Prusik Slipping

[John RB]

Thanks for the information. I have a few questions please.
1. Would you use the Sterling 6MM TRC with the Sterling Oplux and a double Michoacán or do you have a better recommendation?
2. Is the double Michoacán considered a fall arrest system? I use my tether while climbing and I need it to stop a fall with slack in the tether.
3. How does the strength of the double Michoacán compare to the prusik?
4. How long of a rope do I need for the double Michoacán?

Excellent questions. Pasting with responses:
1. Would you use the Sterling 6MM TRC with the Sterling Oplux and a double Michoacán or do you have a better recommendation?
# I would recommend tying that, but have not tried it. My recommendation is built on the manufacturer recommendations that TRC is recommended for use with Oplux. I do plan on doing exactly this. It's possible you might need a 6th turn on the Meech to hold in wet conditions.
2. Is the double Michoacán considered a fall arrest system? I use my tether while climbing and I need it to stop a fall with slack in the tether.
# I have not tested it in a fall arrest capacity. I am also not aware that we have a credible study that tests the other Suite of friction hitches such as a prusik in this same capacity. If anyone has such a reference, please advise. The details of the fall geometry could cause some incredible forces: 6inches and 6 feet are expontially different. My expectations would be that it outperforms other friction hitches because of its design and advantageous strength profile. My recommendation is to minimize slack. Also, static ropes should not be used in fall systems, because they have the potential to deliver more Force to the body. Dynamic ropes are better for systems which might absorb a fall.
3. How does the strength of the double Michoacán compare to the prusik?
# I have not executed a side by side test of those two hitches. But if we did so and determined that one started slipping at 300lb and one at 400lb, that wouldn't necessarily mean one is better. Slipping at high tension could help in fall arrest scenarios.
4. How long of a rope do I need for the double Michoacán ?
# I recommend 6ft.



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[wingnut]

Just a simple Schwabisch worked great for me on my tether. Holds great and easy to tend.

 

[Fl Canopy Stalker]

Excellent questions. Pasting with responses:
1. Would you use the Sterling 6MM TRC with the Sterling Oplux and a double Michoacán or do you have a better recommendation?
# I would recommend tying that, but have not tried it. My recommendation is built on the manufacturer recommendations that TRC is recommended for use with Oplux. I do plan on doing exactly this. It's possible you might need a 6th turn on the Meech to hold in wet conditions.
2. Is the double Michoacán considered a fall arrest system? I use my tether while climbing and I need it to stop a fall with slack in the tether.
# I have not tested it in a fall arrest capacity. I am also not aware that we have a credible study that tests the other Suite of friction hitches such as a prusik in this same capacity. If anyone has such a reference, please advise. The details of the fall geometry could cause some incredible forces: 6inches and 6 feet are expontially different. My expectations would be that it outperforms other friction hitches because of its design and advantageous strength profile. My recommendation is to minimize slack. Also, static ropes should not be used in fall systems, because they have the potential to deliver more Force to the body. Dynamic ropes are better for systems which might absorb a fall.
3. How does the strength of the double Michoacán compare to the prusik?
# I have not executed a side by side test of those two hitches. But if we did so and determined that one started slipping at 300lb and one at 400lb, that wouldn't necessarily mean one is better. Slipping at high tension could help in fall arrest scenarios.
4. How long of a rope do I need for the double Michoacán ?
# I recommend 6ft.



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Hey JRB, I don’t know if this counts as a study or not, but I would like to add a little something to this as it pertains to safety…. Also I am not posting to sell or send anyone to view our channel, and I cannot answer for studies on the double Michoacán or some of the other hitches, but I can tell you that every drop test we perform for our saddles, utilize a low elongation 10mm tether with a 7mm prusik (3 wrap). Both are factory sewn. I’ve seen fall forces as low as 1163 lbs from a 1.5:1 220 lbs drop and I have seen forces that far exceeded 2000 lbs from a 2:1 fall with a 300 lbs dropped. The old school 3 wrap prusik did slide like 8 inches on a 300lbs drop and it burnt the cord pretty good but it held. In the 220 lbs drops of approximately 4’ it slid less than 3” and didn’t even melt the cord. I feel confident saying a prusik loop at 70% of the main rope will definitely arrest a fall. HOWEVER saddles are not fall arrest harnesses and slack should never be allowed into the system. No fall is acceptable from a hunting saddle. Yes dynamic ropes can and do reduce forces but it will not change that all the force will land in your back, hips and pelvic regions and can cause serious injury or death. I truly appreciate you pointing out that static lines are not made to fall on, but I want to add that saddles are not made to fall on either. I mean since the guy specifically mentioned arresting a fall with the gear. Thank you again for the valuable input and suggestions for everyone…(as per usual).

