/ Using cord for a belay, but not in a loop?
Say I have 5 metres of cord for my belay, I normally use it as a loop (connected with a double fishermans) which gives it a usable length of 2.5m. If I use the cord with say, two figure eights at either end connected to the gear, and then equalise where needed I would have much closer to the original 5m I started with.
Question - does that weaken the belay? You would have half the amount of cord running between each knot, but considering it's equalised is that a big deal? Or is it simply safer to run 2 cordelettes to the equalising point?
Well, it weakens the cord part of the belay. Whether it weakens the whole thing depends on whether the cord is the weak point. If it's bomber gear and 5mm cord then it's substantially weakened. If it's marginal gear and 8mm cord it's probably no worse than it was before.
You have half the cord, so half the strength. Cord isn't that strong used as a single strand (although slings would only be 11kN if used in the same fashion). It does presumably have the advantage of being slightly more dynamic than dyneema. How thick is the cord? For Mammut cord, using numbers off the Go Outdoors site, 5mm is 5.5kN, 6mm is 7.5kN, 7mm is 13kN. As a single strand this is always going to be much less than a 22kN sling; the 5mm and 6mm are potentially less than a (hard) lead fall.
A single strand of tape/cord with a loop at each end is a "snake sling" or a "snake cord".
It is weaker where you have a single strand (~10kN) going to a bit of gear rather than a double strand (~22kN for normal sling).
http://www.palmequipmenteurope.com/product/snake-sling <-- only 10kN so not sold for climbing in the EU
They are sold for climbing in the US.
First of all, someone else will probably have more facts and figures than me.
It does weaken the belay, you're using a single strand not two. As for if this is a problem it depends on the cord you're using. The cord I use is either 12 or 15kN depending on which diameter I take. Bear in mind any knot you tie, double fishermans or fig 8 will weaken the cord. When I do use a cordelette (first preference is to use solely the rope) I'll use it doubled up for close anchors or single strand to get some distance.
I have no problem using a single strand, especially when incorporating the rope into the system which would mean maximum loads of 12kN worst case. You want to check you're not going to be using a single strand of 4mm though...
Also, if you end up with three anchors, stick the single strands on the poorer ones and the doubled up cord on best. At the master point you don't have a single strand, and the three pieces will share the load. You'd be doing well to break a well equalised cord rated at 15kN (my 8mm cord)
The cord would be around 7.5kn/13kn (using Andrew's figures).
One strand would be worth about 4k/7kn docking the strength for the knot but there's some slight multiplication and a double strength leg in the middle. So If you're going to do this, go with the 7mm (or above, but if you go above you might aswell carry a 6mm loop for weight purposes).
This is common practice in the USA as allows more distant pieces to be used as you note, but also because it stops the double fisherman's always being in the wrong place and getting in the way when forming the master point knot.
It would be normal to use 7mm when doing this and to clip both ends to the same piece when you don't need the extra length.
The alternative, which I'm sure you know, is to clip a 120cm sling to the most distant piece to bring it closer.
How does this all compare to using a 4m/5m sling? There's no knot here, so is the american method of just "through each piece, draw the loops together and tie an overhand/fig8 to make a master point" a gold standard? Or does the fig8 reduce the sling's breaking point sufficiently that one should still try and design your belay from rope, even if it takes a lot longer?
Technically yes it will, as a loop is stronger than a single strand of any given cord. The question is whether if matters....
The cord I carry is 7mm and 15kn breaking strain and is a single strand with Figure of 8s on each end.
knock say 30% off for knots and you end up with 10.5kn Breaking Strain.
most nuts aren't rated above 10kn (even size 10 for the new WCs), so the end result the cord is pretty much as strong as the nuts. Do I ever expect to load a placement so highly that they metalwork it's self fails? No, I can't see it ever happening.
Also given I'm generally belaying off 3 anchors, each leg of that anchor has the same 10.5kn range. so a combined load resistance of 31.5kn.
Again, can I see this level of loading being applied to the belay? No.
add in that the peak force exerted by most ropes in a fall is about 7Kn and you've even more re-assurance.
So the long and short of it for me is that though technically a single strand is weaker than a loop, the end result is still well within acceptable limits as far as I'm concerned.
You can always link the ends of your single strand to create a look for less spread out anchors as well, and if you are tying a BFK in the cord, single strand is a lot less bulky and messy looking.
Ultimately up to yourself (and your climbing partners) what you are happy with. With weaker cord, I'd re-assess my approach - I chose the breaking strain for a reason.
PS all the numbers there are very approximate.
