Arranging Pull-through Descents

[Greybeard]

Posts moved from Topic '45m rope abandoned on Swinsto pull through' in the 'Dales' Forum.


It's the crab that is the problem. We stopped using that method 5 or 6 years ago and have not had a rope jam since.
What purpose does it serve? It is still the knot which takes the weight.
A fig9 is quite adequate, even on on 9mm rope. Chains can be a problem and you may have to sacrifice a mallion, much cheaper than risk losing a rope and the associated time wasted.

 

[aricooperdavis]

What purpose does it serve? It is still the knot which takes the weight.

It'll reduce rope rub on the loop of the knot as you're pulling it through? This isn't vital in my (limited) experience, but as it can be avoided with a crab/maillon I probably would use one.

 

[langcliffe]

What rope rub? The rope doesn't go through the loop - it just dangles.

 

[rm128]

I’m not sure exactly what’s being proposed here. Can someone please explain how Greybeard’s system works in a bit more detail? If the rope doesn’t pass through the loop, is the knot blocking directly against one of the anchors?

 

[Steve Clark]

The simple system is just a big knot on one side of the bolt(s). The pitch rope is 'NOT the knot' side.

The method with a carabiner still uses a big knot, but has a carabiner clipped between the knot bight and the pitch rope. Effectively to provide a backup if the knot somehow gets pulled through the bolt. That seems to be the standard method taught in the CIC guidance for anything bigger than a single maillion. It has the advantage that you can use it on bigger solid things, like scaffold bars.

https://british-caving.org.uk/documents/cic-pull-through-caving-techniques/?tmstv=1688928526

I've not had a problem using either system so far. We did get a rope stuck on this same pitch recently but that's because we left a knot in the trailing end of the pitch rope that was in the water/over the ledge and didn't notice until it was out of reach whilst pulling it down.

 

[JasonC]

If the rope doesn’t pass through the loop, is the knot blocking directly against one of the anchors?

Yes, as Steve Clark said. Pretty much any knot will stop the rope passing through a P-hanger (or similar). As long as you're confident it won't come undone (and why would it?) the crab round the other rope is really redundant.

 

[langcliffe]

The use of a carabiner originates from when the rope was wrapped round a lump of wood or a scaffold pole. In that case, the crab served to lock the rope in place. That isn't necessary when using P-hangers or chains, when a carabiner adds unnecessary complexity into the system

 

[rm128]

Thanks guys. I have always used the krab method, but will certainly think about the krabless method next time I do a pull-through. I’m thinking the use of a krab will equalise (to a greater extent) the load on the 2 anchors, but maybe the difference isn’t significant.

Whichever method is used, I suspect many of these rope sticking incidents could be prevented by testing that the rope does actually pull through before the last man descends.

 

[Cantclimbtom]

I've had rope stuck where I was threaded through metal - and on the retrieve side I'd tied an alpine butterfly and clipped it with a locking krab to the descent rope. In my case the anchor was back from the drop and the ropes ran over an edge making a 70 degree bend, there was 25m or so to the bottom.

The problem was that the weight of the descent rope held the krab/knot down so it couldn't be pulled past the 70 edge and it wouldn't retrieve. If I'd not clipped it, it probably would have worked.

In the end, I had to jug back up, then removed all knots etc and just ab'd down on both sides of the rope at the same time (not using stop) and it all pulled through easy.

I still use the knot and krab method clipping the rope, but only if there is a clear unbroken descent with no edges to retrieve past

 

[Chocolate fireguard]

I’m thinking the use of a krab will equalise (to a greater extent) the load on the 2 anchors, but maybe the difference isn’t significant.

Now that's worth thinking about.

 

[mikem]

Including a krab usually increases the load on both anchors, however, it helps make it clearer which side to descend (provided everyone is familiar with the system)

If you have a big loop in the rope then the krab will make no noticeable difference to friction, if the knot only makes a small loop then the change in angle of the down rope makes it harder to pull through (having seen it before then I guess this is what has happened)

 

[langcliffe]

There are a number of ways that a carabiner can cause problems. Several years ago I detailed on this forum the ones we have encountered.

 

[mikem]

This started as a split pitch discussion:

Pull-through rigging

The split pitch yes? As it seems common to have problems here, do you know if the issues arise when not splitting the pitch, or does the rope tend to jam even if you split at the ledge? A karabiner is only required when belaying the rope round a scaffold pole or a wooden beam as it allows the...

ukcaving.com

 

[Cantclimbtom]

There are a number of ways that a carabiner can cause problems. Several years ago I detailed on this forum the ones we have encountered.

Also knots can cause issues too. If you have a chain that has very large links (or similar scenarios) part of the knot can get pulled inside the chain and then it might get stuck.
In those cases I'd use a "carabiner block" rather than a "knot block". Clove hitch the middle of the spine of a krab. That can't pass through but won't get stuck sucked into a wide chain (etc) when sometimes a knot might.

I won't clip it to the descent rope for retrieval (or unclip it from the descent rope for the last person descent (if a party >1).

With these various clip the other rope as well solutions, while clipped they're reasonably idiot-proof even if someone tried to descend the wrong side of the rope. Mistake proof is as valuable, probably more, than retrievability!

 

[phizz4]

Is there an argument for everyone in the party except the last one descending on a single rope then the last person removes the block and descends on the double rope using something like a CT Alpine ClickUp?

 

[mikem]

Ropes don't get stuck that often, but there are certain pitches where it happens more frequently. Descending a double rope "could" be a problem where bolts are opposite each other, one in each wall...

 

[wellyjen]

Is there an argument for everyone in the party except the last one descending on a single rope then the last person removes the block and descends on the double rope using something like a CT Alpine ClickUp?

When I used a rack as my usual descender, this was my approach, if I was the last to descend. It removed any doubt that the pull down was going to work

 

[Fulk]

With regard to abbing on the wrong rope – we have a mantra – 'NOT THE KNOT'!

 

[Greybeard]

The safest way with a large group or if there are members who you are not sure about their ability is to make sure that someone you trust is last person down. They bring the bag with the pull down rope in. This way there is only the one rope for the rest of the team and almost impossible to get on the wrong rope. I like the - 'NOT THE KNOT' idea.

 

[IanWalker]

Also knots can cause issues too. If you have a chain that has very large links (or similar scenarios) part of the knot can get pulled inside the chain and then it might get stuck.
In those cases I'd use a "carabiner block" rather than a "knot block". Clove hitch the middle of the spine of a krab. That can't pass through but won't get stuck sucked into a wide chain (etc) when sometimes a knot might.

Biner block (clove hitch on a carabiner) works well in my experience. Very simple to set up, intuitive to look at and easy to test. Very low friction and little to get snagged.

Pic here:

Canyoneering 101 - Biner Block | The Dye Clan

I was warned to only use a tri-act and never a screwgate but cannot immediately find reference to that online.