UKH

Yesterday at the crag - energy felt good on 2x at 6b+ so I tempted a 7a previously completed onsight. I was level with a bolt when foot slipped and I fluttered down - levelling up 3 bolts below :o and minor bloody seepage to nurse.

However I need not have had this ! - my belayer reported softening my fall with dynamic slippage. In full knowledge of the rock-ography - it's sure that the greatest shock went straight to my scarred ankle !

So tell me about it. Who can report 'suffering' from NOT having a dynamic belay ? and on which type style / angle of crag ?

I maintain that on real rock with unknown angle's and features - dynamic belay is worthless. NB. in yesterday's instance I was already 20m up the crag so rope out was in any case adequate to soften fall 

My initial reaction would be to substitute the word crap for dynamic

I’ve fallen off a lot! Most times I go climbing in fact, I’ve been slammed on several occasions which is deeply unpleasant.
There needs to be conversation between the belayer and yourself before you ever set out on the route, to decide when and were to give a dynamic belay, or in fact to take in because of proximity to the ground. 
Even if you have this conversation due to the split second decisions it may all still go a a bit wrong. Good belayers are few and far between and in my opinion as soon as you leave the ground your fait is in your own hands to a large existent, climbing is potentially dangerous so if a bloody knee or a bad ankle is all you end up with at the end of the day then your not doing to bad  

Not a sports climber - when you say 'slammed' did you climb back on afterwards?

I'm with the OP 

let the rope, the plate (both designed to do just this) and the squidgyness of the belayer provide the dynamism  - random guess by the belayer is going to be less reliable.

This sort of sloppiness seemed to creep outdoors from climbing walls about 10 to 15 years ago if my memory serves me right. I'd be sketching about at my limit above a few optimistic RPs only to glance down in horror at the coils of slack paid out by my belayer. Just in case I went for it, apparently? No amount of explaining about keeping the slack to a minimum and actually watching and anticipating your leader seemed to wash with these people. Another reason for giving up climbing. Never fancied decking out much.

Am I being obtuse what’s climbing back on got to do with being a sport climber? If I fall off a usually lower to the ground and have a try at the ground up! Or if I fancy I’ll go to the top and then have another go

Trouble with the path not travelled, is you don't know what route it takes. 

I hear what you're saying about good belayers and good belaying. My belayer needs a thick skin too, I blame them for my failings all the time. But thats part of the partnership. Each others rough and smooth. 

OP hope the ankle heals quickly. 

Sounds like he is using dynamic belaying  as an excuse for his lack of attention/inadequate belay skills.

A dynamic or 'soft' catch/belay is super important, particularly if the belayer is heavier than the climber. I'm a fairly heavy guy and I have to be particularly careful to give lighter climbers a soft catch or there is a real chance of injury from being slammed too hard into the rock near the last bolt. It is also much more pleasant to fall a little further than suffer a hard stop.

That's not to say that the fall zone isn't important too. Given the choice between a harder catch and landing on a ledge the former is obviously better. And giving a soft catch isn't about lazily throwing out loads of slack (bad belaying), it's about carefully moving inwards/upwards as the weight comes onto the belay device to reduce the force on the falling climber.

When working at a wall years ago I witnessed several injuries where lighter climbers where pulled in hard when falling, one of which led to a broken ankle. I have witnessed other occasions outside particularly with petite women or children, there unnecessarily hard catches have caused issues.

It is effectively impossible to give 'dynamic slippage' to the extent of 3 bolts' extra fall.

The problem sounds like it wasn't due to dynamic belaying but due to a mistaken and quite unfathomable belief that having yards of extra slack out could somehow be justified (except in very rare and extremely specific circumstances).

Maybe your belayer just needs to read a good article on dynamic belaying rather than presuming it bears any resemblance to what they're actually doing.

I would say the belayer just needs to catch you properly when you fall off. It's not rocket science and it needs 100% attention and preparation at all times

I think it just be me being obtuse - what I'm trying to understand is what ' slammed' means

Post 'slammed'  is it straight home for a week in recovery or can you continue climbing?

