Stopper knots and terminations

Tall trees and short lines can be a bit of an issue.

An easy precaution against unintentionally running your hitch over the end of your line is tying a stopper knot. If you have a line with a splice in both ends, this will also act as a stopper, as the thickening caused by the splice starts a fair way down the line and ensures that even should you hit it at speed you will have a good 20cm of line left over below your prusik minding pulley.

Splice acting as a stopper
Splice acting as a stopper

One question that has arisen is whether Teufelberger’s SLAICE will also act in this fashion. The advantage of a SLAICE when used as a termination is its very low bulk, constant diameter and very short bury. But obviously if you are using it as a stopper this then potentially becomes a disadvantage – at least insofar as if you are expecting it to a act as a stopper, as it gets pulled right up into the hitch due to the lack of thickening caused by a conventional splice.

SLAICE pulled right up into the hitch
SLAICE pulled right up into the hitch

For this reason, if both ends of your line have a SLAICE on them, it is advisable to tie a stopper knot above the SLAICE on the end of the line, as shown in the photo below.

SLAICE backed up with a stopper knot
SLAICE backed up with a stopper knot

Karabiner gates and foreseeable error

Sorry if that last post didn’t make much sense – and no, don’t worry, I’m not turning into a grouchy old man, just my thoughts – and they don’t always have to make sense… 😉

I was thinking about karabiner locking mechanisms before, prompted by a video posted on Facebook that shows an Locksafe Ultra O rolling out as it the locking mechanism is pushed against and past a limb. This failure mechanism is not specific to one brand, but rather inherent to the lift, turn and push type triple-action gate.

Essentially the limb in the video is doing exactly what you would have to do to unlock and open the gate. This phenomenon is known as roll-out. Statham and Roebuck wrote a report, Karabiner Safety In The Arboriculture Industry, for the UK Health and Safety Executive a couple of years ago, in which – amongst other things – they describe some roll out testing they performed on a range of connectors  commonly used in tree care and how they all struggled with the test set-up shown below.


The locking mechanisms that did best out of the lot was the Petzl Ball Lock, then still the plastic version with the thumb print on it. In my eyes though, it would be a bit hasty to start crying foul and accusing manufacturers of making bad quality gates. Essentially, this is not a design flaw, but rather it is operator error: In a cluttered environment it is up to the operator to ensure that the locking mechanism shall not come into contact with the structure and inadvertently be pushed open. Look at any user instructions and somewhere in there you will find a pictogram or text warning against this exact case, as in screen shot of the Petzl Carabiner Experience PDF shown below…

This is actually talking about something different, which is the danger of cross loads and lever action across the gate, but the fact remains: It is a clear warning against loads on the gate and once again emphasizes the importance for visual inspection, especially in an environment, like in tree climbing, where the connector is frequently being loaded and unloaded, making a cross load on the gate more likely.

What is clear though is that there is not one type of locking mechanism that addresses all issues. The Ball Lock type mechanism mentioned above may solve roll-out type problems, but especially the old plastic version had a low tolerance to outside loading of the gate. So, it is really up to the operator to consider what type of environment he or she intends to use the connector in, obviously the requirements you make of a karabiner is not the same when climbing large, open-canopy trees or when cone picking in the forest – and to choose an appropriate type karabiner. Depending on the situation, this may have a triple-action or a screw gate – or yet another type.

For more info, here is a link to the Go Configure article that Chris wrote a couple of years ago for ISA’s Arborist News.

The video below illustrates a different case:

Here a light tap on the outside of the gate is sufficient to push it open. This is a different matter alltogether: From a design point of view this sort of load is a foreseeable error. Whilst superficially the Skylotec Pinchlock karabiner has similarities with the Magnetron by Black Diamond, the failure mechanism in question is specific to this karabiner as the rods that locate into the slot on the nose have a round profile, rather than the square ones on the Mangetrons, that on top of it don’t only rely on springs to locate the rods, but also use a magnet to ensure correct closure. In an outside-loading situation the round rods on the Pinchlock are simply pushed up and out of the slot, a tap against the side of the hand being sufficient to do so.

Again, this is not a value judgement, it is merely an observation, as for all I know there may be an application where this type gate is spot on, but certainly a busy, cluttered environment such as a tree canopy is probably not one of them.

No more heroes – or gurus, come to that.

What is it with the inflationary use of the term “Legend” that irritates me?

Wow! Did you see that? He’s a real legend!

I suppose what one is trying to say when one uses the term is that somebody has done something especially well or memorably. But does that make someone a legend? To me, the stuff of legends is… I don’t know, Beowulf, Odyssseus, King Arthur, figures in that kind of league. Anyway, not a term I would consider using someone who had done well in a competition – or something like that. Not knocking it, mind you, just saying that it’s not a term that springs to the front of my mind.

This is not to say that I don’t have people who have influenced me over the years. But then that is very subjective, not something I would necessarily go shouting about or make a big thing of, but rather something quite intimate and private, part of the mosaic of experiences and memories that makes me the person I am today.

Essentially, what we are talking about here is about a quality of interaction between two people.

Let me explain.

