UKC

When I'm building a belay I seem to spend a fair bit of time equalising the anchor and avoiding shock loading. I also hear the odd report of accidents caused by shock loading slings.

My questions are; would making a sling out of dynamic rope reduce the likelihood of an accident caused by shock loading and if so why do we use conventional slings?

Any musings appreciated.

In reply to Greasy Prusiks:

You can make a anchor with rope. Making your anchor with your climbing rope is actually very common.

Using seperate pieces of rope isn't uncommon in making topropes either.

However a seperate sewn rope loop is just rather bulky and annoying to tie. But they do actually exsist.

In reply to tjin:

That's true. A rope anchor is my standard method unless either we're not swinging leads or I'm running short of rope.

I'll try have a look at a sewn rope loop, I haven't seen one in the flesh.

Slings aren't stretchy because:

It would be a nuisance in many applications and provided they are used correctly they are plenty strong enough as they are.

Specialist slings do exist (although I can remember where) for dynamic purposes (rope loops) but it is easiest to tie a rope loop. Ditto lanyards where (arguably) dynamic loading is more important because you're more likely to use them in circumstances where dynamic loading might happen. they are generally bulkier and heavier than their non-dynamic counterparts.

In reply to Greasy Prusiks:

The percentage stretch is probably very similar in rope and nylon slings, stretch in dynemma would be much less. Its the short length of the slings that result in shock loading as they dont have the length to absorb the force. You should never shock load an anchor regardless of what its made from, just spend that extra few seconds equalising and ensuring good anchor points.

In reply to mcgovern:

Similar between nylon slings and static nylon rope maybe, surely you don't mean as stretchy as your climbing rope?

In reply to tehmarks:

For a standard belay setup the reduction in shock load by using rope rater than a nylon or even dyneema sling is negligible, the rope length involved is much too short to make a difference.
A rope may withstand a larger shock than a sling, but the load on the anchor won´t be much different.

CB

In reply to cb294:

I'm not disputing that, I'm disputing that a nylon sling has the same percentage stretch as a dynamic rope.

In reply to cb294:

Fall factors cb294, fall factors!

If you fall from the belay ledge with anchor at waist height (FF1)

FF1 on a dyneema sling = (roughly) >17kn
FF1 on a nylon sling = (roughly) 12kn
FF1 on a (semi)static rope = (roughly) 9kn
FF1 on a dynamic rope = <6kn

If you fall with the belay at your feet (FF2ish)

FF2 on a dyneema sling = (roughly) >22kn
FF2 on a nylon sling = (roughly) 15kn
FF2 on a (semi)static rope = >12kn
FF2 on a dynamic rope = Don't know for a FF2, but a FF1.7 is usually between 5kn and 9kn

Hardly negligible.

This is a good watch relating to slings http://dmmclimbing.com/knowledge/how-to-break-nylon-dyneema-slings/

Caveat: Droping a lump of steel usually produces more forces than a human body in a harness, as our squishiness take some of the forces. We also don't just drop from mid-air, so the numbers above are not a given in real life, but it's the best we got to play with sort of recruiting a bunch of people and lobing them off the side of a cliff.

P.S. The edit function is going nuts!!

In reply to Greasy Prusiks:


Really ? I don't think I have other than 'friend of a friend' sort of thing. Problem you have is the distance to the belay is often very short a belay in any material won't take up any slack. Rope has the advantage that its easy to tie off to exactly the tension you want either with clove hitches or half hitches.

In reply to Mr Lopez:

You are quite right.

One reason the different slings and ropes have different dynamic characteristics is the type of nylon used and its heat treatment and other trade secrets, also the weave and the more knots and other squidgy bits the better.

Came across dynamic rope slings from Beal recently - known as "Beal Dynaloop".

Described by Beal as:

8.3mm Dynamic rope sling for clipping in, equalising a belay or extending an anchor point.

Apart from the fact it is dynamic, the rope has another advantage over webbing: the rope’s core is protected from UV and abrasion by the sheath whilst with webbing all strands are exposed. (CE EN 566, EN 354)

Three sizes: 60cm, 120cm and 150cm.

KEY FEATURES:

• Dynamic
• Stitches protected by thermo molded cover
• Strength 22kN

USE:
• Clipping in
• Equalising a belay
• Slinging a rock spike

In reply to Mr Lopez:

I know you can destroy a sling with factor 2 fall with a bit of bad luck, but this is not relevant to the issue in the original post.

As I understand the question, the issue is whether is for a normally constructed belay it would be of any help if the material it is made of was mildly stretchy (rope) rather than static (sling).

My answer to that is that if the belay came under load, e.g. by a leader missing his first clip and falling past the belay, the additional stretch in the system offered by the length of rope from the centre point of the belay / the harness of the belayer to the anchors does not make any difference:

The length over which the anchor components can stretch is much too short.

Nevertheless, this is the classic factor 2 minus a bit scenario. Dummy runners or a low first piece of pro placed from the belay are a good idea, because it prevents shock loading the belay (even if this pieces blows it will dissipate some energy), redirects the pull, and extends the length of rope that can be dynamically stretched. However, this is a different issue from the one raised in the OP.

CB

In reply to Alastair MacSween:

I've got one of their rope lanyards and it's a great replacement for clipping in with a 60cm sling on a big sport route - but invariably just too short to stand on the spacious belay ledge, and so an uncomfortable and entirely unnecessary hanging belay 5cm above the ledge results.

Using the rope where possible is so much more flexible.

