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Friction Hitches
- Thread starter Brocky
- Start date
This exactly @Horn. Great explanation and visual @phatkawOk, take a look at how this is wrong....
View attachment 84860
See the loop starting to form in your tether? That can possibly and very probably will just keep getting longer and longer 'till you run out of mainline. The tag end will just keep getting gobbled up until...
Now if you look at that picture again, unhook the carabiner from where it's at and pull all the tag end out of that small loop in the hitch,, then you could hook your carabiner through there and you'd be in business.
I hope that makes sense?
Oh shoot dude I didn’t know you had a failure I must of skipped over that yesterday. This is exactly what I was trying to warn you about. I’m glad you didn’t get hurt.. sheesh.
Hey @Brocky... This could have been a personal message, but I figured I would ask ya in the presence of our friends here on the thread so as to get as much input as possible.
What do we believe is a decent MINIMUM SLIPPING STRENGTH profile for a friction hitch that we would use for climbing? Obviously, it has to hold the working load... but how much of a safety factor do we really need before it slips?
I can't find much published on it but I have asked a few experts whose opinions can be summarized as:
1. Friction hitches (as well as mechanical friction devices) should be used in minimal slack climbing systems only, and NOT in fall arrest systems. Anyone who is climbing with multiple feet of slack where a measurable fall is possible (like a rock climber) should be using dynamic rope (to minimize impact force on the climber) and a direct tie in, with no devices or friction hitches: the rope is tied to the climber and to the anchor.
2. If ya pull on a friction hitch with a strength test rig, the friction hitch will usually slip before something breaks. Anyone who's done enough tying and trying of friction hitches has experienced where it doesn't quite hold... and ya experience slow creeping slip... and so we will (generally) add a wrap and it holds better. And so we climb on it but we never really know how strong it is. For any combination of cord, rope and hitch, we rarely know the point at which the hitch will slip. We might climb on something for 10 years and never know if it slips at 300 lbs or 3000 lbs. And neither is necessarily unsafe to a rope climber, because we don't have a way to generate that force, because we're always on zero slack.
3. There is a class of climbers (which includes most hunters, including tree stand hunters who wear a harness) who aren't zero slack rope climbers but who use friction hitches in MINIMAL slack systems. They might have a foot of slack for example... they need a friction hitch with good performance, and they are going to need something that can absorb a short fall of that distance and need to know it won't slip. But they might never know for sure that their hitch holds until when and if they experienced that short fall after a treestand or platform collapse. And so... how strong does it need to be?
My opinion: 4x the working load is a decent number. My rationale: If a friction hitch is used properly, in a minimal slack system, it will never see a big load. So if I had a hitch that gave GREAT performance and still held an 800lbs load, with my butt being less than 200, I would use it. That has plenty of strength to absorb my one foot fall. If adding 2 wraps or using a different hitch got me to 1500lbs but it was hard to work with... I can't say I'd use it.
What's your opinion?
Anyone know of reputable publications on the topic?
Sent from my SM-G975U using Tapatalk
What do we believe is a decent MINIMUM SLIPPING STRENGTH profile for a friction hitch that we would use for climbing? Obviously, it has to hold the working load... but how much of a safety factor do we really need before it slips?
I can't find much published on it but I have asked a few experts whose opinions can be summarized as:
1. Friction hitches (as well as mechanical friction devices) should be used in minimal slack climbing systems only, and NOT in fall arrest systems. Anyone who is climbing with multiple feet of slack where a measurable fall is possible (like a rock climber) should be using dynamic rope (to minimize impact force on the climber) and a direct tie in, with no devices or friction hitches: the rope is tied to the climber and to the anchor.
2. If ya pull on a friction hitch with a strength test rig, the friction hitch will usually slip before something breaks. Anyone who's done enough tying and trying of friction hitches has experienced where it doesn't quite hold... and ya experience slow creeping slip... and so we will (generally) add a wrap and it holds better. And so we climb on it but we never really know how strong it is. For any combination of cord, rope and hitch, we rarely know the point at which the hitch will slip. We might climb on something for 10 years and never know if it slips at 300 lbs or 3000 lbs. And neither is necessarily unsafe to a rope climber, because we don't have a way to generate that force, because we're always on zero slack.
