UKH

Thought this was interesting, I'm surprised (and reassured) by some of the measured values 

youtube.com/watch?v=m8z6adEqaOs&

In reply to John Kelly:

Thanks for sharing, that was interesting. Loved his comment about highlining that they've made a hobby out of the death triangle!

In reply to John Kelly:

I was also surprised by the relatively modest forces generated. Max forces (on the anchor of course) of less than 5Kn if I recall. 

It's not a conclusive test but as an example of typical forces encountered it really emphasises how much safety margin there is on most of our modern kit.

Of course, misconfigured or poorly used gear will fail in unexpected ways, but it's re-assuring to know that most kit in good condition has a large safety margin against just being pulled apart.

In reply to John Kelly:

Good to see real world tests with harnesses, squishy climbers and friction. Also good that official tests are worst case scenario so that gear breakages almost unknown.

In reply to John Kelly:

I, along with Rob Bradshaw Hilditch, did a number of force through the foot, knee and hip test s about five years ago using ‘in shoe measurement’ technology. The impact on the lower limb (Ankle,  knee, hip and lower spine) as well as through the first metatarsal/philangeal joint was quite marked even with the use of climbing wall mats. And we used to use beer towels to land on in the Seventies and Eighties so I understand why my knees may need some repair work, probably in the near future?

In reply to Gary Gibson:

Quality, the beer towel not that great then😀

Bet it was lot more than 5kn (nursing arthritic toes)

In reply to Gary Gibson:

You got them from the wrong knee bar. 

In reply to drconline:

The exception being small wires. With their 7 kN they probably blow with a leader weight of 100 kg, reasonably static belay, and 8 meters fall.

In reply to elsewhere:

This is far from worst case. The really bad one is a fall on a via ferrata, after that falls into the belay of a multipitch.

In reply to HansStuttgart:

In most cases they probably 'blow' because the tiny amount of rock they engage with breaks, rather than failure of the gear itself. 

In reply to HansStuttgart:

Then lose some weight, find a better belayer and don't fall off!

In reply to john arran:

My theory is climb with cams....

I was mainly surprised by how easy it is to get to 5 kN with small falls.

In reply to HansStuttgart:

Yes, my first thought was 'ooh, it's really not that hard to get near the rated strength of smaller wires!'

I'd love to see this done with near-as-possible identical falls into a range of belay devices (to see if our presumption that grigris etc are bad for trad) and a range of ropes.

In reply to HansStuttgart:

Think I'm missing something, in the video, none of the falls or forces at any of the 3 points measured got to 5kN. 

I know this wasn't on trad blah blah blah, 

And wasn't on half ropes, and wasn't measured close to the ground or with bigger fall factors. 

But it does appear that generating high impact forces isn't as easy as you might otherwise think. Even to make an rp fail. Which from memory is 7kN??

Falling 8m onto an rp gives you super hero status in my book, my kahunus just can't do that. I know a shorter fall will generate biggish forces too. My kahunas equally can't do that on an rp unless involuntarily ejected from the rock. And even then it's unlikely...

Think I'm saying the video gave me courage, and no 5kN forces were observed. 

In reply to Kevster:

I think it is all comes down to expectations before the video. I assumed a relatively small leader fall (such as those in the video) + thin rope would never exceed twice body weight on the leader. So for 80 kg I estimated max 3 kN. They measured up to 4.5. I think this is close to 7 kN, because in safety system design you generally use a margin of 5 or more. Which is why carabiners are at 22 kN.

I agree that 8 meter falls on rps is hero status! Not planning on doing those.

I'll obviously continue using small wires, though. But I'll think a bit more often about putting the belayer 5 meters down from the belay if the first few pieces are small wires.

In reply to HansStuttgart: 

What the hell kind of a theory is that? As usual, these sorts of blanket statements are about as much use as a chocolate fireguard. If you place a cam behind a thin flake and fall you will soon know about it. As a rule of thumb, outward force exerted by a cam is four times downward load, i.e. a 5kn fall exerts approx 20kn of force on the crack walls. You can easily break a flake. A wire in this situation is much preferable because the wedge force magnifying effect creates a much much smaller force. Yes small gear is marginal. That is why you try to place clusters of gear to share the force, why using two ropes in parallel is preferable to using one (the fall force is split as long as not just one rope takes the force) on marginal placements, and why a 3kN microwire placed as a backup to marginal other gear is a good idea - the first takes the main impact but fails, thereby reducing the impact on the secondary piece to an acceptable level.

As for small falls, well if you understand the way a rope works, you’d understand that short falls are the worst! More slack means more stretch, means more energy absorbed, means lower deceleration forces and lower force on the top piece.

