question about shock loading a rope and blocking

Back on Polydyne and stretchy rope, I made the mistake of tying off a tree on a house with a 9/16" stable braid and that left me with 200' of Polydyne to do the lift. We setup a double whip tackle and proceeded to yard it in with a 5:1, almost all 200' were in the system because of the DWT and the distance to our anchor tree. We pulled that 5:1 all the way down twice and then half again before the tree got light enough to cut. Pulling the stretch out of that rope was not easy work, it was exasperating.

When I rig wood down low I don't use it precisely because it can stretch enough to cause a strike.

I gotta say I really like Polydyne though, especially combined with a stainless porty... it's a smooth dynamic setup that even a climber can use well. We dropped a bunch of big chunks on it the other day and I remember thinking I should've gotten more of a ride but Polydyne absorbs a lot of the energy that Stable Braid (or a polyester 3-strand) will transmit to the anchor. It's a nice advancement.
 
i deff find myself in situations where i dont want my rope to be a rubber band. low stretch doubles all the way. i dont take big pieces either. i usually keep them 3-5 feet long. and use 1/2" for 16" pieces and for 20" i use 5/8's anything bigger then 20" diameter we use the 3/4ths line. that rope collects alot of dust. we mostly use 1/2" ropes.
 
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That video says it all!!!! Dynamic rigging lines are essential to safety and productivity...



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It just occurred to me... do you guys think a rope will remain elastic after you pull on it with a skid steer a few times?
 
Chip,
I was specifically referring to the below post of yours, recommending samson's stable braid for negative blocking..
Here's what Samson says about that rope:

STABLE BRAID COATED Product Code: 806
This double braid is a low stretch, high strength-to-weight ratio, and torque-free construction. It is durable with excellent abrasion and UV resistance.

13,300 lb. average breaking strength with 1.1% stretch at 10% (1,330 lbs)

That said I do appreciate you pointing out that the Polydyne is a double braid. I've always thought of double braids such as your stable braid, as static. SO I look forward to trying out the polydyne. If it can handle the same wear and tear as Samson's true blue, I'd love to use it. The difference between stable braid's 1.1% stretch at 10% ABS, and true blue's 2.6% is huge.. Polydyne's 4% sounds like it would be that much better. Have to see it in use though.

So thank you. I finally learned something from you. Which I have some faint recollection of having done sometime ago, but can't think of what it was.

But don't expect to put a jab out like the following, then try calling some truce.
YOU WROTE:
"that is, with double braid rope and a friction device. If you don't use professional groundies it doesn't matter though because dynamic rigging has a lot more to do with the guy on the rope than the rope itself.

You still don't have a grip on shock loading Daniel, understandable... physics isn't for everybody... and I know how much trouble it is to set a block and that you can't be bothered with it because it's 'inefficient'.

I've had to explain principles and techniques of all kinds to you over and over again. And you make some lame comment like the above and then dis me in the next paragraph. DID YOU WATCH YALE"S VIDEO? Jamie was trying as politely as possible to point out that the stable braid you recommended is gonna get someone killed when the shock load caused by the low stretch in the line causes the tree to fail.

Does anyone know what kind of rope Donzelli was using when the side loading caused the tree to fail? I'd bet money that it was a low stretch double braid and that the man would be alive today if he had been using the more dynamic true blue.

Your comment about "because dynamic rigging has a lot more to do with the guy on the rope than the rope itself" shows once again that its you that doesn't have a clue about controlling shock loading. THE ROPE HAS EVERYTHING TO DO WITH IT!!! WATCH THE VIDEO!!! and the rope is something that the climber can control, while he has little or no actual control of the groundman's actions. And again I have to keep explaing this basic concept over and over..

And then still have to hear your garbage insinuation that I don't use blocks... Total BS.. just like Norm making some comment about me not being able to cable.

You show pictures of cat rescues and tight LZs, while I've put up over 40 videos showing advanced rigging, falling, climbing, crane work etc.. Maybe if you ever get a handle on poductivity and efficieny, you'll be able to save up for a video camera and show us what you can really do, other than talk crap!



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Like has already been said, It's really hard to specify something like that. Stay within WLL and you should do fine but it doesn't guarantee anything.
Shock can create peak loads waaaay beyond WLL. Shock is not your friend.

Keep your pieces under 4', don't drop'em too far, make sure your groundie can run rope and you'll be fine on those pines with 1/2" or 9/16" double braid.

