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Amsteel 1/4" prusik on 8mm sterling oplux?

GetHomeSafe

Active Member
Joined
Oct 1, 2019
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Hayward, WI
Has anyone used Amsteel 1/4" prusik on 8mm sterling oplux as a linesman's rope or a tether? Anyone used a tender with it? What did you think? Thanks for sharing your experience.
 
Has anyone used Amsteel 1/4" prusik on 8mm sterling oplux as a linesman's rope or a tether? Anyone used a tender with it? What did you think? Thanks for sharing your experience.

What's the benefit of using it over a proven, reliable material, like 6mm TRC that is recommended by the manufacturer?
 
Im using 1/4 amsteel swabish hitch on oplux for my bridge. It slides if not careful, not happy with it.
 
Im using 1/4 amsteel swabish hitch on oplux for my bridge. It slides if not careful, not happy with it.
Thank You, good to know, I was wondering if it would be too slippery. Slips not good, slip = friction, friction = heat, heat = potential failure. Why I asked, thanks for your help.
 
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What's the benefit of using it over a proven, reliable material, like 6mm TRC that is recommended by the manufacturer?
No harm in asking. I asked because TRC is rated for 3484#. 1/4" amsteel is rated for 8600# avg, 7700# min. It's lighter and smaller. Fall Factor calculator says if you slip climbing or while on platform. say you are in smaller tree and only have 3' of rope from one linesmens loop to the other. If you fall 2' and weigh 200# with your clothing and gear that is on you. you generate 17Kn of energy on your safety system, or 3,821#. If your climbing and get a bit careless and you linesmens belt actually gets below your hips to your knees or whatever you could fall 2'. The shorter the rope the more Kn generated. See this link if you have not played with it. https://ferforge.tripod.com/Srt002.htm. It is a fall factor calculator. Just fill in weight, length of rope being used from tie off to tie off, rope type, static or dynamic, and the distance of the fall. It will tell you how many Kn that would generate. The numbers can get big in a hurry, a lot more than people realize, or at least a lot more than I realized until very recently. That's why I am asking questions. Since a prusik should be no more than 80% of the standing line it's on. 8mm Oplux puts any prusik to a very small size, and at 6.8mm or less many of the weight ratings are low enough to begin to wonder if they are strong enough. All them will more than hold us in a fall restraint mode. It's the fall arrest mode where it could get dicey, our life literally depends on this stuff working. One of the scariest scenerios I see for us is I see people single sticking using their tether rope and during the process at times because of where they are and where the rope is anchored they could fall 4 or even 5'. That is where smaller prusik rope gets darn scary, as do most of the rope grabs we use. Ropeman 1's, CT RollNLock, and Kong Duck as they can strip a sheath on a rope at those energy levels. Those devices are for fall restraint and work great for that but they are not intended for fall arrest. And we are all on Static rope which also exacerbates the situation.
 
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No harm in asking. I asked because TRC is rated for 3484#. 1/4" amsteel is rated for 8600# avg, 7700# min. It's lighter and smaller. Fall Factor calculator says if you slip climbing or while on platform. say you are in smaller tree and only have 3' of rope from one linesmens loop to the other. If you fall 2' and weigh 200# with your clothing and gear that is on you. you generate 17Kn of energy on your safety system, or 3,821#. If your climbing and get a bit careless and you linesmens belt actually gets below your hips to your knees or whatever you could fall 2'. The shorter the rope the more Kn generated. See this link if you have not played with it. https://ferforge.tripod.com/Srt002.htm. It is a fall factor calculator. Just fill in weight, length of rope being used from tie off to tie off, rope type, static or dynamic, and the distance of the fall. It will tell you how many Kn that would generate. The numbers can get big in a hurry, a lot more than people realize, or at least a lot more than I realized until very recently. That's why I am asking questions. Since a prusik should be no more than 80% of the standing line it's on. 8mm Oplux puts any prusik to a very small size, and at 6.8mm or less many of the weight ratings are low enough to begin to wonder if they are strong enough. All them will more than hold us in a fall restraint mode. It's the fall arrest mode where it could get dicey, our life literally depends on this stuff working. One of the scariest scenerios I see for us is I see people single sticking using their tether rope and during the process at times because of where they are and where the rope is anchored they could fall 4 or even 5'. That is where smaller prusik rope gets darn scary, as do most of the rope grabs we use. Ropeman 1's, CT RollNLock, and Kong Duck as they can strip a sheath on a rope at those energy levels. Those devices are for fall restraint and work great for that but they are not intended for fall arrest. And we are all on Static rope which also exacerbates the situation.

