Trust 5mm prusik

[BTaylor]

I think you and @John RB are saying the same thing but, talking past each other. Technically, a loop is not 1.5 times stronger, it's just that each leg sees 1/2 the load. The cord itself with whatever knot was tied still has the same break strength but, because it's in a loop configurations each leg of the loop has less force applied to it so it breaks at a much higher total force.

You are looking at the total force on the loop and John is looking at the force on each leg. Unless I am misunderstanding John, the examples you provide agree with what he is saying with the exception that he is using a very conservative 50% strength reduction from the knot.

For instance in this example:


You are saying the loop breaks at 16Kn, John is saying the loop breaks when one leg sees 8kN (or 16kN total) and that the side that will break is the side with the knot because it is the knot that reduces the cords break strength from 9.8kN to 8kN.

Exactly what my thoughts were and why I posed the example I did. I was hearing one say trash and the other say garbage.

At the end of the day the strength potential of the system is going to be first determined by the reduction in strength based on the method chosen to connect the ends, hunters bend, fishermans knot, redneck adjoinment, etc.

 

[GCTerpfan]

Exactly what my thoughts were and why I posed the example I did. I was hearing one say trash and the other say garbage.

At the end of the day the strength potential of the system is going to be first determined by the reduction in strength based on the method chosen to connect the ends, hunters bend, fishermans knot, redneck adjoinment, etc.

Exactly, I think the reason people are talking past each other is John's estimate of 50% reduction in strength from the knot is very conservative and was probably partly done to make the math easy. You don't see that reduction in real world testing. If you did, his examples would match the test results posted above.

 

[Fl Canopy Stalker]

Just got out of a meeting and havent watched the video but did the ropes consistently break at the bend or knot?

In most instances yes

 

[John RB]

Right, i am conservatively saying that I assume a 50% knot efficiency. Why? First, because I don't use double fisherman's. I use Hunter's and in the absence of solid test data for every cord I tie it with, I assume its 50% efficient. Its probably more like 65 but we'll wait for my load scale to arrive before i can do real testing. And in a doubled cord system such as a loop, one or a dozen 50% efficient knots at any location will take the system back to the MBS of the cord itself.

Now, if we used a double fisherman's knot as the bend and it is 75% efficient, the overall strength of the system will go to 2x75% or 1.5 MBS. Remember, every bend has different strength and that can vary based on the cord and its properties. Don't assume you're getting 75% unless you've got data or done tests and broken your own cords.

Ps, i am not arguing with anyone... we're a team. Cheers

Sent from my SM-G975U using Tapatalk

 

[Brocky]

You’re muddying the water, the actual break strength of knots and bends, or bend radius, aren’t being debated, we are assuming all those are equal.

 

[Fl Canopy Stalker]

I agree with Brocky. When a cord is tied in loop, the knot or bend is not the only portion seeing the load. The overall strength of the loop is what was in question and it’s not 50 plus 50 or 75 plus 75. In the video, loops using double fisherman’s broke around 18,5 to 19.2 kN which is nearly twice the strength of the original cord. Where as the zeppelin’s bend which is around a 70% break strength knot, broke around 16.5 kN which is about 1.7 times the original mbs of the single strand rope. So a knot that is 50% reduction would theoretically still hold to 1.3 to 1.5 times the cords original strength, not the exact same original break strength. Reread the comments, he literally said it would double the rope strength for the two cords then cut the overall strength of the loop in half due to the knot. While that sounds good in theory, in actual break tests, the math doesn’t add up. Not arguing with anyone when there is clear science backing this statement. I do like John’s numbers for a safety factor. Sorry for derailing the post. To the original poster, while I don’t feel 5mm with a low mbs is sufficient, if you use it in loop form as pictured, the strength of the loop will be stronger than the break strength of a ropeman 1, so people have used worse than your idea. But as stated for safety reasons, there are better 5mm and 6mm options out there

 

[GCTerpfan]

the strength of the loop will be stronger than the break strength of a ropeman 1, so people have used worse than your idea.

I'll let you guys keep arguing semantics but, with all due respect @Fl Canopy Stalker I cringe a little at the statement above. There are a lot of people that are going to ignore the rest of your comment and simply see "It's stronger than a Ropeman, I'm good"

I had zero climbing/rope experience before I started saddle hunting and I imagine the majority of our members are the same way. Before the saddle craze began I listened to a lot of knowledgeable members from this site, some still around and some not, that made really good arguments against using R1's on your tether. A lot or people started going away from that practice and the ones who didn't at least had a better understanding of the risks they were accepting and how to mitigate those risks. Then at least one company that had a lot more marketing experience than they had climbing experience standardized the practice as being completely safe with no mention of potential risks and how to mitigate them. Comparing something to a safety bar that is continuously being lowered by saddle manufactures is a bad idea in my opinion.

 

[Brocky]

It’s not about semantics, more like basic concepts.

The Ropeman itself is very strong, but typically strips the rope cover at around 4 kN. I wonder how they would do on single braid ropes, might take longer for something to fail.