3. There is a class of climbers (which includes most hunters, including tree stand hunters who wear a harness) who aren't zero slack rope climbers but who use friction hitches in MINIMAL slack systems. They might have a foot of slack for example... they need a friction hitch with good performance, and they are going to need something that can absorb a short fall of that distance and need to know it won't slip. But they might never know for sure that their hitch holds until when and if they experienced that short fall after a treestand or platform collapse. And so... how strong does it need to be?
My opinion: 4x the working load is a decent number. My rationale: If a friction hitch is used properly, in a minimal slack system, it will never see a big load. So if I had a hitch that gave GREAT performance and still held an 800lbs load, with my butt being less than 200, I would use it. That has plenty of strength to absorb my one foot fall. If adding 2 wraps or using a different hitch got me to 1500lbs but it was hard to work with... I can't say I'd use it.
What's your opinion?
Anyone know of reputable publications on the topic?
Sent from my SM-G975U using Tapatalk
Great question. triggered a couple of questions for me, testing and defining slippage. Seems like that testing would need to be drop testing like is used for harnesses rather than progressive loading seen in pull test. Is slippage any movement or movement beyond a certain distance like say 2"? If there is an acceptable slip range, how much does that reduce felt loading in a fall event?
Are we talking static pull here or dynamic load? Many hitches will show higher “holding” characteristics when a slow constant static pull is applied but slip much much lower when dynamic loading is applied
With ASTM/TMA drop tests for fall arrest harnesses, the hitch would need to hold to a dynamic load of 1800 with less than 6” of slippage total. Any harness rope/ hitch combination that generates more than 1800 lbs of force is an automatic failure. Any hitch/rope combination that slips, further than 6” at 1800 lbs or less also constitutes a failure. So in my mind a hitch would need to hold to a dynamic load of 1800 lbs with minimal slip. There again work positioning requires the harness be pulled to at least 10x the rated load and able to sustain a fall of 24” without generating 900 lbs of force. So that would “suffice” in our intended uses. However why not make the hitch strong enough to handle the arrest standards? How easily a hitch works for advancing or for breaking under load is a moot point in that standard. That’s where all of this gets muddy. In climbing a weaker hitch that is easier to advance is often sought after. Some hitches are better at dynamic holding than others. Schwabisch didn’t meet the mark in my experience, but a distel and a standard prusik did. I believe Jerry at CGM experienced similar results. Strangely all three hitches hold very well in static pull tests. So again I’m inclined to say 1800 with minimal slip but the 1200 you suggested would work but only if that number was reached via dynamic loading.
Wouldn’t slippage decrease the force received by the body? Sort of like a poor man’s kong kisa?
Not proposing anything here, except for some conversation on this. I would think that slippage (as long as there is a stopper knot) could possibly lower the forces on a human body when a fall occurs when there is slack. Then again, I am not a physicist and not in the business of commercial saddle building.
Thoughts?
Not proposing anything here, except for some conversation on this. I would think that slippage (as long as there is a stopper knot) could possibly lower the forces on a human body when a fall occurs when there is slack. Then again, I am not a physicist and not in the business of commercial saddle building.
Thoughts?
Sterling has some testing results for their rope and cord combinations.
Slip would be a decrease in acceleration and would lower force however too much slip would still increase fall distance and could also burn through the rope or hitch cord and allow you to fall. Gotta find the happy median. A little slip to slow the fall but not so much that it melts the hitch cord until it’s stuck to the rope or breaks
Looks like 8mm distel on 7/16 htp is the way to go to me, based on those charts. Except 35 inches of slip...
I saw this. Noticed they didn’t test the 4 wrap schwabish on different cords also noticed the didn’t add any wraps to the distel… The VT on average had the highest static hold but not the best performance in dynamic loading….
A saddle isn't actually a fall arrest device... its a fall prevention device... and so although its great that some are testing their systems to that level, a fall implies some significant slack. Think about it: It's great that the manufacturer can feel confident that their system held that big fall... but its gonna have a hunter in it who might be unconscious with a broken back. Back to my point #1, that is an application for dynamic rope. And a saddle hunter never should have had that much slack. I hope you agree, and so as we spread the word and encourage hunters to manage slack, I am asking this question in the context of properly managed systems, same as arborist systems. My personal rule is that it should never be possible to fall more than about a foot, about the height of one step. I have tested that kind of short fall several times: when I feel the force of a one foot fall, I realize I never want to feel a 4ft fall. And in a one foot fall, I don't generate anywhere near 4x the working load. We have a ton of great hitches on this thread. I just wanna know what we think they need to hold for us o feel confident.