It's the same really. With cord you can chop it to use as tat or thread it more easily. You also have the option of using single strand as above in the thread. Rope is the best way most of the time and the cord/sling cordelette/webolette/other fancy title is just a solution to certain situations where the dynamic rope is a bit of a faff (climbing as a three, block leading etc).
It's prob a good idea to clove hitch into the masterpoint with the rope anyway though, adjustable and gives a bit of absorption. Or you just remember not to be an idiot and climb above and around when at the belay...!
From http://efclimbers.net/wp-content/uploads/2013/02/Knot-and-cord-strength.pdf page 5:
BW [Blue Water] 7mm static cord that was 18 months old and well used but appeared to be in good condition failed consistently at 60% of the same cord in new condition. Tested three times the used stuff was failing at 2,600lbf [11.6kN] in a single loop configuration and the new
cord failed at 4,200lbf [18.7kN]
Obviously this is hardly definitive data, and whilst used 7mm cord is probably still strong enough it is worth thinking about.
In the scenario you describe surely you'd utilise your rope(the strongest piece of kit we have) to tie into your gear?
Cord should really be for creating small threads or as someone else as suggested for leaving as 'tat.'
It doesn't mean that using cord is necessarily unsafe, and of course it is highly unlikely to fail, but it's not really best practice.
The best belay systems often use the least amount of kit, and always use the rope over and above anything else if at all possible. The more links/knots between you and the anchor the more chance of something going wrong, as slim as that possibility is.
Hope this helps(even though it doesn't really answer your question)
Agreed, in most situations this is true. As covered above though there are a few scenarios where a cordelette is a better option - climbing as a three for instance.
Not that I actually ever use it but itīs hard to believe my 8mm single-strand "cordalette" is any weaker than my 7.8mm half ropes.
But Iīve done loads of testing on cordalette systems and the saving in having a single strand are huge, that central knot with six strands (a 3 piece belay) takes so much useful material out of the system. With six strands of 8mm cord and a fig.8 thereīs over two metres of material dissapearing in the knot alone and if you go down to 4 strands by using a snake sling system there is over 1m less material wasted.
Hang on a cotton picking minute. When you say it's not best practice, can you explain actually justify that? I for example use Apus 7.5mm double ropes. Lets say I get to a belay and tie in to it, using a clove hitch to one of the anchors, and one to the other, they are bomber anchors, lets say a shiny new peg and a tree, i.e. not about to fail. Can you tell me how using a 7mm cord instead is any more likely to fail? Or if you used a sewn "guide" sling, clove hitched to the anchors, i.e. a single strand. Or if you used 5.5 mm spectra cordlette? All of these practices are not eschewed by the MIA examining board as being unsafe.In fact in the US cordlettes are pretty much the status quo, andwe don't have reports of people dying there. In fact we don't have reports of people dying from using belays built entirely from static slings do we? Is this not merely a case of "I was taught this way by a bearded bloke a while ago and now that is what I consider safe, whetherthat's the case or not."
All seems a trifle OTT if you ask me... even if you have worn rope as suggested above, what about if you have worn climbing ropes, surely that's the same as a worn cordlette? And if your rope IS worn, and it's strength is reduced to 11kN strength, but you're tied into more than one anchor, is there really a problem? Especially if the "fail safe" piece is connected with a double strand, i.e. the middle leg... or am I just being daft...
Is it "best practise"? Probably not, there's stronger options.
Is it "safe practise"? For sure it is.
It amazes me people who worry about such things ever go outside.
I bought 10M of 8mm cord today. It is rated at 16.4kN so minus 30% for the knot I have 11.4kN, and considering it is going to be for toproping I think it should be well within the margin of safety.
For anyone interested, it's for a sandstone climb that has no bolts at the top and only a tree or two fairly far back from the top of the route. By the time the tree is roped up, with the knots tied and the belay hopefully backed up I figured a loop of cord would be pretty hefty. I could make the belay with my rope sure, but the dynamic properties would damage the sandstone and I'm not sure I like the complexity of setting up an anchor with the rope when belaying from the ground. If it was harder rock I would just belay from the top, but being sandstone it doesn't really play to the rules.
Hi mike, just wondering, do you really feel safe to take a long dob on to 7.5 rope.
So is your original question less about the use of a 'snake' to equalise multiple anchors whilst on a multi-pitch but more about if you can use 8mm accessory cord as a 'rigging rope' with a couple of trees as anchors?
'Cos that might produce a few different answers.
Hi mike, thanks for your reply, had a look at your review of the mammut 8.9. One time on cloggy I watched a guy fall of the corner, he ripped about four runners then one held, the stretch was so great I was sure the rope was about to break. From then on I decided 8.9 would be my minimum. Double that is not as a single.
Stretch is good! With a thicker rope maybe the fifth runner would have popped.