Nothing to do with your style or how you ascend the route

I never have slack out, usually find standing out a bit where possible means I get dragged in by partner who is over 20kg lighter is dynamic enough. Sometimes I might make a little jump in the air.

I find slack is just taken up quick and arrests the fall with a shock.

Belay glasses and being attentive is key.

And what's this with loads of slack on the first bolt .....ground fall potential which I see all the time....

As has already been covered It sounds like crap belaying rather than dynamic. 

Unless there is a specific reason to not give a dynamic belay by either stepping in or jumping slightly, i.e. a ledge or similar I'd always want one. Less force on me, my gear and my partner. This doesn't mean having loads of slack out, that's just shit belaying. It all comes down to experience.

It sounds like you didn't get a dynamic belay, you got belayed by someone with a load of slack out. 

There's a big difference. 

What belay device was being used?

One thing I’ve never understood is that for many, dynamic belaying seems to be having a load of extra rope paid out in advance. This is obviously fine on very overhanging routes (to allow the fall to be straight down instead of a pendulum), but outside of that it’s always baffled me.

I’ve always given a dynamic belay (if needed at all) by allowing myself to be taken by the force of the fall, so skipping in towards the wall or an small upwards hop.

Lost track of the number of belayers I’ve debated this with, who are adamant that having a big loop of rope hanging from the belay device is the way it’s supposed to be done. Maybe I’m wrong.

You are right. 

Totally agree. I've been dropped a long way only to snap / slam at the end of the fall due to the belayer thinking 'lots of slack = soft catch'.

Equally i've also been given lots of lovely soft short catches.... it's all about the belayer's movement at the point of the fall.

I'd also add as someone who solely belayed heavier climbers when i first started climbing it was easier to let their weight do the work and pull me in... it took a conscious effort to adjust to belaying those who were lighter/ a similar weight to me. Even those who consider themselves experienced belayers need to learn to adapt.

I heartily agree with those here saying your partner doesn’t actually understand what a dynamic belay is. To answer your question, on one of my early forays sport climbing outdoors, my foot slipped just as I was clipping the next bolt. Even though I was a safe height off the ground already, my belayer was inexperienced and sat back on his Grigri rather than allow himself to be pulled in/up. The effect was to bring me slamming into the wall so hard that I broke two bones in my foot. It was a powerful lesson on the risks of trusting random punters to belay me!

OK I accept 'this is a thing' - but given that gravity acts down, what exactly causes a rotational-pendulum moment back towards the rock ? What sort of technique / move might you be executing at the moment of fall ?

If overall angle is vertical or slabby then contact with the rock is inevitable at fall-end. But who has the time to judge which / what a features are in proximity at a given moment !

If you make an intended jump outwards to take control, it's different to an unexpected slip and I suspect dynamics are different in each instance.

Sprained ankle. Malham. Slight overhang. Took me a long time to recover. The problem was a low redirect to keep the rope out of the way, rather than the belayer. It added friction. Stopping too quickly can be painful. Similar effect using an Ohm at Kilnsey managed to avoid an injury, but it hurt. 

gri-gri

I'd just like to support the last few comments about a misunderstanding of what constitutes a dynamic belay. There are many people out there who not only belay incorrectly but dispute the technique, continuing to think that a massive amount of slack paid out somehow softens the impact when they then resist the shock that comes on when the rope comes tight, rather than move with it as has been mentioned. A falling leader can be quite justified in calling this the 'What the f...?' technique.

Well worth watching this video which shows the reality of hard/soft ... 

youtube.com/watch?v=_0GGsBgPic4&

TLDR is that a small amount of additional slack and a small amount of 'dynamic' belay (think 'small bounce forward as rope comes tight') can reduce the force by a lot. Slack on it's own doesn't really help beyond a meter or so but a 'moving catch' can help a lot, especially where the belayer is heavy. 

Safety first and the climber gets to choose what they want but I hate a very hard catch and have buggered ankles already  ...



