/ Knots in slings

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Rock to Fakey - on 18 Apr 2017
Whilst looking at tech data on new slings today, i wondered why the warnings of death for girth hitch, overhand knot, and another knot that looks like a reef but i can't figure out how you make it, are applied.
I understand knots in slings reduce the strength by a fair bit, but then instructors /books etc teach about larks foot / girth hitch a sling from harness belay loop to carabiner at anchors, and overhand knots to limit the shock on a sliding x used on a sling to equalise the anchors and so on, so why the death warning... Seems a bit OTT?
john_mx - on 18 Apr 2017
In reply to Rock to Fakey:

I've often wondered about this, be interesting to see why
CasWebb - on 18 Apr 2017
In reply to Rock to Fakey:

DMM have covered this extensively: http://dmmclimbing.com/knowledge/slings-at-anchors/
2
Andy Nisbet - on 18 Apr 2017
In reply to Rock to Fakey:

Tight knots have become less important as rope/sling strength has improved. So the overhand knot used to be discouraged as the rope could break, but now the only problem is that they tighten up and are hard to undo. Which is great if you don't want them to undo (as in tying ropes together for abseiling).
dommc on 18 Apr 2017

I think this is related enough to the original question to not hijack the thread - but you can tell me where to shove it if not!

Am I correct in thinking that for making a bottom-rope anchor between two bolts, a dyneema sling with an overhand or figure-8 on a bight in it is fine, assuming a dynamic rope carabinered into the knot's master point? That is, that the issues related to knotting dyneema don't apply here, because the force of a bottom-rope fall will be absorbed by the rope, and won't be hitting the knotted dyneema with a dangerous force? And that the potential danger's of dyneema's low melting point don't come into play when the knot suddenly tightens on itself?
Post edited at 22:41
jezb1 - on 19 Apr 2017
In reply to dommc:
You're correct. Setting up a y hang with a sling is a perfectly safe thing to do.
jimtitt - on 19 Apr 2017
In reply to Rock to Fakey:

Manufacturers are required to make slings so they withstand 22kN force, it is quite correct they should warn of practices which may reduce this by 50%.
While instructors and books show tying knots that is their responsibility if they fail, not the manufacturers. Mostly it is unescessary, I doubt I tie a knot in a sling once a year because it is a pain untieing them.
Outside.co.uk - on 19 Apr 2017

If you regularly find yourself knotting slings, some slings can be knotted without too much reduction in strength, such as the Magic Sling from Mammut
http://www.outside.co.uk/shop/12mm+Magic+Sling

JLclimb on 19 Apr 2017
In reply to Rock to Fakey:

Thanks for bringing this up.
Further to this, I always put 2/3 knots along a sling (cows tail) to use when lowering off a sport climb - so I have varied lengths to use when adding my screwgate to the anchor before tying off.
Can anyone advise whether this is safe practice? (I was taught this by a qualified instructor), or should I just use a sling without knots or quickdraws instead?
johncook - on 19 Apr 2017
In reply to Outside.co.uk:

If you regularly find yourself knotting slings, buy some slings of different lengths!
johncook - on 19 Apr 2017
In reply to JLclimb:

Buy a PAS. Designed for the job, tested to 22kN, easy to work with. Worth the money.
If you have doubts about any of your safety aspects, change your practices/equipment.
Greasy Prusiks on 19 Apr 2017
In reply to johncook:

What's a PAS? Never heard of that before.
StuDoig - on 19 Apr 2017
In reply to JLclimb:

For lowering off a sports climb, not much of an issue. Each knot reduces the strength of the rope locally (i.e. at the knot) so it's not cumulative. Additional knots DO add addtional weak points / potential failure areas though so increasing your chance of one going. I'd definitely be untying and inspecting the knotted areas very frequently though!

Even so, for hanging of at the top of a sports climb It's not likely to be a problem. The big problem (esp with small width dyneema slings) is FALLING onto them directly. As they are essentially static (i.e. very, very low stretch) and no rope in the system the shock loading is pretty spectacular and CAN snap the sling. I've never seen one snap, but seen one very badly damaged (needed to be scrapped) after a really innocuous slump onto the belay. Burn / melting on it was really shocking after what seemed an absolutely minor slip and slump. Smaller the diameter of the sling the higher the chance of snapping.

I do use a proper rope lanyard now (petzl Duo adjust) if route seems likely to involve a lot of fixed belays. Single leg version is good too, but I like the double. Previously I used a PAS, but like the ease of adjust-ability on the Duo lanyard. If I'm not keen on the extra weight of the lanyard, I use a round sling (Kevlar) which is part of my rack anyway and a lot better for the shock loading!

End of the day, a knotted sling is safe if used correctly and limitations understood, but leaves little margin if you don't use it correctly. I suspect a lot of people who do know the limitation don't appreciated how little it takes to damage / break them!

Cheers,

Stu
1
StuDoig - on 19 Apr 2017
In reply to Greasy Prusiks:

one of these
http://www.metoliusclimbing.com/pas_personal_anchor_system.html

A daisy chain made up of individually stitched links each rated to the full 22kn, rather than the normal low rating for normal daisy chains.

Work well, but I find a little faffy / untidy with the unused links.

Cheers!

Stu
Greasy Prusiks on 19 Apr 2017
In reply to StuDoig:

Ah OK cheers Stu. I'd always had those down as daisy chains.

nutme - on 19 Apr 2017
In reply to Greasy Prusiks:

> What's a PAS? Never heard of that before.
"Personal anchor system". Normally a chain small slings. A bit reminds daisy, but every link is rated to 22kN.

