I was thinking of this post yesterday, one of my favorites from back in November 2014, so I decided to repost it, seems a bit of a pity for these things to get buried in the damp, dusty depths of the blog archives – it is the story of how different professions manage slack, and the story goes like this…
Managing slack is a reoccurring theme when discussing work positioning in trees.
We use semi-static lines with low elongation, work positioning and sit harnesses unsuitable to arrest a fall and use ventral attachment points that in case of a fall could cause substantial, whiplash-type damage.
But despair ye not, for help is at hand in form of industry best practice guidelines. A key element in all BPGs is the concept of keeping slack to a minimum. Yet still, despite all this, people struggle with this, from a conceptual and from a technical point of view.
But believe me, other industries also need to manage their slack.
Consider laying underwater cables, such as the one allowing maybe allowing you to read this, which might be an intercontinental fibre optic cable, such as Hibernia Atlantic, Hawaiki Cable, Apollo or one of the myriad of other submarine cables spanning the oceans. In his fascinating essay, Mother Earth Mother Board, published in Wired a couple of years ago, Neil Stephenson really submerges himself in the topic of how, physically, data gets piped around the world – it is well worth the read.
The part that I found fascinating was about how, when cables are being laid on the sea bed, slack is managed. The challenge being that if you lay it too tight, it will end up suspended and be prone to snapping or damage. If you lay down too much slack it ends up in a snarl on the seabed which subsequently can get snagged by trawlers – and then there is also the question of expense: the FLAG (Fibre-Optic Link Around the Globe) cable, for example, costs between $16,000 to $28,000 per kilometer, depending on the amount of armoring.
The amount of slack depends on the topography of the seabed.
The average amount of slack aimed for is about 1%. So based on that, the 2500-kilometer route between Songkhla in southern Thailand and Tong Fuk Beach on Lan Tao Island would require 25km of slack. But the big question is where to put it. If the seabed is dead flat, minimal slack may be required. On the other hand, if it is rugged terrain the cable is being laid over, up to 5% slack may be necessary. For this reason the boats laying down the cables are constantly making highly accurate maps of the seabed with the aid of sidescan sonar and satellite geo-positioning data as they are laying down the cable and are constantly juggling the boat’s speed, position and the tension on the line, whilst at the same time modeling the drift that underwater currents may be causing in order for the cable to touch down on the seabed with the exactly the correct amount of tension for the terrain – and in the right place to boot.
Depending on the depth of the ocean, touchdown may occur several kilometers behind the boat. Phew!
Slack management during cable laying operations at sea
Admittedly, specialized software is used to assist in these operations, but still, I found the number of factors involved and the level of complexity quite mind-blowing.
So, getting back on topic… managing slack whilst work positioning in trees is hard?
Really? You reckon?
Compared to some of the formidable challenges the folk laying cables across the oceans face, our difficulties pale somewhat. I believe that we have all it takes: we have the understanding of what the issues are – and also the tools and techniques to mitigate the risks that climbing with too much slack brings with it.
Finally, it is up to the individual to be diligent and to consistently apply best practice at all times when it comes to managing and preventing slack. This is not rocket science and I am confident that it is something we can manage.