Here's my test setup: two identical friction hitches on a rope, set to hold in the opposite direction. Winch pulls to 4x the working load or about 4kn and then I remove tension. Of course, before I did so, I have already sat in it and bounced on it, simulating a one foot fall.
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Here's my test setup: two identical friction hitches on a rope, set to hold in the opposite direction. Winch pulls to 4x the working load or about 4kn and then I remove tension. Of course, before I did so, I have already sat in it and bounced on it, simulating a one foot fall.
Sent from my SM-G975U using Tapatalk
I’m trying to figure out how the 8mm cord held better on 9.8mm rope than it did on 11mm rope. Seems like someone at sterling was having trouble tying that distel
Yes and no John. I 100% agree on safely managing fall distances. In fact I preach this to an almost annoying degree on the site (as I’m sure lots of guys would agree that I do this).A saddle isn't actually a fall arrest device... its a fall prevention device... and so although its great that some are testing their systems to that level, a fall implies some significant slack. Think about it: It's great that the manufacturer can feel confident that their system held that big fall... but its gonna have a hunter in it who might be unconscious with a broken back. Back to my point #1, that is an application for dynamic rope. And a saddle hunter never should have had that much slack. I hope you agree, and so as we spread the word and encourage hunters to manage slack, I am asking this question in the context of properly managed systems, same as arborist systems. My personal rule is that it should never be possible to fall more than about a foot, about the height of one step. I have tested that kind of short fall several times: when I feel the force of a one foot fall, I realize I never want to feel a 4ft fall. And in a one foot fall, I don't generate anywhere near 4x the working load. We have a ton of great hitches on this thread. I just wanna know what we think they need to hold for us o feel confident.
Here's my test setup: two identical friction hitches on a rope, set to hold in the opposite direction. Winch pulls to 4x the working load or about 4kn and then I remove tension. Of course, before I did so, I have already sat in it and bounced on it, simulating a one foot fall.
Sent from my SM-G975U using Tapatalk
A saddle is a work positioning harness which is a little different than the simple fall restraint system and because tree work, line work and even saddle hunting have some potential dynamic loading capabilities, it does have to have some fall arresting capabilities. The standard for work positioning is 24” and 900 lbs of force. Also any slack at all can produce a “fall” or a dynamic event. It doesn’t take “significant” slack to fall. Although as we know more slack equals a greater fall…. When you stand up on your foot loop system to advance your hitches, if your bridge drops or slacks at all, guess what, that’s enough slack for a fall. Notice in Brocky’s post the significant differences in holding power/slippage of each hitch from its static load and its dynamic force load. That’s why a come along to a tree doesn’t produce an accurate measure of hitch holding. It like you described, just a test that is just a portion of the big picture and done to make someone feel better about their equipment
Not to get too far off track here but I tried a stitch on my latitude tether and the 7mm holds better than 6 or 5.5 Kevlar. Pretty sure it's the vaporline, it's just slick feeling. The 7 is the softest of the accessory cord too, that 5.5 will bite but in think it's got 2+ more wrapsI’m trying to figure out how the 8mm cord held better on 9.8mm rope than it did on 11mm rope. Seems like someone at sterling was having trouble tying that distel
The material that the hitch cord is made of absolutely plays a factor. 7mm technora/nylon seems to hold better than 7mm high tenacity polyester in my Bluewater hitches as well. In the sterling test though they used the same size and type hitch cord on different ropes and HTP material is the same in the 10 and 11mm ropes. Although the 11mm is a little stiffer (which is the only explanation I can come up with for those varying results)
When doing tree work, the friction hitch is used hundreds of times to make long and short adjustments. Having a hitch that moves easily and doesn’t slip makes it easier to keep from getting fatigued. I continually search for the “perfect” hitch, which grabs each time and hand tends easily, I want it to slide if dynamically loaded, rather than take the hit. I used the Kong Kisa shock absorber for a number of years when first starting to SRT climb on static rope, and found setting it to release just over my weight gave a short, smooth drop. I found that I dropped a foot and a half with the Kisa on a fall factor 1, which needs to be considered rather than the distance.
I found that hitches that don’t bind, hand tend easily, and a bonus if can be used to descend alone, will slip quicker than something like the Prusik, or Distel, etc.
I'm trying to visualize how/where you connected to with the Kisa while SRTing...
Draw me a picture?