Fifteen years ago, ascent was something you simply did, you either body-thrusted or footlocked, not something that garnered much air time in terms of discussion or controversy.
Today we inhabit a very different world (I realise I have written about this before, bear with me), I cannot help but be puzzled by how tree care has such a high degree of diversity when it comes to ascent configurations – when other industries limit themselves to a handful of standardised techniques. This plethora of tools, combinations and techniques is something that intrigues me, the reasons for which certainly merit further discussion.
One reason would seem to me to be that as an industry we have so far not managed to find a consensus on what boxes a well designed and configured ascent system shall tick. Oh, plenty of opinion and pet techniques out there, but not really anything more in-depth than that. So, are we maybe not asking the right questions? Or getting lost in granular details? Or succumbing the fascination of the newest, shiniest and bestest tool out there?
Let me give you an example:
How exactly do we configure our access lines? A single line over a limb, choked with an Alpine Butterly knot? A single line with a base anchor? Double isolated lines? Lowerable or not? Or no access line at all, because the whole crew climbs SRT?
My take on this is that dedicated access line makes sense. It facilitates access and egress into and out of the canopy and is available in case of an emergency. I also believe that having the working part of the line configured with two isolated lines is good practice. There are a number of reasons for this…
When using a EN12841 (Personal fall protection equipment — Rope access systems — Rope adjustment devices) Type B ascender, such as Petzl’s Ascension or the like, it pays to consider the dynamic request the standard makes of the component:
So, in other words, as far as the standard is concerned, after the line has been exposed to a 100cm fall of a 100kg mass it is still a pass if the mantle is sheared, on the condition that the slippage is not greater than 200cm. The rationale behind the standard allowing for severing of the mantle is of course simply a means to dissipate peak force. The damage of one rope in a industrial rope access context is less problematic, as the assumption is that the climber will be running a permanent back-up line with a back-up device running on it, allowing a transfer off the damaged line and a descent on the back-up line.
Is a fall generating this kind of force likely? In case of anchor point slippage, adjustment or failure, yes.
And remember, this is always assuming good compatibility between the ascender and the line. In case of a misconfiguration, such as an ascender which should be used in conjunction with an EN1891 semi-static line being used on a fully-static HMPE/ Dyneema line, things can rapidly become dramatic. Not only will the HMPE generate higher peak forces due to its low elongation, but it is also very slippery, which makes increased slippage in case of a severed mantle more likely – in a worst case scenario leading to ground contact.
Switch to arborist ascent techniques… one single line? In case of damage to the mantle as consequence of anchor point slippage, adjustment or failure, you might conceivably find yourself suspended off a heavily compromised line. Far from ideal.
You do not used toothed ascenders, you say, but some form of ascender/ descender? That makes a lot of sense, as it allows for fast egress, but not necessarily a reason to drop the second line: in case of incapacitation of the climber, a second isolated line makes for a very easy rescue, the rescuer can simply scoot up the second line and lower the themselves and the incapacitated climber on both lines or transfer the incapacitated climber onto their system and descend on one line – always assuming that the anchor point is not damaged and adequately dimensioned to bear the weight of two climbers.
Anyway, plenty to discuss here: Let’s dig for the right questions before we start acting upon haphazard answers to imprecise or narrowly focused questions.