In reply to HansStuttgart: Think about it, double rope system (or indeed two single ropes - diameter is not an indicator of stretch and impact force) literally instantly halves the max force if plced at the same height, i.e. your scary 5kN becomes a very manageable 2.5kn...

In reply to beardy mike:

It was a joke. Should have put a smiley in.

In reply to John Kelly:

Would be interesting to see what different half ropes would make. 

In reply to HansStuttgart:

Basics of multi pitch leading, always put in a runner as early as possible to protect the belay and give the belayer an upward, not downward pull. 

In reply to beardy mike:

And for the serious part:

You underestimate the outward force generated by wires. If a wire is 8 mm long, 4 mm width at the top and 2 mm with at the bottom, the angle is atan(1/8). This angle also governs the outward force, so the outward force is a factor of 8 times higher. Wires do have an advantage in flakes, because you can typically place them deeper in the crack. This reduces the moment (force times distance) exerted on the crack, which is the prime factor for the flake breaking or not. So in conclusion, a small cam deep in the flake is better than a larger wire further out in the flake.

Having two ropes simply doubles the force on the climber and therefore doubles the force on the placement. Having two placements for two ropes halves this force again, so the result is the same. If you want to reduce the force on the gear, you should equalize the gear cluster and only clip 1 of the ropes into it.

Short falls on short bits of rope are the worst. Short falls on long bits of rope are low-force. Additional slack only helps after the breaking has started. The ideal soft fall is: during the fall the belayer takes in as much rope as possible to limit the fall-time and therefore velocity until the point where breaking starts. Then the belayer gives out more slack again to break very gradually. 

In reply to HansStuttgart:

You need to consider time. Not all force is applied on an anchor at precisely the same time. Belayer locks off, two ropes won't go tight at precisely the same time, knots tighten, harness squeezed, leader bounces or swings!  etc. Etc. 

Whilst it happens quick, it's not simultaneous. 

In reply to HansStuttgart:

Also half ropes tend to stretch less? So force would be higher.

And assisted breaking devices don't allow any slippage, so force would be higher.

So many factors to consider!

In reply to summo:

Yes. In the cases where the placements for the two ropes are not too far apart (and not too close), the belayer can essentially choose between loading mostly the higher placement or loading both placements equally.

In reply to PaulJepson:

Single ropes are rated for 80 kg, a half rope is rated for 55 kg. So a half roped stretches 80/55 times more and has a lower force by the same factor. If you use two half ropes, the ropes stretch less (factor 110/80) and the force is higher by that factor.

Here I ignore the fact that the rating for climbing ropes has a certain range that allows manufactures to make slightly more/slightly less stretchy ropes. This range is quite wide. A beal joker can be used both as a very stretchy single rope or as a very non-stretchy half rope.

In reply to HansStuttgart:

If we were talking pure maths I might agree with you on that first statement, I would have to check the ratio of the wedge shape. By we're not talking pure maths - there is friction between the surface of the nut and the wedge, the crack may have shape too which will affect the strength of the placement via mechanical interlocking. Yes you are right, a good cam placed deep behind a flake could be better than a nut at the edge of the flake. Although that gets on to how good small cams are which is a different subject. But given perfect placements in each I would agree. Place a cam in the same position as the nut and I wouldn't agree at all.

Your second statement confuses me deeply. How is the force doubling by using two ropes? The top anchor is fixed (given a perfect placement). The belayers weight does not change. The leaders weight does not change. If the belayer does not give a soft catch (i.e. he stays in position at the base of the crag with no upwards movement) then the force of the top anchors is a constant. If you split that force between two anchors (i.e. they are placed perfectly next to one another at the same height) then the force at the top anchor will be roughly half that of one anchor. I.e. each rope takes half the total force. They have to dissapate less energy and therefore stretch less, regardless of whether they are single ropes or double ropes. I agree with you that equalising pieces using a sling reduces the force on each anchor - just the same way equalising the force using two ropes does.

As for your last statement I think I agree with most of it other than that in the real world, how much rope can you realistically and safely take in to limit the velocity. Unless you are fast hands eddie, the difference will be marginal at best - if you manage 1m you'd be doing well, unless you are using a trick with a bottom anchor like some do on grit and then run backwards a bit. I'd say it's better and safer to make sure you brace your self well enough and give a dynamic belay as the guy in the video does to give a softer deceleration. As for giving out slack during the fall? whaaaaa

In reply to HansStuttgart:

What the hell has the rating got to do with the price of mustard? If you look at elongation under load you will find that across the board, diameter and whether a rope is rated as single, double or twin the stretch is completely unrelated to the amount it stretches. Infact some single ropes stetch more than a skinny double under the same load. And vice versa. You simply can't make a generalisation like you just did saying a half rope stretches a percentage of a single rope mainly because it's utter bollocks.