 

No no - don't give up, find different partners or go into the discussion. On approach to delicate moves - ask 'I need you to follow me closely here' or 'reduce the slack' etc.

Last week I climbed at a new crag with 6c crux moves straight off a ledge. Impossible to avoid a 'ground' fall with normal leader slack (and rope stretch) - I requested a tight rope to get through until better holds arrived. All went well - but I am left unsure how much effort the rope took from my arms.

youtube.com/watch?v=_0GGsBgPic4&

youtube.com/watch?v=_0GGsBgPic4&

This might be of interest.

I got a broken toe from a hard catch on an indoor wall. My belayer was much heavier than me, using a gri-gri, we were on a well used gym rope, and he sat back in the harness hard despite me being well off the deck

I also ended up with a chipped shin bone from a hard catch in the huntsman's leap. In this case the hard catch was entirely appropriate, as I was not too far off the ground and slamming the wall was a better option than landing on the  boulders at the bottom and potentially breaking an ankle.

There are various techniques for providing a good dynamic catch, all of them take practice, and all of them reduce the chance of injury when used appropriately - obviously there will be times when it is better to be slammed than hit the ground or a ledge, and other times when it really doesn't matter (such as having clipped the lip of a roof and having no chance of swinging as far as the back wall of the cave).

Thanks - great vid, lots of evidence presented with charm

So I accept there's a case for soft-catch. This is most apparent in any instance where the last anchor is forward of the point of fall - you are climbing outwards on an overhang - typical for an indoor wall. But the subtelties of timing and real rock topography leave me in some doubt for the execution - esp on the angles I typically climb on.

Much food for thought !

My normal belayer gives me a natural dynamic belay, being somewhat lighter than me.  She's held hundreds of falls of mine without injury (to either of us). 

Nine months ago I was climbing with a heavier partner, took a fairly bog standard fall (7a, vertical limestone, approx 15m up).  Got a much harder catch than usual.  Result broken foot, still giving me issues even now.  Doesn't necessarily prove anything, but to me strongly suggests the importance of soft catches when appropriate.  An experienced belayer is invaluable.

Using a gri gri presumably rules out slipping the rope, so too much slack or moving forward too much.

At a Californian sport venue , I once ended up near the deck after dynoing for the wrong bit of crag with the sixth bolt by my feet. I had time to check my knot on the way down . My american belayer, who I had just met at the car park  would have been using a bd plate , just shrugged his shoulders. "Dynamic belay, that's what we do, slip the rope."

Well, as a non sport climber you probably don't fall off all that often, so maybe you experience isn't so relevant.

I absolutely hate being belayed on anything (to me) hard via a belay "plate".  To the point that I'll generally refuse such a belay.  Not to use an assisted braking device of some sort if you're sport climbing, and doing it properly (as opposed to the sport climbing that trad-mostly climbers do) is a bit retarded, in my opinion.

"a bit retarded, in my opinion", ignoring your particular choice of words - why?

Totally agree...re soft catching and dynamic belaying interpretation. Though we may be reading too much into the the drama of 3 bolts the OP cites.. Even on an evenly spaced route dropping with a bit of slack if it was waist clip would put you well below bolt 2 of 3 bolts the op cites. 

You got me - I'm a rank amateur when it comes to sport and don't fall off much - it would be more like rolling at the grades I climb

I'm off to shuffle along some damp ledges 

Cheers John

Wanted to post this video. They did a 3 part to this to show the impact of slack and the impact of soft catches.

Their summary is that slack can be both good and bad depending on a few variables but a soft/dynamic catch is always important and always reduces the fall force. 

I'm reluctant to believe anyones anecdotal evidence after seeing this actual evidence.

They didn't look at actual forces (which are pretty much irrelevant in sport climbing anyway since bolts "don't" fail and dynamic ropes protect the climber), though I think extra rope increases peak forces. They were looking at the speed you swing into the rock. Extra slack, as you say, might be good or bad and I suspect it's too variable to realistically take into account, but the moving in/jumping, if timed right, is always good. I think the only real reason for having a bit of slack out is to make sure clipping is always easy. Trad, of course, is a different thing altogether.