Ropes survive factor 2 falls, they don't break (that must be more than 99.999% true).
The rating for a rope is given from a test under perfect conditions with a new rope. A rope that's had regular use for a few years will lose strength, had to this 1000s ft rapping. For me skinny ropes are not up to the job. Ropes are known to break.
I'm sure you've had loads of mathematical answers, some good, some wrong. All I'd say is if it were 7mm+ cord attached to 2 or more bits of gear I'd not worry about it. Then again I'd leave it at home and use the ropes.
That is so incredibly rare you can say it is not true*.
Millions of ropes must take many millions of falls every year without breaking. There must be hundreds of thousands of accidents where the rope did not break. Even where the rope is shredded by an edge it usually doesn't break.
Rope breakage is so rare even a near miss of shredded ropes in another country gets discussed on ukc.
Ropes age with usage and get less stretchy but they don't break.
The first drop of the rope test is under ideal conditions. The second and subsequent drops on the same section of rope represent progressively more and more unrealistic worst case tests as the same bit of rope ages visibly as it invisibly gets less dynamic/stretchy. The rope still doesn't break, the number of falls rating comes when the rope starts exceeding the acceptable peak force.
The test conditions correspond to a very brave and very stupid climber with an unrealistically solid belayer (no slippage in device) who ignores the visible changes to the rope. Even the the rope does not break.
*near enough, unless it happens to you!
My understanding is that a climbing rope has never, ever failed due to overloading.
Having acid poured on them, being cut by a sharp rock edge, and being cut by sharp carabiners yes, but simple falling forces? No.
>Ropes are known to break.
That's not what the UIAA say. The only degrading factors to a rope are corrosive chemicals, wear and usage. If you use your ropes carefully, this is largely reduced to usage, i.e. sharp edges. Over a sharp edges, even very thick ropes can cut easily, and the only factor which would improve this is if you have a rope that has been specifically designed for sharp edge resistance. In some ways I would feel more secure with thin doubles (7.5mm) than a thin single (8.9mm). As ever you need to look at the gear realistically, understand the compromises to your safety you are making and make logical and clear decisions based on the information you can gather, and then mitigate the risks you take in accordance. In the case of ropes, they need to be replaced when worn, or have been fallen on repetitively. However those factors are not sufficient usually to cause breakage apart from after sustained misuse, i.e. you ignore abrasion, don't check the integrity of your cores etc.
Yup. It's all pretty simple really isn't it, the problem being when people try to substitute common sense/experience for 'rules which may never be broken'
So John Harlin , Eiger Direct, Bonnington protested the ropes were too thin, rope broke. Willians portrait of a mountainer, tied ropes together one handed, rope broke. I was once given a peg by a guy trying to produce hard steel pegs, I tested it buy hammering it in a crack, clipping double no3 (9mm) ropes to it then tying the other ends to a bolder at the top of a quarry, trundled the bolder. Both ropes snapped. Years ago I used to work at Clogwyn Climbing Gear I had much more scientific equipment. When test using ropes on various bits of hardware it was alarming what a ten stone weight dropped ten feet would do to a 9mm rope. You,Mike,Andrew and the UIAA are right to a point, how much do you do with 7.5s, is it equal to a pair of 8.9 s. Sorry guys I am not convinced that 7.5 s are up to the job. No matter how careful you are. Course one could always buy new 7.5 every three months to be on the safe side.
Were those ropes modern dynamic kernmantel?
How did the mass of the boulder compare to a climber and did the ropes snap over an edge?
10ft could be a fall factor 10 or a fall factor 0.1. What a strange thing to say without explaining further.
The ropes were no3 hawser laid, breaking strength 3500 lbs, the boulder, if you take one cubic yard of concrete weighs in at one ton or 2240 lbs, the boulder was about a quarter of that size so say 560 lbs, the peg held, the steel crab held, the ropes broke about a foot below the knot no edges, just a straight fall down a vertical face.
We used the drop test on the then new Cosmic arrester, the rope going into and out of the device was flat like tape, if this had been a 7.5 I doubt it could have been held.
You do understand that the tension in the rope in a drop test is as much a function of the rope as the drop? For a given mass being dropped a given distance, there is a certain amount of energy; the maximum tension in the rope will be determined by how that energy is absorbed and over what time.
This is why dropping an 80kg mass 2m onto a 1m sling rated for 22kN (~2.2 tonnes static load) will break it, while it will not break a rope that will probably break at a lower static load - because the force in the rope will be lower as rope is more dynamic.