I like 9/16" Stable Braid for negative blocking.

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We pulled that 5:1 all the way down twice and then half again before the tree got light enough to cut. Pulling the stretch out of that rope was not easy work, it was exasperating.



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Sorry Josh..
no can do... I AM actually just getting started..
To stay on subject, I really want to try out the ploydyne. I AM hoping that so much stretch doesn't have much down side.

Now back to Chip..

This is exactly what I AM talking about when it comes to effieciency being safer. You are taking a tree of a house, like an Egyptian, (except using a dynamic line), and end up by your own admission "exasperated"... While I put a redirect block on the base of the tree, tie the line to the skid steer or truck and with a quick wave of the hand watch the tree lift off the house. Leaving me far more energy at the end of that day and the next day to work safely in a stressful emergency situation, like storm clean up. When people get fatigued they make bad decisions, lose physical coordination etc.. Everyone pushes hard after a storm. Efficiency = Safety...

Same thing goes with climbing and rigging.. the more we get done with the least amount of energy, the safer we are.

FATIGUE is a SAFETY ISSUE.....
 
I agree--->

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i deff find myself in situations where i dont want my rope to be a rubber band. low stretch doubles all the way. i dont take big pieces either. i usually keep them 3-5 feet long. and use 1/2" for 16" pieces and for 20" i use 5/8's anything bigger then 20" diameter we use the 3/4ths line. that rope collects alot of dust. we mostly use 1/2" ropes.

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I don't agree...and don't need finger shaking lectures. Can your 'tude, dude.

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You might have taken the wrong lesson from that experience...The stretch in the line is so important to reduce shock loads that it far outweighs any benefits of the higher tensile static line in preventing the type of damage you describe. I think if you then had the knowledge and equipment you do now, you could have easily avoided the damage while using the same rope you were using then. See if you can find something else to blame/change besides the rope.

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In that situation, and lots of others, using low stretch ropes will keep the pieces where I want them...not boinging down some unknown and hard-to-calculate distance.

My style of rigging accounts for shock loads differently than yours Daniel. You seem to take large pieces and use more dynamic ropes to reduce the shock load on the rigging point. My preference is to take smaller pieces with ropes that have less stretch. There are other ways to reduce the loads on the rigging point besides using stretchy ropes.

I fully understand dynamic rigging and the effects of static rigging on rigging points. You solve the problem one way, I do it differently.
 
Tom Wtote:
"I fully understand dynamic rigging and the effects of static rigging on rigging points. You solve the problem one way, I do it differently. "

That's cool.. each to his own. I believe you, but just don't understand how a person can understand the principles and not want to use them to his advantage. Maybe we're all just products of our training. I certainly keep Big Jon on a pedestal and try to emulate his genius when rigging... On the other hand maybe its personality as well.. I like action, as youve all seen!
 
Like I said before, he does all the work for me anyway. I was NOT looking for a truce, just trying to be civil, clearly a stupid idea.

That said, Josh, I apologize.



Stable braid has been used for blocking a long time. No, it doesn't stretch much... hence professional ground workers. In the video the rope was snubbed off and it took the full impact. That doesn't happen often with professional crews because long before that video we knew the results would be bad. Stable braid is suited for use with pulleys and blocks. Blocks make running rope much more predictable. Stable Braid, a block and a skilled groundie will get the wood on the ground without undue risk. There is no reason whatever to go crying that someone will be killed blocking with Stable Braid because it's not elastic enough.

I don't know if you're a rock climber but dynamic rope and fall factor are well understood concepts that have been saving human bodies from shock loads for decades. This isn't revelation, it's old hat.

They had one of those testbeds at TCIA a couple of years ago. Do that same 220# test over and over with a a good groundie on the load line and most any rope will last all day. S/he can absorb most of the shock by simply slowing down the deceleration, what we call running the rope.

It takes skill and experience to run rope, especially when it's loaded onto a porty or something. The groundman has to predict how much friction to apply at the device and with his hands, how much slack to leave if any, how far the run can be, how much the wood will swing, etc. It's a real job with real skills and risks.

If you've never had a great roper on your crew you are totally missing out. No gear can make that kind of difference, it takes human skill.
 
Obviously, but given that "it is what it is" (the skill of the groundie and the block), why not use the stretch of a dynamic line as well to cushion whatever shock is left... Its that much safer.. you said so yourself

And you know what they say about "trying".. your trying was anything BUT civil...