In general, I agree that there is a fair bit of slack in the system, and no excuse for miles of extra slack paid out. But, you asked if anyone has suffered due to a hard catch- I witnessed this at Tonsai on the beach crag. For anyone who knows this crag , it's super steep and any falls are into space. A tight rope on a fall resulted in the leader being whipped in and breaking his leg. A small amount of slack or the belayer jumping up would have avoided this. it's much more of an obvious risk on vertical rock, but I think most of us present were surprised by the outcome in this case.

Become a pielord.

The lord of pies always gets a nice soft fall because his/her belayer is lighter and gets pulled up as the rope goes tight.

Always beware of the waifs though - if your belayer is too diaphanous then the fall is nice and soft right up to the point the belayer faceplants into the first bolt at which point they probably lose consciousness and you either plummet to earth or get to swing around till help arrives!

With you on this, I'm quite happy for people not to drop me when belaying, I'd much rather they concentrate on this than try and achieve something they have little knowledge about.

Basics first, I'll ask if I want something different.

It is for this reason that I am now very unwilling to be belayed on sport without an assisted device; I'd rather wait for help than be dead.

Does this happen a lot in your experience? I've never seen a belayer knocked unconscious against the wall. I'm quite happy for any competent belayer to belay me with whatever device they feel comfortable using. Tube devices are definitely harder work for the belayer if you're working a route but if they're happy to do that work is all good with me.

No, but I have regularly seen light belayers lifted up and swung into the wall. It would seem all too easy for them to lose control of the device in that situation. I just don't want that possibility in the back of my mind when climbing.

Here's another angle on the problem: for a skydiver in freefall, terminal velocity arrives after 12s and 450m. We never get close to this - but what that means is that the further we fall, the greater speed we collect - with greater consequent force and  potential to damage. 

This means that we want to stop as soon as poss - ie.  fall the minimum distance possible.

The dynamic finish, if correctly executed - must only be done as the tension comes through to the belayer - and need only add 50cm --> 1m to the whole fall. Does this make sense ?

Interesting fall calculator here to look at velocities with height

https://www.omnicalculator.com/physics/free-fall

If you're paying attention it shouldn't be a problem. I wouldn't climb with a belayer I thought wasn't switched on enough to fly safely and keep hold of the dead rope.

My lad - now 15yrs old - started belaying me at 9yrs old. Over the years he's often held me -enjoys taking off ! I used to find this quite alarming but recently - just pesky when he keeps me in suspense  

It's not the flying through the air bit I'm worried about!

There's really nothing to worry about if your belayer is switched on, outside of dropping something on their head (which is possible anywhere, but much more likely at a less frequented trad crag than most sport venues.

At 60 kg and having climbed with a few significantly larger guys, I'm no stranger to taking off myself... It's definitely easier to give a soft catch the lighter you are. I used to climb with someone who was under 45kg. She would belay a mate who was 85kg quite happily. On a project, he would often skip the first clip when he knew he wasn't going to fall till higher up, and launch her to the second bolt. 

Because they're obviously the best choice for the job.  Do I really have to explain why?

[Edit] I see that RB has explained why above. 

I really think you are naive and lacking in imagination if you think that swinging into the rock while controlling a standard belay device might not have issues.

Can you honestly say that while belaying you have had 100% focus, 100% of the time? You've never been distracted, or looked away from your climber for a moment. You've never needed to do some rope management..

I wish I could say that about myself, but I can't. I doubt many can.

If you're using a single rope, on a single pitch, I can't see any valid reason not to use an assisted device. Cost isn't even valid. They're like £40 and they'll last you years and years. 

I was of the 'Use whatever you're comfortable with' crowd for a while. Only took me being dropped from anchor to 1st bolt on a 15 meter climb to make me reevaluate that stance! I fell off an easy route, which he didn't expect me to fall of, and as such almost decked. An assisted belay device doesn't make presumptions about how good a climber I am, and adjust its level of attentiveness based on that assumption. Humans can and do, though. 

