UKC

Hello all

At a climbing gym, is it ok to top rope off only one screw gate carabiner? Or should it always be through two with opposing gates?

Thanks for your advice.

In reply to elliot.baker:
I'm assuming you are in the UK despite your use of the Americanism "climbing gym".

It'll depend on the wall's rules, but it is perfectly normal practice in the ones I go to - that's how the centre top ropes are set up in some (others use maillons).

Where snapgates are used there are two of them opposed (Reading climbing centre is like that).

Neil

In reply to elliot.baker:

One is safe enough.
jk

In reply to Neil Williams:

Thanks for the responses. What is the English-ism of a rock climbing gym?

In reply to elliot.baker:


Climbing wall

In reply to Phil79:

Indeed...wasn't a dig at the OP, by the way, I just genuinely wondered if he did mean the US, though this is UKC and his profile seems to suggest being UK based

I have a feeling this is a term that might well make its way across the Atlantic, anyway...certainly a few walls have started to use it. Quite possibly because it might widen their appeal to include those who might switch to climbing from gym-going.

Neil

In reply to Neil Williams:

I quite like it. I think it gets across the sense of being practice for proper climbing.

In reply to elliot.baker:

As Neil says, most walls will have a system that they will expect you to use, especially if the ropes are preplaced on dedicated top rope routes, and as Jk says one screwgate is perfectly safe enough, especially if the gate is done up, as it should be. In fact often these are taped closed on in situ ones to try and prevent them being left open. In most cases it is pretty hard to assess from the ground if the gate is done up or not.

So two opposing gates is perhaps a notch up on the safety and redundancy scales , plus a bigger radius will make the rope run easier which is good for ease of belaying and less rope wear, but would offer less friction during a fall.

My local wall uses chain lower offs with a ring welded into the middle of the chain that the top rope is fed through, then there is a separate screw gate and a snap gate, for use when lead climbing.

I have seen several different set ups, the bulk of which are safe and have been properly thought out, plus deviating from what is there can create issues with the staff if you start changing what they see as the norm and signed off by the " Elfs" .
Having said that, it is good to do as you are and question these things plus take a quick but critical look at the gear that you are potentially about to fall onto at indoor walls. Accidents happen, and I have seen ropes incorrectly threaded though anchors, badly worn insitu QDs on lead routes, open screw gates etc.

Checking and tightening a gate only takes a second and in most instances quietly reporting any worn or faulty gear you spot is well received by staff.

In reply to climbwhenready:


Me too, it's more descriptive of what they are and how we use them.

In reply to taddersandbadger:

A very common misconception. Two carabiners leads to slightly MORE friction.

The increase is fairly small (IIRC perhaps 10%, but I know that Jim Titt has precise figures) and the same effect is at play when people use two krabs to increase friction with a belay device.

In reply to taddersandbadger:

I´m sorry, but there's so much wrong with that post that i have to reply. Nothing personal but...


The what? One screwgate is safe enough ONLY if the gate is done up. People have died because their single attachment via snapgate at the anchors unclipped when faffing about.


It certainly is not. A matched pair of screwgates won't ever have both gates undone and opened by accident, even if we ignore the fact that the gates being jammed together effectively act as a lock making it impossible to undo them. So it offers no advantages in terms of safety.

In fact the effect of having carabiners set up with opposing gates is that their strength gets reduce well below their rated strength.


Yet another urban legend. There is more contact between rope and metal, and therefore more friction. Wrap a rope round a very thin tree and pull it, and then try the same around a very thick tree. You'll see which is easier to pull.

In reply to Mr Lopez:
Hiya mate, I was curious about one of the points you made:


How does this set up reduce strength rating. Just asking because I'd never heard it mentioned before.

Thanks in advance...

In reply to Oldsign:

It doesn't.

In reply to ianstevens:

Without wanting to offend Mr Lopez, I was under the same impression.

I'm always curious if there happens to be contrary evidence though.

In reply to Oldsign:
Different reasons depending on the carabiner's shape, which in some cases can all occur at once. Interaction between the carabiners and/or the rock forcing the load to be off the spine's axis, the compression load between the carabiners from the rope/sling beoing applied directly to the gates, sideways, which is specially bad if using oval carabiners, torsional forces to the top of the carabiner when unable to rotate independently, etc.

