Abseiling riddle

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bjorniam
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Abseiling riddle

Post by bjorniam » 25 Jun 2018, 08:53

I was recently posed an abseiling related riddle, which I was told "you will love, eventually, conditional to your success in solving it".

Working through potential solutions was indeed as enjoyable as advertised, as well as being surprisingly educational (the correct solution is particularly good to add to ones bag of tricks but even the more dodgy methods I devised along the way were good to have thought through).

So here it is: "So you find yourself at the top of a 40m climb, split in 2 pitch of 20m with a belay station in between. So you're at the top, alone, with your 30m rope. You have the usual basics with you, meaning your atc, carabiner, prusik, safety and a knife. How do you get to the ground safely? Without cowboying anything."

To which I'll add: there are no other anchor options along the way (no bolts, trad gear, shrubs etc) - you could imagine the abseil pitches being free-hanging; the sum total of your worldly possessions (prusiks, slings, shoelaces etc) have a combined length of less than 10m so "extendo-ropo" won't cut it.

Have a think (without google or anything else you won't have with you at the top of the cliff) before scrolling further.































Then share your solutions creative/cowboy/elegant.



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Re: Abseiling riddle

Post by Kosta » 25 Jun 2018, 09:15

My first solution was, that it was impossible to get down safely and the correct answer is to use the PLB and wait for help. But then I figured something that I would consider practical and safe.

Don't scroll further if you don't want to read it.


































First, cut the rope into a 10 m and 20 m piece. Measuring this is doable since it is a third of the rope. Tie the 10 m piece to the anchor and add a loop/mailon/carabiner at the end. Now abseil down the first 10 m single rope. Use the end of the rope as anchor and abseil the remeining 10 m double rope after doing a knot traverse. The second pitch can be done single rope leaving the 20 m behind.

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Re: Abseiling riddle

Post by T2 » 25 Jun 2018, 11:06

Ha, nice riddle. Way to make me waste time on a Monday morning!

My first thought would be that as I now almost always carry a fiddlestick this wouldn't be a problem. But assuming that's not available, I think Kosta's solution is the safest.

My first thought was to let down 20m of rope to the next anchor, set it in place with a 'biner block, then add any slings etc to the remaining 10m of rope, and tie my pack to the end of those slings. Once at the bottom of the first abseil, the weight of the pack should (hopefully) drag the rope through the anchor. You then catch it, pull the rest of the rope through, and repeat. This would be reasonably safe because if the weight of the pack didn't budge the rope, you could still safely prusik back up it because of the 'biner block. Of course, this would only work if you had a really clean pull as otherwise the weight of a pack would have no hope of shifting it.

I think there are also some really terrifying knots that hold firm when loaded, but fall apart once released. Using something like that would potentially get you down, with your rope intact, but it would scare the living crap out of me and drastically increase the chance you'd plunge to your death.

Was Kosta's response correct? Or is there a more impressive solution we should be finding?

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Re: Abseiling riddle

Post by Kosta » 25 Jun 2018, 11:24

T2, if the pull isn't 100% clean, we could combine our approaches: cut just enough rope to get over the edge. Then add your Pack-block anchor right there. The advantage would be, that the first pitch could be close to 30 m whereas the second can be as long as the length of the remaining rope.

This assumes, of course, that the re-belay is on a ledge or something so the backpack lands on the ground instead of just rushing past you.

It also assumes that you have a backpack in the first place. I seem to recall a trip where the very reason you only brought a 30 m rope was that your pack was at home on your front porch... ;-)

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Re: Abseiling riddle

Post by T2 » 25 Jun 2018, 11:29

Kosta wrote:
25 Jun 2018, 11:24
It also assumes that you have a backpack in the first place. I seem to recall a trip where the very reason you only brought a 30 m rope was that your pack was at home on your front porch... ;-)
Yeah, I'm not going to live that down am I? Still, at least we now know that it's possible to go exploratory canyoning without a pack or the 60m rope you intended to bring.

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Re: Abseiling riddle

Post by bjorniam » 25 Jun 2018, 12:23

Kosta's answer is what my mate was looking for. It seems like a general solution that is worth having on hand when next stuck in a pinch.

I really like your solution T2! It's not something that had crossed my mind, and hence a further enrichening of my toolbox. It'd be a great solution where you've got a reasonably wide anchor to be sure to catch the bag on.

Thinking more like a climber I'd imagined rapping fixed single strand to the halfway anchor. Tying the rope off hard there. Prusiking back up half the first rope. Tying into the rope hard at that point. Then cutting the rope and taking a massive whipper (assuming lots of free air to fall into), before Prusiking up to the half way anchor with a total of 20m of rope remaining to do the second single strand rap.

BTW I didn't force you to check the forum on a Monday - you were itching for this type of procrastination :)

I reckon there are still some other interesting solutions out there though. I'll be checking back to see what others come up with.

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Re: Abseiling riddle

Post by Kosta » 25 Jun 2018, 12:38

Just wondering: has anyone ever tried to tear apart a rope to make a longer cord? When you look at a rope, it is made out or a few dozen or so individual strands. Each of which should be strong enough to serve as a pull cord. Thus, we could take 2 m or so of rope and manufacture a 20m pull cord out of it by pulling it apart and tying the strands together.

I've never tried anything like this, but it would be interesting to know whether it's feasible.

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Re: Abseiling riddle

Post by T2 » 25 Jun 2018, 12:49

Not all static ropes have a braided core, although most do. The materials used in the core usually lack abrasion / heat resistance, but for use as a one off pull cord I think it should work in theory. I'd probably want to cut up a longer section of rope though, as you'll lose a reasonable amount of rope with the knot at each end, so the shorter your strands, the more knots you will need, the less length you'd get out of the system. I might pull apart an old rope and try this out.

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Re: Abseiling riddle

Post by bjorniam » 25 Jun 2018, 13:04

Another creative idea! Let us know how you go T2.

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Re: Abseiling riddle

Post by Flynny » 25 Jun 2018, 19:03

Macrame knott, extra long shoe laces and a lack of fear

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Re: Abseiling riddle

Post by johnmurray49 » 25 Jun 2018, 19:31

A sheepshank on single rope at the top. Keeping weight on the rope cut middle strand (make sure it is the right one), abseil down. Once weight is off the rope the knot comes undone and your rope, minus a foot or two drops down.

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Re: Abseiling riddle

Post by T2 » 26 Jun 2018, 10:58

johnmurray49 wrote:
25 Jun 2018, 19:31
A sheepshank on single rope at the top. Keeping weight on the rope cut middle strand (make sure it is the right one), abseil down. Once weight is off the rope the knot comes undone and your rope, minus a foot or two drops down.
Just don't accidentally take weight off the rope when pausing on a ledge etc...

The use of a knot like this truly terrifies me. That said, I probably should play around with it at some point so I know how to use it if needed in an absolute emergency.

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