And from a belaying perspective, I like knowing the safety of my climber isn't reliant on me being a perfect human being. 

I’ve not read all the responses to this thread so sorry if this has already been posted.

Here is an interesting bit of research into the  subject.https://mojagear.com/overcoming-fear-falling-scientific-approach/

I really think you are native and lacking in imagination if you think is not possible to belay in a way that allows you to control a standard belay device whilst swinging into the rock.

You don't need to be 100% focused 100% of the time, you just need to keep your hand on the dead rope and your body appropriately aligned to the pull direction of the fall 100% of the time.

After that, the result of your loss of focus will be similar whether on a tube or a locking device.

What about rock fall? 

Related video: https://www.instagram.com/p/CCrGvcZJGIv/

Or heart attack.. Or seizure... 

Also, I think even if you're facing the wall if you're not paying attention is easy enough knock your head during a big unexpected whip from your climber. 

I just don't see the issues with assisted braking devices that makes some people seem so adverse to using them. It's like arguing seatbelts aren't needed because you're a super duper careful driver. 

Used a click-up recently. It's functionally identical to using an ATC.. 

I wouldn't bank on any assisted device to function as intended if it smashes into a first quickdraw at speed, certainly this is likely to disengage the cam on a Grigri, and injury to a belayers hands is also possible with any device. What you should be perhaps doing instead is thinking of appropriate mitigation - if you want a soft catch or your belayer is much lighter then an option is to stick clip the second bolt instead of the first when sport climbing to give your belayer more room for safe airtime.

This discussion also shows that the term dynamic belaying is to some extent misleading, as some use it to describe a deliberate technique, others to something that happens by circumstance due to belayer/climber weight differential, and yet others to something related to the use of different devices. Informed technical discussions should ideally differentiate between "belayer dynamics" and "device dynamics" both of which have techniques applicable to them.

I'll use an assisted locking device where someone is working a route but apart from that I don't see any real benefit from using an assisted locking device. 

If, when I'm climbing, I need the reassurance of the assisted locking I sack my belayer and get one that can pay attention. 

If I'm climbing multipitch sport I much prefer to use a guide mode plate because that really is the best tool for the job.

If I'm climbing single pitch sport I'm not really bothered either way but I generally can't be arsed to lug a grigri-a-like to the crag when I've got better, lighter and more flexible alternatives.

The best tool for the job is, without doubt, a decent belayer (who is preferably climbs a notch harder than me) what they use to belay with is is very much a secondary concern.

People make mistakes. Shit happens. I am genuinely astonished how blind some people are to this fact.

Yes, they happen, but that doesn't mean it's all right or acceptable

E.g. my pilot makes a mistake on landing causing a crash, "Oooooh sorry about that, I made a mistake". Not all right

E.g. my belayer makes a mistake causing me to crash into the ground, "Oooooh sorry about that, I made a mistake". Not all right

Obviously, but they happen and so it makes sense to build in safeguards.

What about shit happening?

Assisted locking devices bred complacency and unskilled belayers and that leads to accidents and I'm often surprised how blind people are to that.

Just be sure never to do any trad, bouldering, alpine or winter climbing because you'll have not to worry about than some idiot dropping you by misusing a grigri!

Not sure it's necessarily relevant here, but this is precisely what you don't want. It is not the fall, but the sudden deceleration that does the damage.

If you came to a rapid dead stop in mid air it would kill you as surely as hitting the ground.

Have you tried climbing with knowledgeable belayers instead?

Have you ever seen Birth of Extreme Rock? The sequence of Jerry climbing Liquid Amber, with his belayer using an Italian hitch and repeatedly letting go of the braking side of the rope?

Crap belaying has been around forever, regardless of the method.

I saw that too, and wondered if Jerry is aware that he is the first person to have soloed 8c?

Let's consider the limit case: tight rope with no slack. Let go of the rock. What happens? Does your back snap? No. It's how you lower off from a sport route.