There's been a bunch of pull tests done on it and though the mechanisms of failure have varied depending on the models, the results are always uninspiring. Off the top of my head there was as pull test done with 2 50kn ovals which failed at 25kn. That is 2 opposed carabiners failing at 50% the strength of a single one. Somewhere else there was a schematic from some BMC type association which showed that opposing carabiners when loaded tri-axialy (like when you are equalising a belay) only had 20% of the original strength

It is commonly known now, in part thanks to the more widely availability of test rigs, that opposing carabiners is definitely bad practice. All said, there has to be a compromise sometimes between safety and strength, so in the case of snapgates it is better to have them opposed. However it is very important that they are not ovals, as in the process of applying the load very easily they open each other gates and you end up hanging on what is effectively 2 opposed hooks

In reply to Mr Lopez:

Which is all very interesting, but probably has little to do with "top roping off one caribiner in a climbing gym"

So, nothing useful whatsoever to the OP.

In reply to Oceanrower:



I apologise profusely for having answered a question that was directed at me.

In reply to elliot.baker:
I don't know why some climbing walls use carabiners for fixed ropes rather than the solid ring. I can see that it is marginally harder to thread the rope, but this is not hard for the wall staff to do from an adjacent line. Perhaps the solid ring system is harder to inspect, more expensive to equip or wears out faster?

Often when arriving at the top of the wall, I have found the screwgate not tightened up and given them a few turns to tighten them again.

Perhaps when the ropes are moved about and the carabiner bangs on the wall it works loose? Or kids like to fiddle with them? Does the repeated loading/unloading of them cause them to flex slightly which makes the gate work loose (especially on older carabiners)?

Some walls have them through a snap gate and screw gate co-located, which means the top snap gate is unavailable for leading. One wall I go to has them through a steel carabiner only, with a nearby snapgate for lowering off if the route was led. This approach is more user friendly if the route is equipped for leading and toprope - you just have to hope that the screwgate is done up if top roping!

It seems to me that a solid ring is a more robust attachment for a fixed rope by eliminating the potential for the screw to be open or only partially closed, which cannot be seen before the route is completed. I'd be interested to hear the downsides.

In reply to Neil Williams:

In reply to Mr Lopez:

Well, I fear I have been schooled a bit here.
While I find the science interesting and I am sure the test rig data is certainly correct. Sadly for me, my brain does not work that way.
I guess we all measure and assess risk differently.
I Do always spin my gates closed, and often catch myself checking them again.
I can't stop myself checking my partners knot, even though he has 10 years more climbing experience than me, and I will probably still use opposing gates, as these habits have served me and others well over the years.

So Elliot, hats off to you for asking the question an sparking this interesting thread, I am off to find a diagram of triaxially loaded opposing carabiners....
Paul

In reply to The Ex-Engineer:

Cheers for that, it makes sense.

In reply to taddersandbadger:
What I have seen (and now look out for) is centre top-ropes put through the single snapgate (which is there only for lowering off when leading with the other clips in) rather than through the maillon/ring. I suspect this came about because someone had (against the rules) pulled down the centre top-rope and led on it. I was not impressed when I got up to that having top-roped the route on that line. Having lowered off carefully I pulled the rope down and reported it...

Neil

In reply to richard_hopkins:

A ring (or maillon) does seem better, with a separate screwgate/snapgate for leading. The disadvantage of having a ring and a snapgate is that if you move your top ropes round you then can't (unless you thread the lower-off, which most indoor climbers won't be able to do and the wall may frown upon anyway) lead on a line with no top-rope then have someone second it.

Big Rock has all three (maillon/ring for centre toprope, screwgate, snapgate) at the top of most lines. If I had to choose any two one of them would be a screwgate so seconding can be done safely. But getting to the top of a lead and finding only a screwgate tightly screwed in is a pain

Neil

In reply to Mr Lopez:


Do you know where we can find any of this data? I'm genuinely interested in seeing it, as I'd always assumed that two opposing gates were fairly safe.


Again, I wasn't aware that it was bad practice. I've principally used them at the top of sport routes, with a quickdraw on each bolt then clipped to back to the rope, with the lower 'biners on each draw clipped with gates opposing, either for lowering off, or to work the route - do you get the same kind of effects in this situation?

