Big trees

We started work on an alignment of 27 large plane trees, which must stand around 35 tall. The trees are quite challenging, they were pollarded at various times during their lives and have extensive cavities, numerous fruiting bodies of Inonotus hispidus, large limbs infected by the Massaria fungus to name but a few. In the past they were pruned from a cherry picker, so it was clear from the get-go that this would make for some challenging climbs.

We got stuck in yesterday, after lengthy ascents, to my relief, the canopy structure turned out to lend itself quite well to the type of pruning we were supposed to do. This kind of challenge really makes you use all the tricks in your toolbox when it comes to work positioning or accessing pieces a long way out, lots of fun though.

So we worked our way through the first few trees, but once we reached number three and four, it became apparent that these were less forthcoming when it came to anchor points. Therefore we installed a line into tree number six which was overhanging the other two, at least height-wise, and accessed the other two from there. However, the points we were looking at were well offset from the centre and on long whippy limbs. Therefore, and also due to the fact that there were four climbers in the trees, we decided to put a number of remedial actions in place: First off, we re-routed the fall of the access line (orange in the image below), redirecting it over a limb, so as to put the stem on which the anchor point was on in compression, rather than loading it laterally. This is easy to imagine, if you consider the vector forces from the access line anchor point (yes, this is very much kitchen physics, described in layman’s terms, ignoring friction at the anchor point, I realise. But this is, after all, not the physicsmagineers’ blog) and imagine the two vector forces, F₁ and F₂ pointing away from it, the resultant force from adding the two together, F₃, halves the angle between the two lines – and this is what puts the stem in compression, as it lies in the same line as the direction of the vector force.

Next, we secured the out-lying anchor points back to one of the central stems.

We did this using arborWINCH, a Dyneema rigging line line, which is extremely light, but more to the point of course has a very low elongation. With this we braced back the anchor point in the middle tree to tree number six. We did this by rigging simple mechanical advantage systems, which we then tensioned up (see below).

The effect was quite surprising. 

The arborWINCH really limited the movement of the anchor points very efficiently, this brings considerable peace of mind with it, allowing you simply to focus on the task at hand, rather than having that niggling doubt in the back of your mind regarding the point you are tied into. 

You definitively need to use a Dyneema, or some other  material with low-elongation for this measure to be effective. Also, considering vector forces when defining anchor points can make a big difference, as you can see when you test load the point. Initially, we had this rigged straight up and down. When a two-person load was applied, there was considerably more movement than after re-routing the line.

Once we had done all this, we got to work on the two trees, working from the secured anchor points (climbing lines indicated in the image above in blue).

All of the above just goes to show how with a little bit of advanced planning and discussion, as well as investing a bit of time in set-up, can make a big difference to how safely and efficiently you can get the job done. I also think it is fun to working stuff like this out…

Strange daze

Strange days indeed.

On the one hand, an increasing body of scientific evidence is emerging that trees and other plants communicate amongst themselves at some level, creating synergies and demonstrating behavioural patterns which are mutually beneficial to themselves as well as other creatures. When discussing this matter, it can be tempting to fall prey to the trap of anthropomorphising behaviour of beings that are fundamentally very different from us – yet the fact remains that this insight is very relevant and profound, causing one to rethink the Victorian take on nature, which viewed it very much as a bloody tooth and claw business, this point of view led to Darwin coining the term survival of the fittest. Whilst of course, some genetic traits may prove to be more viable or better suited to certain environmental factors than others, it is now becoming apparent that this does not exclude cooperation and altruistic behaviour.

On the other hand, moving away from the natural realm, humans seem to be faring less well.

This first and that first, make this that or the other great again. Like, really?! Common sense seems to have been launched into a ballistic orbit, strapped to a pair of JATOs belching flame at full thrust, along with truth, reason and facts – to be replaced by simplistic, jingoistic slogans and apparently oh-so easy solutions.

Surely, we all stand to loose if we start to fragment into increasingly granular, jealously guarded, heavily militarised units. Alex Shigo once said, I am paraphrasing here, that compartmentalisation in trees is a good thing – yet in humans it is deadly. I could not agree more! Maybe this is a sentiment that someone ought to point out to the Trumps, LePens, Farages, Blochers, Höckes, Orbans and the myriad of populist leaders out there, who seem hell-bent on leading us back into the dark ages of nationalism, ecological destruction and ego-centrism – and we all know where that led last time round.