Grivel makes one like this:
http://www.grivel.com/upload/istruzioni_file/56/130/IS_Grivel%20Dasy%20Chain2_5A.pdf
Greasy Prusiks on 19 Apr 2017
In reply to nutme:

Cheers Nutme.
Rock to Fakey - on 19 Apr 2017
In reply to JLclimb:
> Thanks for bringing this up. Further to this, I always put 2/3 knots along a sling (cows tail) to use when lowering off a sport climb - so I have varied lengths to use when adding my screwgate to the anchor before tying off. Can anyone advise whether this is safe practice? (I was taught this by a qualified instructor), or should I just use a sling without knots or quickdraws instead?

I guess so long as you are crucially still on belay,... But say you attach the sling by larks foot from belay loop to screwgate on 1st bolt anchor, then put your feet a bit higher and pull up on that sling, or holds, to clip something to the second higher / further away anchor, but your feet pop off + yr weight drops onto the sling... that's a shock loading scenario, and if you aren't still on belay, could be fatal.

I'd clip into both anchors if coming off belay.
Post edited at 12:26
Rock to Fakey - on 19 Apr 2017
In reply to CasWebb:

> DMM have covered this extensively: http://dmmclimbing.com/knowledge/slings-at-anchors/

Why the dislikes on this post?
4
JLclimb on 19 Apr 2017
In reply to StuDoig:

Thanks very much for your helpful advice
johncook - on 19 Apr 2017
In reply to Greasy Prusiks:

A PAS is a purposely designed nylon personal anchor system, made of a series of linked short loops of nylon that eliminates the risk of mis-clipping inherent in a daisy chain, is easy to use and to extend and shorten. I can't remember the name of the manufacturer and my gear is in the car and not close to hand. A PAS is one of my most useful sport climbing accessories and also works well on trad routes with fixed anchors. When I remember the make I will post it on here!
(At my age my memory is not as good as it was, now what was I talking about?)
beardy mike - on 19 Apr 2017
In reply to Rock to Fakey:

You also need to bear in mind that worn slings can see rapid deteriation in strength. For example, some thin dyneema slings have been found to lose 30-40% of their strength after a couple of years use - so by the time you tie a knot in them they are getting close to the point at which they are sufficiently weak to break during a very big impact. It's why slings are supposed to be replaced every few years unlike metalwork.
CasWebb - on 19 Apr 2017
In reply to Rock to Fakey:

Mystery to me as well
1
george mc - on 19 Apr 2017
In reply to Rock to Fakey:

Tie in using the rope - simples.
Greasy Prusiks on 19 Apr 2017
In reply to johncook:

Thanks John. They sound intriguing, I'll have a look into them.

I'm currently using quite an esoteric belay method - I build the belay using dynamic slings I've made out of rope with all gear equalised to one master point then clip into this using either a dynamic cowstail or my end of the rope.

All that so my partner doesn't necessarily have to lead through. A pretty high quality of service if you ask me ;)

Rock to Fakey - on 20 Apr 2017
In reply to Rock to Fakey:

Pg 2 of this pdf (=pg 24 + 25) is about slings.. http://libbypeterclimbing.co.uk/techpdfs/trad4.pdf
Rock to Fakey - on 26 Apr 2017
In reply to Rock to Fakey:


Check out “How to Break Nylon and Dyneema Slings” from DMM Climbing on Vimeo.

The video is available for your viewing pleasure at https://www.vimeo.com/27293337
PMG on 26 Apr 2017
In reply to beardy mike:
You might find this article interesting: http://www.alpenverein.de/chameleon/public/1710c3f7-77d8-c1dd-d63b-f619124ee2c1/Aging-of-Slings_2636...
Post edited at 23:54
John Stainforth - on 27 Apr 2017
In reply to Rock to Fakey:

If one of the end of a reef knot ever gets caught on something and is pulled back across the knot, the knot becomes a non-knot - completely useless, except for conjuring tricks requiring a disappearing knot!
Rock to Fakey - on 29 Apr 2017
In reply to John Stainforth:

So far i can only think of a reef knot been used in the middle of a double Fisherman's, in which case it's protected from that happening by stopper knots.
When else are reef knots used?
jon on 29 Apr 2017
In reply to Rock to Fakey:

> When else are reef knots used?

The cord on my chalk bag.

scott titt - on 29 Apr 2017
In reply to Rock to Fakey:
Shoe laces, properly tied a bow is a double slipped reef.
pec on 29 Apr 2017
In reply to Rock to Fakey:

The DMM videos show nylon slings perform better than dyneema in almost every respect and other data seems to back this up. I know dyneema is stronger but only weight for weight because they are thinner, dyneema slings aren't actually stronger in practice. They also have a lower melting point which could be a problem if a rope runs over them.
The only advantage seems to be they are a bit lighter but since the total weight saving on a few slings is trivial I can't see any overall advantage in dyneema for slings.
When my slings needed replacing I moved back to nylon after seeing the evidence.
andrewmc - on 29 Apr 2017
In reply to pec:
> but since the total weight saving on a few slings is trivial I can't see any overall advantage in dyneema for slings.

I don't disagree with your other points, but both the weight and bulk savings are not necessarily trivial. I wouldn't want to carry a 4m 16mm nylon sling; quite happy carrying a 4m 8mm dyneema sling. I can carry 1 x 4m, 2 x 240cm, 4 x 120cm slings in 8mm without turning into 'SlingMan' (just) which I not sure would be true in 16mm nylon...

Some random example weights:
8mm 120cm 35g
8mm 240cm 68g
8mm 400cm 115g (?)

