Close Call: Rigging Point Failure

Muggs

Muggs

Been here much more than a while
Location
Canuckistan
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, shit, 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?
 
The top very well may have been too big, but I suspect your setup is at least partly to blame. The way the second block was set was sideloading the two leads. Loading just the main one in compression and i think you could've gotten away with it.
Glad no one got hurt and good on you for bringing this up for discussion.
 
The analysis starts with the day you looked that the job. At that point you seemed to have recognized the tree was hazardous and thus not one to be climbed. Why? Was it your weight in the tree or that it would be putting you in a dangerous situation due to the need to rig this tree off of itself? You had access to a 60' spider lift. While it took you out of the tree how did you spec the height? Was the tree measured to determine what the lift height would need to be? Knowing the lift height available did you measure it against the tree to see where it would put you? At that point you would have been able to see that it was going to come up short against your standard of practice. Then it would've been much easier to revise your plan and find a taller lift or look to a different solution.

In my view, it put you in the situation that, you were already committed to the work and too much was invested at that point for you to back out. Was that the case? What were you telling yourself, in detail, at the point where you realized the lift was leaving you in a predicament? What did you tell yourself to allay your concerns and go ahead? Knowing this will tell you a lot about what you need to think of and adjust for in the future.

From a rigging standpoint, it looked like you hadn't thought through the point loads. Sure it was in compression but how much was on that point? From the video it looked like the rigging line was nearly at right angle coming off the failed spar. Moving that block lower would have reduced the load on it but then you'd need to account for the increased angle at the final rigging point.

As for the weakest link in a rigging system the rope can still be but only within the known parameters. The tree still stands out for being the wildcard factor. It's the configuration of that system that is most important and needs to be designed to reduced the point loads as much as possible.
 
Bam ..hit it hard on them 90 ish degree angles. This is where span rigs shine within a line moving through anchor point placed on piece to be removed. And widened up angles approached as treehumper so well explained. while utilize something that will create more friction like a few rings or the good ol natural rigging union point instead of reduce friction and increase force such as a smooth pinto.. they're great for speedline and lifting ..I prefer natural and rigging rings for just topping down.. was there any signs of decay on the lead that broke out.. thanks for sharing. I think the take it small and keep it all theory has substance.
 
Rob, we have access to a 60ft spiderlift through a friend, so that's the size of lift that we were using. No, it was not ideal for this particular tree by any means, but it was still safer than climbing. This tree was sketchbag. This is one of the biggest cemeteries in the city, and they let stuff go way, way too long. But at the same time, they are our biggest client, so I couldn't just pass on the work. Yes, at the point that I had to make that final cut, I was way too invested to just pack it in and tell the guys that we would have to figure something else out.

As far as the rigging is concerned, as a concept, I have always split the load between at least two spars. This concept however makes far more sense when the spars in question are at roughly 45 degree angles, so that they load in compression. The leader that broke in this case was basically vertical, which meant that it was being side-loaded. It snapped at a big squirrel's nest 25 feet below where I was cutting. There were 3 little gaffers all curled up inside. I should have been much more critical of that spar and done a much more thorough inspection before rigging off of it, but it had been supporting a live crown, so I figured it would be ok.

Yes, in hindsight, NOT splitting the load would actually have been much safer. Like most accidents, it was not just down to one single error, there were a whole bunch of things that I did wrong that compounded to produce that result. What I didn't explain very well at all in the video is that, in the moment, the thing that I was actually the most concerned about was that big hanger, which completely blinded me to the actual danger staring me in the face...
 
Thanks a bunch for sharing this. It's important (but very rare) if something like this is captured on video it is shared. Because in most cases the only way anyone is going to see this happen is if they do it, and it might be the last thing they see.
You are not an idiot, or even close. You were using accepted theory/practice and it failed (trees are dynamic structures there are no two alike). Yea maybe a better assessment, maybe a a different roping plan or a pole saw. All that matters is that we all can learn from this, and most importantly you and your crew were unharmed and allowed to learn from it.
Be safe, and do the best you can. That's all that can be expected!
 
Muggs
I say this yesterday on your channel. The first thing I thought that it takes a big man to share a mistake like this with the world. After viewing it again you pulley is still there so I don't see where the rigging point failed. It looked like the rope grabbed a limb that was lower down. Mistakes happen and thank you for sharing this. Lord know I have made my share of mistakes in my life. Nobody was hurt that is the big point!!!
 
You the man Muggs. Much respect for posting this. I have run bucket trucks and lifts for a little bit, enough to say that I'm pretty sure most people have done work in a lift have had that EXACT moment with themselves once they reach their furthest reach.
Some kinda order in their thought process (at least mine anyway) where its, "that's a big top", "it that too big", "this is kinda sketch", and "well, I'm here and it's gotten come down one way or another". People reading, tell me that's not relatable!