 

[GeoFish]

Cruzr sells a 21" sewn eye to eye hitch cord in TRC that works well on Oplux. After I bought mine it was problem solved.

Thanks. I am ordering two of them.
I still have not gotten a response from Wild Edge!

 

[John RB]

Hey JRB, I don’t know if this counts as a study or not, but I would like to add a little something to this as it pertains to safety…. Also I am not posting to sell or send anyone to view our channel, and I cannot answer for studies on the double Michoacán or some of the other hitches, but I can tell you that every drop test we perform for our saddles, utilize a low elongation 10mm tether with a 7mm prusik (3 wrap). Both are factory sewn. I’ve seen fall forces as low as 1163 lbs from a 1.5:1 220 lbs drop and I have seen forces that far exceeded 2000 lbs from a 2:1 fall with a 300 lbs dropped. The old school 3 wrap prusik did slide like 8 inches on a 300lbs drop and it burnt the cord pretty good but it held. In the 220 lbs drops of approximately 4’ it slid less than 3” and didn’t even melt the cord. I feel confident saying a prusik loop at 70% of the main rope will definitely arrest a fall. HOWEVER saddles are not fall arrest harnesses and slack should never be allowed into the system. No fall is acceptable from a hunting saddle. Yes dynamic ropes can and do reduce forces but it will not change that all the force will land in your back, hips and pelvic regions and can cause serious injury or death. I truly appreciate you pointing out that static lines are not made to fall on, but I want to add that saddles are not made to fall on either. I mean since the guy specifically mentioned arresting a fall with the gear. Thank you again for the valuable input and suggestions for everyone…(as per usual).

Great info. If you wouldn't mind, could you message me here or on FB? If you have drop test gear, I have a test pr two that i am willing to pay for...

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[El Diablo Amarillo]

I was out today trying out my Dryad and a ring of steps. I was only 1.5 feet of the ground.
I have Sterling Oplux tether with a 6" factory sewn eye and I am using a Sterling 6.8MM T-Vac prusik with a 13" factor sewn loop. I have used this before some without a issue.
Then the first time the prusik slipped about 6" a little later the prusik slipped all the way to the stopper knot as I went to the ground.
I have not had this tether very long, any ideas as to why?
Now it is 88 degrees out today and I may have gotten some sweat on the rope???

Another trick you can try is retying the prussic and putting a half twist or up to a full twist on the last wrap. Since a Prussic is a bidirectional hitch and you seem to only have an issue when it loads in the 1 direction so no need to put twists on both sides of the finish unless both directions are problematic. Arborists use that trick often to fine tune any style hitch for production climbing. Make sure when you have the hitch apart there is no evidence of glazing on the hitch cord or what its tied around.

 

[Brocky]

 

[BlindBuck]

OP:

I had a similar experience when I used OpLux with that exact prusik. At first it worked great, I "believe" what happens is the core of OpLux gets crushed and goes almost flat very quickly when used as a tether((I'm certainly not a rope expert though)(plenty of people use it and trust it.)). Here is a photo I took from the ground after my prusik slipped. You can see it is really elongating thus shrinking the diameter of the rope (the prusik looks nearly the same diameter). After having this happen I went back to using Samson Predator rope for both my tether and linesman as I really don't care how good something packs if I can't trust it.

The thing about the diameter makes sense though, but again mine held so tight to begin with my tender didn't work and I would have to loosen the prusik to adjust the location.

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[Brocky]

The cover looks to be bunching below the hitch, normal for most ropes. If the rope end is sealed it needs to be cut off to release the extra cover. Start from the another end and milk whole length to get the slack out. There should be a uniform diameter after that. The hitch should be more consistent also.

 

[BlindBuck]

The cover looks to be bunching below the hitch, normal for most ropes. If the rope end is sealed it needs to be cut off to release the extra cover. Start from the another end and milk whole length to get the slack out. There should be a uniform diameter after that. The hitch should be more consistent also.

I'll try that (I might have pitched the rope). The core of the rope where my prusik rode didn't feel near like the last few feet where it never touched though. It was much softer feeling, maybe that is normal with OpLux, but my Predator line does not feel like that.. What I do know is when that slipped it really shocked/startled me.


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[Brocky]

The Predator is a different type of construction, a double braid, the cover and core work together. Oplux is a kernmantle, the strength is in the core, the cover just protects it. The last couple feet probably haven’t been squeezed by the hitch.