In reply to Greasy Prusiks:

Or why don't they develop webbing slings with the lightweight, narrow convenience of a sling but the dynamic stretch of a rope

Can think of a few specific scenarios static is better: to not wear a groove when setting up top ropes on sandstone, more efficient prussiking up a rope, very run-out lead don't want an extra 10cm fall???

I think you raise a good point

In reply to cb294:

We probably understood the OP differently. There loads of ways a belay can come under load, and the example of a leader taking a FF2 onto the belay is the most unlikely. However, in that sitation a more dynamic belay will still be of benefit.

Keep in mind if the leader falls from 2m up, and the belayer is hanging from a 60cm sling or a 60cm tail of rope, the fall factor would be 4/2.6= 1.54. So having a belay made from dynamic rope instead of a dyneema sling will lower the effective fall factor from 2 to 1.54.

If the belay is made up of a nylon sling then the actual forces are ridiculously hard to calculate as we got 4/5 and 1/5 of the material with different modulus, but will still be considerably lower than if it was made with a more static set up.


Destroying the sling is the least of our worries. The forces at which the slings break are unsurvivable, so before any sling breaks we'll be dead, or the anchors would have failed. What we are trying to do is to limit those forces so that neither the slings nor our backs snap. Guy in Yosemite died last year just like that...

In reply to GrahamD:

Is it possible to make an anchor with half hitches? Pretty sure they slip under load, I can't picture how this would be safe.

In reply to Appleby:

I can't see any reason you couldn't tie to the anchor with a round turn and two half hitches on the bight - but I also can't see any good reason why you'd want to. A clove hitch is far quicker and far more convenient.

In reply to Appleby:


Its actually quite a common thing because its very quick to do. Its a way of tying the rop back to yourself that doesn't need karibiners. Easy to demonstrate but hard to describe: Thread the climbing rope (which is tied to you, obviously) through the belay anchor and back to you. In this rope coming back to you, take a bite through a loop on the harness (I use the loop formed by the tie in knot) and tie the bite of rope off with two halfhitches.

I'm not advocating just tying the rope to an anchor with two half hitches, although with a suitable anchor and a round turn that would be safe enough as well.

In reply to Greasy Prusiks:

Perhaps I haven't read all the replies thoroughly enough, forgive me if this has been covered.
When using a sling in a belay it will normally have overhand knots and/or clove hitches in it, perhaps even a fig8 knot. How much energy do these absorb when loaded fully?

In reply to Rog Wilko:

They absorb a little, however, they also lose a lot of the strenght (about 50% of the strength in slow pull tests), and in the case of Dyneema which has a low melting point chances are the sling will break by melting and slicing through itself at very low impact forces.

In the link i posted above some of the tests are with knotted slings

http://dmmclimbing.com/knowledge/how-to-break-nylon-dyneema-slings/

In reply to Greasy Prusiks:
Stretchy sling for building belays or using on multi-pitch abseils as a cow's tail -

http://www.beal-planet.com/en/home/412-longe-dynaconnexion.html

In reply to GrahamD:

Have used this type of system for past 45+ years and clip the bight of rope left over to a second anchor with appropriate length adjustment via knots/slings etc.
However I suppose there is little elasticity in this system ie double rope to each anchor compared to using single climbing rope rope clove hitched to anchor which stretches more easily. The single climbing rope clove hitched to an anchor appears to be the gold standard at least regarding absorbing shock loads.
I'd consider using a 'home-knotted' dynamic rope snake sling or snake cordelette but as far as I am aware one would have to buy a 60 metre length of eg Bluewater dynamic prusik cord or a thin climbing rope as neither is available in cut lengths (as far as I know).

In reply to oldie:



You don't want much dynamic element between you and the belay, though, because it makes you more unstable and potentially vulnerable from being pulled off a stance (it happened to me only once when an out of sight second unexpectedly fell off). The dynamic part of the system should be your belay and the rope to the other climber.

In reply to GrahamD:

That makes sense. But I suppose if a leader falls from just above the belay with no gear in place then elasticity in the anchoring system may of some importance, especially if little rope is allowed to run through the belay device eg (mis)using a GriGri. Time to revert to waist belays?

In reply to oldie:


I guess, but if there is any chance of being unseated and losing hold of the rope in the process I'd go for that. Accept that you are getting rope burned in that factor 2 scenario in any case

In reply to Greasy Prusiks:
Cavers use cowstails made from dynamic rope. They do this because they move about on those cows tails (e.g. on traverses) where taking a FF1 (or even most of FF2) fall is quite possible (even more so when rigging the traverses), and this could easily be directly onto a bolt.

Climbers generally don't because they use a sling to stay still so avoid the risk of a significant FF fall by not buggering around at/above the anchor.

In terms of cowstails, you have to get all the components 'right' to get the acceptable shock loads down below the magic 6kN limit (in some testing Lyon did, I think - will obviously vary a bit with different rope thicknesses etc).
Firstly, most of the energy absorption is in the knots, not the rope. Don't use the pre-sewn dynamic rope lanyards because they are rubbish (less dynamic than knotted cowstails in static rope). Secondly, using dynamic rope does shave a little bit of force off (only a kN or two if I remember correctly). Thirdly, barrel knots (half a double fishermans) on the cowstail carabiner were better than Fig 8s. Half a triple fishermans is probably better again.

So there is a hierarchy here:
(least dynamic) absolutely anything that isn't one of the below two options - do not fall on.
(moderately dynamic) cows tails made of dynamic rope, tied WITH KNOTS (not pre-sewn). Avoid falling because it will HURT but you probably won't die - acceptable if buggering around above the anchor is unavoidable but falling is unlikely.
(most dynamic) industrial shockabsorber/VF lanyard type kit.

