Rope Rigging

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Postby ek » Dec 21, 2007 11:42 pm

On the topic of new tricks to learn: as I mentioned earlier in the thread, I am wondering if there are any significant disadvantages to rigging an unrebelayed drop with a fixed brake lower (i.e. with a securely tied off rack or other descender at the top), leaving half the rope above the drop. This seems like a real good idea to me, as if it becomes necessary to lower someone, it is already set up. I wouldn't always rig this way, but given the serious consequences associated with being stuck on rope for a significant time, and the serious consequences of being stuck on rope where there is flowing water, I think there are many situations where it would make a whole lot of sense to rig like this.

Even in cases where rope for lowering is not available, rigging near the end of the rope with a fixed brake lower and *not* tying a knot at the end of the rope would provide for untying the anchor under load once a separate lowering line is attached to the load, or a prusik or rope clamp is attached to the rope.

The additional gear needed for this would be minimal--just an HMS carabiner, if a Munter hitch is used as the descender. When it comes down to it, rigging with this method might not end up using more carabiners. Consider the following three cases.

Case 1:

When one rigs with webbing and attaches the rope with a knot, a carabiner is used. If an HMS carabiner is brought along instead of whatever other kind, a fixed brake lower with a Munter hitch can be rigged with the same amount of gear.

Case 2:

Where one rigs with a tensionless hitch in the middle of the rope in the usual way with a carabiner, one could instead rig with the *end* of the rope (e.g. with a carabinerless tensionless hitch or bowline or rethreaded figure-eight on a coil to keep the anchor from slipping down), and then tie a figure-eight on the line as it comes out from this anchor, attach the HMS carabiner to this figure-eight, and tie a Munter hitch on the HMS carabiner in the middle of the rope. This would also use the same amount of gear, and would automatically brake once all the rope is out, should a mistake have been made and the rope not be long enough. In cases where one expects to give out all the rope and have it still be taught, one could tie an inline figure-eight or alpine butterfly instead of the figure-eight on a bight.

Case 3:

Where one rigs in any other way (e.g. with an endline loop around an anchor point, with a endline double loop knot clipped into two bolts), one could tie the figure-eight (or other midline loop knot) below the anchor on the rope and attach the HMS carabiner to it, with the Munter hitch tied on it in the middle of the rope, just as in the previous case. Here, this would use more gear--exactly one more carabiner.

Drawbacks:

(1) Some complexity is added. Tying the Munter hitch wrong, or locking it off incorrectly, could result in death. Many cavers are not familiar with the Munter hitch, and many more don't know how to lock if off correctly. At best, incorrectly locking off a Munter hitch makes it impossible to unlock. Furthermore, many cavers don't know how to correctly use a Munter hitch. Recently I was teaching a friend of mine who has belayed with belay plates for years how to belay with a Munter hitch. He caught my fall fine but when he went to lower me he ended up dropping me to the floor.

(2) You have to bring HMS carabiners, which tend not to invert easily in most bolt hangers. HMS carabiners are often weaker than D and offset-D carabiners too, but those types also tend not to invert easily in bolt hangers and oval carabiners, which tend also to be weaker but which invert easily in bolt hangers, are often used. Anyway, you have to bring at least two kinds of carabiner, and ultimately that translates into bringing more gear.

But wait...do you really need to tie your Munter hitches on Munter-compatible (HMS) carabiners? Typically the Munter hitch is used to belay, and when belaying the load is expected to be able to change direction. Thus the Munter must be able to invert and the carabiner must be big enough on top to allow this to happen. But when using a Munter for emergency lowering only, one could simply tie it on any old (locking!) carabiner and make sure it is tied in the lowering form.

(3) The Munter hitch, once tied off, is (like) a knot and reduces the strength of the rope...but this rarely, if ever, really matters in cases where you'd be wanting to rig like this.

(4) To be useful for lowering, lots of extra rope must be brought--but if you're bringing it anyway, why not rig like this?

(5) Putting the Munter hitch on a figure-eight tied in the rope itself may not always position it in a safe or usable way.