"There is no reason whatever to go crying that someone will be killed blocking with Stable Braid because it's not elastic enough."

USE EVYTHING to your advantage!

There are people here that knwow what happened the day Donezelli died.. can we get a witness on tthe rope he was using?

So Chip, run the math on a sidelaod with stable braid, vs. true blue or polydyne, and you'll see it can be a difference of life and death. Guy at the local arb supply house tells me he sells a ton of the NE 1/2" double braid.. he had to prder the true blue for me, which tells me that most of the arbs around here think like you.. F THAT!! LOL!
 
Just think about it.. your added strength of a static double braid doesn't do you much good, as the static loads faced in arboriculture are not going to max out above the SWL of the line. Its only the shock loads that we have to worry about when it comes to SWL.. the added stretch in the dynamic lines more than makes up for its lower tensile by reduceing shock loads.. Add to that the EXCELLENT wear of true blue and its a no-brainer.. But for some reason, even Samson doesn't get it. They still try to sell the stuff as climbing line, which is crazy as we are days away from 2011..

ps. happy new year Chip :)
 
In what way is this not civil?
http://www.treebuzz.com/forum/showflat.p...e=0&fpart=2



I don't go trying to use EVERYTHING to my advantage unless I need every advantage. Normally, I use what works from what I have.

A skilled roper absorbs more shock than elasticity by orders of magnitude. When there's a clear path to the LZ it's possible to reduce the load the rope sees to LESS THAN THE WEIGHT OF THE PIECE, never mind shock load, it's completely eliminated. The rope isn't the key, the roper is.

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Now back to Chip..

This is exactly what I AM talking about when it comes to effieciency being safer. You are taking a tree of a house, like an Egyptian

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I LOVE THIS!!!

Oh My God! Daniel... I made a mistake! Holysheepshite! I should quit while I'm still alive! How could I have DONE that? A mistake, an error, how can I live with myself after this?

Perhaps it was the fact that it was the third tree on a house that week and my ropes were spread around a few sites. I worked with what I had... which doesn't include a frikkin skid steer. I'm starting to hate skid steers just because of you now! Every time I see one I think of plump flapping jowls and a poorly cut mullet.

But take a look why your idea would completely suck in this situation...

613ShadyLawn-4.jpg

Note the flexion in the crane tree, that's a straight pine, two thirds the diameter of the downed tree we were lifting. It was displaced from the lifting point by about 50' and made noises when we loaded it. We had a DWT and a very heavy, busted up red oak. Yanking on that with a skid steer would be stupid. Never mind that you couldn't have gotten anything bigger than a mini in there anyway. What the hell would you do without hydraulics?

The point of the story was that Polydyne stretches a LOT.



Thank god we have perfect people like Daniel to safely do our trees. Thank god we can count on him to jump on whatever video or forum post he happens to see and try to make it into his own 'advanced technique' that he's been using for YEARS.

Daniel it's hysterical that you're on about dynamic rope when you stretch them beyond the elastic limit the first time you hook up your heavy, ugly, rusting creativity crutch.

Your ropes don't stretch like they used to, fundamental strengths of materials -- when you exceed the elastic limit, elasticity is out the door... oh wait, you probably haven't studied strengths of materials or physics of force and motion have you, thermodynamics maybe? I thought not, based on your utterly flawed idea that natural crotch rigging doesn't affect cambium.

This is too easy Daniel, can you maybe look something up on Wikipedia and copy/paste it so at least something you say is worthwhile? Because that other stuff is drivel, at best you're parrotphrasing from multiple sources and not well.

Josh, again I apologize, I'm behaving like a jerk here but in this particular case I feel justified. The mods can decide. If you guys want to delete my post, feel free, but do not modify my words... they're mine. I ask that you delete Daniel's as well if you delete mine.
 
Again it gets back to efficiency.. I don't mind overloading ropes from time to time and then taking the money I made with all the time and energy saved and buying new ropes... Its money well spent IMO.. Though like Tom thinks, each to is own..

No skid laoder, no mini, no GRCS.. just bubble gum, duct tape and two ropes huh? LOL... Good for you for getting it done.. Nasty tree..

Though the strength of the gin shouldn't make a difference in what you need to do the lifting.. its should be the same lift, wether by hand with MA or equipment...

Did you climb those gin trees and set blocks or just send up floating blocks?

You want to get personal with smack talk and then be taken seriously when it comes to tree work? Its blatant... you have not much of substance to say, so you attach the personality of your adversary..