In reply to beardy mike:

Hi Beardy Mike,

I know you're in the gear designing buisness so have a better concept of the physics involved than most, and maybe I have missed some context to the statement above, but I got to disagree with the above.

Slack in the system will result in a further fall, and assuming the climber is not at terminal velocity, they will be accelerating through that distance, gaining momentum, and so the momentum change to bring them to rest will be larger.  The increase of momentum goes with the square of the distance falled if accelerating at a uniform rate.

This is of course countered by more rope in the system, which for a certain force will have more extension than a shorter rope. The extra extension will grow linearly with extra distance falled if modeling the rope as having a linear spring constant (a BIG assumption I realise).

As such I would predict higher impact forces with longer falls, as even though there is a longer distance and hence time to decelerate on a longer fall, you have more momentum to start with.

So I guess my question is in the industry, how do you model ropes?

Cheers

Chris

In reply to cp123:

I know next to nothing about the technicalities of rope stretch or fall factors but I have a general question that’s been bothering me for a while so here goes.

When at the wall I see people taking multiple falls of around 10 feet, sometimes intensional. I wonder how many of these short falls add up to the number of falls quoted as tested by the rope manufacturers and if people realise that these falls are going some way to ending the rope’s life.

Would a number of small falls add eventually add up to the 8 or 10 falls quoted by the manufacturer?

In reply to cp123:

Thanks for saving my thumbs some work and asking the exact same question I was going to. I see this a lot. Yes falls low down have less rope to absorb the impact. But intuitively, isn't the mitigation of the extra rope in the slack is outweighed by the increased energy from a longer fall?

Presumably the relative weighting changes with the height gained (the length of rope in the system) too?

In reply to cp123:

My point was that short falls close to your last piece tend to be rather abrupt - the anchor acts as a source of friction, hence why you tend to see a lower force on the belayer side of the system than the climbers side. Having just a little slack in the rope allows the rope to do it's job better and just even out the forces a bit. Maybe I was exaggerating a bit when I said worst, but I suppose what I'm trying to get at is that Hans worry that long falls onto a marginal piece is bad is unfounded. Yes, you accelerate more during the fall, but you also decelerate for longer because of the longer rope paid out. If you can further attenuate the force by belaying dynamically it will also make a massive difference. I suppose I should have said worst case...

In reply to Baz P:

That's not what the UIAA 'number of falls' means.

To obtain that number, they subject the rope to a particularly brutal fall (from memory, it's factor 1.77 with an 80kg mass over a fairly narrow edge) and then they repeat that fall with no time for the rope to recover until it fails.

It's a decent proxy measurement for 'how tough is this rope if it's loaded over a sharp edge', but it is in no way a limit to how many times you are allowed to fall before the rope needs to be retired.

In reply to Baz P:

To be completely honest I don't know enough about the energy absorption methods of ropes, as they act both like a spring, by stretching, and as a dampener, or shock absorber, as you don't carry on bouncing up and down after a fall.  I think it is down to the twists in the core untwisting slightly under the tension, but how that relates to number of falls before it breaks I'm not sure of.
 

What you can see however is people regularly taking shortish falls repeatedly when sport climbing, and we don't here of ropes just snapping unless factors such as sharp edges come into play. So on the whole it is safe. It probably shortens the lifespan of the rope but as the fall factor is generally small probably not by much.

Cheers

Chris

In reply to beardy mike:

I think I get it - in any case with sliding ropes, friction on a piece as a function of angle, dynamic/non dynamic belaying plus the rope having non-linear stretching/damping it is a very complicated system which can be hard to model - and using a solid 80kg mass with no bending or movement is going to produce different results compared to a human in a harness.
 

A bit of slack, as long as the ground or an edge is not in range, isn't always a bad thing.

Cheers

Chris

In reply to beardy mike:

You are right here, my mistake, sorry.

with giving out slack during the fall, I meant slowly breaking by letting the rope slip through the device, instead of statically holding the rope.

The standard example where you can take in a lot of rope during a fall is belaying on 50 degree snow slopes. During practice in mountaineering courses we typically could take in about half of the rope between leader and belay.

In reply to Baz P:

I think that the rated number of falls is for the absolute max impact on the rope. So FF2 with the 80kg mass (or whatever the spec says)

In reply to HansStuttgart:

OK, please ignore everything I said above, the situation is more complicated. Here goes:

Situation: Leader falls h/2 meters above a bolt, so the fall height up until the moment the ropes starts stretching is h. The amount of rope out is L. We define the point where the ropes starts stretching (= exerting force on the leader) as position u=0. We ignore the belaying by simply tying the rope to a bolt at the base.

the differential equation:

mg + ku = m d^2u/dt^2

Here, m is the mass of the climber, g = 10 is the acceleration in free space, k is the spring constant of the rope, and t is time.

solution:

u = C1 * sin (omega*t) + C2 * cos (omega*t) + mg/k

here omega = sqrt(k/m) and C1,C2 are constants that depend on the initial conditions.

