Alright gang, I'm new to hunting and saddles, so let me know if I'm off base in my stuff here. I'm trying to follow a similar setup to what G2 Outdoors covers in the video on one stick climbing, and figure out how to do it safely. There's a bunch of Math in the excel sheet linked if you wanna check my numbers.
First off: An ounce of prevention is a pound of cure. Preventing the fall in the first place is the way to go. That said, I screw things up, and don't want to rely on prevention alone.
Saddle setups generally function on static ropes. From what I've seen on treebuzz, arborists climb with static ropes as well. I can buy into the static ropes for work positioning, since I really don't want a bouncy rope messing up my shot. However, arborists have a 6x injury rate from the national average, so I want to make sure my setup is safe before I go up a tree.
The problem: falling on static ropes
Falling on static ropes really sucks. Shock loading is a problem, and static ropes don't have much stretch. That means a fall is stopped over a few inches instead of feet. I've attached an Excel spreadsheet that calculates falling loads on a few different ropes using manufacturer's specs. I've been looking at a 6ft fall with 5 ft of rope in the system (including the hitch around the tree). I think that represents the absolute worst-case fall you could experience (6ft fall with the tether at your feet). Forces can reach over 18kN depending on the rope - which is a lot. OSHA says fall arrest should be a max of 900lbf (~4,000kN) for a belt-style arrest device (similar to a saddle) back when they were allowed. Even with a 2ft fall on these ropes, the math shows you'd exceed that limit. A 5ft fall on a couple of these ropes shows you'd be over 14kN, which would probably give you a spinal injury. Obviously these numbers are worst-case, and don't account for trees bending, and people being squishy, but I think it all demonstrates the point.
This is all just the ropes. The one-sticking setup uses a belay.
The belay I'm using (Petzl GriGri) seems to slip around 9kN but the other belay tested in that video actually destroys its rope after pulling hard enough. I think the slip could be a good thing assuming it keeps slowing you down. IDK if that's the case though.
Falling on static things sucks, and you shouldn't do it. However, I'm dumb, and I mess things up. I don't want to rely on prevention alone, because someday something's gonna go wrong. But how do you fix the shock loading? Add stretch into the setup, right?
If you use an autoblock (which slips before it breaks) hitch instead of a prussik (which will break before it slips) on the bridge, would that act as a "semi-dynamic" setup? In my head I imagine the autoblock slipping when overloaded (which is how it behaves), but still exerting that slowing force as as it moves toward the stopper knot in the bridge (IDK if that part is true). If that's the case, then it spreads the arresting load over the length of the bridge until it stops, but that's a big if.
Questions
Do autoblock knots actually behave this way?
Even if they do, is a stopper below an autoblock even safe?
How do you folks make sure you don't get spinal injuries falling from a tree?
Is this kind of fall actually a concern that you guys plan for, and how do you mitigate it?
First off: An ounce of prevention is a pound of cure. Preventing the fall in the first place is the way to go. That said, I screw things up, and don't want to rely on prevention alone.
Saddle setups generally function on static ropes. From what I've seen on treebuzz, arborists climb with static ropes as well. I can buy into the static ropes for work positioning, since I really don't want a bouncy rope messing up my shot. However, arborists have a 6x injury rate from the national average, so I want to make sure my setup is safe before I go up a tree.
The problem: falling on static ropes
Falling on static ropes really sucks. Shock loading is a problem, and static ropes don't have much stretch. That means a fall is stopped over a few inches instead of feet. I've attached an Excel spreadsheet that calculates falling loads on a few different ropes using manufacturer's specs. I've been looking at a 6ft fall with 5 ft of rope in the system (including the hitch around the tree). I think that represents the absolute worst-case fall you could experience (6ft fall with the tether at your feet). Forces can reach over 18kN depending on the rope - which is a lot. OSHA says fall arrest should be a max of 900lbf (~4,000kN) for a belt-style arrest device (similar to a saddle) back when they were allowed. Even with a 2ft fall on these ropes, the math shows you'd exceed that limit. A 5ft fall on a couple of these ropes shows you'd be over 14kN, which would probably give you a spinal injury. Obviously these numbers are worst-case, and don't account for trees bending, and people being squishy, but I think it all demonstrates the point.
This is all just the ropes. The one-sticking setup uses a belay.
The belay I'm using (Petzl GriGri) seems to slip around 9kN but the other belay tested in that video actually destroys its rope after pulling hard enough. I think the slip could be a good thing assuming it keeps slowing you down. IDK if that's the case though.
Falling on static things sucks, and you shouldn't do it. However, I'm dumb, and I mess things up. I don't want to rely on prevention alone, because someday something's gonna go wrong. But how do you fix the shock loading? Add stretch into the setup, right?
If you use an autoblock (which slips before it breaks) hitch instead of a prussik (which will break before it slips) on the bridge, would that act as a "semi-dynamic" setup? In my head I imagine the autoblock slipping when overloaded (which is how it behaves), but still exerting that slowing force as as it moves toward the stopper knot in the bridge (IDK if that part is true). If that's the case, then it spreads the arresting load over the length of the bridge until it stops, but that's a big if.
Questions
Do autoblock knots actually behave this way?
Even if they do, is a stopper below an autoblock even safe?
How do you folks make sure you don't get spinal injuries falling from a tree?
Is this kind of fall actually a concern that you guys plan for, and how do you mitigate it?
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