Just "try" answer this question.. if dynamic line reduces shock loading, why not use it? What is the advantage of the static lines that makes them a better choice... Cause no matter how good my rope man is, I can lower a bigger piece with the dynamic line. I have more margin for error and I'll be taking less of a ride..
So why use the static?
is it cheaper, lighter, longer lasting? etc..
The only thing I can come up with is that it's stronger..
What good does stronger do you when it is not better at handling shock loads, which is the only time strength is an issue?

Can we leave the my hair and waistline out of this and stick to the topic? Mr Civil...
 
i respect both of you and i have no right to talk here because i don't have half the experience and my climbing and rigging knowledge cant compare to either of you. i will say this though. stretching ropes beyond their elastic limit is very dangerous and can cause a violent failure resulting in the rope whipping back at the climber faster then you can react.

i have experienced this when i was pulling over a 24" diameter 4 foot section of mango. the rope being used was a 1/2" arborplex that stretches even more then true blue(3% at 10%WLL).

i called for the pull and the piece began to lift up and start to come over when the truck slipped in the wet grass causing the piece to sit back down.

when this happened it yanked the rope hard enough to break it at where the bend radius was weakest(the truck hitch). the rope came violently whipping back at me and missed my head by a couple of feet.

this could have been prevented by using a low stretch double braid with a higher breaking strength.

basically what happened is the rope was already at it's elastic elongation limit and the added shock load of the piece sitting back down caused an irreversible catastrophic failure at where the bend radius was the smallest....the hitch on the truck. i am still to this day a bit nervous when pulling pieces over with the truck. just my 2 cents guys.
 
Josh,
Valid point and every time something like that happens, its crucial to review the whole process that lead up to it, and get a good idea of what things went wrong (most often a series of things), and what can be done to correct for them in the future. Without that understanding, you walk blindly towards your peril...

So how else could that have been prevented???? A number of ways no doubt, with the most important IMO being using a different knot!!!!

Simple, fast, easy, and makes a huge difference in the strength of the line. HUGE!!!! a better knot will also save time in untying.

Were you using a bowline?.. I used that knot for 20 years before reading about how untrusted it is by the rescue folks. Now its relegated to extremely light duty, in my repetoire. ANYTHING that even approaches a couple hundred pounds will get a DOUBLE bowline.. MUCH stronger, and plenty fast. Its a matter of habit at this point...

The other thing I like to use is a old-school porty on the pindle hitch of the truck or the bucket of the skid loader (on a big shackle). That's even less bend and easy to control, untie, re-tie, etc.. I welded a special D ring on the loader bucket for that purpose.

Then you can go back and review communication with driver, placement and gearing of truck, body position relative to the line etc.. So there are a lot of lessons that can be learned, and a lot of changes you can make in your game, that will do you far more good than just switching out lines to a static line, (which could do you far more harm than good)...

So don't just the blame on that line. Just as in Tom's example, that would not be the "right" lesson to learn from that experience. Thanks for sharing and good luck with it.

I put up a thread some time ago called "broke my first rope"?, I think.. Learned my lesson about using shackles in the tree, rather than rigging blocks.. (For real heavy stuff)..

Also of note was that the only thing at risk were the service lines to the house, which though embarassing, was not a hard or expensive fix. SO an important point to keep in mind when rigging heavy stuff is weighing the risk involved. I don't take the risk of "going BIG", when there are valuable obstacles or human safety in the mix!!!
 
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i respect both of you and i have no right to talk here because i don't have half the experience and my climbing and rigging knowledge cant compare to either of you.

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Josh,

Don't ever think that just because you don't have as many hours doing a job that you don't have standing in the conversation. Your observations and comments are fresh and unbiased...or jaded.

After you experienced what happened when you lost traction I bet you learned a LOT. One of the best take-aways from that setup is to use a larger rope AND not to rely on tire friction to generate a load. You stored all of the stretch energy in the rope. When the tires slipped the energy released. This is another example of what Shigo called dynamic equalibrium, not a balance of nature. See how many lessons we can learn from trees?
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Oh no Daniel, civil went out when you picked my name to call out... no civil, that was before.

Josh, you have every right to say anything you want. I'm pretty sure you'd stack up well compared to me, I'm just a cranky old guy.... but compared to the great Daniel though, obviously no one stacks up except his hero du jour.

