Strongest Block Attachment Sling
- Thread starter southsoundtree
- Start date
Mangoes
Participating member
- Location
- Greater Toronto Area
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Is the goal that if a mistake were to occur to have the attachment of the block fail rather then the tree itself? I am not clear as to how D.B. would protect tree failure (if this is indeed the impetus for the rationale). Would it really stretch that much? I also do not understand what specifically you mean by the competency level required to employ Amsteel, care to elaborate?
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I might be able to get inside Tod's head here;
A fairly astute tree worker should understand the principles in my last post. If you employ 60+ people it is harder to ensure that all potential users of the tool(amsteel......more accurately Dyneema)are competent in the usage of the tool. As an employer your are required to ensure that workers usng tools, systems and practices are competent, if not you are liable and accountable for their misuse of the tool. If they are trained, deemed competent and misuse the tool you potentially have an arguement in defense of your liability.
Is the goal that if a mistake were to occur to have the attachment of the block fail rather then the tree itself? I am not clear as to how D.B. would protect tree failure (if this is indeed the impetus for the rationale). Would it really stretch that much? I also do not understand what specifically you mean by the competency level required to employ Amsteel, care to elaborate?
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I might be able to get inside Tod's head here;
A fairly astute tree worker should understand the principles in my last post. If you employ 60+ people it is harder to ensure that all potential users of the tool(amsteel......more accurately Dyneema)are competent in the usage of the tool. As an employer your are required to ensure that workers usng tools, systems and practices are competent, if not you are liable and accountable for their misuse of the tool. If they are trained, deemed competent and misuse the tool you potentially have an arguement in defense of your liability.
Right on. Other considerations of dyneema are melting point and how the fiber responds after heavy loads. I do believe it breaks down faster when pushed closed to it's tensile strength, and that can be hard to manage when dumping wood. I do use covered dyneema for crane work or complete static loads. As far as slamming wood into a block I prefer Poly double braid.
Aside from the obvious limitations of the dyneema fiber (melting point etc) that are a given, is there a suggestion here that if we had to pick a part of our system to fail that the block attachment would be best?
- Location
- Chapel Hill, NC
I can't think of any part of a rigging system I'd want to fail first. I can't think of any rigging system I would want to push anywhere close to failing... it's like deciding which body part would you prefer to lose first.
- Location
- Chapel Hill, NC
Having gone to the ground with a tree when it failed I couldn't agree more that structural failure is my biggest concern working compromised trees. Gear now really is so strong for weight and size, that's where we are. Tree structure is becoming the weak component in a rigging system... certainly for weakened trees anyway... species is another indicator.
There's no heroism in taking giant pieces... fun, excitement, impressing your friends, yes... but it's something I only do in ideal conditions. I never hesitate to go small if I think it adds to a skimpy safety margin.
There's no heroism in taking giant pieces... fun, excitement, impressing your friends, yes... but it's something I only do in ideal conditions. I never hesitate to go small if I think it adds to a skimpy safety margin.
chris_girard
Branched out member
- Location
- Gilmanton, N.H.
[ QUOTE ]
There's no heroism in taking giant pieces... fun, excitement, impressing your friends, yes... but it's something I only do in ideal conditions. I never hesitate to go small if I think it adds to a skimpy safety margin.
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Words to live by Blinky.
There's no heroism in taking giant pieces... fun, excitement, impressing your friends, yes... but it's something I only do in ideal conditions. I never hesitate to go small if I think it adds to a skimpy safety margin.
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Words to live by Blinky.
I agree we have the tools to push the trees to and over the limit for sure but just to kick around. What makes an exotic fiber exotic?....Price? Availability? Or?
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...Other considerations of dyneema are ... and how the fiber responds after heavy loads. I do believe it breaks down faster when pushed closed to it's tensile strength...
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I believe this is incorrect. It is interesting to cruise the technical papers at the Samson site, where I found this:
http://www.samsonrope.com/site_files/Dynamic_Fatigue_of_High_Performance_Synthetic_Ropes_.pdf
When repeatedly stressed to 80% nominal breaking strength, polyester failed after 100 cycles, while Dyneema survived 30,000 cycles.
...Other considerations of dyneema are ... and how the fiber responds after heavy loads. I do believe it breaks down faster when pushed closed to it's tensile strength...
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I believe this is incorrect. It is interesting to cruise the technical papers at the Samson site, where I found this:
http://www.samsonrope.com/site_files/Dynamic_Fatigue_of_High_Performance_Synthetic_Ropes_.pdf
When repeatedly stressed to 80% nominal breaking strength, polyester failed after 100 cycles, while Dyneema survived 30,000 cycles.
I believe I was wrong. One thing to keep in mind while slamming heavy wood close to the ground like in the attachment is that the force comes into the sling very quickly. On such peices I have seen some melting on the sling at the hitch. For this reason and the fact of unknown loads I would rather push the limits of a poly sling and just simply replace it rather than use an exotic fiber and perhaps be pushing the limits.