The initial conditions are:

u (t =0) = 0

du/dt(t=0) = 10* sqrt(h/5) = v_max

The latter is simply the free fall acceleration integrated over the time it takes to fall h meter, so the maximum velocity (v_max) during the fall.

From condition one follows:

C2 = -mg/k

From condition two follows:

C1 = 10*sqrt(h/5)

The maximum force applied to the climber by the rope is k*u_max. Where u_max is the maximum displacement. 

The easy case first: h =0. So letting go when the rope is already tight.

It follows that C1 = 0 and u_max = 2mg/k

This gives a maximum force of 2mg, so twice bodyweight. This force is independent of k therefore the situation discussed above by Mike applies: Using two ropes (thereby doubling k) does not change the forces on either the climber or the bolt.

The general case: h is finite

Now the displacement u has both a component that is k dependent (C2) and one that is not (C1). The C1 component to the displacement generates a force that depends on k. Therefore, in the general case, the forces on the climber and the bolt do depend on whether 1 or 2 ropes is used.

The main question now is when C1 is dominant and when not.

u_max in the general case is sqrt( v_max^2 + (mg/k)^2 ) + mg/k.

example: h=5, L=10, the ropes stretches 10% under a 80 kg load. We also have and 80 kg climber.

This gives: v_max = 10, mg = 800

from the 10% stretch and the length of the rope we can calculate k:

k= 8000/L = 800

which gives 8.8 kN.

This is seriously high. Presumably due to the extremely static belaying.

The main failure of the model are the lack of friction. Friction breaks more in the initial stage because its force is proportional to velocity whereas the force of the rope is proportional to displacement. Therefore the maximum displacement will be reduced and therefore the maximum force on the climber exerted by the rope will also be reduced.

Conclusion. Doubling the amount of ropes can result in larger forces during falls. This becomes more relevant the larger the fall-factor is (larger fall factor is larger product of maximum velocity and spring constant).

PS. This equation should be cut off after the time where the leader has bounced back higher than position u=0, because from that point on the force exerted by the roped becomes zero as opposed to ku

In reply to HansStuttgart:

This is far from the worst physics I've seen on an internet forum, but it's entirely pointless as anything other than an interesting academic exercise so I haven't looked at it much beyond skimming through. You're trying to make authoritative statements about complex, real-world scenarios based on wildly over-simplified assumptions. Climbing ropes are not springs, nor are they all identical. Human bodies are not static masses. Friction is significant (and isn't normally proportional to velocity, where did you get that from?). Falling isn't necessarily even freefall. Belays are never 100% static.

In reply to HansStuttgart:

Dear god man... what are you? A mathematician or a physicist?

Your figure of 10% stretch under 80kg, well that is a static elongation, i.e. what happens when you hang 80kg from it, not what happens after a fall. So for example, your standard UIAA test takes a 55kg weight for a half rope or an 80kg weight for a single rope, exposes it to a factor 1 dynamic fall (which in normal use is somewhat harsh and of course they are using a static, solid weight making it harsher again) and then they measure the impact force on the climber end of the rope, i.e. the peak force "seen" by the weight during the fall. They then measure the elongation of the rope and this gives them a figure called stretch after first fall. This is much higher than 10%, in the region of 30%. So impact force will be much lower because ofthis. To be fair you can look at the results for impact force and that gives you real world impact for such a fall.

But the most important thing here is that "modelling" this sort of thing accurately is virtually impossible/a massive waste of time because there are so many variables at work. Nearly all belay plates slip to some extent, without you paying out anything and this adds to absorbtion. The amount it slips will depend on:

diameter of rope

the belay plate used

The age and condition of the rope

whether the rope has dry treatment or not (reduces friction)

the grip strength of the climber

the squishyness of the climbers

the type of knot used

whether the climber belays dynamically, i.e. launches themselves upwards a little to allow the leader to fall further thereby reducing impact

amongst god know how many other things.

In reply to beardy mike:

Hi

Physicist, an experimental one though.

I do obviously understand that the model above ignores loads and presents a worst case scenario. The big reducers of the force on the climber are friction in the system and dynamic belaying.

So it is just a bit of fun in the right direction. Having real data would be much better, but I am not bothered to do tests with different types of ropes and fall factors myself.