All of the reasons you just listed is why I would recommend NOT using amsteel as a friction hitch. There are more properties than just breaking strength. Amsteel does really bad with a tight bend radius (like around a caribiner), and with shock loading. This is just two of the reasons why Sampson does not recommend their product be used in the way that we often use it in the saddle hunting world.

If you search you should be able to find a couple threads where people discuss those properties and why amsteel may or may not be a good idea.

Edit: here is a recent thread where this was discussed. https://saddlehunter.com/community/...-prussic-combos-and-selling-them-on-fb.31999/
 
You also need to consider that a 6mm rope with a 3,400 lb rating used as a prusik is actually loaded in a basket condition which means you are supporting the weight/force on the rope with a doubled length of rope. So, it’s breaking strength capacity would be double, ie 6,800 lbs. This means that the Oplux is actually the weak link in this situation.
 
Oh, and thanks for that fall calculator. I had no idea that much force is generated in such a short distance. I punched in 230 for my weight and 6’ for both the rope length and distance from anchor point and I ended up at 21.5 kN. Totally shocked by that?!
 
All of the reasons you just listed is why I would recommend NOT using amsteel as a friction hitch. There are more properties than just breaking strength. Amsteel does really bad with a tight bend radius (like around a caribiner), and with shock loading. This is just two of the reasons why Sampson does not recommend their product be used in the way that we often use it in the saddle hunting world.

If you search you should be able to find a couple threads where people discuss those properties and why amsteel may or may not be a good idea.

Edit: here is a recent thread where this was discussed. https://saddlehunter.com/community/...-prussic-combos-and-selling-them-on-fb.31999/
Thanks, I will check out the link. Good to know that the strength for the prusik doubles, prior to the knot loss of course. I was not aware of that so you taught me something, good to learn something everyday. Since slipping seems to be a problem with Amsteel anyway I will likely switch to a Beal Jammy as those rate at 4946# as opposed to TRCs 3484#. Plus the knot reduces strength by 25 to 40%. So worst case trc 3484 *2 = 6968 * 0.6 = 4181. Beal Jammy 4946*2=9892*0.6=5935. 5463# for Oplux with sewn eye, less up to 40% if knotted to form an eye. I am researching this as currently I have 10mm sterling static line and ropeman 1s, I am thinking of switching to Oplux with sewn eye for my two linesman ropes (one becomes my tether at height). I thought of going with CT RollNLocks but then learned all these rope grabs are not intended for fall arrest but rather fall restraint. Sounds like the safer method in case of a fall is the prusik as it is more gentle on the rope sheath. A bit tougher to adjust but safety is worth a lot, as our lives hang in the balance. Thanks again for the info and God Bless your hunt.
 
Oh, and thanks for that fall calculator. I had no idea that much force is generated in such a short distance. I punched in 230 for my weight and 6’ for both the rope length and distance from anchor point and I ended up at 21.5 kN. Totally shocked by that?!
I misswrote. It's actually 23.5 kN. If I switch to a dynamic rope with the same variables, I got down to below 12 kN. That's a remarkable difference and has me seriously considering dynamic ropes for my tether and bridge?!

@GetHomeSafe thanks again for that link.
 
I misswrote. It's actually 23.5 kN. If I switch to a dynamic rope with the same variables, I got down to below 12 kN. That's a remarkable difference and has me seriously considering dynamic ropes for my tether and bridge?!

@GetHomeSafe thanks again for that link.
I think serious climbers know this. I did not until just recently. Bowhunting is great fun, but what a challenge, it involves knowledge is so many disciplines. We're never done learning. The challenge I think is one of the things that keeps it interesting. I am so glad it was informative. I hope many other hunters find it as our lives literally hang by this equipment. I suppose it makes sense as when things stretch or move it's more difficult to break them as opposed to rigid. I to was shocked at the forces generated by such a shortfall. I should perhaps think of going dynamic as well. I suppose the rope would stretch more than what we have when used as linesman or tether but we adjust these anyway so if it stretches a bit we shorten as needed? I have to be careful I am 67 now and although God has blessed me with good health I know I don't bounce well. I weigh 185 and with temps in the teens, heavy boots, and layers of clothing, I have never weighed it all, I suppose easily 20 or 25# more?
@RMerrell thanks again for brain storming with me. So appreciated .
 
Does the dynamic rope force calculation assume a longer piece of dynamic rope fed through carabiners and such? A short piece of dynamic rope doesn't stretch much because stretch is a percent by length.

Look into a Yates Screamer. I'm considering it. You would add somewhere in attachment to tether (before or after prusik or whatever you use to adjust on rope). They break away if you fall.
 
Does the dynamic rope force calculation assume a longer piece of dynamic rope fed through carabiners and such? A short piece of dynamic rope doesn't stretch much because stretch is a percent by length.