16mm 120cm 84g
16mm 240cm 160g

Couldn't find a 16mm nylon 4m sling, probably because it would enormous and silly, but for me that means:
391g in 8mm dyneema
276g in 8mm dyneema without 4m sling
656g in 16mm nylon without 4m sling

(and no, I don't carry all of those slings all of the time...)
Post edited at 12:10
1
Rock to Fakey - on 30 Apr 2017
In reply to andrewmc:
about 400g weight saving is significant, almost the weight of another harness.
You could then still carry your sarnies to the top, even a tin of beans + meat free sausages (ring pull top tin type to save tin opener weight, + use plastic spoon), a multipack of trek bars, etc, using dynema slings to save weight, so long as you can be sure you won't shock load at the belay.
Post edited at 09:25
Rock to Fakey - on 30 Apr 2017
In reply to jimtitt:
> Manufacturers are required to make slings so they withstand 22kN force, it is quite correct they should warn of practices which may reduce this by 50%.While instructors and books show tying knots that is their responsibility if they fail, not the manufacturers. Mostly it is unescessary, I doubt I tie a knot in a sling once a year because it is a pain untieing them.

Do you larks foot / girth hitch a cows tail sling to your harness to clip a biner to a sport or trad fixed belay?
That is using a knot.
Post edited at 15:56
pec on 30 Apr 2017
In reply to andrewmc:

> I don't disagree with your other points, but both the weight and bulk savings are not necessarily trivial. I wouldn't want to carry a 4m 16mm nylon sling; quite happy carrying a 4m 8mm dyneema sling. >

I wouldn't want to carry a 4m sling made of anything, it would be almost completely pointless. In over 30 years I've never owned, placed or even wished to place a 4m sling and neither has anybody I've ever climbed with. On the very rare occassions I've needed something longer than 120cm to set up a belay I've just used the rope.

> I can carry 1 x 4m, 2 x 240cm, 4 x 120cm slings in 8mm without turning into 'SlingMan' >

Wow that's a lot of slings! I almost never carry more than 2 x 60cm and 2 x 120cm slings.
I've just weighed my nylon vs dyneema slings and the extra weight penalty of nylon is 86g which is next to nothing compared with the weight of a trad rack. Its 2 solid gate krabs, a Dragon Cam 0 or a wallnut 8+9.
Each to their own but the advantages of nylon seem worth it to me. Oh yes, and they're cheaper as well
MFB - on 30 Apr 2017
In reply to pec:

https://www.decathlon.co.uk/dyneema-sling-6mm-id_8003876.html

These are awesome, go places other slings won't, weigh 16g, never leave ground without a few
Leearma on 30 Apr 2017
In reply to Rock to Fakey:
In relation to the opening post, differing knots can reduce the sling strength, add a dynamic load and this can result in failure of the tape or slippage of the knot. The reason for the warning is that like the many replies, there are many ways to use a sling incorrectly.

If using a sling in a belay, do not introduce the possibility of a shock load (fall factor) or the risk of failure will increase. Bad practice is where you have slack in the sling and even minor falls onto a slack sling can generate a high fall factor resulting in damaging forces to you or the belay.

As this in on a beginners forum I would suggest that you don't waste your money on daisy chains or other bits of connected tape, some products introduce bad practice and some are specialist pieces.

You simply need a small selection of round slings (60 & 120cm), the number will be dependent on where and the style of your climbing, but a good start will be 2 of each, nylon or dyneema.

I will second the best bit of advice I have seen on this thread from George Mc and use the rope where you can to arrange your belay.

The rope and some sound knowledge will allow you to construct sound belays for many years to come... safely.
Post edited at 20:26
Rock to Fakey - on 30 Apr 2017
In reply to Leearma:
... "add a dynamic load and this can result in failure of the tape or slippage of the knot"...

Did you mean add a non - dynamic load, i.e a shock load?
Presumably /theoretically a dynamic load could too, but not likely?
Post edited at 21:41
johncook - on 30 Apr 2017
In reply to Rock to Fakey:
You should not use a dyneema daisychain/cowstail for sport anchors, it has too many failure modes. Use a PAS, made from nylon, much safer and much more idiot proof.
Post edited at 22:08
johncook - on 30 Apr 2017
In reply to Rock to Fakey:

A dynamic load is a moving load, which gives a 'shock' load if there is no 'give' in the system, like elasticity in the sling. A loaded sling or rope that is held tight is statically loaded.
For years ropes and slings were tested statically, ie, they were pulled slowly until they broke. Now they are tested dynamically, ie a load is dropped onto an anchored rope or sling, hence originally gear was marked in kg, a unit of weight, how much weight it could lift, now it is marked in kN, a unit of force, how much force it can withstand.
BarrySW19 on 30 Apr 2017
In reply to pec:

> I wouldn't want to carry a 4m sling made of anything, it would be almost completely pointless. In over 30 years I've never owned, placed or even wished to place a 4m sling and neither has anybody I've ever climbed with.

I do sometimes carry a 4m sling but, I have to admit, there are not many occasions when it is any better than having a 2.4m one. Every now and then you come across a really big boulder, but the real use of them is in creating an anchor across three bits of gear. Having said that, if you are climbing with half-ropes you can equalise said anchor more quickly using the ropes (although the sling does give the second a far better point to clip in to).

Overall, I think it can sometimes be a nice bit of gear to have, but if I lost it I don't think I'd bother replacing it.
jimtitt - on 01 May 2017
In reply to johncook:

> A dynamic load is a moving load, which gives a 'shock' load if there is no 'give' in the system, like elasticity in the sling. A loaded sling or rope that is held tight is statically loaded. For years ropes and slings were tested statically, ie, they were pulled slowly until they broke. Now they are tested dynamically, ie a load is dropped onto an anchored rope or sling, hence originally gear was marked in kg, a unit of weight, how much weight it could lift, now it is marked in kN, a unit of force, how much force it can withstand.