So, if the argument is that a lot of slack is good, at what point does the situation flip?

What determines the intensity of the fall is the length of fall over the total length of rope out. Reduce the length of the fall, and you reduce the intensity of the fall.

This might be useful reading:

http://lamountaineers.org/pdf/xRopes.pdf

Agreed ! Attentive belaying for many of us becomes a priority 'background' task which is as automatic as driving to miss on-coming traffic. Without belay glasses or even looking I constantly test rope tension and make appropriate adjustments - all while taking in the scenery.

Assertive and informative communication would further help correct a lot of rope handling risks and issues.

I do it all the time, cheers.

The problem being when new people come into the club, they think you have to be able to dynamically belay,  when they don't even get the basics right.

So let's walk before we can run.

Besides that I've been climbing for over 30 years now, and have never thought, "Oh! I was Johnny had learnt how to bely me a bit more dynamically".

No, because in this scenario you have not decelerated. However, how realistic is it to be able to achieve this in actual practice when a climber will need at least *some* slack in order to make upward progress and to clip, and that a fall is not likely to be completely predictable?

That is not the argument. The argument is that if the climber falls, you want to avoid injuring them. That depends on several factors, the most important probably being an attentive and experienced belayer.

From a purely mechanical perspective, and in the absence of any other considerations, you want to reduce the deceleration of the falling climber as much as possible.

Me. 

Before I had learned slack is my friend I got my partner to take in slack then fell. 

Twisted my ankle pretty bad when I hit the face.

Whenever there's a discussion about belay devices somebody always makes this point.  It's totally valid and that's why I always drive my car without my seat belt on, as I want to avoid complacency. 

Whilst we're at it, I wish motorcyclists would stop wearing helmets and buildings would stop installing sprinkler systems as all this complacency about safety is driving me crazy!

youtube.com/watch?v=NJHVgkchcbw&

This thread has reminded me of the above.

Seat belts / motorbike helmets are completely different examples and ones that are backed up by massive evidence and you shouldn't conflate these with this issue.

The case for autolockers for experienced belayers is much weaker and can be countered by evidence of complacent belayers banging their heads by being pulled over, people decking out with grigris and misuse of the thumb.  I doubt you're able to build a decent evidence base once you eliminate bad belaying and normalise for different disciplines.

By contrast I'd argue the case for helmets when climbing in nearly all circumstances including sport climbing (except bouldering*) but part of this argument is the benefit is usually obvious and the penalty usually negligible. 

I wouldn't argue for compulsory helmet wearing for push bikes because the evidence base is weak and conflicted, helmet wearing for bikes comes with penalties that can have population wide health effects and there are more effective safety interventions.

By comparison with these other examples assisted lockers are really a tool for convenience than safety and I don't find them all that convenient. 

This is not anywhere in the same league as seatbelts, motorbike helmets, lead in petrol or smoking - don't adapt the data to fit.

* There isn't usually much above you to fall on you when bouldering.

Agreed. That's where proper dynamic belaying comes in; allowing rope slip, jumping up, moving in, etc.

Slack is necessary to climb, yes. Adding lots of unnecessary slack is not dynamic belaying; it just means a longer fall before deceleration. Longer fall means climber gains more kinetic energy, and more speed. Which requires longer deceleration, and the need for that kinetic energy to be dissipated (friction, heat in elastic deformation). Longer falls also mean potential ledge, or, ultimately, ground impacts. 

Nice jab at irony but if we go down that road we will also need electronic bleepers to tell us when we haven't properly attached / prepared. The BIG difference here is that cars (esp)  make us feel too safe. When climbing the sense of danger is elevated for most - which is why there is less risk at the crag than there is on the road. 

I know I was being facetious ;0)

Of course there is strong evidence for seat belts motorcycle helmets etc...

However, seeing as the discussion about belay devices has been done to death I'd say the same thing that I've said countless times before - complacency is a human condition, not a device.  If your belayer becomes complacent because they are using an ABD then it's your belayer who is at fault, not the device that they are using.