In reply to Greasy Prusiks:

One advantage of slings being static is that you know that they won't extend when pulled and move the position of the rope end of them.
So for example if you've carefully setup an anchor so that the krab attaching the sling to the rope is not over an edge then if you had a stretchy sling it might extend over the edge when put under tension, like when the climber falls!

Given that it's unlikely to stretch much it's not a huge advantage and one you can probably avoid when considering your belay anyway but it could be an issue.

In reply to andrewmcleod:

This is probably a completely stupid question. Thankfully Greasy Prusiks did say that any musings were appreciated! You say:
"most of the energy absorption is in the knots, not the rope."
"(least dynamic) absolutely anything that isn't one of the below two options - do not fall on.
(moderately dynamic) cows tails made of dynamic rope, tied WITH KNOTS (not pre-sewn). Avoid falling because it will HURT but you probably won't die - acceptable if buggering around above the anchor is unavoidable but falling is unlikely."

One could make a sequence of barrel knots along a cow's tail, eg clipping into krabs on the anchor AND the harness with a half barrel knot, and also possibly tie barrel knots at either end of krab(s) interposed along the length of the cows's tail (even possibly just around H-shaped metal bars). Would this have the effect of getting shock loads down even further than just using one knot and would this be worthwhile?

Incidentally many thanks to the originator of this thread. Like many people I use techniques which are accepted as safe, but just accept the theory without thinking much about it.

In reply to Greasy Prusiks:


I'm still curious about this, because I've never heard of any actual accidents confirmed as being caused by shock loading of slings (or more importantly shock loading the anchor and or the climber). Plenty of talk about the theoretical possibility of that event obviously.

In reply to Greasy Prusiks:

Equally, why aren't stretches slingy?

In reply to Greasy Prusiks:

Some interesting points raised on this thread.

Considering trying out the Beal Dynaloop mentioned and seeing how I get on with it.

Thanks for the posts people.

In reply to Greasy Prusiks:


Might a cordelette do the job for you?

In reply to Greasy Prusiks:


Don't.

Tie your own in a bit of dynamic rope (or even static if you want) - you will get much more energy absorption.

As already stated, the major contributor to energy absorption is the knots, not the rope - the pre-sewn slings are worse than static rope cowstails.

In reply to Timmd:

Because we can't yet make something simultaneously stretch, strong and small. Dynamic rope is stretchy and strong, but not small. As you make it smaller, it becomes too weak (sub 7mm or so). Slings compromise on stretchiness for strength.

In reply to oldie:


You could probably make something like this, but it would be massively bulky and you wouldn't know how well it would actually work unless you were able to test it. Why not just buy a proper energy absorber/VF kit?
Barrel knots are not critical; they are slightly better than Fig 8s but not much. Fig 8s are also fine at absorbing energy.

In reply to andrewmcleod:

That's a good point. I'll have a look for some short dynamic rope.

In reply to Greasy Prusiks:




The most important musing is to upgrade your technique. With the pieces in place, you should be able to rig a distributed anchor (please abandon any notion of equalization!) in well under a minute. The secret, actually, is to use the rope. Most people I've seen who spend a lot of time are trying to cobble together something with a bunch of separate slings. A second choice (and for some applications the first choice, eg if leads aren't being swapped) is a cordelette, but the rope is as fast if not faster (once the time wrapping and unwrapping the cordelette is figured in), it accommodates all gear positions without needing either shortening or something extra, and is more dynamic as well as being more robust than slings and cordelettes.

When it comes to energy absorbtion, I think it is a distraction to concern oneself with the energy-absorbing properties of the rigging, which might just as well be done with chains. Energy absorbtion, such as it is, is best viewed as coming from the climber's connection to the rigging, not from the rigging itself, and that connection is best accomplished by using the climbing rope and not cow's tail, especially not a cow's tail made of static material. Cow's tails have lots of uses, but the primary connection of the belayer to the anchor is safest, strongest, and most robust if it is the climbing rope itself, and this connection will incorporate knots with whatever energy absorbing properties they may have.

In reply to rgold:

Spot on - you see people faffing around doing clever stuff with cordellettes with 20 m of rope lying at their feet doing nothing, bonkers. Using the rope and knots to rig adds a bit of stretch but as you say the rope from belayer to lead climber is the real deal and when that distance is short you need to be extra attentive.
Direct belay are much less forgiving than squishy climbers. Stretchy slings! why not stretchy nuts and cams

In reply to Greasy Prusiks:

http://www.hse.gov.uk/research/crr_pdf/2001/crr01364.pdf
around page 79-80ish

also this probably has good links
http://sarrr.weebly.com/lanyardscowstails.html

and yes, just using the rope remains often/usually the best solution. That said, having a cowstail can be handy in certain circumstances (like when you are climbing in a three and it is easier for you all to untie and rotate the rope ends rather than reflake the rope).

In reply to andrewmcleod:

Great link, really useful.

Thanks.

In reply to andrewmcleod:



I don't get this 'energy' absorption malarkey on your belay anchors. When did that become a desireable thing as opposed to being connected solidly to the rock ? last thing I want when trying to hold a fall is worrying about being tied on with a piece of elastic. Being unseated from your belay stance because of too much dynamism in the connecting system is not pleasant and does not make anything safer.

In reply to tehmarks:

Nylon slings have considerably less force absorbtion than even standard semi static rope. I suspect the kernmantle rope construction absorbs more force than a sling. See table http://dmmclimbing.com/knowledge/how-to-break-nylon-dyneema-slings/

In reply to CurlyStevo:

Interesting to know, and not entirely surprising.

