- Location
- Retired in Minneapolis
Re: SRT\'s
I'm sure that some combination of events could cause a hitch to slip and not grab.
I'm not advocating descent on a double line. It's been years since I did anything on a doubled line so I can't comment. All of my investigating has been on SRT.
Proper descent protocols have backups of varying sorts. At a minimum a brake hand on the bitter end of the rope placed below the hip. Leg and body wraps are sometimes used. Of course some sort of mechanical device is better in a lot of ways.
The biggest concern would be the accidental bumping of a hitch which causes it to start a slide. Would it grab again or slip to failure?
For many years I've read friction hitch tests from other rope access disciplines. The conclusion of almost all of the tests is that any of the spiraling hitches will slip/grab and stop quicker than a Prusik configuration. In some of the tests the Prusik performed at close to the same level as any of the other friction hitches tested.
Since the load on the Prusik is sort of perpendicular to the line it doesn't pull the knot around the line as easily as the spiraling hitches. In one report I read it went into the mechanics of the various hitches and described them like machines. That info disappeared when I had my hard drive reformatted.
In many discussions and articles that I've read Prusik's have fallen out of favor because of the irregular performance. Klemheist has a more regular performance.
As I was typing I realized that I have to clarify how I worked on SRT with a hitch to prevent a catastrophe. Before I would go off the ground I would spend time getting the hitch's tails set to the right length. After that I would do some short drop tests with slack in the hitch to make sure that it would grab. After several different tests I would use it in the tree for work. With every new hitch I would ALWAYS tie stopper knots in my climbing rope below my hitch. This is common practice in other rope access disciplines and not a bad idea for arbos.
There were a couple of hitches that would work when I tied them with one cord but not another. Some would work better with stiffer cord others using limp cord. At the time I never kept written records of what I found. What I did conlude was that finding a hitch that worked for me would be no different than finding one that would work on DdRT. Too many variables to test thoroughly without a research grant to pay for the testing.
When I was ready to take a longer descent to the ground I would use a friction device above my hitch as a backup safety. What I found was that all of the hitches would bite down too hard on the rope for a smooth descent. Also, the hitch would get very hot in my hand. Then I would change over and use the device for friction and the hitch as a backup.
I'm sure that some combination of events could cause a hitch to slip and not grab.
I'm not advocating descent on a double line. It's been years since I did anything on a doubled line so I can't comment. All of my investigating has been on SRT.
Proper descent protocols have backups of varying sorts. At a minimum a brake hand on the bitter end of the rope placed below the hip. Leg and body wraps are sometimes used. Of course some sort of mechanical device is better in a lot of ways.
The biggest concern would be the accidental bumping of a hitch which causes it to start a slide. Would it grab again or slip to failure?
For many years I've read friction hitch tests from other rope access disciplines. The conclusion of almost all of the tests is that any of the spiraling hitches will slip/grab and stop quicker than a Prusik configuration. In some of the tests the Prusik performed at close to the same level as any of the other friction hitches tested.
Since the load on the Prusik is sort of perpendicular to the line it doesn't pull the knot around the line as easily as the spiraling hitches. In one report I read it went into the mechanics of the various hitches and described them like machines. That info disappeared when I had my hard drive reformatted.
In many discussions and articles that I've read Prusik's have fallen out of favor because of the irregular performance. Klemheist has a more regular performance.
As I was typing I realized that I have to clarify how I worked on SRT with a hitch to prevent a catastrophe. Before I would go off the ground I would spend time getting the hitch's tails set to the right length. After that I would do some short drop tests with slack in the hitch to make sure that it would grab. After several different tests I would use it in the tree for work. With every new hitch I would ALWAYS tie stopper knots in my climbing rope below my hitch. This is common practice in other rope access disciplines and not a bad idea for arbos.
There were a couple of hitches that would work when I tied them with one cord but not another. Some would work better with stiffer cord others using limp cord. At the time I never kept written records of what I found. What I did conlude was that finding a hitch that worked for me would be no different than finding one that would work on DdRT. Too many variables to test thoroughly without a research grant to pay for the testing.
When I was ready to take a longer descent to the ground I would use a friction device above my hitch as a backup safety. What I found was that all of the hitches would bite down too hard on the rope for a smooth descent. Also, the hitch would get very hot in my hand. Then I would change over and use the device for friction and the hitch as a backup.