Slings are pull tested like all other climbing gear except ropes where weight is dropped to obtain the dynamic characteristics of the rope. The change from kg (and then kgf) to kN was due to changing to SI units. The breaking strength of ropes is neither measured nor published.
jimtitt - on 01 May 2017
In reply to Rock to Fakey:

> Do you larks foot / girth hitch a cows tail sling to your harness to clip a biner to a sport or trad fixed belay?That is using a knot.

I girth hitch into my harness sometimes and clove hitch into karabiners, as they are hitches they are easy to undo. Knots aren´ t.
Rock to Fakey - on 01 May 2017
In reply to jimtitt:
Do you class a girth hitch / larks foot as a knot?
Is the strength of the sling halved when you do this?
When you clove hitch (your sling) to a carabiner, is that a knot you just tied that halves the slings strength?
Post edited at 18:03
jimtitt - on 01 May 2017
In reply to Rock to Fakey:

A hitch is a hitch, a knot a knot. The reduction in strength is either of no consequence to me or a known reduction that will have no consequences.
Rock to Fakey - on 01 May 2017
In reply to jimtitt:

I don't find your answer very informative! I'm a bit too exhausted too!... to dig around for test data, but reading some older threads, i see now that a larks foot to a 10mm pin, eg screwgate, ( but some biners are abount 8mm pins) causes little reduction in sling strength (NB... but can be significantly reduced if used direct on a wire to extend the biners position to prevent crossloading.... use a basket hitch then as it's stronger).
On a 10mm pin a dynema sling attached by larks foot broke at 19kN instead of 22kN
.... and a clove hitch will slip a little absorbing some force.

So a knot could have consequences, but a hitch, little change in strength.

Older thread... https://www.ukclimbing.com/forums/t.php?t=559130

Just puzzled as to why you made the effort to reply with such little info to share with novices!
jimtitt - on 02 May 2017
In reply to Rock to Fakey:

Well girth hitching into my harness I only need it to be strong enough to hold me up and clearly it does so actually how strong it is doesn´ t interest me and the once in a blue moon that I clove into a karabiner about 5kN will do. As I wrote, I rarely if ever tie knots in slings and as other have mentioned it is never nescessary to do so.
A sling is simply a sling, it is designed to function without knots, tested without them and included in the safety system without them. If others want to tell climbers to tie knots in them that is their affair.
Donny M - on 02 May 2017
In reply to Rock to Fakey:

I recently climbed a route with dozens of limestone/calcite threads (Under the Avon Gorge Suspension Bridge) which i larks footed slings over, I did take 2 falls on the crux which were saved by a 10mm sling on a thread on one rope, and an in situ cord on a larger thread on the other. My question is, is the larks foot around the thread bad practice, would a basket hitch be better?
maxsmith - on 02 May 2017
In reply to Donny M:
To my knowledge there are two reasons a basket hitch is better than larks foot in this scenario.

- sling has a higher breaking point
- thread is loaded more evenly

But I wouldn't expect either to fail..
Post edited at 09:54
oldie - on 02 May 2017
In reply to Rock to Fakey:

Always thought one shouldn't use tape (or probably rope) directly on a wire due to danger of cutting. In late 60s/ early 70s wires were often sold with a hard nylon(?) tube over part of the wire to avoid using a krab but this was thought not to be much improvement (don't know the evidence).
highclimber - on 02 May 2017
In reply to oldie:

it's perfectly fine to thread a nut with a sling. I do this if a krab is badly oriented over a bulge on a rock. look at the DMM videos with pull tests.
oldie - on 02 May 2017
In reply to highclimber:

Sorry for the confusion. I meant using a sling directly round the actual wire (not through the metal wedge itself). Incidentally I have seen this done on belays and for runners quite recently.
oldie - on 02 May 2017
In reply to highclimber:

I didn't read your reply carefully enough...I'll try and find the DMM video. Incidentally in the scenario you mention I might have tried using another wire instead of the sling though don't actually know if this would be better.
oldie - on 02 May 2017
In reply to highclimber:

Thanks for the info. The DMM results do indeed show that a sling basket hitched round the wire is a good way of preventing loading a krab over an edge. Also this method is better than using a larks footed wire, and Dyneema appears better than nylon in this instance.
I do wonder if the results might be a bit worse, by putting more strain on the hitch, if the sling did not run over an edge, though in practice a krab is should be used anyway. Also maybe the larks footed wire would give better results if one or both was wider diameter. As is obvious I don't have much engineering knowledge.
Offwidth - on 02 May 2017
In reply to beardy mike:

"You also need to bear in mind that worn slings can see rapid deteriation in strength. For example, some thin dyneema slings have been found to lose 30-40% of their strength after a couple of years use"

At a Peak Area meet a couple of years back the BMC live tested a brand new sling rubbed for about 30s on a lump of gritstone and it was weaker than a sling cut half through (below 50% rated breaking strength ). Hence I''d be impressed if any dyneema slings that had been well used on grit or granite would meet the 30% mark after a few years.
MFB - on 02 May 2017
In reply to Offwidth:

Good point but still gives a reasonable 7kn, I use 6mm slings but not grit or granite, thinking 5 yrs
Rock to Fakey - on 02 May 2017
In reply to oldie:
+ Donnie M, + others...

DMM test vid Girth hitch vs Basket Hitch to extend a wire to prevent crab cross loading
... would apply to threaded Rock too i dare suppose...

I was looking at this the other day after doing a route + wondering what would be a betterway to extend a wire where the biner was going to get crossloaded.. (as i had extended it by threading another wire to it!)...

http://dmmclimbing.com/knowledge/improvisation-larks-foot-or-basket-hitch-vid/
Post edited at 21:27
Leearma on 02 May 2017
In reply to Rock to Fakey:

Hello Rock to Fakey


In response to your point about my use of dynamic / non dynamic.