Regarding our discussion about clipping one or two ropes:

I agree with you that in the static case the force is always simply dependent on the weight of the climber and does not depend on any property of the rope. So I can take multiple ropes and thereby split the load over different protection pieces.

But in the dynamic case there arises a problem. Because if the force of a fall (on the climber) stays constant between going from 1 to 2 ropes, I might as well use 10 ropes parallel. And in the end this is the same as using a static rope. And nobody does that, because you break your back in a fall. So no matter all the other issues like friction and dynamic belaying, there has to be an increase in the force on the climber when going from 1 to 2 ropes.

In reply to HansStuttgart:

Ha - thought so! Too much practical application for a pure mathematician!

I guess you may well be right that there is an increase on the climber. I suppose I'm concentrating more about thinking about anchor failure. In the end whether your body is exposed to 5kN or 6kN is a moot point as it doesn't really matter whereas total anchor failure is definitely a possibly crater shaped problem

In reply to HansStuttgart:

My theory is place whatever gear you can and back up small wires or cams if possible and depending on what / where your previous piece was. 

In reply to John Kelly:

Loving the thread. 

Only on ukc do you get such a discussion....

So to cut to the quick.

1 don't fall. 

2 place gear often. If the rocks garbage then place passive gear over cams. 

3. Clip the rope

4. Place some back up gear (and preferably 2nd rope), especially if the gear is garbage or near your belay anchors.

5. Grit your teeth harder and don't fall. Or choose to back off. 

6. The more complacent your belayer is on multipitch the better. See item 1 and 5.

In reply to Kevster:

Incorrect. Replace all those rules with Rule no. 5 of the Veluminati. Harden the f*ck up. If you harden the f*ck up, you won't fall and all this discussion will be for nought.

In reply to beardy mike:

Now that we can all agree on

In reply to HansStuttgart:

This is wrong.  Two ropes rather than one do increase forces because they constitute a stiffer system, but it is nothing like doubling.

This actually contradicts your previous statement.  How do the ropes know they are running through two anchor points rather than one?

This is wrong as well, because those aren't "ratings," they are the weights used for testing.  When half ropes are tested as singles, they stretch and impose maximum loads that are comparable to singles. 

The difference between halfs and singles is that half ropes may not hold the UIAA mandated 5 factor 1.85 falls with an 80 kg weight. (They will hold one or two such falls.)  The 55 kg weight is used for more reliable statistical information about breaking half ropes using an 80 kg weight.  (Even rope manufacturer's materials sometimes get this wrong)

In reply to HansStuttgart:

Here is the mistake

This should have been C1 = 10*sqrt(h/5)/omega.

Correct formula for the impact force (frictionless case):

F_max = mg + sqrt(2mgkh+m^2g^2)

So in the large fall factor limit, where elasticity becomes dominant, doubling the amount of ropes increases the force by a factor of sqrt(2). As this force can be split over two placements, the force on the placements becomes 30% smaller.

This results in about 4.5 kN for the 5 meter fall discussed above, which is actually in agreement with the data from the video

In reply to John Kelly:

I think if the loads were any higher I would worry. The stiffness of the rope will increase at low temperatures, and in  an unexpected fall a belayer will often give a less soft catch, increasing peak force. A safety factor of about 3 seems about right!

In reply to HansStuttgart:

With double ropes you land mainly on one or the other as placements determined by irregular rock, gear available, bravery and fear.

Fall factor is a good indicator for "more is worse" and that is about the limit of useful calculation. The other factors are undefined and unquantified.

The issue of friction though was well illustrated in the video.

In reply to John Kelly:

I did some drop testing the other day. The first test was on a jumar which had 100kg on it and then had another 100kg dropped with a factor 1 fall of 60cm on a dynamic lanyard and it sheathed the rope by around 4m. The jumar was on 11mm static rope and had a peak tension of just under 6kn.

The second test was with a 140kg solid manikin which we dropped 4m in a factor 2 fall upside down on 11mm dynamic rope. There was no load cell in this test and everything held OK and the knots (bowlines) came undone easily, although the rope was quite kinked afterwards. I seen the knots melt when we've done factor 2 drops before. 

In reply to Baron Weasel:

Be interesting to see what force was generated in the 4m,140kg, ff2, 11mm - even better if you did it with an 8mm

In reply to Baron Weasel:

Interesting how destructive the test can be without being catastrophic - the rope core held.

Are you testing industrial fall protection?

In reply to Baz P:

The math is very complex, given changing friction and system 'gives', but Fall Factors (FF) give the best easy way of thinking about fall forces. Ropes are rated on a cumulative  FF basis (fall distance /length of rope absorbing the fall). Forces are approximately proportional to FF.  The stretch deceleration force is acting for longer to account for the energy absorption difference of a longer fall on the same FF.