Secondly, in this debate people always quote either anecdotal evidence or study stats that seem to support the view that ABD are more dangerous than tube style.  What these studies or recollections don't take into consideration is the amount of accidents avoided because of their use.  Accident reports only record accidents that happened, not ones that didn't.

Interestingly, there was a similar misunderstanding of the stats around seat belts in cars for a long time - the manufacturers always thought that seat belts in cars were more dangerous than not having them (they felt it was better to be thrown free of the car in the event of a crash) it was only when they realised that they were only looking at half the data that they twigged seat belts are actually a very good thing.

Anyway, like I said, let's not turn this in to yet another discussion about belay devices.  The OP asked if I had suffered because of a non dynamic fall and I have.  Can't even remember if we were using an ABD or not.

Fair point....

I'm with you on this one.  I've never been injured by having a hard catch.  If you're high enough up then there's enough rope out to cushion the fall anyway and if you're low to the ground you don't want a soft catch as you might deck out.  

Last time I had a "soft catch", my belayer who had 20+ years of experience, let so much rope slip that he dropped me flat on my back from the third bolt.  Since then I always prefer my belayers to use a gri-gri.  

A freind once suffered a nasty broken angle after being violently swung onto the slab of chalk storm at the roaches by a hard catch so it can happen! Allthough in this instance he might of decked if the belayer hadn't locked off hard...

This is exactly the point I was making above, about learning to hold a fall first and belaying properly.

I've seen loads of "new to climbing" people think that slack = dynamic belaying, or trying to dynamically belay and then fooking it up and dropping someone.

So let's get the basics first, the number of times people need to be dynamical belayed are few and far between, apart from specific sections of specific routes. This is especially true if the weight difference between the two people is minimal.

I don't know how "dynamic" became such a must have, that absolute beginners think it's a necessity.

Is that true for the belayer?

I'm still accumulating dislikes for pointing out the fundamental concept, though... I'm happy for someone to explain the error in my thinking, providing they can provide an explanation that discusses the physics. For instance, if someone wants to argue how the capstan effect might come into the discussion, regarding stretching rope lengths to and from the highest anchor. Or if they can explain how we go from no slack being good, to 1m of slack being terrible, but 20m of slack being good again (to restate my original limit case scenario more explicitly), that would be interesting.

I'm assuming a side runner, so I'm a bit bemused how you can be "violently swung onto the slab" on Chalkstorm but I've been injured on that route myself - foot hit/caught the (by then tensioned) rope from belayer to gear when I was mid swing - should have made sure belayer was stood under gear rather than under me - would have been less likely to hit rope at end of any swing - silly mistake, easy to see in hindsight.

Are you sure your mate didn't do something similar catching rope, because being actually swung onto the rock on Chalkstorm would IMO require some serious bad luck.

I wasn't actually there but I understand no side runner was involved (my mate was going for the E3 tick) hence the hard catch leading to a heavy impact on the slab.

The dislikes are coming because you - and you are not alone in this - persist in talking about excess slack as if that were somehow related to "dynamic belaying" or soft catches. They are entirely different things.

A soft catch involves moving with / letting yourself be pulled by the rope as it comes tight. It reduces the deceleration and thus lowers the peak force on the climber. And probably more importantly, it reduces their inward velocity towards the rock. And has nothing whatsoever to do with how much rope was or wasn't out prior to that moment. And yes, there ate times and places where it isn't appropriate, like when the climber is close to the ground or just above a ledge.

It requires quite a bit of alertness, timing and practice if you are heavier than your belayee, which I usually am. It's also a skill that a lot of old traddies haven't bothered to learn because they've gone decades hardly ever falling off or holding a fall.

I know what dynamic belaying is, and that excess slack is not it; see my third post.

