what's the first mistake made in this rigging failure

[the.schultz.effect]

first mistake: not building a rigging system that can handle the worst case scenario (a no run scenario, whether on purpose or accident) aka not doing the math!

when designing systems, rigging or climbing, especially negative rigging, they should be able to handle the maximum force that could possibly be generate by the piece! it should never hinge on the groundie being able to let it run. that's a poor rigging system.

it says the MBS of the rope is 9,390kg (20,700lbs), as soon as you add a running bowline you've reduced that by at least 40%, (something people always seem to forget ). 9,390kg - 40% = 5,634kg (12,420lbs) is what you're left with. you can very easily generate 10x's the weight of a piece when negative rigging, even more if you increase the fall distance like they did here, having the sling like 3ft below the notch! so basically a 563kg (1,242lbs) piece could break that rope. a quick look at a log weight chart and conservative guess on the dimensions of that lump will tell you it could easily weigh that much or more.

 

[the.schultz.effect]

That piece seemed small to me.... guessing he had to keep it small to clear the ground.... I rig pieces that heavy on 1/2" true blue all the time..

the MBS for 1/2" True Blue is 7,300lbs, add a rope strength reducing running bowline (-40%), and you're down to 4,380lbs, divide by 10 for a WLL of 438lbs (or 5, which is a mistake in my opinion if you're negative rigging, giving you 876lbs WLL), either way you must have the best rope smoking ground man in town!

 

[evo]

first mistake: not building a rigging system that can handle the worst case scenario (a no run scenario, whether on purpose or accident) aka not doing the math!

when designing systems, rigging or climbing, especially negative rigging, they should be able to handle the maximum force that could possibly be generate by the piece! it should never hinge on the groundie being able to let it run. that's a poor rigging system.

it says the MBS of the rope is 9,390kg (20,700lbs), as soon as you add a running bowline you've reduced that by at least 40%, (something people always seem to forget ). 9,390kg - 40% = 5,634kg (12,420lbs) is what you're left with. you can very easily generate 10x's the weight of a piece when negative rigging, even more if you increase the fall distance like they did here, having the sling like 3ft below the notch! so basically a 563kg (1,242lbs) piece could break that rope. a quick look at a log weight chart and conservative guess on the dimensions of that lump will tell you it could easily weigh that much or more.

math hurts

 

[the.schultz.effect]

math hurts

so do mistakes

 

[evo]

so do mistakes

more so meaning the repercussions of not doing math = hurt.
The Truth is, this is the dividing line of good tree work and great tree work. You can push the limits of a half inch rope, knowing how to smoke it all the way to the ground. We never know the true numbers day in and day out. We just guess, and wing it. You can do this well, or very very poorly, this is the skill which divides.

 

[Stephen Moore]

It’s simple, if you don’t know, don’t do. Never push the limits of your gear. Another guy on a separate thread here is doing advanced math to represent the theoretical efficiency of a rope system to make things more safe. Sorry, but slide rules and complex math had no place in a tree. Recognize the limits of your gear and stay well below that.

 

[the.schultz.effect]

It’s simple, if you don’t know, don’t do. Never push the limits of your gear. Another guy on a separate thread here is doing advanced math to represent the theoretical efficiency of a rope system to make things more safe. Sorry, but slide rules and complex math had no place in a tree. Recognize the limits of your gear and stay well below that.

true but unfortunately the main problem i see is people not knowing that they don't know the reality of the numbers just doesn't even occur to them.