(6) If you are forced to tie two ropes together in mid-pitch for the drop (EDIT: and therefore are forced to attach at least a third rope to make sure there is twice as much rope as the length of the drop?), this could not be used to lower all the way (though it could still be used to get the load off the anchor and onto something else), because the knot would have to pass the Munter hitch (which can happen if the HMS carabiner is large enough, but never when the Munter hitch is actually loaded). But then if you're tying ropes together, you probably don't have enough rope to want to use this method anyway.

(7) The tensionless hitch is already available, and in cases where the environment permits its use, it has some advantages over the method I propose. A tensionless hitch around a round object has no problem passing knots and preserves 100% of the rope's strength. It also is more widely recognized than the method I propose, and fundamentally simpler. If tied correctly then *usually* it can be used to lower a load. If tied incorrectly, a safe anchor usually still results. While it is rare to practice lowering loads on tensionless hitches, and common to practice use of the Munter hitch, one could remedy this situation by practicing lowering loads on tensionless hitches. Lowering loads on tensionless hitches does not twist the rope and with most anchor points doesn't abrade it significantly. A tensionless hitch takes less rope than a tensionless hitch holding up a Munter hitch.

On the other hand, the Munter hitch has the distinct advantage in lowering that its operation is *way* more predictable, does not abrade the anchor point, and does not require unwrapping the rope from the anchor point. A belay on the same rope, if desired, can more easily be applied to a Munter hitch.

(8) If you're using quicklinks or non-locking carabiners to rig then replacing them with locking carabiners of any kind (HMS or not) is going to add significant weight and bulk to your kit. But then, if you care so much about weight and bulk, you're not doing this anyway because you're not bringing twice as much rope as you need.

NZ or anybody...what do you think of this?
Eliah Kagan
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Postby NZcaver » Dec 22, 2007 11:04 am

ek wrote:On the topic of new tricks to learn: as I mentioned earlier in the thread, I am wondering if there are any significant disadvantages to rigging an unrebelayed drop with a fixed brake lower (i.e. with a securely tied off rack or other descender at the top), leaving half the rope above the drop.

A releasable anchoring method is fundamentally a good idea I think. Practically, it is seldom done. Why? Because it takes extra time/thought/effort (and often more equipment) - and most riggers probably weigh this up against the extremely remote possibility of it actually being needed to lower somebody.

Although I've rigged numerous releasable systems before, I'm as guilty as anyone in "not bothering" to do it by default. Often the experience level of the group and any special challenges related to the activity and/or location will dictate to me whether this extra precaution may be especially warranted. I can think of 3 examples which spring to mind.

When I attended my first abseiling (rappelling) instructor's course in the late 80's, we were taught to tie off the main static rope (doubled) with locked Munter hitches - leaving enough rope at the top to potentially lower a stuck or otherwise immobile student the full length of the drop. Each student was also belayed separately using a dynamic rope and Munter hitch operated from the top.

When the NCRC teaches pickoffs in the gym etc, in case you haven't noticed the ropes are usually looped up to the ceiling and then tied off with Munters down near the floor - with plenty of extra rope to lower students. With this type of complicated/confusing/potentially frustrating activity, the releasable anchor system gets used far more frequently than in your average rigging situation.

The third example is where a friend of mine was canyoneering recently, and his colleague got into difficulty stuck/exhausted on the rope while trying to climb out. (I will spare you the details, this is not an accident report.) My friend tried unsuccessfully to assist him directly, so he climbed to the top. Fearing harness hang syndrome, he tied an extra length of rope onto the end of the tensionless hitch around the BFT and lowered the subject back into the river. My friend then chose to seek help. The fire dept tech rescue guys arrived quickly, and the subject was successfully rescued.

I guess that's another plus for the good old keep-it-simple tensionless hitch. :cool:
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re: Rope Rigging

Postby ek » Dec 22, 2007 12:45 pm

I do recall that Munter hitches were tied and locked off to lower us during the SRT skills test and pickoff practice.

Before anybody goes vertical caving with SUOC for the first time, they have to demonstrate some basic skills: climbing, rappelling, changing over from climb to rappel, changing over from rappel to climb, controlling their own bottom tension near the ground, and downclimbing. (If you're already experienced and claim to know these things, we believe you and don't make you show us if you don't want to.) We set up a fixed brake lower, generally with a rack, for people who are practicing, so that (1) they can get the hang of climbing a longer distance than might be available, and (2) so that they can be lowered if they have trouble.