Attachments
treebing
Been here much more than a while
- Location
- Detroit, Mi.
In a rigging sling is there enough rope to have any stretch anyway? I cant imagine that even a double braid sling would have any stretch that would make a difference. The stretch would have to come from the rope.
- Location
- Chapel Hill, NC
Anything braided will stretch some, but it may be only a tiny amount. But that little bit of stretch makes a big difference in breaking strength. It's a fine line. between making something too stretchy to work with and not stretchy enough to absorb shock.
I'm with ya Todd. Heavy loads close to the ground make me scratch my head quite often pondering a better way. And they stretch without a doubt, just look at the throat after dumping big wood. So just cause I'm overly curious always does anyone know the criteria for what we consider "exotic" or not?
- Location
- Chapel Hill, NC
When I hear 'exotic' with reference to rope fiber I think of advanced engineering fiber like Ultra high molecular weight polyethylene which is Dyneema/Spectra, or aramids like Kevlar and Technora, or aromatic polyester like Vectran.
They have different properties but what they have in common is, they are just stupidly strong.
They have different properties but what they have in common is, they are just stupidly strong.
I can't seem to get away from this and have many questions in my mind now after reading all these posts so here goes. Is it better to "push the limits" of poly instead of being well within the limits of dyneema? And I know heat is an issue so I included the amsteel II plus because it has a poly cover so does this solve our problem and let us retain a good part of the strength. win win?
Amsteel blue Amsteel 2 plus Stable braid
3/4" 64,400 43,800 20,400
7/8" 90,800 62,500 29,900
( avg break strength published by samson)
Oooooor are we not creating enough force to stretch the dyneema therefore seeing no melting???? In theory the 7/8" amsteel elongation is about 1% at 30% of the tensile load equaling roughly 30,000lbs by which the stable braid would already done???? Or it hangs on for that one shot load and its off to retirement??? Just curious and want to be making the best choices for us so thanks to all for any input..
Amsteel blue Amsteel 2 plus Stable braid
3/4" 64,400 43,800 20,400
7/8" 90,800 62,500 29,900
( avg break strength published by samson)
Oooooor are we not creating enough force to stretch the dyneema therefore seeing no melting???? In theory the 7/8" amsteel elongation is about 1% at 30% of the tensile load equaling roughly 30,000lbs by which the stable braid would already done???? Or it hangs on for that one shot load and its off to retirement??? Just curious and want to be making the best choices for us so thanks to all for any input..
- Location
- Chapel Hill, NC
Wow, those are BIG numbers. How often do you rig a 2000# chunk of wood likesay 24" diameter red oak by 10' long? To me, that's a monster piece of wood to be catching on a natural anchor point. You could block it negative with 3/4" Stable Braid and stay inside a 10:1 safety factor AND have enough stretch to protect your anchor point from the GIGANTIC shock of a 2' or 3' drop. With Amsteel you'd be no safer but banging your rigging and anchor a LOT harder. Seems pointless.
I'm more than happy with double braid poly and Tenex. My idea of pushing it would be taking that 2000# chunk with a butt tie on an overhead anchor with a bitchin' good roper. If I had to go negative, I would go no more than half that size... That leaves me with better than a 10:1 safety using 9/16" stable braid.
Just as an aside, I had to cover for a climber once who tried to take a ~20" by 20' chunk of white oak on a block. He was in a big hurry so he was cutting big pieces... but he failed to notice that his cut was about 18' from the deck. The rope hardly got a taste of it when the piece swung around and pinned him to the trunk. I finished that tree the next day and it was not pretty.
Why risk it?
I'm more than happy with double braid poly and Tenex. My idea of pushing it would be taking that 2000# chunk with a butt tie on an overhead anchor with a bitchin' good roper. If I had to go negative, I would go no more than half that size... That leaves me with better than a 10:1 safety using 9/16" stable braid.
Just as an aside, I had to cover for a climber once who tried to take a ~20" by 20' chunk of white oak on a block. He was in a big hurry so he was cutting big pieces... but he failed to notice that his cut was about 18' from the deck. The rope hardly got a taste of it when the piece swung around and pinned him to the trunk. I finished that tree the next day and it was not pretty.
Why risk it?
I'm in no way suggesting to rig obsurd pieces. My only concern is trying to sort thoughts as to why it'd be superior to rig with the poly over the stronger counterpart so I'm solid in reasoning to myself. I think if your counting on a poly sling to save your anchor point your system would be misguided to begin with. As for how u can drop a 2000# pound piece 2-3 feet and stay within the 10:1 of the 3/4" stable braid (2040lbs) is beyond me. I must be missing something blinky and I'm always open for enlightenment 
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