Joining ropes for pull-through

[Huge]

Wondering how people join their ropes for pull-throughs.

On the CNCC pull-through course I attended last year, we were shown to tie a fig 9 as the stopper knot, after threading the end of the abseil rope through two anchors. The last person down then clips the pull-down rope to the fig 9 with a crab. This means two knots and a crab to potentially become caught up.

Do people join the ropes in other ways, such as tying them together directly?

 

[langcliffe]

Wondering how people join their ropes for pull-throughs.

On the CNCC pull-through course I attended last year, we were shown to tie a fig 9 as the stopper knot, after threading the end of the abseil rope through two anchors. The last person down then clips the pull-down rope to the fig 9 with a crab. This means two knots and a crab to potentially become caught up.

Do people join the ropes in other ways, such as tying them together directly?

We just use a threaded figure of eight without any metal involved.

 

[topcat]

In mountaineering we use overhand with long tails. However, this is in [typically] sub 9mm and soft ropes. The overhand is the least likely to snag and can be untied. Years ago the standard knot was double fisherman's but this is hard to undo after loading, especially on wet/frozen ropes with cold hands, and more prone to snagging.

My personal caving ropes, and some club ropes, are soft 9mm and would be ok with an overhand, but stiff 10.5's probably not.

 

[JoshW]

for knot passes I tie a capuchin at the end of each rope then tie the new rope in ‘through’ this knot, double fisherman’s style. I guess for a pull through there’d be nothing stopping you tying a looped knot in one end and then just boshing a bowline into the loop using your pull through cord/rope - removes the need for a carabiner in the mix, but obviously adds a split second to tie a bowline.

 

[nobrotson]

Join ropes with an EDK, and use a biner block as the blocker to set the rope length. This method has always resulted in a clean pull for me, can be backed up with a short link to the bolt for redundancy until the last abseiler descends and you don't need to worry about slip on the EDK as highlighted above as it shouldn't actually be weighted at all. Clove hitch might slip with a particularly thick or muddy caving rope, I've never experienced this myself and doubt it happens at all regularly.

In general I've found that canyoning resources are far more useful on the subject of retrievable abseils than any caving resources as they do it all the time rather than just some of the time.

 

[Cantclimbtom]

Clove hitch slip is just not going to happen at those loadings and even if did it could only slip as far as the EDK so it's belt and braces safe (IMHO) when deployed as described by nobrotson

 

[andrewmcleod]

I would say that _in general_ the risk of getting the rope stuck somewhere and consequently being stuck on a ledge for many hours generally greatly exceeds the risk that whatever sensible knot you are going to tie will unexpectedly fail (by many orders of magnitude).

Your personal risk assessment may depend slightly on things like:
a) is the drop very clean i.e. rope very unlikely to get hung up when pulled down
b) is the drop very short i.e. same as above
c) getting the rope stuck would not be a major problem e.g. this is the bottom pitch, or the pitch can be easily free-climbed to free ropes (had to do this in Wilf Taylor's passage after getting ropes tangled once)

but I'd probably still argue that picking one technique and getting good at it and used to it is better than swapping and changing everything all the time (particularly something like pull-throughs where there is less redundancy in some elements than standard SRT, and a single mistake can be catastrophic).

 

[Mark Wright]

What andrewmcleod said.

I must have done a dozen through trips from 2 of the upper entrances to the Grotte de la Diau in France.

I was only 16 when I first did it and I remember the very serious looks on everyone's faces as they pulled the ropes down on the entrance pitch. None of us had ever done it before but we did have a trip up the Diau resurgence the day before, so we at least knew where we would drop in.

The only issue I ever had was when the Alpine Butterfly knot and the linking carabiner kept getting stuck after pulling about 2m of rope through one of the bigger pitches in the 3B cave. Local cavers had installed a rope protector made from plastic sheet and bolted it to the wall at the corners. Unfortunately the edges of the plastic curled up and the rope and carabiner were getting caught behind it.

As we didn't know what the problem was, Dave Cowley clipped himself onto one side of the rope and I climbed up the other until I saw what was causing the problem and managed to rectify it.

IIRC there are a couple of pitches where you get off part way down and then pull your ropes through. You definitely need a topo to be sure.

Didn't a couple of ex SUSS members in the early 1980's have to be rescued from a cave in the USA when they pulled their ropes down from the wrong place?