Not too long ago, someone who was new to vertical caving had demonstrated all these skills. He had taken some time to learn the changeovers (as many people do), but having learned them he demonstrated them in an efficient and correct manner. We have one loaner Mitchell system that is rarely used, and lots and lots of frog gear, so he was using a frog.

Actually, many people who are new to vertical caving demonstrate these skills and go vertical caving. What is different in this particular case was that after we rappelled into the cave, caved the cave, and came back to the entrance, and he got on rope, he told me that he didn't remember how to climb out.

I can only imagine the "deer in the headlights" look that must have been on my face after he said that. Fortunately it came back to him when I mentioned sitting down and standing up and sitting down and standing up...

This person had important matters to attend to the night before, and wasn't able to get any sleep. This sort of thing never reduces risk, and perhaps it was a bad idea for me to let him go on the trip under those conditions. Once he started climbing, he did so very well, as he had when he was training. His form was excellent and he climbed quickly to the top.

I mention this story because it is one of the things that has made me question how extremely remote the possibility really is of having to lower someone. Certainly rigging with a fixed brake lower for an actual cave is no substitute for everybody knowing what they are doing...but maybe it would partially mitigate the dangers associated with me making a mistake in judging whether or not someone knows what they're doing.

Other than that, you could get hit by a rock or something and rendered immobile on ascent...or any of the other classic things that can happen to someone to keep them from getting all the way out or changing over. And when it comes to improvising solutions even to simple problems on rope (e.g. the tail of the rope is caught on something above you and you can't keep rappelling, your microrack is stuck on a knot on a muddy, swollen rope and you can't get it off), I find that it's in-cave experience that provides for that more than any practice in a tree.

NZcaver wrote:The third example is where a friend of mine was canyoneering recently, and his colleague got into difficulty stuck/exhausted on the rope while trying to climb out. (I will spare you the details, this is not an accident report.) My friend tried unsuccessfully to assist him directly, so he climbed to the top. Fearing harness hang syndrome, he tied an extra length of rope onto the end of the tensionless hitch around the BFT and lowered the subject back into the river. My friend then chose to seek help. The fire dept tech rescue guys arrived quickly, and the subject was successfully rescued.

That reminds me of "the releasable abseil". (Though I'd be worried about what happens if the left bolt blows out during lowering!)

This also suggests another reason to rig with a fixed brake lower--that way, provided that good communication is maintained, you can send down very close to what you think is exactly enough rope...if it turns out not to have been enough, the first one down doesn't have to change over, but merely has to call "down rope". This could effectively be used to prevent excess rope from accumulating at the bottom of the drop, in cases where that matters.

Ironically, the origin of my idea of rigging with a fixed brake lower in a manner that takes up just one more carabiner (if that) was when I did it as a simple, improvised solution. The evening after the NRO in Massachusetts, two friends and I were on our way back to Syracuse and decided to stop by Gage Cave for a swim. One of my friends had not rappelled before. (For those who don't cave in the northeast, Gage Cave has a fixed ladder rigged for the entrance drop.) After the mile hike to the cave, I realized that I had forgotten the rope pad and the webbing. We used some shirts as rope pads. I had a 20' length in my pack, as I always do, but I preferred not use that up before going in the cave, in case it might be needed. So I pulled some rope out of the rope bag's grommet, tied a tensionless hitch around the tree, pulled the bag down right to the drop, tied a figure-eight in the rope (between the anchor and the rope bag's grommet), and used that as the anchor to belay him down the ladder with a Munter hitch. Then I locked off the hitch and my other friend and I rappelled down. Especially in those dark (outside) conditions, I think it worked better than belaying directly from the tree, which is what I was going to have done if I had remember the extra webbing. (For a belay climbing out, we each used a single ascender rigged for
"progression with the aid of a structure"--i.e. attached directly to our maillons with a locked carabiner through the top holes of the device and around the rope.)
Eliah Kagan
NSS 57892
Syracuse University Outing Club

Fund vital White Nose Syndrome research--donate to the NSS and select the WNS Rapid Response Fund.
Facebook users can also donate here.
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ek
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