Look into a Yates Screamer. I'm considering it. You would add somewhere in attachment to tether (before or after prusik or whatever you use to adjust on rope). They break away if you fall.

https://m.petzl.com/US/en/Sport/Fall-factor-and-impact-force---theory?ActivityName=rock-climbing

Exactly. Such a short piece of dynamic that we would be on would generate damn near same amount as static


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https://m.petzl.com/US/en/Sport/Fall-factor-and-impact-force---theory?ActivityName=rock-climbing

Exactly. Such a short piece of dynamic that we would be on would generate damn near same amount as static


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Not exactly. From what I’ve seen looking at various ropes online, the static ropes have an elongation of around 1.5% - 3% and the dynamics are around 20% - 30%. Using the lower ends of those two ranges for my example of a 6’ rope, that works out to 1.1” of stretch for static and 14.4” for dynamic. These numbers are based on a 300 lb weight, which is a little high for me, but the difference still stands and it’s not an insignificant difference.
 
Not exactly. From what I’ve seen looking at various ropes online, the static ropes have an elongation of around 1.5% - 3% and the dynamics are around 20% - 30%. Using the lower ends of those two ranges for my example of a 6’ rope, that works out to 1.1” of stretch for static and 14.4” for dynamic. These numbers are based on a 300 lb weight, which is a little high for me, but the difference still stands and it’s not an insignificant difference.

I was meaning no matter what it doesn’t change the fall factor. Maybe it’ll feel a little less shi*ty


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Fall factory has nothing to do with rope type. It's strictly length of rope versus length of fall. So, you are absolutely correct, a dynamic rope and or yale screamer will hurt much much less on a fall than a static rope even though they will have the same fall factor if all other variable remain the same.

I'm really glad you made me go back and take a second look because the numbers I was getting from that calculator were really blowing my mind. My example of 6' of rope and 6' from last anchor point is actually a 12' fall and results in a fall factory of 2. I misunderstood the variables and used the program incorrectly. This scenario means I would be 6' above my tether point, which I would never do.

What I sometimes do is climb down below my platform without moving my tether down. I just pay out slack so I can drop below my platform to make adjustments to my platform and/or platform anchor line. When I climb back up, my hands are usually full hoisting my fat ass back up, so I would get back up on my platform and have all that slack. If the platform broke at that moment before I reinged in my slack, I could see myself falling 6', but the anchor point is right at eye level or so. I'm not sure how to force the program to do that calculation. A belay persons responsibility is to keep slack out of the line, so my scenario would not be a typical climbing scenario.

I went back and made some changes to the variables to see what's what. I kept the rope length at 6' but changed the distance from last anchor point to 3'. That would give me a 6' fall. Even though my configuration is a little different than intended for the program, I think this setup represents my situation pretty good. That resulted in a fall factor of 1.5 and impact force of 17.6 kN. Still seems high to me, but at least it's not pushing the limits of typical gear like it was as 23.5 kN.
 
Fall factory has nothing to do with rope type. It's strictly length of rope versus length of fall. So, you are absolutely correct, a dynamic rope and or yale screamer will hurt much much less on a fall than a static rope even though they will have the same fall factor if all other variable remain the same.

I'm really glad you made me go back and take a second look because the numbers I was getting from that calculator were really blowing my mind. My example of 6' of rope and 6' from last anchor point is actually a 12' fall and results in a fall factory of 2. I misunderstood the variables and used the program incorrectly. This scenario means I would be 6' above my tether point, which I would never do.

What I sometimes do is climb down below my platform without moving my tether down. I just pay out slack so I can drop below my platform to make adjustments to my platform and/or platform anchor line. When I climb back up, my hands are usually full hoisting my fat ass back up, so I would get back up on my platform and have all that slack. If the platform broke at that moment before I reinged in my slack, I could see myself falling 6', but the anchor point is right at eye level or so. I'm not sure how to force the program to do that calculation. A belay persons responsibility is to keep slack out of the line, so my scenario would not be a typical climbing scenario.

I went back and made some changes to the variables to see what's what. I kept the rope length at 6' but changed the distance from last anchor point to 3'. That would give me a 6' fall. Even though my configuration is a little different than intended for the program, I think this setup represents my situation pretty good. That resulted in a fall factor of 1.5 and impact force of 17.6 kN. Still seems high to me, but at least it's not pushing the limits of typical gear like it was as 23.5 kN.

So I think there are too many variables going into the calculation. When watching someon on how not to high line, they were falling against their “trick rope” which is obviously a dynamic line of some sort meant for elasticity. Judging the 180# person fell onto it at roughly 4-6’ it generated nearly 14kn. I made this point on one of my posts that imagine falling 4-6 on a static line with 2-3% elongation vs the latter. It makes you re think a little.

