning & anchor safety

What your instructor never taught you. Continuing your education and learning from others. Climbing safety topics and accident/incident discussions.
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mokganjetsi
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cleaning & anchor safety

Post by mokganjetsi »

can't verify the numbers in this picture, but it makes sense to me. what i do see a lot at sport crags is the configuration on the far right - generally safe for static loads of human weight, but considerably weaker than the intended rating (and will decrease in strength as the sling ages). why take the chance?
Cleaning & anchor safety.jpg
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robertbreyer
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Re: cleaning & anchor safety

Post by robertbreyer »

14KN = Force exerted by a 1,400 kg weight. You weigh say 80 kg? So that would be 18 g's. I don't think a human being will survive half that g-force wearing a regular climbing harness - your back and neck will arch and break. 14 KN is still bomber.
Warren G
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Re: cleaning & anchor safety

Post by Warren G »

100% with Robert on this, however, on a practical note girth hitches can get super tight, made worse by the sling stretching. Only other thing is to remember those numbers you read on slings/biners/cables are breaking limits in ideal circumstance, but even a stroke of a pencil over a sling will make it notably weaker.

I would love to see an experiment based on the following: a rope/webbing under tension can break far below its ideal limit if a hard/sharp edge nicks it- you can cut a rope in two with one stroke of a butter knife! I would love to see at what tension the various rope and webbings would break at as this does have a major bearing on climbing.
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hendriks
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Re: cleaning & anchor safety

Post by hendriks »

Have a look here. Some good info from the Rope Access community.

http://www.ropelab.com.au/

Look for the free content, rest requires membership.

A while ago the SAR bunch did some drop tests where a loaded 11mm static rope was cut by about 1.5 strokes of a brick if I remember correctly. Also cut 11mm rope under tension using 6mm prussik cord and was like a hot knife through butter.
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Nic Le Maitre
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Re: cleaning & anchor safety

Post by Nic Le Maitre »

That picture is good for a general idea but weak on the specifics, i.e. the bunching and folding of the slings would make them much weaker than the "ideal" strength indicated. The 112kN is complete BS for instance. Folds and tight turns reduce the strength greatly. Precisely the same reason the larks foot/girth hitch is so much weaker.

Further, larks footing/girth hitching dyneema or spectra will make it break at far lower loads than the rated strength so only do this with nylon slings (the low melting point of dyneema and the friction through the hitch make it break, nylon has a much higher melting point).
Warren G wrote: but even a stroke of a pencil over a sling will make it notably weaker.
Really? Data please.
Warren G wrote:I would love to see an experiment based on the following: a rope/webbing under tension can break far below its ideal limit if a hard/sharp edge nicks it- you can cut a rope in two with one stroke of a butter knife! I would love to see at what tension the various rope and webbings would break at as this does have a major bearing on climbing.
There is a significant difference between cutting a rope that is already under tension (even blunt things will cut it) and cutting/nicking a rope and then putting it under tension. In the first case, the you will be constantly cutting new fibres and make your way through the rope, in the second the same set of remaining fibres are exposed to an increasing load.

After the Todd Skinner accident in the US Black Diamond did some experiments with cutting belay loops to varying degrees. They found that they are super strong even when cut very deeply: http://blackdiamondequipment.com/en/qc- ... loops.html
Happy climbing
Nic
Old Smelly
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Re: cleaning & anchor safety

Post by Old Smelly »

I think the original point is well made - why teach people to use Lark's foot or Girth Hitches when they are as a fact a lot weaker.

There seems to be a total lack of understanding as to why one would do best practice when it comes to gear - so that it always comes through for you and continues to do so over it's entire lifespan. Frankly I am quite happy that I will loop the sling and use a locker and retain the full strength of the sling, instead of deliberately dropping its strength and then getting a surprise when it somehow gets dynamically loaded and fails.

I seem to have this argument with so many people nowadays - why do marginal solutions for things and then argue that the equipment is over designed so it can take it?

Do you honestly think that the Engineers are sitting saying " Let's totally overdesign this thing because everyone are going to be total a**holes and do all sorts of stupid nonsense repeatedly with the gear? - Where does this form of thinking come from? Or are they designing so that the gear will always come through for you when things go horribly wrong and the gear needs to do a little bit more than normal that day? Which one do you think it is?

My rope is a 8.5 single - so I use a device that is rated for a 9.7 single - and my argument is "I tested it and it works" - Stuff you the designer - I know better. Really? Where does that thinking come from?