As a result small falls high up with a lot of rope paid out are not as serious for the rope ( or the runner, climber,  belay or belayer) as they have have smaller fall factors: eg a 4m fall with 20m of rope paid out would be FF0.2 ....the fall from say 20m to 16m.  A similar size fall of 4m, onto a hanging belay on a multipitch will be FF2 as you fall from 2m above the belay to 2m below (on 2m of rope) with approximately 10 times the previous examples forces. Hence, forces on belays and belayers and climbers can be huge in relatively small distance FF2 scenarios.

Another factor not often thought through properly by some climbers is, unlike ropes, new slings will snap if subjected to a FF2 (f you clip one from a belay point direct to your harness and climb the full distance above it, fall off, and take the force the full distance below it). Furry slings won't even hold a FF1. Take care how you set up a belay!

On the other argument above, having experienced high sport falls on overhanging terrain when the belayer removes slack before the deceleration starts, the force feels higher and certainly  with a larger inward component (and climbers have been injured this way, being slammed into the wall); in contrast when a similar high fall is made on a belayer partly giving slack it feels like a lower force with a definite lower inward component. There were some nice demonstration of this on the web a couple of years back, where sadly I can no longer track the link.

In reply to elsewhere:

Yes, it was interesting to see how the sheath bunched up and stopped the jumars and weights. 

Yes

In reply to Offwidth:

"the math" shudder

In reply to Offwidth:

Made my head hurt but thank yo for the explanation. Those dynamic catches can be witnessed at best in competition climbing, sometimes with the climber stopping 3 or 4 metres from the floor after a 17m route. 
Back to my original query though, weeks or months of working routes and continually taking small falls surely has a cumulative detrimental effect on a rope. 

In reply to Baron Weasel:

New underwear required when you see the rope disintegrating as you fall!

In reply to elsewhere:

Happened to me while 500m up and descending from a new bigwall route, abbing on a fixed 9mm static line and heavily laden, suddenly hearing a disturbing rasping sound and seeing the single strand I was dangling from become core only. Not something you forget in a hurry.

Thankfully there was a crack in front of me, I had plenty of gear on my harness, and there were other people just above with extra ropes.

In reply to Baz P:

Wrecks the bit of sheath that's continually being fallen on, which is why people cut a few metres off when the end gets knackered. But I've never heard or suspected that the rest of the rope is particularly affected/degraded.

In reply to john arran:

Bet there was a dirty crack behind you too! 

In reply to Baz P:

The best way to judge a rope that only takes small FF falls is to look for rope damage. If there is none, the rope is almost certainly OK for continued lead use. A furry sheath isn't such a big issue, a holed or heavily slipping sheath or a lumpy feeling core would be.

In our club at one point we were told we had to log the FF of each fall (following manufacturer advice to always rest the rope between falls for a good few minutes to allow elasticity to recover) and officially when the sum of the individual FF values reached the limit assigned to the rope  (always above  5x1.77 for a single rope), to retire the rope from lead use. This is excessive as the rope tests don't include resting or the 'give' in normal climbing use. However in the big falls you describe (probably only around FF 0.6 as there is a soft catch, ropes stretch a lot in big falls and the wall was presumably overhanging), if done repeatedly for many times with no rest between falls, this may well be damaging the elasticity of the rope.... I wouldn't lead on such ropes. I'd add that even excessive FF overuse of this type has never snapped a rope, so they will still be OK for top-roping. Climbing ropes only snap due to being physically damaged, tensioned over sharp edges, tensioned under abrasion or tensioned after chemical damage.

In reply to GrahamD

Any opportunity to make UKC 'english' pedants shudder is gladly engaged

In reply to Offwidth:

I'm continually amazed at how many ways people find to completely miss the point of any safety-related climbing advice. This one's a bit like saying "I can't do 10mph in a 30mph zone more than three times or I'll have broken the speed limit"!

In reply to john arran:

Frankly it was because the SU were clueless. We had to retire perfectly good kit as well due to manufacturer specified lifetimes. The BMC really helped us out on equipment issues and more importantly on the increasingly idiotic SU requirements on trip planning (for one of our annual Easter week's winter climbing trips to Lochaber, they suddenly decided we needed to provide a matrix of which of the 20 climbers would climb which route, on each day, before we even left on the trip).  

In reply to john arran:

I don't think its like your analogy at all.

I have an ebike battery that accumulates  "damage". It is warrantied for X number of full charges (1000 I think) but each partial charge is recorded and the accumulation noted.

It is more difficult to record small falls onto a rope but they must surely have an accumulative effect on lifespan. I would also assume that accumulative hours in direct sunlight will have a detrimental effect. 