What you are trying to avoid is a heavy shock load through the sling caused by slack in the sling. This is why the DMM presentation talked about factor 1 and 2 falls. In reality this would be where the sling is slack and the climber is level with or above the gear, and then falls onto the sling.

Slings do not absorb energy particularly well in this scenario and therefore are tested end to end on a pull rig where the load is increased until failure. If used correctly there are other elements of the safety chain that will fail before a serviceable sling. With significant strength redundancy built into the sling, this allows for the right knots in the right circumstances to be introduced to the system without a significantly reduction in the safety of the system. To confirm, good use of a sling is to ensure that it is not slack in your safety chain.

Unlike a dynamic rope (half, full, twin) who's energy absorbing properties are related to the construction and manufacturing (weave and autoclave) techniques. Dynamic ropes have various tests carried out for EN certification, one of which relates to a drop test with a fall factor over the value of 1 (can't remember the actual value - 1.8 I think but I'm sure that someone will correct me). The weight of the falling mass varies depending on the type (half, full, twin)of rope tested.

This is why it was suggested that you use the rope in the construction of your belay, and simply use the slings to extend the attachment point or simplify the equalisation of your gear. The differing dynamic properties is most noticeable if you take a big wipper with plenty of rope out, as long as you don't hit the floor, the fall is arrested more comfortably that those horrid short slips with little rope out.

Hope that helps
oldie - on 03 May 2017
In reply to Leearma:
" suggested that you use the rope in the construction of your belay"

May seem obvious but I assume that having only a short length of rope interposed between belayer and anchors may not do much energy absorbing. I wonder what sort of length of say a typical single rope might be necessary to clove hitch to a good static anchor setup when holding a factor 2 fall?
Incidentally I generally use a rope doubled back through the anchor and attached to the harness. I assume this doubling may actually be less effective in reducing the potential impact on the system?
I suppose these are all considering absolute worse case scenarios, which can be avoided if recognized. In fact there must be many different setups that are perfectly safe so long as anchors are bomber.
oldie - on 03 May 2017
In reply to Leearma:

Partially answering myself. Holding a factor 2 fall the protective effect of length of rope (A) hitched to static anchors would decrease progressively as the distance led without runners increased as A could possibly be considered as part of the rope out. If 1 metre of rope out giving 2m fallen and A is 1/2 m then F is 1.3, but if 5m climbed without runners F is 1.8.
(Also if belayer had static slings hanging 1m vertical distance from anchors with only 1/2m of rope to harness, and for some reason went up 3m and fell off onto the anchors, then fall factor would be 6.)
Apologies for rabbiting on about something when my knowledge of mechanics is basically nil. I do have a genuine interest in all this, and do alter the ways I use my own gear accordingly.
jimtitt - on 03 May 2017
In reply to oldie:

Ignore any dynamic effects the anchor may give, they have never been considered as part of the safety chain, are nearly impossible to quantify and are irrelevant as the overriding control over the maximum force the anchor will ever experience is performed by the belay device so in the region of 6-7kN.
The belayer climbing above the anchor and falling is also not part of normal climbing.
NoddyBoulder on 03 May 2017
In reply to jimtitt:
> The change from kg (and then kgf) to kN was due to changing to SI units.

But kg is an SI unit already. It's even a *base* SI unit, and Newtons aren't base SI units (they're defined in terms of mass and acceleration, i.e. kilogram metres per second squared).

Changing from kg to kN is a change from an SI unit of mass to an SI unit of force ... so changing from measuring mass to measuring force, not just changing the units used. I don't know the history, but purely in terms of the physics involved that would be consistent with changing from measuring a static load to a dynamic one.

Edit: Ah, but kgf isn't an SI unit, even though it is a unit of force. Since it's defined in terms of gravity it still seems (to my ignorant noob mind) to be about a static load being pulled by gravity.
Post edited at 18:06
jimtitt - on 03 May 2017
In reply to NoddyBoulder:

What on earth are you on about?
Gear used to be rated with breaking load in lbs and was then changed to kg under SI.
This was changed to force in kN (or daN) for the European standards.
I and many others also still use kgf where appropriate or even caption the axis of our graphs in with "force" and use kg as the intervals. Whether the force is applied "dynamically" in your thinking is irrelevant as the thing that changes mass to force on earth is constant.
NoddyBoulder on 03 May 2017
In reply to jimtitt:
> What on earth are you on about?Gear used to be rated with breaking load in lbs and was then changed to kg under SI.

Which makes sense, but isn't what you said earlier. I was on about your earlier comment that said "The change from kg (and then kgf) to kN was due to changing to SI units." If you'd said from lb to kg, or lb to kN then I wouldn't have been confused!
Post edited at 19:28
Rock to Fakey - on 03 May 2017
In reply to NoddyBoulder:
According to Libby Peters book, Rock climbing, Essential skills + techniques, the change from kg to kN was because gravity needed putting in the equation.
So x kg under the influence of gravity, eg when just hanging on the end of rope = y kN, and when falling obviously more than just gravity so the kN figure gets maybe even as high as somewhere approximately = to z kN.
Pg 51to 53. Climber with 100kg mass on end of rope of rope exerts 1kN of force just through gravitational pull., bouncey abseiling = 2 kN, falling second exerts 2-3 kN, leader falls max possible force on top runner = 12kN, (Ff more than 1 scenarios) but more likely 3-7 kN in Ff 1 or less scenarios.
FF of more than 0.75 or 0.8 ish means you will be more or less hitting ground at rope stretch.
Post edited at 23:00
Rock to Fakey - on 03 May 2017
In reply to oldie:
Think you might have this muddled a little fair bit. But i might be wrong. I'm not sure about most of what you tried to figure, but i don't think you can have a fall factor greater than 2.
Ff = distance fallen / rope lenth out.
... Unless you are super strong and can continue to climb up when on bungey cord and stretching it, so thus climbing higher than the length of bungey so you start stretching it, eg if you are super OndraMegosSharmaMoffattDunne, climb 4m high above belay, no gear between, on a 2m length of stretching bungey, and get pumped out + pulled off, f-doink... fall 8m on 2m bungey = FF 4. In theory that is.
Post edited at 23:15
jimtitt - on 03 May 2017
In reply to NoddyBoulder:
One of the joys of joining the EU, the directive says a force will be applied and it was defined in N, previously a load was applied and this was measured in kg. The British and USA used lbs naturally enough until we metricated (using cgs not SI) and the Americans use both.
Post edited at 23:09
NoddyBoulder on 03 May 2017
In reply to jimtitt:

Gotcha - thanks!
oldie - on 04 May 2017
In reply to Rock to Fakey:

" i don't think you can have a fall factor greater than 2.Ff = distance fallen / rope lenth out.... Unless you are super strong and can continue to climb up when on bungey cord and stretching it, so thus climbing higher than the length of bungey so you start stretching it, eg if you are super OndraMegosSharmaMoffattDunne, climb 4m high above belay, no gear between, on a 2m length of stretching bungey, and get pumped out + pulled off, f-doink... fall 8m on 2m bungey = FF 4."

Thanks for bothering to reply! Also to Jim Titt for putting things in perspective(" the overriding control over the maximum force the anchor will ever experience is performed by the belay device" )
I'm really the last person able to argue formulas but here goes. In my theoretical example Static anchor sling hangs down to 1m so this point can be regarded for our purposes as a "bolt" (it doesn't matter that it can be moved up and return to its position in the fall). 0.5m dynamic climbing rope from here to harness ie sling + harness= 1.5m. Thus our stupid climber decides he wants to put a higher anchor in and can climb 1.5m above static sling anchor point ie total 3m. He then falls off (ie 3m) onto "bolt" with just 0.5m rope out. Thus FF = distance fallen / rope length =3m/0.5m = 6 (with no bungey required).
I really put this in as an aside as to why one shouldn't fall off when slackly attached to the anchors. As Jim says this is not part of normal climbing.
This type of situation with very high FFs can occur on via ferrata which is why special shock absorbing lanyards should be used. You are absolutely right that FF 2 is the max that occurs in normal roped climbing.
Hope this isn't all cobblers.

Rock to Fakey - on 04 May 2017
In reply to oldie:

I see what you mean now, so could you apply that like this and get massive fall factors..., not that any one would, but just as a demonstration of an example giving a huge fall factor....
Climber is lead climbing on static rope (!), but the last 1m of it is a length of dynamic rope... Let's assume that excluding the knot tying the dynamic rope to static + excluding the length required to tie into harness, that there is 1m of dynamic on the end of the static.
Climber climbs 10m above belay, no intermediate gear, falls off, falls 20m, onto 9m of static + 1m of dynamic rope, 10m total rope out, similar to the normal FF 2 situations, but the 1m of dynamic rope, has the force of a 20m fall, so that 1m piece is subjected to a Ff of 20/1 =ff 20!

Would that be true / calculated correctly?
Leearma on 04 May 2017
In reply to Rock to Fakey:

Looks like this has gone way off piste from the original question but two quick points:

In normal rope climbing with a dynamic rope you will not have a fall factor greater than 2. Lead climbing on 9m of static is not normal climbing...it would be rather daft..as it would hurt if you fall off, that is an understatement! In Via Ferrata you can get up to a fall factor 5, this is due to the length of the lanyard and the length of the potential fall, hence specialist lanyards with built in shock absorbers. You may get some joy from this link: https://www.petzl.com/US/en/Sport/Fall-factor-and-impact-force---theory?ActivityName=Rock-climbing#....

Fall factors are only part of the physics of a fall and be aware of peak force, note I have said aware and not able to present to a group of Physics students. Again these are elements of the safety chain, and when climbing the grades you climb I would suggest that you look to the whole system and understand fully how it works. As you progress you do not need to be thinking about one element of you safety system as this will result in your mind not being in the right place to proceed through difficulties of you will get properly spanked by a route...and it will hurt.

I have done my normal three responses and it is drifting way off the OP so I won't put any more on this thread...

stay safe.
jimtitt - on 04 May 2017
In reply to Leearma:

Many in the industry (including myself) and senior figures in climbing feel introducing fall factors as a way of explaining the physics of falls was a big mistake. The biggest danger in FF2 falls is the belayer may be unprepared to hold a fall in that direction, the forces are relatively irrelevant whether it´ s a FF2, FF1 or whatever.
andrewmc - on 06 May 2017
In reply to jimtitt:

> Many in the industry (including myself) and senior figures in climbing feel introducing fall factors as a way of explaining the physics of falls was a big mistake. The biggest danger in FF2 falls is the belayer may be unprepared to hold a fall in that direction, the forces are relatively irrelevant whether it´ s a FF2, FF1 or whatever.

So redirecting through your anchor = A Good Idea?
jimtitt - on 06 May 2017
In reply to andrewmc:

Each to their own, there are pluses and minuses. I rarely bother but then I don´ t usually climb with people who fall off.
pigeonjim on 06 May 2017
In reply to andrewmc:

Saving weight over safety is not good. You put a knot in dyneema and shock load it the heat will often melt it.
Rick Graham on 07 May 2017
In reply to jimtitt:

> Many in the industry (including myself) and senior figures in climbing feel introducing fall factors as a way of explaining the physics of falls was a big mistake. The biggest danger in FF2 falls is the belayer may be unprepared to hold a fall in that direction, the forces are relatively irrelevant whether it´ s a FF2, FF1 or whatever.