 

[GeoFish]

OP:

I had a similar experience when I used OpLux with that exact prusik. At first it worked great, I "believe" what happens is the core of OpLux gets crushed and goes almost flat very quickly when used as a tether((I'm certainly not a rope expert though)(plenty of people use it and trust it.)). Here is a photo I took from the ground after my prusik slipped. You can see it is really elongating thus shrinking the diameter of the rope (the prusik looks nearly the same diameter). After having this happen I went back to using Samson Predator rope for both my tether and linesman as I really don't care how good something packs if I can't trust it.

The thing about the diameter makes sense though, but again mine held so tight to begin with my tender didn't work and I would have to loosen the prusik to adjust the location.

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Thanks, I just checked my Oplux tether and the diameter of the rope varies, looks like where the prusik dug in it is smaller. If the 6.8mm was marginal when the Oplux was at 8mm and if the Oplux gets smaller, wouldn't this increase the issue with the prusik rope being too large?
Not sure if I should keep the Oplux and use the 6mm T-VAC or go with the Predator.
Are you using the 6.8mm T-VAC prusik with the Predator?

 

[BlindBuck]

Thanks, I just checked my Oplux tether and the diameter of the rope varies, looks like where the prusik dug in it is smaller. If the 6.8mm was marginal when the Oplux was at 8mm and if the Oplux gets smaller, wouldn't this increase the issue with the prusik rope being too large?
Not sure if I should keep the Oplux and use the 6mm T-VAC or go with the Predator.
Are you using the 6.8mm T-VAC prusik with the Predator?

I would think so.

Apparently from the other guy's post that is fairly common and rope needs milked due to the construction. You would think when you are buying something that is 7.5' with a sewn eye and it has prusik attached along with the end being melted it would have already been done. I totally understand if I buy 80' cut it in half that I need to milk the rope . Irrespective if I can milk the OpLux melt the end and get a smaller prusik I'll never trust that rope in my brain again. The core is definitely different where the prusik would be. Like I said I'm not a rope expert which is why I bought that kit to try OpLux in the first place.

No I have a 8mm one with two sewn eyes for my prusik that I got from EWO.

8mm Flex Hitch Cord Eye to Eye 28″

Sterling 8mm Flex Hitch Cord Eye to Eye 28″. Works well with Sterling 10mm HTP, Samson Predator 11.4mm, and other ropes like TETHRD tethers.

doublesteps.com

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[Fl Canopy Stalker]

Thanks, I just checked my Oplux tether and the diameter of the rope varies, looks like where the prusik dug in it is smaller. If the 6.8mm was marginal when the Oplux was at 8mm and if the Oplux gets smaller, wouldn't this increase the issue with the prusik rope being too large?
Not sure if I should keep the Oplux and use the 6mm T-VAC or go with the Predator.
Are you using the 6.8mm T-VAC prusik with the Predator?

8mm cord works great on 11mm rope such as the predator rope. If you’re trying to gauge if a hitch cord will reliably bite onto a main line (tether or climbing rope) take the diameter of the hitch cord and divide it by the diameter of the main line. If the answer is .60 to .80 it’ll bite the main line reliably. If it’s lower than .60 it’s too small and you will have trouble getting it to move after it bites. If it’s above .80 ten the cord is too large and it might bite but it won’t bite reliably every time. The optimal percentage for grip and slip is around .68 to .74.
So using 8mm on 11 mm rope will be around .72 so that is optimal. When someone uses 6.8mm on 8mm rope it’s .85 which is far out of spec. If you use 6.8 on 11 mm it will bite. It’s .61 but that is at the very bottom of the acceptable percentage so getting it to adjust will be hard. I hope that helps. Also any rope that is double braided or has a kermantle cover has the ability to have a little slack in the cover that can be milked out. In my experience that doesn’t stop the prusik from biting, it actually stops the prusik from sliding as well because as it pinches onto the cover, it’ll milk the excess slack toward the bottom of the rope. You will know when you have slack because the whole tether will be one size until you get an inch or Two from the stopper knot and it’ll be bigger sometimes even bunched looking.

 

[Brocky]

I haven’t heard of that precise of ratio of hitch cord to main line, always used 2mm-3mm less diameter cord to rope size. Type of materials, bumpiness of covers, and stiffness of the cord’s braid come into play along with compatible diameter.