In reply to Baz P:

The retire criterion being used reportedly was when the number of UIAA-class falls reached the number published for the rope. This number apparently was being reached despite no UIAA-class falls ever having been recorded, which is plainly absurd.

As for your assertion that "small falls ... must surely have an accumulative effect on lifespan", if you have any evidence to support this, and particularly if that evidence suggests that small falls reduce the ability of the rope to hold a UIAA-class fall in proportion to their cumulative fall factor total, then I'm sure we'd all love to hear it.

In reply to john arran:

Any use of a rope has a detrimental effect otherwise we would never replace them. I would never take dozens of small falls on a rope and then sell it on as still having the original UIAA fall rating. 
My thoughts on this are based on logic, if they are not the same as yours then we must agree to differ. 

In reply to Baz P:

Damage to elastic core performance from falls will accumulate but nothing like as fast as my old SU thought (their view was based on no research or expertise). They accumulate alongside other core damage from use (especially top-roping or ascending on a climbing rope weighted over an edge, which can affect core and sheath).  When damage is significant you can feel it by hand  when you check along its full length (non-uniform core, or sheath slippage). However, sheath damage is the most common reason to retire a rope. Friction on a rough surface will cause furring and eventual sheath failure, a rope weighted over a sharp edge can cut the sheath (and core). Weighted rope differentially moving on weighted rope will quickly melt the sheath (and core).

Sunlight does trash webbing (slings etc) as every strand of the material comes to the surface. In contrast rope performance is based on the core which is protected to a large degree from sunlight by the sheath. I've snapped sun-bleached slings (on abseil stations in the US) in my hand, that when new would hold a truck. It's much safer to use static cord for abseil tat. 

In reply to Offwidth:

Can I be a "don't use obscure acronyms & jargon in a public forum" pedant? Wtf is an "SU"?

In reply to Baz P:

Baz, please go back and read my previous post. I'm afraid you have fundamentally misunderstood what the UIAA 'number of falls' statistic means. It has nothing whatsoever to do with measuring the life span of the rope.  That's what Offwidth and John are trying to tell you.

In reply:

Some twenty years ago, while I was employed testing rope access PPE for the HSE, I had a fairly protracted argument with a colleague about this. Back then I said something along the lines of John's first comment quoted above. Now having had some time to reflect I'm pretty sure I was wrong.

A rope is not a perfect spring and will not recover perfectly. Whether you want to parse that as 'damage' or not is moot. The sharp end of a sport rope gets trashed quicker than the middle because it gets fallen on. I suppose you can argue that's due to abrasion from the top draw but even given a perfect surface there I can't see the repeated elongation around a tight bend having no effect.

In reply to Adam Long:

But accepting some degree of likely damage isn't the point here. The point is the nonsensicality of trying to equate that to UIAA falls and come up with some formula for accumulated damage that equates to one or more UIAA falls.

In reply to Jamie Wakeham, john arran and Baz P:

Could someone explain what they mean by:

• UIAA number of falls statistic
• original UIAA fall rating
• UIAA-class falls

Are people referring to the "number of falls sustained without breaking" as specified in EN 892:2012 + A1:2016?

In reply to galpinos:

Each rope you buy will have a Fall-rating, which is the number of falls it can take before failure. The definition of a fall used for this is a severe one that follows very strict criteria, with a given weight dropped from a given height.

In reply to john arran:

...and, critically, without relaxation time. 

To the best of my understanding, galpinos, UIAA is an international standards body, and when the EN criteria were drafted they simply took the UIAA specs, so the two things are essentially the same.  I may have oversimplified that, though.

One of the UIAA criteria is that (for a single rope) you have to hang an 80kg mass from it, and subject it to a factor 1.77 (ie MASSIVE) fall over a relatively thin edge.  You then repeat that fall with little* time for the rope's fibres to relax.  This is an extremely brutal and unrealistic test.  If you took a single one of these falls you would probably be sacking it off for the day.  You certainly wouldn't be looking to repeat the experience several times in a row!

The criterion is that, to be classed as a single rope, it must stand this treatement for a minimum of five falls in a row.  The 'UIAA falls' that is quoted when you buy a rope is how many times it can take this fall before it breaks.  A 10mm Galaxy Classic manages 9, for example, whereas a Serenity only gets to 5.

What this number tells you: how many times it survived the UIAA test fall over a 5mm radius edge with insufficient rests.

What this number is good for: giving you a proxy measurement of how tough the rope is at being loaded over an edge.

What this number does not tell you: how many times you are allowed to fall on it before retirement.  Not even big falls.