In reply to GrahamD:


There's more to life than swinging trad leads...

The simple answer to your question is when you are doing the falling onto your lanyard, not belaying and holding a fall of someone else. It's fine to be totally strapped to the rock if you are belaying (in fact, as you say, it is often advantageous).

Sometimes, when climbing, I have wanted to attach myself quickly and simply to a single point. Often, it is best to use the rope I am tied in with. Sometimes, this is not the case. These cases exist and are sensible, and depend on what you are doing.

Generally when climbing and the above condition applies (i.e. I am attached by a cowstail rather than tying in directly) I can avoid the major risk factors of falling onto a static lanyard by not climbing around above the anchor, keeping the lanyard taut and generally not moving about. Consequently I am perfectly happy with a static lanyard for climbing.

For caving, where you often clip into a traverse line or a bolt at a variety of heights then start buggering around either traversing along or bridging across pitches trying to move your cowstail onto a higher rope or other tricky tasks, using a sling is a terrible idea. Such situations rarely occur in climbing, but they could.

A vaguely climbing example that comes to mind is the sketchy bit traversing around the tricky corner at the bottom (I think?) of Comes the Dervish where you clip a pair of long slings into bolts for protections as you move around the corner. This would be painful at best if you actually fell off; real cowstails would be much better.

I also wonder about bigwallers, whose tethers presumably get quite long by the time they have snuck out of a sleeping bag and passed through the wall of a portaledge through one of those tube thingys. If the bottom did fall out of the portaledge, I suspect the fall factor would be reasonable and the fall rather painful...

Any time you clip into something bombproof, perhaps to rest, you have to be aware that even if you are on belay it is probably the bombproof bit that will catch you - and so you can't afford to be climbing above it (with a static sling).

All these things are outside of 'standard UKC approved lead-swinging trad climbing'. But it's not unreasonable if someone wants to provide themselves with an attachment that provides energy absorption.

In reply to andrewmcleod:

So your saying that the times you need anything other than the rope are vanishingly small or non existant for most climbers
Of course if you are benighted enough to be a caver!!!!!!!

In reply to John Kelly:
Yes.

But surely if there is one thing that climbers are supposed to hold dear, it is freedom - including freedom to make your own decisions about what equipment you bring for what risks, as opposed to being required to rigidly follow the UKC approved minimal equipment list or be pilloried for it! :P

Wouldn't it be boring if we all used exactly the same kit and did everything in exactly the same way?

In reply to andrewmcleod:

I saw my comments as giving climbers an option to escape the slow inefficient systems that seem to be the current vogue

The freedom to climb more routes more quickly rather than the freedom to purchase the latest kit was my motivation

<There's more to life than swinging trad leads...>
Plainly wrong

In reply to John Kelly:
If you are just swinging leads in a pair, pretty much anything that isn't exclusively using the rope is indeed slow and inefficient (unless you have bolted belays I guess). If you are doing anything else, everything else becomes more comparable with using the rope with different advantages/disadvantages e.g. if you are climbing in a 3, leading a novice/block leading...

Options are good, if they are good options!

If you are swapping leads in a threesome then all having cowstails and using a sling belay avoids faff (you can all untie and rotate ropes).

Incidentally if you do have a rope cowstail you can put a knot halfway along it for your abseil device for an extended abseil (any excuse for an alpine butterfly), just like you do for a sling.

Edit: depressingly having actually looked at the Beal Dynaloop thing it isn't the Beal thing I thought it was (I earn stupid points) and the longer versions are probably long enough to have enough stretch to be a reasonable stretchy-sling thing, should you need one to build an anchor, although I agree that I can't possibly imagine when you would actually want that. Although a tied loop is still probably better.

In reply to andrewmcleod:
Options, you're right, the more options you have the merrier, but I would argue that rope is the default and the other choices should generally stay in reserve.cheers john

In reply to andrewmcleod:

The post is about building belays isn't it ?

In reply to GrahamD:
I did kind of miss some of the point, in retrospect. Generally when people talk about slings and not falling onto them I assume that means they have a sling somewhere with themselves at one end and something solid at the other, so my ramblings are not completely off-topic with relation to the original vague question. But I appreciate that the context of building a belay was also raised. See the stupid points I gave myself in my last message.

In reply to andrewmcleod:

Just to say that - having used both - I think the Beal sewn rope loop is way better than a knotted length of rope. Firstly, not having a bulky knot makes it much easier to use and rack; secondly not having a knot eliminates a potential source of error.

In reply to nb:

It all depends what you want it for, and those are perfectly legitimate criticisms. If you are after the dynamic performance when using it to connect yourself to an anchor (given as a use on the Beal webpage), however, I would point out that Beal quote 10.2 kN for a FF2 fall which is not safe, whereas Lyon found 60cm cowstails of 11mm dynamic rope gave about 6-7 kN which is a lot better (albeit not quite good enough). If you are talking about the longer loops of the Beal stuff for building anchors then it is probably great; knots would make less difference anyway as the rope starts to be the dominator energy absorber (actually it might be even for shorter lengths but the extra absorption from the knots gets increasingly important as the rope gets shorter).
If however you are comparing clipping yourself to a bolt with a 60cm Beal sling 'because it's dynamic' or a traditional cowstail of a single strand of dynamic rope plus knots, then the cowstail is definitely the superior solution.
Lyon tested Petzl Jane sewn termination things, made of dynamic rope, and found >10 kN (estimated 10-11kN) which tallies with the Beal loop FF2 results.