Rather than repeating history, we would do better to look towards nature for a lesson, striving for cooperation and working towards mutual benefit rather than heading down a path which is increasingly blinkered and destructive.

Heed the X, Y and Z

There are old arborists and bold arborists, but there are no old, bold arborists.

There is certainly something to the arborist dictum above, I am not sure who to credit it to, should you know, send me the answer on a postcard. But actually, thinking about this today, I realised that I would like to suggest that we expand it, so that then it would go something like this…

There are old arborists and bold arborists, but there are no old, bold arborists. Oh yes and spatial awareness is also helpful in becoming an old arborist. 

Yes, yes, I know it does not roll off the tongue very well, but you get the gist of it.

But, you say, why spatial awareness?

Well, I believe that knowing where you – and the bits and bobs attached to you – are in space at any given point in time is essential to being safe and efficient when working at height.

Want an example ? This sense helps you…

  • to know where your lanyard is while you are making the cut,
  • to know where your hands are in relation to your hand saw,
  • to be aware of where safety-critical components of your PPE are whilst handling sharp power tools,
  • to know where you are in relation to where your anchor point is before you make that swing so as to be able to judge how hard and fast it is going to be,
  • to anticipate the movement of the section of stem you are lifting with the rigging system and where you are positioned in relation to it,
  • to correctly judge the centre of gravity of a limb you are attaching with a balancer,
  • to position the crane hook correctly above the limb prior to a pick.
  • and to efficiently envisage a sequence of movements through a canopy.

And so the list goes on.

All of the above relies upon having spatial awareness.  This sense helps you to visualise where you are, to make sense of the space around you and to judge depth and distance.

I actually do not think that this is either something you are born with – or not. Well, maybe to a degree, but it is certainly something you can train: You could make a game of playfully guessing how the swing is going to unfold or the lump of wood is going to lift of the cut, to then check whether your guesstimate correlates with how the situation actually played out.

But above all else, you need to be diligent, focused and pay attention to what is going on around you.

Let’s pay attention to the x, y and z!


Fully excited about this year’s edition of Vertical Connect, the inter-disciplinary work at height forum on 1 and 2 September in Meiringen in Switzerland.

I just got back from a planning meeting, the program is coming together – and is looking really exciting, the two day topics will be Risk and Connectors and Connections, with speakers on the first day discussing risk culture, management and the right to risk from a wide range of disciplines, such as cave diving, from an academic, base jumping, tree care or canyoning perspective.

Connectors and Connections will examine various aspects of creating connections, be it of physical nature with hardware or between people. We will be taking a closer look at themes as diverse as helicopter transports, team dynamics, evolution of connectors, configuration and a differentiated approach to use of connectors.

More details will follow when the speakers are confirmed and the program is definitive.

Once again, consider yourself warmly invited, should you be in the area around that time, to stop by and join in. We will be offering simultaneous translation between German, French and English, there is camping and hotels close by, not to mention a plethora of Alpine activities close at hand in the Bernese Alps. This event offers an unique opportunity to interact and meet other folks working on rope from all over Europe.

Reserve the dates, come and join us – and get connected!

Nice job

I stumbled across a video by an old friend of ours, Danny Courtis, who is based up in Frankfurt where he runs his business, Freelance Baumpflege. Over the years, Danny has run some pretty… colourful crews, to say the least, some of the shenanigans they got up to have passed into the lore of arboriculture.

OK, the video is in German, but you get the gist of it. And, if it is any consolation, Dany does the whole thing in German with a slight English accent, maybe that helps?

On a more serious note, when I clicked on the link of the video and started watching, I was expecting another one of those vids with wobbly head cam footage, guys swinging round trees whilst running big chain saws. Not so. This one turned out to be something a little different: Danny and the Freelance crew demonstrate in a very professional and authentic fashion what it means to be an arborist, the passion, care and diligence it involves. The tree (watch out, spoiler coming up!) they end up felling is a beauty that Danny had been working on for 16 years, until finally a point was reached where it was clear that the tree was truly no longer safe.

I believe this is a very central question to what we do: when is the point reached when you condemn a tree? How do you strike the balance between safety and conservation? Danny and the Freelance crew did the profession proud with the way they approached this job.

I found myself wishing we saw more of this kind of material and a little less of the rampant self promotion that seems to have become so ubiquitous nowadays, as I found this video genuinely interesting and engaging, whilst the alternative tends to be, well, a tad tedious, to be honest.