Fair comment, but it might be a bit late to suggest we all stop thinking about fall factors as a way of explaining fall physics.
I have been climbing for almost fifty years and cannot remember not having fall factors used in "explanations " .

Its fairly simple in real life climbing.
Know which are dynamic and static materials.
Only " fall " on a dynamic rope.
Oh, and read the instructions.
jimtitt - on 07 May 2017
In reply to Rick Graham:

I´ m not sure when the concept was first introduced (at least in the form it´ s used nowadays), it certainly wasn´ t around 50 years ago when I started climbing.
The problem is the basic concept is simple so beginners latch onto it but the difference between the theoretical fall factor and the effective fall factor isn´ t emphasised enough. For example adding more pieces of protection to reduce the fall factor will usually be contra-productive as the effective fall factor is increased.
The concept also completely ignores the effects of belay device effectiveness and belayer weight which are the dominating factors defining the forces in moderate to larger falls, let alone that the rope dynamics aren´ t a simple spring, all of which make the fall factor concept basically meaningless even for expert climbers let alone a suitable theme for beginners.
Knowing about fall factors isn´ t going to keep anyone alive
Rick Graham on 07 May 2017
In reply to jimtitt:

> I´ m not sure when the concept was first introduced (at least in the form it´ s used nowadays), it certainly wasn´ t around 50 years ago when I started climbing.

Need to do a bit of research but TBH, I cannot remember it not being used.
Were you paying attention then

>The problem is the basic concept is simple so beginners latch onto it but the difference between the theoretical fall factor and the effective fall factor isn´ t emphasised enough. For example adding more pieces of protection to reduce the fall factor will usually be contra-productive as the effective fall factor is increased.

Admittedly a free running rope helps, but so does a close runner to avoid a long fall and possibly hitting ledges.

>The concept also completely ignores the effects of belay device effectiveness and belayer weight which are the dominating factors defining the forces in moderate to larger falls, let alone that the rope dynamics aren´ t a simple spring, all of which make the fall factor concept basically meaningless even for expert climbers let alone a suitable
theme for beginners.

We know it complicated

>Knowing about fall factors isn´ t going to keep anyone alive

I think it is a useful simplification. But TBH being good at placing gear is far more useful for trad climbing

What has pissed me off for years is being told fall factors are the be all and and all.
My gut feeling always was that it was far more complicated.
Rock to Fakey - on 12 May 2017
jliungman - on 19 May 2017
In reply to Rock to Fakey:

I think there is some confusion regarding fall factor here and there in this thread. FF is really only relevant as a concept if you are using more or less dynamic rope. It has to do with the amount of energy-absorbing material actually absorbing energy. Falls of the same FF become comparable regardless of length.

To talk about FF in static scenarios (as DMM, somewhat oddly, do in their famous drop-tower video) is wrong. Basically, in a static situation, the length of the fall is everything. If you fall 2 meters on 2 meters of dyneema, this is NOT equivalent to falling 4 meters on 4 meters of dyneema.
Rock to Fakey - on 19 May 2017
In reply to jliungman:

Interesting... so without anything dynamic in the system, the longer the slip / fall directly onto static sling / rope, the greater the force, the higher the risk of it breaking.
If illustrated using static rope dropping a weight from a fixed anchor from 1m, 2m, 4m or any figure, the ff is always 1 as rope and fall length are always the same, but the force is getting higher for longer falls, until from a certain height it is too much + breaks, whereas with dynamic rope in each case the extra rope being dynamic will absorb the force.
So a 50m dynamic rope can take at least 1 100m fall, but static would break at much shorter lengths, and be very painful even in short falls where it doesn't break.
GrahamD - on 19 May 2017
In reply to Rock to Fakey:

> Interesting... so without anything dynamic in the system, the longer the slip / fall directly onto static sling / rope, the greater the force, ...

Its a lot like falling directly to the floor (nothing dynamic in the system). The further you fall, the more it hurts.
oldie - on 19 May 2017
In reply to Rock to Fakey:

I believe the abseil ropes climbers buy are in fact semi-static Type B (just googled this). They should have a minimum static strength of 18kN (12kn with fig8 knot) and hold 5 successive falls with 80kg from a distance equal to the length of the rope: which presumably implies there is a degree of elastic elongation in a fall which at least partially reduces any increased forces with longer falls that you mention.
Note I do NOT have much understanding of the physics involved myself.
jkarran - on 19 May 2017
In reply to Rock to Fakey:

> Do you class a girth hitch / larks foot as a knot? Is the strength of the sling halved when you do this?

Only data I've ever seen came with some 6mm Mammutt slings I used to re-sling my cams, they were rated at 22kN open, 16kN larksfooted onto a bar (standard 12mm(?) presumably) so not half but weakened. I suspect the exact set-up is suite significant in determining the breaking load.

> When you clove hitch (your sling) to a carabiner, is that a knot you just tied that halves the slings strength?

Clove hitches in slings are mostly used on stakes. Only other use I can think of is to improve an american death triangle (but not by much). It's a hitch, it never locks down hard like a knot does.
jk
Rock to Fakey - on 20 May 2017
In reply to oldie:

> I believe the abseil ropes climbers buy are in fact semi-static Type B (just googled this


Cheers, good point, just noticed while looking at getting a new half, that semi statics are available too.
Rock to Fakey - on 20 May 2017
In reply to GrahamD:

> Its a lot like falling directly to the floor (nothing dynamic in the system). The further you fall, the more it hurts.