Looking at the Beal stuff again, I'm not sure I would have put a green smiley face next to >10kN of force, to be honest...

In reply to andrewmcleod:

I'm talking about the 120cm beal dynaloop thing which I mostly use as lanyard for multi-pitch abseils, but it can also be used to equalise an anchor. Equalising anchors is better with a stretchy rope coz the load is more likely to be shared between the pieces of gear (that said equalising anchors is now apparently old hat and we should just be linking the pieces, but I'm not going to start on that coz it's not completely clear in my head yet!!).

As for knots providing extra absorption, this is especially the case if they haven't been well-tightened. However for a cow's tail you want them super tight.

In reply to nb:


There is a difference between hand/body-weight tight, and you-took-a-FF1-fall-on-them tight. In the Lyon study I quoted earlier they had already pre-tightened the knots to 2kN for 20 seconds, which is at least as tight as you will ever get them in normal use. A similar French study tightened to 3kN.

If you have actually taken a fall on your cowstail of any significance you probably won't be able to untie the knots and should probably throw them away.

In reply to andrewmcleod:

The french study mentioned is here

http://british-caving.org.uk/wiki3/lib/exe/fetch.php?media=rope_testingan...

Well worth a read and it's been particularly useful to me as it has been for some time my default reply to anyone who tries telling me off for not dressing my knots.

Those sewn lanyards don't seem like fun to take a big fall onto though, but as with everything in this game, if you know your gear's atributes and limitations and act accordingly they do offer a lot of benefits.

ETA: Ha, ha. UKC is changing the link with a smiley in it

Link here http://bit.ly/2h9Sxvz

In reply to nb:

Can you link to a page describing this linking Of anchors?

In reply to CurlyStevo:

Fraid not, I've only discussed it with a couple of engineers who have been testing the principle but they haven't published anything on the web yet. Basically if you equalise one good piece of gear - which holds say 800kg - and another poor one that holds 300kg and you load them with 1000kg then the load will be shared equally so 500kg on each piece. That'll make the weak piece fail, in which case you have the whole load on the 800kg piece which then blows as well. However if linked under tension, the whole belay should be able to hold a load of 1100kg.

That's the figures but there are other variables involved as well, which is why I'm not going to take this any further!

Apparently the Austrians and Germans make belays according to this principle (my vagueness is deliberate!), so there might be info available there. The French are testing it.

Only applicable if you have one piece of gear above the other however. Horizontally aligned gear would still have to be equalised.

Right, gonna stop now before I get completely out of my depth!!

In reply to nb:

The flaw with all load-distributing anchor systems is knowing what each point will hold, if you get it wrong the situation is worse than if you assumed they were all the same.

In reply to jimtitt:

Absolutely! I think the idea is if you have a bomber piece of gear and a dodgy piece, you basically don't trust the dodgy piece at all, meaning you don't equalise it with the good piece coz even half the force of a fall could make it fail. However you still link them with no slack so that that you add on the extra holding power. If you have 2 pieces of bomber gear, it doesn't really matter how you link them (within reason) so you keep it simple. And if you have two pieces of dodgy gear you're in trouble coz, as you say, how dodgy is each one?!

In reply to nb:

In German it´ s called "reihenschaltung" (connected in series). It might have some effect but nothing to bet your life on! You can´ t make a silk purse out of a sows ear.

In reply to jimtitt:

Indeed! I don't there's any remotely practical way to get series-connected gear to test at the sum of the values of the individual pieces. Hypothetically, if the spacing made it possible, you could make the connecting strand of tie-in rope short enough so that , when stretched, the tension would be just under the failure load of the top piece. At that point, the top piece would actually be exerting an upward load approximately equal to its failure load on the bottom piece, and now the bottom piece can withstand the sum of the failure loads.

Of course you can't do anything like this in reality, and I think the linked pieces will fail at the higher of the failure loads for the components. This will be the case if the connecting link is chain or something that doesn't have elastic properties.

However, if you rig vertically-aligned pieces in series with the rope and make the connecting link shorter than the distance between the pieces, then the connecting link will be stretched under load and that will allow the top piece, as long as it stays in, to exert an upward force on the lower piece and so increase the load the anchor can withstand. (Just don't expect this to be the sum of the individual failure loads.

In reply to rgold:

The problem being (theoretically) that if you use a stretchy element between the two pieces there can only be one condition where the stretch allows the forces to be shared optimally. You need something like a balance bar where you can accurately direct the proportion of the force to each piece, since the strength of the pieces is only a very vague guess it´ s going to be more a matter of faith than science

In reply to rgold:

I can think of a few ways you could tension a linking rope quite precisely. Imagine you have one bomber full-length ice-screw and a shitty one sitting above it in a big air pocket. You could tie a short length of rope to one and tension it to the other with some kind of auto-lock device. Could be something like a reverso, or a ropeman or even the waist-belt buckle on a harness. Maybe this piece of kit needs inventing! Is this better than equalizing them? (Real question btw.)

In any case it's not about trying to make a silk purse, just using the best technique out there to avoid total anchor failure.

In reply to nb:
That leads to an interesting idea. I wonder how the loads would share if you had a munter in the lower piece and the life rope clipped to the higher one. Slippage at the munter will transfer weight to the higher piece. A sort of self-equalising set up.

It would be interesting to know what forces would that get you on each piece at different loads, and with different variations of hitches

In reply to nb:

It´ s the "quite precisely" that is the problem. You think you know roughly what one piece will hold and roughly what the other holds and then roughly guess the tension required. Exactly how you judge the 500kg in your example is beyond me.
The better solution is to remove the crap screw and place it elsewhere.