Thanks, Dany, for a job well done and for sharing.

More storm damage

Continuing on the theme of storm damage, last Thursday served up a wind-blown birch tree with a tipped root plate, leaning into a hornbeam. Nothing huge, but tricky none the less, as if it were to roll off, the next stop would be the neighbouring building.

After doing a risk assessment, we decided that as the roots on one side of the root plate were still intact and the tree was well jammed up against the hornbeam, with limbs interwoven, it was safe enough to climb, so we proceeded to remove the limbs which were clear of the canopy of the hornbeam…

Next, we rigged up a large 3:1 mechanical advantage system onto a suitably positioned tree. As there was no space to also install the GRCS onto this tree, we rerouted the line by 90° to an adjacent tree off to one side.

The interesting thing with rigging the MA system with Impact Blocks is that it is connector free, using an Alpine Butterfly to attach a large Impact Block onto the line tied to the birch tree, a tRex dead eye sling to attach to the anchor tree and webbing slings doubled through the hollow spindles of the large Impact Blocks to integrate the small Blocks.

We used another, lower diameter pre-rigged MA system to attach to the top of the birch tree, as this had a bit of a back lean on it. I faced the top with a large, open notch, leaving a good 8cm hinge on a 30cm diameter stem, Vito cranked it up, but when it reached the upright position, the hinge snapped and it took off at 90° to the intended direction! Eeeek! It is really surreal watching something go profoundly wrong like that, you’re like, This. Is. Not. Happening! Yes, it is! Nooooooo…

We were lucky, the top clipped the corner of the building on the second (No!), first (Nooo!) and ground floor  balconies (Noooooo!)… yet did no damage (Pheeeew!). What went wrong?

It was a cold day, the hinge wood was obviously more brittle than it would normally be, the pull was a little off to one side due to the position of the anchor tree – so really, it was a classic example of factors compiling: had it been only the back lean, only the cold or only the slightly off-set direct of pull, it might have another matter, but the combination of all three led to the hinge failing. Having said that, I had considered this possibility and decided that as there was nothing all too serious to damage, therefore it was worth taking a calculated risk.

After that, we decided to add the small MA system to the large one to redirect the direction of pull to where we needed it, then we tensioned up the large MA system, raising the birch off the hornbeam, removed the interwoven limbs, took a bit of height off the top of the birch to ensure it would come nowhere near the neighbouring building should the base fail, then pulled it over into the garden – which all went smoothly.

I thought this was an interesting case, as it illustrates clearly how storm damage poses its own set of challenges. These can be managed by systematically and diligently assessing the risks – yet even then, you need to expect the unexpected and leave yourself adequate safety margins, anticipating potential failure.



Not really anything new

On and off I keep on bumping into discussion about rigging with karabiners, images or videos of choked lanyards and other more outlandish uses of karabiners. This is nothing new, it is a discussion that has been rolling along for many years. Well, maybe the social media-based iteration has some more aggressive, assertive overtones (I think it is fine to do this, so it is safe to do so – talk about a self-fulfilling prophesy!), yet the facts remain the same as when we first started looking into the matter, and the discussion was not new then!

Manufacturers are absolutely unambiguous about how karabiners are designed to be used and what constitutes safe and correct use, unless otherwise specified, this will be loading along the major axis, avoiding torsional or sideways loading over the spine or pressure against the locking mechanism due to contact with structure.

As you can see from the images above from Petzl’s Carabiner Basics on correct use of connectors, the doc warns very specifically about jamming karabiners against structure, three-way loading or cross loading the frame. DMM make similar statements in their user manual, shown above on the right.

And here is what puzzles me: in face of such clear statements, how is is non the less possible for individuals to declare that they know better than the manufacturer (who designed, tested and builds the device) how to use it correctly? This just really has me stumped.

To be completely clear: Choked karabiners, unless otherwise specified by the manufacturer, are a misconfiguration.

Back in 2006 we did a series of tests on choked configurations on a range of karabiners. We performed a 15kN static pull for 3 minutes on three diameters, 82, 127 and 245mm, representing a small and a sizeable limb and a stem. As you can see from the images below, all karabiners struggled with the smallest diameter, there was some serious deformation and even a failure on the 82mm “limb”. Even the large 245mm diameter posed an issue for a number of the krabs we tested. This does not highlight a quality issue, but rather the fact that the connectors are not intended to be loaded in this fashion.