In reply to elliot.baker:

Given the sheer number of top rope routes climbed the current system must be really safe or it would be obvious from the accident statistics. When you hear of a bad accident indoors on a top rope its almost always not tying in properly or not clipping into an autobelay. I guess something similar to the DMM belaymaster could be used with a plastic clip that makes it obvious the screwgate is done up and prevents it coming loose.

The idea of random customers on top rope lines putting their hands on the screwgate to check it and tighten it does creep me out a little. I'd be worried someone with more self-confidence than experience would mess up and leave it unsafe.

In reply to tom_in_edinburgh:

Because a lot of the points brought up in this thread are real engineering truths, but not danger of death scenarios. Karabiners with their strength reduced by 50% will still hold any forces encountered in top-roping by at least a factor of 2. Lowering off a snapgate (or a screwgate with the gate not done up) is not best practice, but imagine the rope gymnastics required for it to unclip. You're always below the karabiner, it's not a lead fall scenario - if this was dangerous people would die lowering off a draw in an indoor sport route.

As always, it's about understanding what you're doing and the possible points of failure. I have not been convinced not to oppose snapgates sometimes on my belays, because the nut will fail before the karabiner does.

In reply to Mr Lopez:


You had my interest right up to this point. I understanding your argument that by "doubling up" on carabiners one may not be at the optimal orientation, but the other probably will be. So surely it will retain its maximum breaking strain?

Either way, as a man weighing in at well under ~1000 kg, I reckon I'd have to eat a few more pies before breaking a carabiner as a result of lowering off it, even at half strength.

In reply to elliot.baker:

I think it is a good question. I would like to add one to this. Would it be unsafe if a top rope route has only one bolt at the top (regardless of the number of karabiners hanging in there)?

I came across this in a wall recently but am normally used to two bolts and a chain (as you would see in a sport-climbing situation)

In reply to vinni:
Not necessarily dangerous, though not 'best practice'.

After all, you're only on one rope, one harness, one belay plate etc., etc.

In reply to elliot.baker:

I don't know why one would not build in redundancy.

Why use one when two would do?

In reply to vinni:

Would it be unsafe? Probably not.

Is it as safe as two? (I never saw any wall with only one) - no.

Neil

In reply to Mr Lopez:

Is the study you were thinking of?
http://www.mountainproject.com/v/two-opposite-and-opposed-carabiners-possib...

It seems as if it only relates to oval screwgate karabiners where the gates under lateral load from the other karibiner.
There is no information on asymmetric snapgates (what people actually use) where the gate is in free space.

In reply to Neil Williams:

I quite like the term 'Climbing gym'. Much better than climbing wall.

In reply to tom_in_edinburgh:

Good answer.

In reply to climbwhenready:

Good point.

In reply to vinni:


'Someone told me' (treat this with the usual suspicion) that two bolts are (usually?) needed inside as the fittings are not as strong as rock bolts (makes sense as they are just going into a bit of wood rather than a solid bit of rock). Which is to say that their kN rating would be lower for the whole bolt-panel system than the usual 25kN or so for a rock bolt. They are presumably much more reliable though as rock is an inherently unpredictable medium.

In reply to andrewmcleod:

In my most regular climbing centre they're hung off the girders that hold up the building.

In reply to andrewmcleod:

The 'standard test' is 8kn (call it 800kg) for 10 seconds on every clip in point and lower off bolt.

In reply to elliot.baker:

If you take a fall you fall onto a single krab. If you lower off because you cannot complete the route you lower off a single krab. By all means clip both if there are two but its's massive redundancy unless it is a non-screw krab hard up against something solid - which could in theory open (though this does not explain how a rope under load can slip out).

Hi,

I think the point is being missed here, it's not that a single carabiner is likely to break when new, but as the rope runs over it then metal will wear down and eventually it will become weaker, and also sharp which can cause damage to the rope. I'm not sure a second carabiner solves the problem but it certainly adds redundancy in the system.

Normally for a professional set up the top ropes would run through two rings connected with chains to two anchors, or there would be two carabiners which are statically fixed so they don't push against each other.

That said, I doubt the top rope failing something you should worry about too much, but I would worry if the climbing centre isn't professional what else could go wrong....