In reply to jimtitt:
Look it's my example and I say you can't get a better placement for your crap screw - it's just crap. And your other screw is bomber and that's all you need to know - one screw's bomber, the other is crap. If you equalise them in the classic way the strength of your belay = strength of bomber screw. But can you make it stronger by linking the bomber screw to the crap screw?

Or in random numbers: 3X + (any fraction of X) is greater than 3X (where 3X = bomber screw and X = crap screw)

And here's the piece of gear that might do the job https://www.petzl.com/LU/fr/Sport/Longes/CONNECT-ADJUST#.WFWrvIWcHIU

No idea how tight you'd want it to be to get the biggest fraction of X. But I do think you can make it stronger than just equalising it in the normal way.

In reply to nb:

I can think of a few ways you could tension a linking rope quite precisely. Imagine you have one bomber full-length ice-screw and a shitty one sitting above it in a big air pocket. You could tie a short length of rope to one and tension it to the other with some kind of auto-lock device.

Wouldn't the lower piece of gear have to be multi-directional?

In reply to nb:


Maybe and maybe not, and the climber has no way to know which outcome it will be.




Not necessarily. if you ratchet too much tension with your Petzl Connect (which an expensive choice when you could just use the rope an a Garda hitch) then when the anchor load further stretches the link, you might just extract the weak top piece and all the load goes to the other piece just as in the other "equalization" scenario.

I never mentioned tensioning the connection, because this preloads the weak top piece and so essentially lowers its failure level by an amount equal to the preloading tension. All you can do, and a rope with clove hitches is all the gear you need, is to use the small amount of play in the position of the lower carabiner to make the connecting link a little shorter but not tensioned. In other words, clove to the lower carabiner with a little bit of slack in the anchor line, clove to the higher biner, and then adjust the top clove so as to lift (but not tension) the lower biner.

That's it. It might buy you a little extra total load capacity if the connecting rope link is relatively short, but I don't see it as a way to make a questionable anchor any better---there's far too much uncertainty involved I do think it is a sensible way to rig basically good anchors that are connected in series, because at least some of the load will be distributed, rather than having the higher anchors function solely as backups in case the lowest anchor fails.

In reply to rgold:


This was one of the variables that I wasn't sure about. I'd guessed you shouldn't pre-stress the weaker piece too much but wasn't sure if the decrease in holding power would be proportionate.

>All you can do, and a rope with clove hitches is all the gear you need, is to use the small amount of play in the position of the lower carabiner to make the connecting link a little shorter but not tensioned.

Admittedly the idea of some sort of tensioning device was me going off on a hypothetical tangent. The guys I've been talking with who are testing this have come up with a knot that works pretty much like you say. I'll post a link once they have something up on the net (don't hold your breath!).

So in reply to FactorXXX; if the linking rope isn't under tension then this system would be no more difficult to set up with uni-directional anchors.

In reply to nb:
As Richard says, you just clove the pieces in series with the rope with some guessed pretension in it. There´ s no special knot or piece of gear required. There´ s no real downside and there might be some benefit.
This is what is taught in Germany and the times I´ ve seen it demonstrated the benefits would be marginal due to underestimating rope stretch at the loads we are talking about.

In reply to Mr Lopez:



You could use any force-multiplying system like a belay plate or an Italian hitch to get varying amount of load distribution. This only works if the weaker piece is the higher one.
If the upper piece fails the impact on the lower one could be enormous.

In reply to rgold and jimtitt:

Ok guys how good is this thought?!

You have a bomber piece of gear and a crap piece of gear. You link them in series and apply tension. Until the crap piece fails, it is still adding some degree of strength to the anchor.
eg
bomber piece holds 1000 kg
Crap piece holds 300kg

Using a piece of kit per my previous posts, I link the 2 pieces using my 80kg of body weight to provide tension.

The anchor now holds 1220 kg, which is a 22% improvement on equalising it (is this good maths?)

Improving anything by 22% is pretty significant in my opinion, especially something your life depends on. By worrying about not being able to provide optimal tension, are we not missing out on an opportunity to make our belay anchors significantly stronger?

And of course you wouldn't have to apply anything like 80kg. By pulling hard with one arm I doubt I'd get much past 50

In reply to jimtitt:



Those could be worked around by simply extending the anchors so that for example, if the higher piece is the stronger the carabiner with the hitch ends up below the lower piece, and also ensuring that the knot on the life rope is only a couple of cms above the hitch, so that if it fails it only travels those 2cm before it jams against the munter. It could also be used with gear that is not vertically aligned in the same way.

Applying that in practice would be i admit much harder than writing about it, but as a thought experiment it sounds like an interesting way of sharing loads unequally.

In reply to nb:

Your logic escapes me somehow!
If the lower piece holds 1000kg, you clove the rope from yourself into it and free hang on it then use whatever on the upper piece to haul yourself up until the rope starts coming slack and lock the whatever device then you have added exactly whatever your bodyweight is to the strength of the lower piece. Adding more tension by guessing what the stretch is is pure guesswork, as is the strength of the pieces is anyway.
Building belays (as with most climbing gear) "stronger" does not equal "better". Strong enough is good, not strong enough is bad. Making something already strong enough stronger is not an improvement in safety.
The standard when I started climbing was the total strength of the pieces in a belay should equal the strength of the rope and the current view of at least two good pieces each capable of holding 6-8kN is similar. With movable protection this is still a good rule to follow since redundancy with an inherently unreliable system is good.
Your idea may add strength to a limited extent but relies on your judgement of "bomber" and the hope that the bored worker who made your piece of gear did it properly. If the belay is so bad you need to resort to scratching for the last 0.8kN of strength to survive then abseiling off is the better solution.