Phooey, 15 kN, you say, like really? That is never going to happen!

Well, if part of this discussion is indeed about rigging, these kind of loads are well within the range of what a connector will encounter, also in a climbing situation in case of dynamic fall or a rescue scenario, 15kN cannot be excluded – always bearing in mind that the Petzl Carabiner Basics document specifies that a 1kN (≈ 100kg) sleeve strength of the locking mechanism on the gate is all that the standard requires, this kind of load is obviously easily reached in the field should pressure be applied to the gate. The ANSI 359.12 standard demands 16kN gate strength when loaded from the outside for certain applications, this is an interesting development, yet will not be the solution for all situations as it makes for quite bulky locking mechanisms.

This discussion is by no means limited to tree care, it seems to be a feature wherever connectors are used to protect people from falls. I winced when I saw the way in which a karabiner is used in the images below in a fire fighter evacuation kit. O-kaaaay, I get it, the kit is used in life or death situations, the fire fighter needs to get out of the building in a serious hurry – but actually you would have though especially in a situation like that, the last thing you would want to be worrying about is failing connectors?!

As I said above, none of this is new, by any stretch of the imagination, yet some things obviously bear repeating and facts need pointing out. So, let’s go configure, work on our connector issues and make sure we are putting them to correct use!


Making decisions

In the blog post yesterday, I mentioned the importance of discussing how you intend to run a job in the team. I realised after the event, however, that this topic actually merits a bit more blog space, so here you go…

In the Rigging Research document there are a number of decision-making flow chart, aimed at making the process of choosing how to run a rigging operation consistent, efficient and safe. The one below came to my mind when I was writing about Friday’s storm damage job. The idea is that you work your way through a yes/ no flowchart in the build-up towards the lifting/ lowering operation. What this demonstrates a very clear and graphic fashion is how each point shall be a yes before proceeding – should one of them be a no, you work your way backwards until you have resolved whatever the conflict was.

The last point prior to the lift is especially pertinent: Communicate the plan of action efficiently to the other members of the team. […] Do any issues need to be re-addressed? In other words, is everybody in agreement about how we are planning to proceed. This is easy to say, but can present a formidable challenge in the field, depending upon the team constellation, the chemistry between the team members, their level of competence and the level of pressure we are operating under.

The last point of the flowchart is not certainly not being addressed in a situation where the climber assumes sole responsibility for all decisions. This kind of mentality exposes operators to pilot error, where the pilot/ climber sits at the apex of a narrow-based pyramid and any bad call on his or her part will potentially lead to catastrophic failure. On the other end of the spectrum is over-discussing of how best to run a job. In such an instance, proceedings can get totally bogged down by endless discussions about how to run an operation in the most safe and efficient manner. Take a team of four, you will have five different options beging thrown out there (five because one guy cannot make up his mind), obviously, this is not conducive to getting the job done. In all likelihood, a number of the proposed plans have merit, yet ultimately it is about deciding on one of them, and then getting stuck in!

Worst case is that everybody ends up grumpy and feeling unappreciated und unheard, resentfully going along with the option that was put forwards most forcefully or by the person with the most clout on site. I do not believe this is the right way to go about things – I am not implying that these are easy mechanisms to address; they take time, effort and trust in the other members of the team to resolve, yet it is feasible!

During the site briefing in the morning, by all means, let us discuss options… to a point. In my experience, an over-engineered solution for the sake of over-engineering is hollow. When you can chose a simple route, why not do so? After all, simple solutions are less prone to human error. On the other hand, some problems we are confronted with are complex, so naturally these demand complex solutions. This is probably the first thing which needs to be differentiated, what are we actually dealing with here, what is an appropriate solution?

Once the job is underway, in my opinion it is important to differentiate between issues which are safety-relevant and those which are not. So what if the climber decides to do something differently from how I would have chosen to? It takes a bit longer? Not really a major headache, so long as it is safe and gets the job done. However, if I see a basic flaw in a plan, something which has been overlooked or mis-assessed, I will communicate it to the climber. From a climber’s perspective, I know it can be really disruptive being bombarded from the ground with well-intended advice, this is not helpful and I will tend to blank it. The aim here is to have an understanding amongst team members that necessary aspects shall be communicated – and heard, bearing in mind to stick to the relevant stuff.