Do not listen to what he's saying Josh... he doesn't understand what he's talking about, physics is way beyond his bailiwick. He didn't know elastic limits even existed 24 hours ago but mark my words, the conversation is coming in which he'll be THE expert on it. That's Daniel dude, that's how he rolls. He is the classic example of a little bit of knowledge is a dangerous thing.

It's clear as a bell he doesn't understand the principles of physics, only examples... and in tree rigging that's a great way to hurt someone. He's making up his own mini-principles as he goes along and he's missing the boat on some of'em.


Daniel, all ropes are dynamic... it's a question of how dynamic. There is no 'static rope' vs. dynamic.... all ropes stretch, it's a matter of degree. Should I go out and buy bungee cord for rigging rope because it'll be the ultimate in shock absorption? Stable braid does stretch, obviously enough because Samson sells a lot of it to tree guys.

The idea that Stable Braid isn't suitable for blocking is absurd, it's been done for a very long time, I've worm out ropes doing it, no rope ever broke. How Daniel got on this little tear I have no idea but it makes no sense.

The rope is a shock absorber, a skilled groundie is a faaaaaaaar better shock absorber. So much so that a groundie could get wood on the ground safely when the best, stretchiest tree rope would snap if it were locked off.

Daniel is going on about the difference between 2% and 4% stretch when it's basically meaningless when you factor in the hands and brain of a skilled groundie.

Yes you can drop bigger pieces onto stretchy rope when you are snubbed off, but if you aren't, why wring your hands over it? Daniel uses some mean street, dumpsterfire of a groundie and is afraid to to tell him how to run rope. Daniel NEEDS every advantage in stretchy rope... most people don't.

And that's right Daniel, 2 portys, 2 blocks, 250' of 9/16" Stable Braid( some in side loading configuration!), 200' of Polydyne, a 5:1 and something which you clearly lack... creativity.
We tied it off in the dark (and yes I climbed the pine, DWT, remember?) Two of us took 3/4 of the next day to clear the tree and fall two others. And you have a problem with that how? Mr. efficiency?

The reason the skid steer is different from the 5:1... and you've been told this so many times now it's just pathetic... the reason is, you have no idea how much force you're putting on a rope by pulling it with a vehicle. Exceeding the elastic limit or the breaking strength is easy with hydraulics... and you have no gauge to measure it. With a 5:1 you can exceed WLL on some ropes with two guys, but barely.

Like I said, you do all the work for me.
 
I only know one person, there may be more, who does real weight calculations of logs that are being cut. Knowing the weight, in this case, for crane lifts, is critical. Not any less critical though when doing slam-dunk rigging.

If stretch is going to be used as a factor in rigging, are measurements taken and the numbers run through a calculator to find out how much of a load will be taken at the rigging point? Unless all of the variables are calculated the work is being done by the seat of your pants. Promoting the incorporation of rope stretch without calculating the loads isn't a complete presentation.

Add another variable to the rope stretch calculation. Each time a rope is loaded it stretches, like bubble gum. Until it is given time to 'relax' the stretch is still sorta stored in the rope. This falls into the discussion of cycles to failure.

Many years ago I spent close to an hour talking with Dick Hilldebrand about how stretch was measured in ropes. He started his response with a little chuckle and said that, at the time, there wasn't an accepted methodology for calculating stretch in a rope. It was no different than measuring rope in 'foot' lengths without using something as variable as the length of your or my foot.

My style of rigging doesn't calculate or use rope stretch as a tool. In my roof smash example the lesson was that I couldn't calculate the amount of stretch. This was YEARS before bollards were being used. We certainly did sweat up the rope, I learned to do that in my late teens...do the math, it was a while ago.

since rope stretch is so difficult to calculate I choose not to use it in my favor. I use it as a seat of the pants variable. If I'm going to dump a piece and I know that the rope might stretch, allowing the piece to move further than I want, or load my rigging point too much, I take a smaller piece or grab a bigger rope. There's no efficiency in breaking things or getting hurt.
 
I couldn't disagree more with both of you...

Big Jon tore me me a new one, one time when he showed up to rig out a monster oak over a house and all I had was double braid. He wouldn't rig the tree with that and acted Like I was trying to get him killed by asking him to rig with double braid.

Once he got a more dynamic line in hand (hi-V), he proseeded to lower out 40' red oak leads, tied perfectly at their balance points. So well balanced that you could move them with one finger. It was a beautiful thing.. Guy M was actually on site for a few minutes..



enough said... I gotta go!
 
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