Like being tied on a steel cable, i guess even a 10ft drop would be quite painful/ injurous,
and long falls the impact would cause internal trauma and death!
deepsoup - on 20 May 2017
In reply to oldie:

> I believe the abseil ropes climbers buy are in fact semi-static Type B (just googled this).

They're EN1891 type A.

Type B ropes are not designed to be used routinely, they're generally thinner and less robust than type A ropes and intended to be used in an emergency only (and probably binned after a single use).
deepsoup - on 20 May 2017
In reply to Rock to Fakey:

A "semi-static" rope is not more stretchy than a "static" rope, they're just two slightly different names for exactly the same thing.

As oldie points out, the standard they comply to (EN 1891 type A or type B) specifies a maximum impact force in a drop test - which means any static rope a climber is likely to buy is required to be a little bit dynamic.

People started calling it "semi-static" instead of "static" to reflect this, but both terms are a little bit old-fashioned now, these days most of the manufacturers are calling it "low stretch kernmantle". Three different names for the same stuff, what it's called mostly just depends on who you're talking to.
oldie - on 21 May 2017
In reply to deepsoup:

Thanks for the correction.
Then looking at type A ropes they are stronger and provide better dynamic performance than Type B. They must hold at least 5 factor 1 falls with a 100kg weight and the impact force must be less than 6kN.

I imagine they are actually safe for bringing up a second in most situations and indeed for bottom roping. However in an emergency might they also be acceptable for leading bearing in mind that not all falls are vertical, and runners, harnesses and belay device come into play to reduce impact on the body?
After all some falls were once held on hemp rope which would be far weaker and have poor dynamic properties.
(Interestingly HSE has the following in a document on rope standards: "EN 1891:1998 - PPE against falls from height - low stretch kernmantle." Quote with no context.....presumably industrial setups often involve shock absorbing devices.)

I'm definitely not saying one should go out with the intention of using these ropes in such a manner and repeat I have little understanding of the physics of all this.
oldie - on 21 May 2017
In reply to oldie:

"falls were once held on hemp rope which would be far weaker and have poor dynamic properties."

Probably a stupid comment on my part.....falls were held without a belay device using body/indirect belays ie usually a gentle, dynamic, arresting force.
deepsoup - on 21 May 2017
In reply to oldie:
> I imagine they are actually safe for bringing up a second in most situations ..
Yes

> ..and indeed for bottom roping..
Yes

Perhaps even safer in some situations, as there's less of a risk of decking on rope stretch low down on a longer pitch and the sheath is generally harder wearing.

> However in an emergency might they also be acceptable for leading..
Woah there, steady on now. ;-)

(Seriously though - I wouldn't.)

Edit to add, in reply to the above:

> Probably a stupid comment on my part
Nope, not at all. Bang on, I'd say.
And of course in those days the mantra was very much "the leader does not fall".
Post edited at 21:31
oldie - on 22 May 2017
In reply to deepsoup:

Despite the "the leader does not fall" mantra, falls onto hemp rope did occur and people did survive them. The one in the literature that springs to mind is Menlove Edwards holding Noyce in a 180 foot fall on Mickledore Grooves: Noyce was badly injured though not by the rope. He would almost certainly have had no running belay and a direct waist tie.

In a fantasy situation, where one had to escape by serious climbing with only a low stretch rope but otherwise modern PPE I think I might still lead on the rope and expect/hope to be OK in the event of falling due to the rope having some dynamic properties in addition to wearing a harness, using runners etc. Probably self delusion.
baron - on 22 May 2017
In reply to oldie:
Does the story continue where several years later Menlove was still using the rope used to hold Noyce's fall, having spliced the unravelled strands back together and taped them up, leaving a large lump in the rope.
Menlove obviously thought it was good enough but I think his climbing partner was less than happy!
jimtitt - on 22 May 2017
In reply to oldie:

1/2" Hemp rope holds about 11kN so with a reasonably dynamic belay obviously worked fine.
daWalt on 22 May 2017
In reply to jkarran:

> rated at 22kN open, 16kN larksfooted onto a bar (standard 12mm(?) presumably)
It's a hitch, it never locks down hard like a knot does.

I think your comment could be easily misinterpreted; or it's at least unclear what you're conclusion is.
a larksfoot is a hitch - and a hitch can just as well compress the material, and similarly reduce the breaking load; accordant with the first part of your comment.
oldie - on 22 May 2017
In reply to baron:

" Menlove was still using the rope used to hold Noyce's fall, having spliced the unravelled strands back together"

Unable to confirm this delightful story, Perrin's biography is lost in the attic together with my hemp waistband. Do remember something of the sort about him climbing postwar on Tryfan with a spliced rope. Obviously it was safety first as a good splice is apparently stronger than a knot!
jkarran - on 22 May 2017
In reply to daWalt:

> It's a hitch, it never locks down hard like a knot does.I think your comment could be easily misinterpreted; or it's at least unclear what you're conclusion is. a larksfoot is a hitch - and a hitch can just as well compress the material, and similarly reduce the breaking load; accordant with the first part of your comment.

Sorry, I thought I was clear what the one data sheet I've ever seen giving numbers said about those specific 6mm dyneema mix slings. Others slings and set-ups may produce quite different numbers though in my unqualified opinion I suspect they'd be in the same ballpark for reasonable seeming set-ups (not hitched onto sharp objects, thin wire etc). Others are free to form different opinions.

Hitches are easy to undo/remove after loading, knots in slippery slings pull so tight they can easily become fixed when loaded. That's all I meant by the second part of my post.

What I think: The strength reduction doensn't weigh heavy on my mind when knotting or hitching slings, the consequences of the knot or hitch slipping are considered and knots are generally avoided so as not to ruin my slings should they get set in place.

HTH, jk

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