Then there is the debrief: During this session, let’s discuss why we ran the job the way we did. Who made which decisions when and why, what were the alternatives and how might they might have panned out.

By creating different platforms for discussion and communication, we are enabling team members to feed in their opinions and views. It makes sense to aim for a broad-based decision making pyramid, that it is not always the same person calling the shots, in a sense you are tapping into the full potential of the team by enabling communication and an exchange of ideas. The job site may well sometimes not be the right – or the only– place to have these discussions.

If every person in the team considers when and how to communicate their ideas or concerns, this reflection may well lead to an improved over-all result and better cohesion amongst team members.

Blow me over

On Thursday the low pressure weather system Dieter dumped quite a strong winter storm on us, which in combination with snow on trees caused a number of failures. Consequently Friday turned out a bit busier than I had anticipated, clearing storm damage.

One call out was interesting, part of a fir tree had broken out at the base due to included bark and was leaning on a three storey building. I only had photos to go on beforehand, so we loaded up plenty of gear to cater for a range of eventualities.

The part of the tree which had failed turned out to be reasonably sizeable and the inclination in which it was learning against the building was quite flat. Luckily the remaining part of the tree was sound at the base and high enough to place rigging gear – whilst still retaining an efficient angle to winch the piece off the roof. I placed a large Impact Block at the high anchor point, attaching an arborWINCH line though the hollow spindle, then down to the failed failed part of the tree, to which I attached a small Impact block, making sure the angle between the line and the axis of the stem was more or less 90°, to ensure maximal efficiency when winching. From there back up to the high anchor and down to a GRCS.

Next, before moving anything we secured the base with 16mm Sirius rigging line, rigged a floating anchor on which we had a Port-a-Wrap to blocks of concrete on the roof, from this we rigged a control line down to the tree on the building and in the other direction we installed a further rigging line, with a mechanical advantage system rigged to it.

Then we tensioned up all the lines, lifted the tree off the roof, used the control line and the MA system to move the tree to one side and lower it.

Not rocket science, admittedly, but none the less something you could come unstuck on. A couple of observations here: I love working with arborWINCH in non-dynamic rigging situations: This 12mm rigging line with a braided Dyneema SK78 core is super-lightweight yet strong and adds an extra level of control to a job like this. Using conventional Polyester rigging lines, you would spend more time winching to tension the line, the whole rig is more spongy and less responsive. Using arborWINCH, once you have taken up tension and the knots are cinched up tight and bedded down, you have a very high degree of control when lifting and lowering.

Where possible in a rig like this it can be a good idea to do away with knots, to secure the butt of the stem, for instance, we simply took wraps with the rigging line around the base of the remaining fir before ending the wraps with a clove hitch. In case the butt did kick out, this would dissipate the energy in a much more rope-friendly fashion, compared to a knot.

Finally, storm damage is notoriously fraught with risk. Ensuring the highest degree of control possible makes a lot of sense and allows you to take a step backwards if things do not move forwards as planned. In this case the two lines either side of the stem allowed controlled lateral movement, the arborWINCH controlled the up and down movement.

Add to this the fact of having enough competent people on site, taking the time to talk the plan through, designating roles, defining danger zones, considering what might go wrong and not rushing it, then indeed, it is not rocket science. On the other hand, if you did cut corners and tried to simply bosh it out, things could quite easily get… dynamic and dramatic – not my idea of an ideal end to a Friday…

Thanks to Flurina and Vito for the photos.

Clickety click

Isn’t it funny how when you go for a coffee break with a couple of tree guys, there will be that typical thunk, click, thunk, click of that one person who didn’t reckon it worthwhile removing their foot ascender.

In fact, between Christmas and New Year my friend Knut came to visit… we sat around a bit, chatting and drinking tea, then because it was a nice day outside, we decided to go down to the local alternative pub. Walking through town, guess what? Yep, thunk, click, thunk, click. Which was really quite funny, as there was definitively no tree work on the horizon, but I suppose it is one of those failed to prepare, prepared to fail situations: Knut would most certainly have been laughing at me if, for some reason, we had needed to quickly shimmy up a line to escape from a boiling pit of lava filled with orcs, for instance (yes, funny that, orcs in boiling lava seem to be cropping up rather regularly, not quite sure what that is about).

Ultimately, I was wondering whether this could lead to a next evolutionary step in the Homo sapiens genealogy? I am thinking Homo sapiens pantiniensis