My first post was addressing the statement that the length of fall doesn't matter, and suggesting a thought experiment that would allow a reader to explore that point. I backed it up by a link to a very useful and practical analysis of roped systems. It was trying to address the very misunderstanding you mention. I didn't mention dynamic belaying at all in my first post, and was not trying to address that issue, only to explain that excess slack is a bad idea (and, by implication, that excess slack is not dynamic belaying). Obviously I did a bad job of making my point... And I was probably addressing a very minority point of planetmarshall's post...

I am afraid you made such a bad job that a lot of people thought you have no idea .

It is well accepted that the length of fall divided by the length of live  rope ( the fall factor!) plus or minus the effect of rope slippage ,hard or soft catch etc defines the impact forces.

I apologise. I confess to only having skimmed a long and rather depressing thread.

Thanks, but there's no need. You have explained why my post attracted dislikes, which has allowed me to read my first post in a new light, and see how badly I explained my point...

I would hope so. But there were so many posts apparently extolling the benefits of excess slack, it seemed not...

The argument was maybe useful..... like a lot of safety analysis in climbing you can lead the horse to water but you can't make it drink... a bit of hot air followed by agreed clarity can help get the point over.

The numbers belaying with excess slack and/or too far out from a sport climb (especilly with a low clipped first bolt) seem to me to be increasing. Worse, this seems to be becoming more common on trad routes, as just terrible practice (combinations of risks like unzipping pro and the leader falling further and hitting something like a ledge). Maybe to an extent I'm noticing it more because I find such belaying worrying, but it should be such a rare sight that you can have a quiet word with the belayer when the route is complete and point to everyone else following better practice.

It's not the worst.. last year we watched, rather bemused, as a big middle-aged man at Burbage North was draping a sling over a flatish blister shaped boulder in what looked like some kind of bad teaching, for a small kid that was with him. We shook our heads and continued to sort out gear for a neighbouring route. We heard a collective sharp intake of breath (from other climbers) and turned round to see the kid was now belaying him from that sling, when stood about 8m from the crag base, as the man was half way up a lead on The Knights Move, whilst climbing rather badly. Another climber quickly (and bravely) moved close enough to grab the kid/rope in case of a fall.

Going on from what Alan said it's a delight to watch dynamic belaying well done but I get the impression way too many know it's 'a thing' that helps but have somehow gained completely the wrong idea about how and when to do it. It should be a standard technique for regular sports climbers, with mainly good practice on view. In trad, dynamic belays are really more of an advanced technique needed on very particular routes.

That unrelated to the issue of whether dynamic catches with a tube are safe, and whilst a valid  concern rock fall is much more likely at trad climbing venues than most sport climbing venues... And I'd generally trade of the extra flexibility of a non locking device for giving soft catches when trad climbing over the ability to prevent groundfall if the belayer is incapacitated. You can always put backup hitches into the rope if rockfall is a particular concern.

If you're used to taking catches, and standing facing the wall with one foot in front of you, at an appropriate distance from the wall, a pull on your belay loop from the direction of the first bolt, no matter how hard or sudden (and what you might be daydreaming about), should not result in your head hitting the wall. If it does, you're not fit to be belaying and should have taken a break.

If you're doing something more involved that puts you in a position where an unexpected fall might result in your head hitting the wall, your climber should be aware that you are distracted and they need to stay where they are, and your device should be locked off/tied off/backup knotted/etc. to ensure your climber is safe. This is very basic belaying safety, and should apply regardless of what level of assistance your device provides.

I'm not averse to them in the slightest - I've been using the alpine up as my main device for years. I love being able to switch between assisted locking mode for single pitch sport and dynamic mode for hanging belays and trad. I am, however, averse to the idea that tube device used correctly is inherently an unsafe device for sport climbing. I will quite happily accept a belay on one from a competent belayer whatever the climbing situation, and would have no hesitation in using the spare one that hangs with my sport rack should I happen to lose my alpine up on an afternoon at the crag.

I'd say it's a bit more like arguing ABS isn't needed because you've practiced threshold and cadence braking

I recommend having a go with the alpine up - it's a great multi-purpose device, and operates exactly the same as the click up in assisted locking mode.