 

[John RB]

I have tested that 60 to 80% ratio on a lot of cords and ropes and a lot of friction hitches. Here are some observations:
1. An exception: For the Bachmann, a very useful and under utilized friction hitch, a 55-60ish% ratio is better. I climbed for many years in an MRS system with 5mm cord on 8mm rope. So smooth. So secure.
2. The stiffness of the cord has a big effect on the hold: For example, I can make some solid friction hitches using standard and flexible Sterling 7mm accessory cord on an 8mm rope, an 87% ratio. I can even take an EXTREMELY flexible 8mm Yale Beeline and get it to hold on anything from 8mm to 11mm rope. That surprised me. And some of my STIFF 6mm cords wouldn't grab as well as flexible 6mm cords, in side by side testing on 8mm rope. Incidentally, the JRB Climbing Method is ideal for side by side testing cuz i use 2 hitches in parallel and can compare performance cuz they take the same load.
3. After experiencing slippage during the middle of a rainy day hunt, i always wet test my hitches now. Typically, that testing will cause me to add a wrap.

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[Fl Canopy Stalker]

I haven’t heard of that precise of ratio of hitch cord to main line, always used 2mm-3mm less diameter cord to rope size. Type of materials, bumpiness of covers, and stiffness of the cord’s braid come into play along with compatible diameter.

The suggestion is 2 to 3 mm but you wouldn’t want to run a 10mm cord on a 12mm lead line. 60 to 80% of the size of the lead line for correct friction ratio. (That should keep it 2 to 3mm different depending on size). As you said some lead lines are very stiff and require the line close to the 60-70% for reliable bite. Some are very soft and will slide better around the 75% mark. I know that technora or Kevlar are great for high heat applications but personally I like polyester for a hitch cord better because it tends to have better bite characteristics even when wet. My original set up was 11mm Samson predator with 8mm bail out for my prusik. Then I tried the Oplux tether craze with 6mm trc. Technora (Japanese Kevlar) is strong and super low stretch but I wasn’t impressed with its handling characteristics. It was great that it is small and light but flex fatigue and sunlight wreck havoc on Kevlar more than nearly any other synthetic rope material. So I went up to 9 or 10mm pro tac (which is polyester/nylon blend) it’s stronger than oplux and nearly as small. The 10mm allows me to use the old ropeman 1 instead of the kong… The only draw back is it isn’t as pliable so the knots don’t tie down as small and tight. But my stopper knot has never slipped and with 7mm hitch cord it bites incredibly well. I plan on sticking with that combo for the foreseeable future.

 

[Fl Canopy Stalker]

I have tested that 60 to 80% ratio on a lot of cords and ropes and a lot of friction hitches. Here are some observations:
1. An exception: For the Bachmann, a very useful and under utilized friction hitch, a 55-60ish% ratio is better. I climbed for many years in an MRS system with 5mm cord on 8mm rope. So smooth. So secure.
2. The stiffness of the cord has a big effect on the hold: For example, I can make some solid friction hitches using standard and flexible Sterling 7mm accessory cord on an 8mm rope, an 87% ratio. I can even take an EXTREMELY flexible 8mm Yale Beeline and get it to hold on anything from 8mm to 11mm rope. That surprised me. And some of my STIFF 6mm cords wouldn't grab as well as flexible 6mm cords, in side by side testing on 8mm rope. Incidentally, the JRB Climbing Method is ideal for side by side testing cuz i use 2 hitches in parallel and can compare performance cuz they take the same load.
3. After experiencing slippage during the middle of a rainy day hunt, i always wet test my hitches now. Typically, that testing will cause me to add a wrap.

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You were using an 8mm rope on a moving rope system? Were you having to use hand ascenders to pull? I tried getting 3/8” double braid for MRS once and it was almost sawing into the tree. For me with MRS, the larger diameter of the rope, the easier it moves through the crotch.

 

[John RB]

You were using an 8mm rope on a moving rope system? Were you having to use hand ascenders to pull? I tried getting 3/8” double braid for MRS once and it was almost sawing into the tree. For me with MRS, the larger diameter of the rope, the easier it moves through the crotch.

Yes. Either a mechanical hand ascender or a DIY rope grab i made with a friction hitch or a leg loop. Because i climb a lot of leaners. No hip thrust. And i have an inline friction saver, DIY design. So the Rope never touched the tree. It was very smooth. And my rope never got damaged

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[John RB]

You were using an 8mm rope on a moving rope system? Were you having to use hand ascenders to pull? I tried getting 3/8” double braid for MRS once and it was almost sawing into the tree. For me with MRS, the larger diameter of the rope, the easier it moves through the crotch.

And so with your MRS experience, you should appreciate how EASY and efficient this climb is. No friction. No moving rope. 100% efficient on the rising move. And twice as fast, because it is a 1:1 instead of a 2:1. No knots to tie. Clip and climb. I literally CAN'T use MRS now. I am spoiled.

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