Antje Schrupp, a German professor of politics discussed the relationship between power, violence and authority from a feminist point of view in a very thought-provoking paper a couple of years ago. One of the points she focuses on is the question of authority. I found her definition of authority very striking: She says that it is a quality of relationship and always has to be negotiated between two individuals. So, if I were to meet you and we got chatting, I might think: Hey, this person seems really knowledgeable about fungi on trees. And you might think: What Mark is saying about configuring karabiners makes a lot of sense (well, you can always hope!). Based on this interaction, I might decide to grant you authority in all matters fungus on trees and you might in return impart a degree of authority regarding configuring karabiners to me. Authority can only be granted, never demanded. If the crew foreman puffs himself up and demands you to respect his authority, this is not a negotiation, according to Schrupp he is using the power granted to him by his position in the hierarchy to force you to subordinate yourself to him. This is not authority, rather it is power being put to work.

Getting to my point here…

What Antje Schrupp says is that if a negotiation does not take place and a mass of people concedes power to a person, this person is then not an authority, but rather a guru. Take an example… Ueli Steck, a well-known alpinist with some crazy speed ascent records. If I were to place blind faith in all he says and take it as gospel, without having sat down with him and decided for myself, based on 1:1 interaction whether he actually is as knowledgeable as everyone maintains, then in fact he is not an authority to me, but rather I am looking up to him as a guru.

To me this was quite a profound insight.

It makes me realize that when I am out doing workshops and lectures that actually every person in the audience has stories to tell and if we had the time, we could grant each other authority in lots of different matters, which would be really exciting. Sadly, due to time constraints this will not be possible, however, I do urge people to question what I am saying and to add their opinions to the discussion, as I have no ambition whatsoever to be a guru to anyone, as then exchange becomes impossible, as a guru can never admit to ignorance. And then I have to ask the question of why go to all the effort, if you are not learning as you go along?! Seems rather stale and hollow to me.

So. Legends for me belong in the realm of sagas and fairy tales. I prefer to think of such individuals as contributors, bridge builders and role models. After all, according to Antje Schrupp’s definition, authority, once it has been negotiated, brings responsibility with it – and shall not serve to merely boost one’s ego or to make you feel warm and fuzzy.

Reflections after a gear check

Don’t worry, not running out of topics to write about here, just energy to do so. Have I mentioned that there must be easier ways to make a living than tree work, some days you just end up shattered. Mind you, having said that, I can’t think of any better way of earning a living.

Swiss comps over the weekend, which took place in one of my favorite parks, Margarethen Park, here in Basel, an English landscape park with a population of beautiful, big trees. Once again, a big thank you to all volunteers, congratulations to all climbers and, finally, congratulations to Florim and Anja for winning it. Hopefully we’ll be seeing them compete at ITCC and ETCC later this year.

I was reflecting – once again – upon some of the gear that I came across during the pre-comp gear inspection. Let me explain…

What are your safety margins?
What are your safety margins?

I have to admit that I am sometimes surprised by how varied people’s approach to their equipment can be. Especially in regards to what kind of safety you incorporate into your system design. Safety factors are ubiquitous in the world of engineering and describe the margin integrated into the design between the Safe Working Load (or Working Load Limit) and the Minimum Breaking Strain (MBS). This relates primarily to lifting equipment, the MBS quoted by the manufacturer on an item of PPE (Personal Protective Equipment) is just that, but there also, it is necessary to consider safety margins.

One of the things safety factors takes into account are wear and tear and the resulting degradation that equipment is exposed to.

This is especially relevant when incorporating low diameter lines and high-modulus fibres into systems.

Of course on paper, these may all look just fine, considered from a MBS-centric point of view. However, other factors come into play also, such as tolerances or intolerances of specific materials. Add in a splice, for example, or abrasion and prolonged exposure to UV and the picture can change considerably. For example: a home-made pulley saver, made from 10mm Beeline, spliced into a hollow ART ring for the big eye, using a 6mm Edelrid Aramid stitched sling to attach a Cocoon pulley. New, this may be ok for all I know, but over time one does have to question how it is going to age: according to the Yale Cordage website the mantle of Beeline is a 75%/ 25 % Technora/ Polyester cover braid. Teijin, who manufacture Technora, state on their website:  The strength of Technora can be lowered to a half when exposed to sunlight for about 3 months. Umm. That then does beg the question of how well this cordage is going to age when used over a longer period of time, as it will be in a false crotch (unlike in a friction hitch, where life cycles are shorter). And as an anchor point it will also be exposed to UV. Of course, you could argue there is still the Vectran core, but the point remains that due to choices of materials, in this case environmental factors have radically changed the properties of a central element of this assembly. Don’t get me wrong, I am neither pointing fingers here, nor knocking a specific product, in the right place, Technora is fantastic  stuff, but the point I am trying to get to is that it is necessary to consider a wider range of factors than merely the MBS in mint condition when configuring systems and assemblies

And that is just one example. The exponential use of Dyneema is another worry. 6mm Dyneema is super-strong, no question. But one does have to wonder when a whole ascent systems is based around it – what kind of tolerances does this system incorporate? What would happen if heat were inadvertently applied to the cordage? How will the use of mechanical devices on such cordage affect its performance?

In my books, safety factors are a good idea. Imagine, if Boeing or Airbus removed say 50% of the rivets from their planes, just because when new this would work – not taking into account that their planes do not only fly when they are brand-spanking new, but also when they are older. I’m not sure I would be one very relaxed passenger.

A number of high-profile recalls the past year in the field of fall prevention PPE also fall into the category of light-weight designs rather than ones that incorporate somewhat more material, but with sufficient safety margins. Or with a focus on design rather than resilience and wear-resistance. This is a worrying development, especially when discussing class three PPE and the serious consequences a failure might have.

Ergonomic, light-weight gear is all very well, but it should never become a trade off for safety.