I needed to see that video. Imagine being in the basket and that piece that broke smashing the operater in the dome piece. No video there, just an Awakenings thread.
It takes maturity to reach that point of reach on your lift, realize that what's left is a bad scene, and make a smart plan. You posting this video helps me grow a little cause I haven't had that moment of failure yet, but the closer any of us get without thinking about the dangers of what we did, the closer we are to reliving that scenario.
Thanks for sharing that Muggs
 
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Thanks for sharing Muggs, I learned something. Also, you're not an idiot. Shit happens sometimes and what matters is no one got hurt. Aside from it falling on someone, my first thought was "what if that tree had hit the lift."


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Watching this with the volume off, so I may have missed your commenatary on this point: The squirrel cavity sapwood is extremely thin on the tension side, with respect to the rigging forces. The sapwood is thin but fine on the compression side. Those rigging forces were mainly sideways, so sapwood tension was needed there. Vertical strength - a tree's strongest asset - didn't come into play with this rigging system.. Easy to say in hindsight.

One solution is to rig forces along the vertical axes of trees, in a v- shape, right? One more pulley/ring down at the crotch and maybe you're money. I haven't seen anybody rig in a v configuration, but I've thought about doing it for a while... This video makes me want to try it out next time I feel top hangry, lol.

Another solution is to spot the squirrel hole. That was something I definitely might miss, yet very important information.

Really glad nothing happened to y'all.
 
Colb, I have been thinking about this V-setup as well. It would be a great way to load both stems in compression as well as splitting the load, and there would be way more rope in the system to help absorb shock load. I think it would be a great option in sketchy circumstances. I'm going to try it. Obviously easier to set up in a lift, would be a pain if you were climbing, but still doable.
 
Muggs said:
Colb, I have been thinking about this V-setup as well. It would be a great way to load both stems in compression as well as splitting the load, and there would be way more rope in the system to help absorb shock load. I think it would be a great option in sketchy circumstances. I'm going to try it. Obviously easier to set up in a lift, would be a pain if you were climbing, but still doable.
Click to expand...

Let me know if/when you get to it and I will too. It might not be so bad to throw in a low crotch redirect on the way up. Or, it might bugger things up with multiple up-n-downs... I think that guys working with rings will take to it easier because the rings force the rigger to plan more, which is cool.

It's interesting how compression can have two meanings - compressing the wood grain in the vertical axis, or compressing two stems horizontally towards each other. Anyone want to sort me out? Are there better terms?
 
Much respect to you Muggs for posting this to begin with. The lift situation reminds me of the adage, "When the only tool you have is a hammer, everything looks like a nail". It's about fitting the job to the tool instead of the other way around.

All that you said created the box that limited you from finding alternatives. From rationalizing the lift as "better than climbing" to the client being the biggest. That they are the biggest behooves the company to come up with the best solution not just the one they have readily available. From renting a higher reach lift, to cranes, etc…

For me this reinforces the need for the crew lead or better yet the climber to be able to step away from a job if they feel that the current set up isn't the best to get the job done safely and with known outcomes. Everything that came after that initial decision became much more acutely sensitive and left no safety factors.

You lived to tell the tale and the client suffered no damages. This is an ideal teachable moment, just what is the lesson to be learned?
 
Muggs, I'm not following the entire V-rig thing mentioned. Two high stretch ropes controlled by the one groundman (one rope hitched/ attached to the two rigging ropes' standing ends) would give redundancy as compared to double whip tackle-ing it, and have better loading angle initially.



A clinometer app and/ or Tree Height measuring app, and tape measure is a good tool for the bid to determine height.

The "stick-trick" and measuring tape will help, but be less accurate, and not able to account for slope.
 
southsoundtree said:
Muggs, I'm not following the entire V-rig thing mentioned. Two high stretch ropes controlled by the one groundman (one rope hitched/ attached to the two rigging ropes' standing ends) would give redundancy as compared to double whip tackle-ing it, and have better loading angle initially.
Click to expand...
I think that it subjective to how the rigging is placed in either scenario. Hard to argue the redundancy of two lines , but if it's placed in a position that sets it up for loading a stem in a bad angle . Similar results could happen. I bet in Muggs scenario if the one failed stem wasn't decayed it would've held. P.s. I love the clino meter app too. Good stuff.
 
Treetopflyer said:
I think that it subjective to how the rigging is placed in either scenario. Hard to argue the redundancy of two lines , but if it's placed in a position that sets it up for loading a stem in a bad angle . Similar results could happen.
Click to expand...
Understanding the purpose behind each aspect of setting up rigging is vital. Setting up rigging isn't subjective is quantitative. That's to say, where each piece goes needs to be defined by the angles established and the point loads created. The less subjectiveness we apply to this the better our analysis is going to be. Two lines set in the same place only divide the load between the ropes, thus the purpose is driven by limitations on the SWLs. Unless they are attached to different points do they change the specific point loading.

The stem not failing if it weren't decayed is moot. It was and this is something that wasn't accounted for over the range of the changing load dynamics as the tree was dismantled.

We need to do our rigging set up with the whole process in mind, working through it from start to finish to best match the capability with the demands.
 
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