Close Call: Rigging Point Failure

[TreeMuggs]

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A couple weeks ago I had a very close call rigging out the last top on an ugly Silver Maple at the cemetery. My rigging point failed and a 25 ft chunk of log went freefalling towards the earth. Nobody was hurt – thank God. One stone got hit but it didn’t do any damage. As fate would have it, my apprentice wasn’t there that day to see and learn from what happened. After much thought and analysis, I believe it ultimately comes down to complacency and normalcy bias: the top was just too big, and I knew it.

 

“Normalcy bias causes people to underestimate both the possibility of a disaster and its possible effects, because it causes people to have a bias to believe that things will always function the way things normally function. This may result in situations where people fail to adequately prepare.” That pretty much sums it up. I knew the top was bigger than what I would normally take, but that’s all I could reach with the lift.

 

Do you know how many times I have done something similar when I'm in a lift? I end up cutting something bigger than what I am totally comfortable with, and, at least up until this incident, it has always worked out fine. It makes me question my own judgement in a way, like, if I was uncomfortable with it but it turned out fine, is it just that I have drawn the line in my head between what's safe and unsafe, in the wrong spot? You know, like can I actually take stuff far larger than what I first thought? I mean, you start thinking about tensile strength with the gear we use. When I was in school, we always talked about designing rigging systems with the rope as the weakest link. But I think, in reality, we have designed our gear to make the tree as the weakest link, in the majority of cases.

 

For anyone wanting more detail, I have a more in-depth article about this incident, available here:

 

https://www.educatedclimber.com/clos...point-failure/

 

I am embarrassed to admit that, right when this happened, I was thinking, ****, I don't want to share this with anyone. This makes me look like an idiot. But later that night, I had made a 180, and I thought, first, much of the time, I am an idiot, and second, this is exactly what I need to share with the world. This is the kind of stuff that can help someone. So, like I said in the video, I'm actually glad that it happened. It was a real eye-opener. If this helps someone, sometime, to second guess a decision, or think critically about a setup, then I am so glad that this happened. Go small AND Go home.

 

So, I wanted to hear from other professionals. What would you have done differently, or is it simply a case of "right to refuse"? Bottom line, I shouldn't have taken that top where I did. I knew it was too big right from the get-go, when I went up initially to set my blocks. I ignored my gut and made a huge mistake. But thankfully, nobody got hurt and I came away with a greater awareness of my own complacency as well as an excellent teaching video. So, any thoughts?

Edited May 25, 2017 by TreeMuggs

[Marc]

Thanks for sharing, the piece didn't look that big in the video, but it rarely does it justice. Looks like the as the pulley loaded up and dropped the force changed ripping your secondary out as this became the primary, perhaps if you just rigged of the main stem you who would of unfavourably loaded the timber?

I have done similar without being in a MEWP I never thought the anchor point would come at me so felt confident pushing the limits when it failed the whole rigging point came at me and actually cut through to the core of my climbing line!

[slack ma girdle]

Every day is a school day.

Every one has suffered from a 'f***k it cut'

[Mark Bolam]

Ballsy post.

I've long reckoned that the weakest point in the system is sometimes the crappy trees we work on.

I ripped an 8" dia limb off an oak yesterday pulling an ash hanger out of it with a throwline.

Unseen defect.

 

 

Sent from my iPhone using Arbtalk

[MattyF]

Hi mugs , I think another reason it failed and bear in mind your main rigging point didn't is because you had the second pulley in so effectively doubling the load on that anchor point , I did some thing similar and caught it on film my reasoning for doing it was I just needed to clear one side of the tree to fell it and there was no decent rigging point high enough on that side of the tree so I set up a double kind of rigging point on smaller stuff with the idea it would share the load and would be high enough to get the back top out with the intention of moving it down to a more suitable diameter for the timber which stupidly I didn't as I had another tree to get down and it was Saturday so it was a rushed job...like you I'm assuming at the time with the idea in my head it would share the load but I think what it actually does it double it like with an SRT base anchor and it ripped the lot out .. tbh I was kind of expecting it hence the one handed saw use so I could grab my hitch quick and bail out !

I've been too embarrassed to post in the forum before this mess but like you said if others can learn by it ..

[Marc]

Thanks for sharing Matt, I think we have all been there or close to it, but the positioning and thought that goes into it hopefully mitigates any further risk of injury.

 

I see a lot of redirecting like this it's usually only a significant problem when you rigging points are a similar level like you said creating a pulley effect, was there much difference in height of your 2 pulleys as it's hard to see in the video.

 

Like I said the only time I have ripped my anchor point out it was the other side of the tree, you get lulled into a false sense of security steadily getting greedier, I can say it makes no odds if you create the force to make it fail it's coming at you! Every force has an equal and opposite reaction or something like that.

 

I should add, I've also snapped rigging lines and slings and various other bits, as well as barber chairing whilst on spike which was jolly unpleasant.

[Clicky]

Wait, so having two pulleys on two different stems at the same height doesn't spread the weight?

[MattyF]

The pulley to the lowering device has to be higher! I think in the case of the OPs vid it was not so it acts to put more force on that stem.. in my case I had one pulley but had ran the rigging strop through two crotches and then did a lower base tie on thicker material so it acts like an SRT base anchor which doubles the force in the top anchor..

in hindsight now I try and fishing pole the rigging strop with half hitches to a more substantial point and not directly to it... another way to work bigger trees and tops is have two rigging lines too on separate stems and tip tie one of them so you can drift tops and not put all the force on one stem /line. A lowering device at the base basically doubles the load at the top rigging point so on dodge trees a safe block would be another good bet ??

[Clicky]

I always thought it's was more redirects = more strength, I've been living a lie!! When I did my cs41 one was really looking forward to learning about forces in conjunction with redirects and all that jazz, then it literally covered none of it apart from the doubling effect. Was a bit annoyed really.

[MattyF]

Clicky I'm no expert on forces and angles ! That's just my theory so I'll wait for some one to tell me I'm wrong which I probably am .. I recon though that if that top had been ran off a higher block on the spar that broke it would of been different also biting more gently on a running rope decreases the shock loading.. I'm very wary about who I have on my ropes when negative rigging.