The 'breaking' strength of a rope is only relevant to static loading, not to climbing falls. And it is not surprising that when dropping large boulders (considerably heavier, and less squidgy, than your average climber) off cliffs tied to chunky bits of steel metalwork it is the rope that is the weakest link. You don't know that if you replaced the rope with something indestructible that the crab wouldn't then explode in turn...
Yes we can all read the science but I was pointing out ropes can and do break. Thin ropes leave much less safety margin, what's your opinion using the science and say a regular years climbing that being many weekends, summer and winter, 30/40 evenings, an alpine trip .
Hawser laid is no longer regarded as a climbing rope.
Dynamic kernmantel is designed to stretch so that the peak force does not exceed the limits of the human body even in a factor 2 fall. As a result the peak force is not sufficient to snap the rope.
In the absence of battery acid or a sharp edge I doubt a dynamic kernmantel climbing rope has ever snapped in a climbing fall.
You're not telling me anything I don't know. From what I have read and experienced over many years I feel that 7.5s or a single 8.9 do not have a big enough safety margin. What do use.
Article from over the water. Key phrases: How to big wall climb, building anchors, magical cordlettes.
Read it, make your own mind up!
Ropes do not break _in climbing_ unless cut or chemically damaged. Can you dispute this point with a counterexample?
You say single 8.9 ropes do not have a 'big enough safety margin'. What ratings/testing protocals are you considering here, and what values would you consider acceptable? Please elaborate on what you consider inadequate in the current UIAA test and certification process applied to ropes.
You say this comes from what you have read and experienced. Please list your sources which support your claim that 8.9 rope do not have a big enough safety margin. Please describe your (relevant) experiences of breaking ropes purely due to overloading in a climbing context (dropping boulders off cliffs has no relevance here).
You are not being scientific (which is a synonym for probably wrong).
In normal climbing use, including factor 2 whippers, a dynamic rope is designed to absorb the fall without breaking. In normal use, an undamaged rope hardly ever breaks, even the skinny 7.5mm ones - all of which you know of course. The safety margin you're referring to is the fact that it is well tested and you have a 99.9% guarantee that your rope will not break if you factor 2 onto the same piece at least 5 times in a row. Resistance to wear on tear over many uses on rough rock and stretchiness are probably more important factors when choosing rope diameter. A fall taken from say 5m up onto runner just below your feet can end up being a ground scraper on a very stretchy rope.
You've pointed to the Harlin accident, - the willans one I'm not familiar but in terms of the Harlin accident, are you serious? A badly worn 9mm fixed line that was being jugged most days over winter? That is a world away from a well maintained thin rope. Ropes were simply not aswell constructed back then - you're also talking about hawser laid ropes, and chucking boulders off cliffs which quite frankly is utterly different to a body falling - it's about as harsh a test as you can give a rope - a factor 2 with a static, non energy absorbing mass on the end of it... I assume you also tied both ropes into the single peg aswell, thereby massively reducing rope stretch an increasing impact force?
Personally I use my 8.9, quite often as a double rope, and my 7.5's I save for trips when weight is a prime consideration over daily use and robustness to heavy usage. Most of the time these days I climb on a 9.8-10 single.
I said ropes have broke, I have never said ropes break in normal climbing situations. The Harlin situation is an example, no matter how it was used, it was a climbing rope that broke that's all. There are other ropes that have broke for various reasons( do a goggle search) so as I keep saying, I have a personnel choice as to what rope I am prepared to use. As to the bolder drop,that was to test the peg but to see climbing ropes break under any circumstances is alarming for me. I repeatedly say what I'm prepared to use, if you and others want to go out on 7.5s or 8.9 single, it's your choice. People are asking me to give some sort written evidence for my choice. My choice comes from experience, 51 years of it on a lot of routes.
Stop squabbling. And that goes for Mike Kann as well :-)
The OP intends to use a single length of 8mm accessory cord tied to two separate trees and brought to a single point as a top-roping anchor if I have kept up.
I would prefer that he invests in a chunk of 10mm static rope.
For the situation the OP described, yes I agree.
Well yeah, preferably semi-static - there's enough stretch in a climbing rope on top rope as is without adding more from a thin stretchy piece of line to add to your woes. add to this the knot being placed over the crag edge (as it should with a top-rope) and you genuine have a concern if the toprope is to be used all day or even multiple times - even with a heavy rope you should be using an edge protector or simply an old piece of carpet and pay attention to how the rigging rope runs over the edge, making sure that you position the knot above the "fun line" also known as the fall line.
As for squabbling, he started it ;)
8mm is pretty strong, so should be fine for a top-rope anchor (if you have >10 kN forces in a top-rope situation you are doing it wrong). Obviously 10mm static would be better. The important thing is that the rope is protected over the edge; obviously this is where 10mm would be better (edge resistance).
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