In reply to jimtitt:
When you're a couple of pitches from topping out on the NF of the Jorasses, abseiling off is probably not the best solution. Making your belay 20% stronger is! Maybe we don't do the same kind of climbing.

We're actually both describing the same technique - using body-weight and an auto-block device made by a bored worker.

I think we might actually agree on the mechanics, maybe not so much on its relevance!

Much as I love crazy theories, the time spent working out all the possible options, both from the comfort of your own home, would I suspect be much better spent:

a) training so you don't fall off anyway
b) finding some better gear
c) climbing more so you don't let yourself end up in stupid arbitrary and unlikely situations...

In reply to andrewmcleod:

Strange comment...

May as well point out that AFAIK, nb is a UIAGM mountain guide who i'd assume is a pretty nifty climber if the routes he climbed are anything to go by. When he uses as an example having to deal with crap gear for a belay a few pitches from the top of the GJ he's probably not making shit up for laughs and giggles either, but probably talking from experience when otions a, b, and c don't work out the way they should...

In reply to nb:

I must be missing something here: how to you use body weight to supply "tension" without changing the rigging rather significantly (and in ways I can only imagine are detrimental)? Honestly, I think the method I described which shortens the link but doesn't tension it is the best bet (and we are speaking of placing bets here).

Actually, for that belay at the top of the NF of the Jorasses, there are some things perhaps worth mentioning. One is, if crap is the only alternative, to try to place the crap piece as far above the good piece as possible and then rig with classical "equalized" rigging. Such rigging, with one short arm and one long arm, will deliver more of the load to the short-arm piece, so you'll get distribution but not equal distribution and the crap piece gets less. If, relying on intuition I have no access to myself, you decide the crap piece is 1/3 the strength of the good piece, then if you can rig it so the arm to the crap piece is three times as long as the arm to the good piece, you'll be heading for a load distribution that makes use of what both pieces have to offer.

If you can't get the crap piece far away from the good one, use as static a sling as possible on the good one (thereby lowering it two feet and use the rope for the tie-in and connecting link (which just got two feet longer).

Of course, this is still full of uncertainties, and there is a (pretty good) possibility that it will be no better than the strongest piece anyway, but you don't need special gear and it takes no faffing to set such an anchor up.

Another option is to put a screamer on the higher crap piece and rig with standard equalized rigging. If that rigging delivers more than 550 lbf to the crap piece, the screamer is activated and as it lengthens, more of the load is shifted to the good piece while the load to the crap piece is held at 550 lbf. This could result in a modest increase in the anchor's strength and is easy to rig, but you have to have a screamer on hand...

In reply to rgold:

I obviously explained myself badly. You tie a rope to one piece (could be your climbing rope in which case clove hitch it to the lower piece), run it through an autolock device on the other piece and pull to provide a small degree of tension. The only reason I mentioned bodyweight was to be able to give a value to my calculation.

This system is at least as simple as equalising, you can set it up with normal kit and you only need a very rough idea of the strength of the each piece of gear or the tension you provide.

I work it out to be always stronger than equalising if you have one piece of bomber gear and one crap piece vertically aligned (but happy to be proved wrong).

In reply to nb:

Ok, I get that now---or maybe I don't, because it seems to me that by tensioning the strand above the low piece to 80kg, you've added just that much as an upward force on the bottom anchor; it now holds 1080 kg rather than 1000 kg, an 8% increase, not the 22% you seem to have obtained. Where do the extra goodies come from?

I still think the Garda hitch---possibly tied off after tensioning---is the way to go for the upper piece. You just need two carabiners rather than one at the top anchor point.

As mentioned by FactorXXX, the lower piece can't be compromised by this upward load, which limits the applicability and/or requires extra rigging to hold down the lower piece.

In reply to nb:

Not sure tension isn´ t confusing here. The idea is to link the two pieces with something stretchy and shorten the connecting length by the amount of stretch a force equal to the strength of the upper piece would give.
If the lower piece holds 300kg and the upper 1000kg then you need to join them using a length of rope stretched by 1000kg or more practically you estimate what this length would be. The better you can estimate this the more the improvement. Make the joining dnamic element too short and there is no benefit. Too long and there is no benefit.

In reply to rgold:

Just googled Garda hitch and see what you mean (I call that an alpine clutch). Would be a great way of doing it if it's strong enough. Never seen any test results.

My calculation is based on this: total strength = sum of strength of both pieces minus the tension in the rope linking them.

So in my example; 1000 (bomber piece) + 300 (crap piece) - 80 (maximum tension you can apply) = 1220
By equalising them the belay is only as strong as the bomber piece = 1000

So that makes a 22% advantage.

Ok I see what you all mean by only adding 80kg of holding power rather than 220. Maybe my idea is crap after all!

In reply to nb:

Yep, you need to stretch the rope with 300kg to get 300kg load at the end. Easier is to know how much our rope stretches with 300kg and just use this length in between. That is:- test all your ropes under varying conditions and different loads in the lab. Write a simple script and when you build your belay you whip out your notepad or whatever, measure the distance between the two pieces, plug this, the strength of the pieces and whatever into your calc program and it tells you the length to use. All this at the top on an Alpine north face

In reply to jimtitt:
nb, as for only adding 80 kg, I'm afraid that's correct. You take the perspective that the engineers call the "free-body diagram," which is to say look only at the good lower piece and analyze all the forces (the engineers would call these "actions") on it. All you've got is the load acting downward and the force from the link tension acting upward. (Sorry Jim, this wasn't addressed to you...)

