UKC

Offset figure of eight for abseiling

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 Suncream 30 Mar 2021

A couple of months ago, I was ice climbing with a Swiss guy. We finished the route and he set up the abseil using an offset figure of eight. I immediately told him I believed this was dangerous and changed it to an offset overhand, but he assured me that he'd been taught this by a Swiss guide on a course. I sent him a few links to articles that suggested it's dangerous, and the subject didn't come up again.

However, I just watched this video: 

youtube.com/watch?v=9_sGyjr8IKo&

The relevant part starts at 3:45. This seems to suggest that the offset figure of eight is fine for abseiling. So was I wrong to call this guy out?

 Luke01 30 Mar 2021
In reply to Suncream:

Interesting. This is the first time I've seen the fo8 suggested as safe to use in this context.

Not going to change my mind based on this though, so I'll stick with an overhand for now.

I've just re-read the relevant section of Andy k's book 'down - core' and apparently it's common to find tests that show the offset 8 is safe, and people advocating it. But don't be fooled! It's a cold blooded killer! 

Post edited at 12:25
 spenser 30 Mar 2021
In reply to Suncream:

It's important to differentiate the two orientations of a figure of 8 bend, you have the one shown in the video with the ends of the rope on the same side (as per EDK/ Overhand which has extensive evidence of being fine, including this video, when joining ropes) and the flemish bend which has the ends on opposite sides of the knot (a'la the double/ triple fisherman's bend).

I am sure I have seen stuff before saying the flemish bend is safer than the offset figure of 8 bend, however given the similarity in tieing and the fact that confusions like this do legitimately arise I use neither for abseiling due to the potential of getting them mixed up when tired etc.

They also mention about blocking knots in karabiners/ maillons for abseiling with a tag line which seems a bit dodgy to me, I tend to tie a bight on the knot side of the maillon (figure of 8, overhand, alpine butterfly etc), clip a krab into this and clip the krab to the live rope (going from me directly up to the anchor with no knots in it) and then pulling on the tag line (noting this increases the risk of a stuck rope in some situations unless you are able to walk back from the base of the abseil).

 tehmarks 30 Mar 2021
In reply to Suncream:

My favourite reference on the subject is https://www.needlesports.com/Information/Need-Advice/Abseil-Knots - and based on their conclusions, I wouldn't really fancy trying it. Safe or not, it seems suboptimal. There are better options.

Post edited at 14:25
 crayefish 30 Mar 2021
In reply to tehmarks:

The Needlesports link is a good summary indeed.

Not sure why anyone would want to tie a figure of 8 though... its not easier or quicker than a euro death knot or double overhand.

Personally, the euro death with long tails has always worked fine for me.  Though it was particularly icy, I'd probably go with a double.

In reply to Suncream:

I found I could tie the ends of my ab rope in a flat fig 8 and if not particularly well tightened, standing on one strand and pulling on one was enough to roll the knot off the end. Even with generous tails. So... it's a no from me.
Stacked pair of overhand knots with a decent tail is all you'll see me use.

Post edited at 16:14
 TobyA 30 Mar 2021
In reply to Suncream:

Saw the title and thought you meant one of those funny offset fig. of 8 descenders that I think DMM used to make. "Anka" maybe? Can anyone remember them and what they were meant to do?

 Timmd 30 Mar 2021
In reply to TobyA:

> Saw the title and thought you meant one of those funny offset fig. of 8 descenders that I think DMM used to make. "Anka" maybe? Can anyone remember them and what they were meant to do?

https://helixtactical.com/Products/Belay-Abseil-Ascent/Rope-Controllers/Man...

There's blurb about them here, from another company.

 Philip 30 Mar 2021
In reply to Suncream:

What is going on in the final abseil. It looked like having joined two roles he was ab'ing on just one rope with the knot jammed to the maillion effectively anchored only by the knot not passing through. 

 Timmd 30 Mar 2021
In reply to Philip:

If there was equal load on the 2 strands (with it being 2 ropes tied together), I don't suppose that would be the only anchor?

 GrahamD 31 Mar 2021
In reply to Suncream:

Always struck me as a fiddly one to tie compared with a standard overhand joining knot so never saw the point.

 AndyRoss 31 Mar 2021
In reply to Philip:

The thin white rope is just a tag line for pulling down the blue rope, rather than being load bearing. But I think most people clip the tail of the blue back onto the loaded strand so you don't have a problem (other than needing to reascend) if the knot goes through the maillon.

 LastBoyScout 31 Mar 2021
In reply to TobyA:

> Saw the title and thought you meant one of those funny offset fig. of 8 descenders that I think DMM used to make. "Anka" maybe? Can anyone remember them and what they were meant to do?

Yes, I've got one in my bag of climbing exotica. Rarely gets used by me these days, but I often take it out with groups, as the wings mean it's very hard to accidentally lark's foot the ab rope, which you can with a standard fig-8.

It's also got an offset in the stem, which means that putting the rope through from one side gives a tighter bend - and therefore more friction - than the other, for more control.

As mentioned in Timmd's link, it also solves the issue of the 90-degree twist in the system when clipping into a belay loop.

 TobyA 31 Mar 2021
In reply to Timmd:

> There's blurb about them here, from another company.

I'm not completely certain but what with it being the same postal address and so on, I'm pretty certain Helix is just the armed wing of DMM!

 nikoid 31 Mar 2021
In reply to AndyRoss:

I agree with your observations, but why wouldn't you ab on both strands in that situation? You'll have a problem if the thin rope blows out of reach. 

 Timmd 31 Mar 2021
In reply to TobyA:

> I'm not completely certain but what with it being the same postal address and so on, I'm pretty certain Helix is just the armed wing of DMM!

I wondered if it might be. 


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