 

[Fl Canopy Stalker]

It’s not about semantics, more like basic concepts.

The Ropeman itself is very strong, but typically strips the rope cover at around 4 kN. I wonder how they would do on single braid ropes, might take longer for something to fail.

I wondered this myself. Or possibly even on a 3 strand twisted line. Where cutting into one strand wouldn’t cause an extreme sudden failure. That would be some testing I would like to see. A ropeman on a 12 or 16 strand single braid, and on a 3 strand twisted line.

 

[bfriendly]

I wondered this myself. Or possibly even on a 3 strand twisted line. Where cutting into one strand wouldn’t cause an extreme sudden failure. That would be some testing I would like to see. A ropeman on a 12 or 16 strand single braid, and on a 3 strand twisted line.

Following along for the ride, but would sure like to see y’all bust up a few ropeman 1s….I have two and I may be too comfy on them.

to the OP, I’d check EWO and get some Beal 5.5 by the foot. I’m using it for prussik back ups and my ATC brake. I like it and it tends really good below my ATC when rappelling on 8mm resctech But I also just got some TRC which I’m playing with,

 

[GeoFish]

It’s not accurate. It depends on how far you fall, your weight, your fall factor (height above or below your connection point) and the amount of stretch in your tether, saddle ect… if you generate over 9kN of force in a fall, the most likely outcome is you’re permanently paralyzed or even deceased. On a 1:1 fall factor of less than 18”, most falls generate less than 900lbs of force which is the reason ANSI sets fall distance standards for work positioning harnesses.

Watching some of the one stick videos I see people climbing with about 5 foot of slackin there tethrr. I think that may not be a good idea.
I am not looking for a exact answer since it can not be calculated with all the variables. But as a general rule for saddle hunters. What is the most slack you would want in a tether? I am going to climb with a one step aider on steps or sticks. I was planning on connecting my tether for a fall arrest if something went wrong. Is it safe to move my tether every 2 steps or 34"?

 

[Iron_llama]

Watching some of the one stick videos I see people climbing with about 5 foot of slackin there tethrr. I think that may not be a good idea.
I am not looking for a exact answer since it can not be calculated with all the variables. But as a general rule for saddle hunters. What is the most slack you would want in a tether? I am going to climb with a one step aider on steps or sticks. I was planning on connecting my tether for a fall arrest if something went wrong. Is it safe to move my tether every 2 steps or 34"?

The Dangers of Short Static Falls

I was going to post this in response to an ongoing thread but think it deserves more attention. This is a great read for everyone on this forum just as a reminder of how short falls on static systems can be devastating...

saddlehunter.com

This is a thread on the dangers of short static falls. My takeaway is that a 1' fall is (probably, unless things go horribly wrong) not going to kill me, but is enough force to ruin my hunt, and probably the next several months. So I'm a bit more aggressive about tending out my slack than a lot of the 1-sticking videos I see. Mind you, I'm a rank novice and have no expertise on anything, but that's my take.

 

[tailgunner]

 

[Fl Canopy Stalker]

Watching some of the one stick videos I see people climbing with about 5 foot of slackin there tethrr. I think that may not be a good idea.
I am not looking for a exact answer since it can not be calculated with all the variables. But as a general rule for saddle hunters. What is the most slack you would want in a tether? I am going to climb with a one step aider on steps or sticks. I was planning on connecting my tether for a fall arrest if something went wrong. Is it safe to move my tether every 2 steps or 34"?

You should read the link that was attached above in Iron llama’s post. If you climb 34” above your tether, your fall in total would be nearly 6’. That would be catastrophic. If you are even and you fell exactly 34” it would still generate nearly a ton of force. As a general rule for work positioning harnesses (ie lineman arborists ect) the requirements are 18” maximum “allowable” fall distance and their maximum fall factor is 1:1 meaning they can’t climb 18” above their connection point because that’s a 2:1 fall factor. Really you don’t want slack in your lead line (tether) anytime if you can help it. Any fall even a very short one can hurt. Maybe it will, maybe it won’t but the possibility of injury increases as slack increases.

 

[tailgunner]

 

[GeoFish]

Thanks guys.
My take away is;
1. First dont fall.
2. Move your tether each step or more often if possable.
If you can't do 1 & 2, use your pac seat. LOL.

 

[dalton916]

Y’all would kill more deer if you’d quit doing mental math in the tree.

 

[Samcirrus]

Thanks guys.
My take away is;
1. First dont fall.
2. Move your tether each step or more often if possable.
If you can't do 1 & 2, use your pac seat. LOL.

#2 sounds like the best non-throwball/preset climbing method out there....2T.....see!

 

[Weldabeast]

So can we use Paracord for friction hitches or not? I spent the extra money on 750 cord vs 550

I mean 750 x 1.5 is 1125 but u can actually x 3.8 cause ultralite, high speed, low drag gear equates to a higher strength percentage increase in loops and single strands...u would be 2xs smarter and probably 5xs cooler than anyone else on the internet with a factor of 17:1

 

[Weldabeast]