So lets be honest about this - use the equipment according to specification - in this case do best practice because it ultimately could save your life when things go pear shaped - why compromise because you are lazy or it's your habit (those are the things that will kill you in the outdoors) and understand when you do something that's a compromise that you are compromising.

To me a Larks foot is always a compromise - so it is not in my set of standard practices - I just never use it so that I do not have to wonder if it is right in the current application. That's what I do, but then I always use locking biners on stances...
Really, its not that bad...I think it's my shoes...
Warren G
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Re: cleaning & anchor safety

Post by Warren G »

A few years ago I was researching webbing for slackline kits. A big part of this is the stretch characteristics, and so I would go into a supplier/manufacturer and have them do a destructive test that demonstrated the stretch.

Test one: demonstrated maximum breaking strain.
webbing wrapped around two bars, which are then pulled apart until failure.

Test two (three and four): same as one, but before installing webbing measure a 100mm length on the webbing and mark with two pencil lines. Every 3kn measure the length between the two lines.

We conducted of these experiments on differing webbings but the un-penciled webbing would always break at a lower rate than on test one, typically about 5%, depending by how hard the line was placed (I think), and the strength of the webbing.
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deSouzaFrank
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Re: cleaning & anchor safety

Post by deSouzaFrank »

You guys input on my method of clipping into the anchors would be appreciated.

I use a 6mm accessory cord. Figure 8 to harness with two tails about 1.5m each and tied to locking biners with fishermans knots?

Would the fishermans knot have the same effect as the larks foot?
Should I rather change the fishermans to figure eights, or should I abandon this method entirely?
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henkg
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Re: cleaning & anchor safety

Post by henkg »

Frank, there seems to be redundancy in your system, but it is A-typical.

Do you tie the figure of 8 through both loops on your harness or to the belay loop? If to the belay loop, this can lead to exactly the problems Todd Skinner had. Your belay loop should be free to rotate and not tied indefinitely at the same spot.

There is a way of cleaning anchors where you never exit the rope system. If you do this, your sling system is only a back up.
You may still be here tomorrow, but your dreams may not. Cat Stevens
mokganjetsi
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Re: cleaning & anchor safety

Post by mokganjetsi »

henkg wrote:here is a way of cleaning anchors where you never exit the rope system. If you do this, your sling system is only a back up.
Like! :thumleft:
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henkg
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Re: cleaning & anchor safety

Post by henkg »

Daisy chains are always larks footed. Not?
You may still be here tomorrow, but your dreams may not. Cat Stevens
Old Smelly
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Re: cleaning & anchor safety

Post by Old Smelly »

And that is why Daisy chains are only really for AID climbing.

The real point is that of course you can larks foot to your cleaning slings -as long as you only use them for cleaning. Your body weight statically loaded onto slings that are rated at 28 Kn but reduced to 14KN is fine.

The moment they are used as part of an anchor system i.e. you belay off them - for a top rope or for a leader leading away from you then this a really BAD system - sort of on the level of a Darwin award scale. It will look ok and may work ok BUT as soon as things go pear shaped and you are pulled in a funny direction due to a leader fall - well you stand to lose more than just the smile on your face...
Really, its not that bad...I think it's my shoes...
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Nic Le Maitre
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Re: cleaning & anchor safety

Post by Nic Le Maitre »

Warren G wrote:Test two (three and four): same as one, but before installing webbing measure a 100mm length on the webbing and mark with two pencil lines. Every 3kn measure the length between the two lines.

We conducted of these experiments on differing webbings but the un-penciled webbing would always break at a lower rate than on test one, typically about 5%, depending by how hard the line was placed (I think), and the strength of the webbing.
Ok, thanks for letting me know. That's really interesting and I'll look into it more
Happy climbing
Nic
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Nic Le Maitre
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Re: cleaning & anchor safety

Post by Nic Le Maitre »

deSouzaFrank wrote:You guys input on my method of clipping into the anchors would be appreciated.

I use a 6mm accessory cord. Figure 8 to harness with two tails about 1.5m each and tied to locking biners with fishermans knots?

Would the fishermans knot have the same effect as the larks foot?
Should I rather change the fishermans to figure eights, or should I abandon this method entirely?
Knotting rope weakens it for the same reason that folding, bunching, pinching, larks footing, etc, slings weakens them. The fibers are strongest when straight, forcing them through tight bends is what weakens them. A knot weakens a rope up to about 50% of the rated strength depending on the knot. 6mm cord is about 12kN rated so your's is now about 6kN, worst case. If you're happy with that (and I would be fine with it myself for a sport climbing cow's tail) then go for it.
Happy climbing
Nic
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