I’m guilty of climbing and allowing my tether to be at my waist while climbing onto my platform knaider/swaidering. The objective is safety, I’m just trying to figure out how to continue up the tree while minimizing the dangers.

We all accept the risk climbing into a tree, but it’s our job to minimize the risks and get home safely to our families. So trying to find a balance can definitely be daunting between speed and safety


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Investigating further, I too am seeing other variables that make it difficult to know exactly what's happening with my limited experience and knowledge. You just look at the specs for at static rope versus a dynamic rope and even the categories in the specs are very different. Static ropes just list elongation but dynamic ropes list static elongation and dynamic elongation. I think the static rope elongation is just the elongation from a static load and does not account for any type of fall inertia because that would be using that type of rope inappropriately, so there's no reason for the manufacturers to list it. So, my elongation comparison above is not comparing apples to apples because the static rope elongation is not based on a dynamic loading. With that said, I think we can still glean some information from that calculator website that can help us be safe and make good decisions so that we can come home after the sun sets.

I've been saddle hunting for over 10 years, and this is the first time I actually took a look at the numbers. I never bothered with it before because I thought my scenarios were so far below the extremes of climbing that I would be no where near the potential forces generated by an actual climber. A perfect example of this is that most climbers would never use an 8 mm rope as there sole climbing line. I've never used anything heavier. I looked at the breaking strength of my 8 mm rope and figured I was good. Much to my embarrassment and surprise, especially considering I have an engineering background, I am definitely in the realm of actual climbing forces.
 
Investigating further, I too am seeing other variables that make it difficult to know exactly what's happening with my limited experience and knowledge. You just look at the specs for at static rope versus a dynamic rope and even the categories in the specs are very different. Static ropes just list elongation but dynamic ropes list static elongation and dynamic elongation. I think the static rope elongation is just the elongation from a static load and does not account for any type of fall inertia because that would be using that type of rope inappropriately, so there's no reason for the manufacturers to list it. So, my elongation comparison above is not comparing apples to apples because the static rope elongation is not based on a dynamic loading. With that said, I think we can still glean some information from that calculator website that can help us be safe and make good decisions so that we can come home after the sun sets.

I've been saddle hunting for over 10 years, and this is the first time I actually took a look at the numbers. I never bothered with it before because I thought my scenarios were so far below the extremes of climbing that I would be no where near the potential forces generated by an actual climber. A perfect example of this is that most climbers would never use an 8 mm rope as there sole climbing line. I've never used anything heavier. I looked at the breaking strength of my 8 mm rope and figured I was good. Much to my embarrassment and surprise, especially considering I have an engineering background, I am definitely in the realm of actual climbing forces.

This was a great back and forth. It’s just crazy how we can be so complacent because we “think” things are fine. But in all actuality if we were to sustain any fall, it would be much more than we bargained for.

I’m new to the saddle game, but whenever I do anything I dive deep, and want to know in’s and outs of everything. Knowing everything I can builds my confidence in my system. It doesn’t seem like it is ever discussed into detail like this or it never goes this deep. We see high kn ratings and say I’ll never come close, where in reality it is possible to generate more than we thought. Especially for the heavier guys. They’ve always said the most dangerous part is going up (and down if you’re not repelling). I’d like to think if I began to slip while standing on my platform that I would grab the tree like it owed me Money but you never know!


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Investigating further, I too am seeing other variables that make it difficult to know exactly what's happening with my limited experience and knowledge. You just look at the specs for at static rope versus a dynamic rope and even the categories in the specs are very different. Static ropes just list elongation but dynamic ropes list static elongation and dynamic elongation. I think the static rope elongation is just the elongation from a static load and does not account for any type of fall inertia because that would be using that type of rope inappropriately, so there's no reason for the manufacturers to list it. So, my elongation comparison above is not comparing apples to apples because the static rope elongation is not based on a dynamic loading. With that said, I think we can still glean some information from that calculator website that can help us be safe and make good decisions so that we can come home after the sun sets.

I've been saddle hunting for over 10 years, and this is the first time I actually took a look at the numbers. I never bothered with it before because I thought my scenarios were so far below the extremes of climbing that I would be no where near the potential forces generated by an actual climber. A perfect example of this is that most climbers would never use an 8 mm rope as there sole climbing line. I've never used anything heavier. I looked at the breaking strength of my 8 mm rope and figured I was good. Much to my embarrassment and surprise, especially considering I have an engineering background, I am definitely in the realm of actual climbing forces.

If you want your mind blown, look up on youtube the tests DMM has done dropping weights onto dyneema slings (I believe the core of Oplux is same or similar). It snaps way easier than we'd all like. A weaker nylon sling does better in the drop tests. I believe the Canyon rope is nylon core. This might mean it makes sense to use it over Oplux if you have any concerns.
 
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