What this number really does not tell you: some maximum wear indicator after which a rope must be retired, to be done by multiplying the FF1.77 by number of falls and the subtracting every single fall you ever have.  This is utter madness, which is why Offwidth was mocking the SU (Student Union) who tried to impose this made-up rule.

Knowing when to retire ropes is tricky, and takes experience, which is why I can understand that people want to put some sort of measurable metric onto it.  But that is absolutely and categorically not what the UIAA number of falls stat is trying to do.

* edit - Tom is correct, it's a five minute rest, which is nowhere near long enough for the rope to recover.

In reply to galpinos:

A factor 1.77 fall (dropped from 2.3m height) from a static belay (i.e. completely tied off, so there's no give in the system).

There's 30cm of rope from the tie-off point ("belay") to the carabiner (that acts as the quickdraw that you've just climbed past) and it's dropped from 2.3m. This means a 4.6m fall on 2.9m of rope. The carabiner has a 5mm radius (essentially a standard carabiner).

The weight is 80kg for a single rope, or 55kg for a double rope. The rope gets a 5 minute rest between falls, and must withstand at least 5 falls.

A "UIAA fall" is particularly harsh because there's no give at the belayer or climber end, which always reduces the force on the rope. The effects of a climber bouncing down the rock, or even just a human squishing inside a harness (compared to a 80kg steel weight) can reduce the forces significantly.

*Edit*: If it's not clear - the only time you'd ever experience such a high load is if you were on a multipitch and fell back to the belay (and then carried on falling past the belayer). For single pitch climbs, your feet hit the floor before you exceed a factor 1 fall - which is why the test is seen as particularly strenuous.

In reply to John Kelly:

And to try illustrate the adding up fall factors point...

If you can stretch a big elastic band 20cm before it snaps, doing 10x 2cm stretches doesn't cause it to snap. 

You can probably do your 2cm stretches for hours and the elastic band is totally fine.

In reply to john arran:

Well that's not what you wrote. I agree, with the data we have, there's no point trying to equate a certain number of small falls to the UIAA test. But it clearly isn't nonsense to suggest that a rope which has taken a large number of small falls will have reduced performance if subsequently put through the UIAA test.

If you want a quick way to drastically reduce your rope's ability to pass the UIAA test you can always get it wet.

In reply to tomhardie:

Yes that's what I thought twenty years ago. Nowadays I'm not so sure a dynamic rope is that comparable to an elastic band. Try that with a knot in your elastic band for starters.

In reply to Offwidth:

Thank you for the reasoned reply.

I asked the question in this post about the cumulative effect that small falls would have. I now understand that it is not quantifiable with regards to the UIAA standards but some people keep labouring the point.
What I can’t agree with is that small falls cause no stress or damage whatsoever to a rope as some seem to be implying. Will the rope stay the same forever then or will it get better with age and accumulated falls? One of the three must apply. 

In reply to Baz P:

Old ropes have been tested by various people.  In general they get stiffer, i.e. higher maximum peak loads during fall arrest, and weaker in terms. of total strength, in some cases weak enough to possibly break in a climbing situation.  I don't think that when the ropes were subjected to a UIAA test fall (as opposed to static pull tests), any of them broke on the first test, but the number of UIAA test falls they held also declined, in some cases, I think, below the UIAA standard of 5. There were some European tests that indicated high-volume rappelling significantly decreased the number of UIAA falls held.

One of the things that emerged from many of the tests is that deterioration is sectional and is concentrated at the rope ends.

I wish I had links to share but I am reporting what I've read over the years accurately.

In reply to rgold:

I have been avidly noting any rope safety information since I started climbing in 1968.

I think the current consensus is that if the rope is within the manufacturers age /use limits, core not visible through the sheath,  core feels intact and no chemical especially acid damage, its OK and safe to use.

​​​​​​Also retire any section of rope subject to a fall of more than ff1 and "rest" the rope between falls.

Edit, I presume you knew all that and a lot more.

Should have replied to bazp, really.

In reply to Baz P:

Of course, as ropes are used, wear will accumulate. But counting cumulative FF isn't a good way to measure this. There are many other unquantifiable factors at play - how grabby the belay device is, whether the rope is running against rock (and if so, which rock type), swinging 'sawing' actions, and many more.

This will all gradually add up as wear to the sheath, or (less commonly) as wear to the core, which you can spot by feeling for lumpy bits or soft spots.  That's how you know your rope is still good - regular careful examination of the condition of the sheath and core, not a log of how many FF0.1 falls it's taken. 

It's really worth emphasising that (at least to the best of my knowledge) no modern rope has ever snapped in a climbing accident solely due to wear.  In all the cases that the rope has failed there has been some clear mechanism - a sawing action over rough rock in a pendulum fall, or chemical contamination, or similar.