Jim wrote:

It's the Bolt Products North Wall Anchor Rigging App, coming to an iPhone soon, right? You'll be rich beyond measure!

In reply to rgold:



I couldn´ t possibly charge for such an obviously essential safety item that could save the lives of thousands of mountaineers, I prefer to be rich in my soul rather than my bank account.
Next up is a knot-recognition program for those do-it-yourself buddy checks.

In reply to jimtitt:


Next up is a debate on do you belay a leader on your harness or directly to the belay. Get swotting!

ps haven't completely given up on this one yet either. Could ice-screws be a special case coz they bend considerably before pulling out thereby auto-tensioning the linking rope?

In reply to nb:

You certainly don't use a direct on the anchor belay with one of your concoctions!

I don't know about the bend in the ice screws, but you can potentially get a lot more tension just from the fact that you've lifted the carabiner on the bottom screw all the way up. In fact, depending on the distance between screws, it shouldn't be too hard to blow out the top screw before the bottom screw is weighted---this is the danger of the method.

When loaded, that lifted carabiner eventually has to end up down below the screw in the usual position, which means the clove hitch on it has to move down as much as 8 inches for a full-sized biner. How much tension you get from that 8 inches depends on the ratio of total elongation to the length of the unstretched linking strand, which since you have tensioned it with body weight is equivalent to taking a piece 10% shorter and stretching it back to the pro distance; this will be about 11% stretch. Now you stretch that even further by pulling the raised carabiner down through its (potential) 8 inches of travel. If the distance between pro is about 26 inches, that 8 inches of elongation is going to be about a 30% stretch, as much as you get from a factor 1.8 UIAA fall, and so developing the same tension, in the realm of 7--9 kN for most ropes. That upper piece is ancient history long before that tension develops.

Some theoretical calculations are possible and not hard to do, but there are a host of questions about how well at the basic equations for simple harmonic motion model rope behavior and what modifications give better modeling, and then none of it might apply to your particular rope(s) anyway.

But, if you can get your hands on a load cell (or something more primitive that measures forces), it is "easy" to conduct a few tests (I hear Jim roaring with laughter) on a tree in the back yard or at a climbing gym during off-hours. Forget about tensioning, just rig so the lower carabiner is lifted, weight the system, record the amount of lower carabiner lift, the tension in the linking strand, and the distance between protection points. Use full lower-carabiner llfts (so 6--8" extension) and half-lifts (carabiner rotated 90 degrees from normal hanging position---3--4" extension).

In addition to bringing Jim's reign as a captain of internet commerce to an untimely end (iPhone app not needed), this will give you a rough sense of how much added tension you get from lifting the lower carabiner for some different pro linking distances, enough to possibly to formulate a rational---which is not to say correct---approach to using such a system in the field.

In reply to rgold:
My 'concoction' is still actually stronger than an equalised belay with a bomber and a crap piece of gear, and just as easy to construct. As Jim says, not enough to make a big difference, but sometimes even an 8% increase can save your life (could very easily be increased to 16%).

You don't need to use a karabiner on the bottom screw to attach the linking rope/sling. It can be tied directly so that's not an issue.

I'll leave the testing of this to others because it involves dynamic loading rather than the static loading required to test abseil knots. But I have some friends who might be persuaded... Interesting that as a mathematician you consider the idea could have some potential.

Ps 6 hours after a hip replacement I am about to start walking. Isn't science wonderful !

In reply to nb:

I think Richard is thinking more just clipping a karabiner into the ice screw (or whatever) like normal then clove hitching the rope into it then the same with the one above but with the rope a bit shortened, that´ s my concept anyway.

In reply to Greasy Prusiks:

Because a *trivial* task of equalizing static slings has proved to be actually nearly impossible, doing it with stretchy components. .. let's not go there, shall we.

In reply to nb:


No wonder you're hanging out here geeking out over anchor rigging! (Now what exactly is my excuse?). Hope the rehab goes well. Almost all the climbers I know with hip replacements have fared very well in returning to their chosen form of insanity.

Jim wrote:


Yes, that's my idea, such as it is. When you shorten the rope, it lifts the carabiner, and when the load draws the carabiner back down, it tensions the rope connecting the pieces.

In reply to Mr Lopez:
You know if a piece of gear is (probably) bomber, you tend to know if a piece of gear is probably crap (won't even hold bodyweight in some cases), and then there is the mystery gear that might be OK, might not. If you have any of the bomber gear then you don't need anything else (at a push). If you only have mystery gear, the uncertainties about how good the gear is probably make the whole exercise a bit pointless.

Buy a screamer. I would even suggest these wonderful devices are probably more useful in practice...
http://www.kakibusok.plus.com/Equipment/CTDQ1/CTDQ1.htm
http://www.kakibusok.plus.com/Equipment/CTDQ2/CTDQ2.htm

Personally if I was in a situation with a belay so crap that I was even beginning to seriously think about a) trying any of this and b) thought there was a reasonable possibility of using it, then I would do anything I could to give up and go away. I recognise this is not always possible, but I'm still unconvinced this is practical or useful (or is likely to get you out of trouble more often than it gets you into trouble). There are simple things you can do which will definitely improve the success chances of a belay, such as hanging yourself well below the belay (so reducing any possible fall factor). This is both complicated and not necessarily going to make things better?