Rope Rigging

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Postby NZcaver » Dec 18, 2007 10:48 am

I'm with Ralph on this.

But then I originally learned the "proper" way to rig to natural anchors is by using webbing. I'm not saying the tensionless hitch doesn't have it's merits too - I just try not to use it as my automatic default method like many others do.
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Postby wyandottecaver » Dec 18, 2007 8:20 pm

having attended Bruce's On Rope course and NCRC courses (weekend and weeklong) I find that at least in my experiance, most people rig webbing for rescue and use tensionless (or 1 wrap and go) for "sport" applications. While it is nice to drive up to a cave with a NCRC trailer, the reality is I have a hard enough time convincing people that hard-used ropes do "die" for caving purposes...hopefully before taking you with it!. Even I rarely use a webbing anchor for tree rigs for normal caving loads.
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Postby ek » Dec 19, 2007 4:56 am

But NCRC does teach and advocate use of tensionless hitches alongside wrap-3 pull-2's and basket rigging. I think the reason why webbing tends to be used more often in rescue rigging is that in rescue an anchor is often used to rig more than one thing, or something other than a fixed rope, rendering a tensionless hitch inapplicable. But that doesn't mean that tensionless hitches are somehow weaker or less secure. While the breaking strength of a wrap-3 pull-2 or basket rigging is very high, you have to tie a knot in the rope to attach it to such an anchor, rendering this way of anchoring for a single, fixed rope weaker than a properly tied tensionless hitch.

But then, who cares? They're all quite strong enough for most applications (and all sport caving applications).

In "Considerations for Rope Rescue in 2002" Ken Laidlaw describes the use of a "soft interface" (p.16) to preserve the full strength of a rope attached to an anchor with a knot. A 3-wrap Prusik is tied to the rope in front of (i.e. farther from the anchor than) the knot and attached to the anchor. The knot is also attached to the anchor. When the rope is loaded the Prusik takes all the load. When the load becomes very high the Prusik slips and shares the load with the knot.

http://www.basarc.org/papers/roperescue ... ue2002.pdf

So it is possible to rig with webbing and maintain full rope strength. Compared to a tensionless hitch (rigged with a carabiner), a basket rig with a soft interface would require webbing (or a long pre-sewn sling) and a loop of accessory cord, but is probably at least as fast to rig, with the only drawback being that it cannot be untied under load.

One benefit that I can see of rigging with webbing is that you then automatically have something to clip into at the anchor.
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Postby NZcaver » Dec 19, 2007 11:18 am

The tensionless hitch is great, but you're forgetting the actual anchor(s) will dictate the type of interface you should be using - at least to a point. If a conveniently-located single bombproof tree/rock will do the job, and rotational torque won't cause any issues, then go ahead and use a tensionless. Assuming you have the rope to spare, of course.

On the other hand, carrying a little webbing to rig with doesn't mean you have to pull up to a cave with an "entire NCRC trailer." Each of my rope bags contain 1 or 2 lengths of webbing, a carabiner, a couple of pads, and of course the rope. If I choose to use the webbing option, there it is. Simple.
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Postby ek » Dec 19, 2007 12:04 pm

My understanding is that there are also situations where there is no single bombproof anchor, and the tensionless hitch is still a reasonable option as part of the anchor. For instance, suppose I have decided to rig a load-sharing anchor off of the bases of two trees that look real good but are a bit thin to consider bomber. Then I might take a short piece of low-stretch rope and tie a tensionless hitch to each one and a figure-eight on a bight in the middle (of course keeping the angle of the "V" as low as possible). Then I could attach the pit rope and other items to the figure-eight.

NZcaver wrote:If a conveniently-located single bombproof tree/rock

I am curious about using a tensionless hitch on a rock. Since rocks tend not to be rounded, I was always taught that rocks should be rigged with a loop knot in the rope (e.g. bowline, rethreaded figure-eight, double bowline a.k.a. bowline tied on a bight), or with webbing. Is this not so?
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Postby Tim White » Dec 19, 2007 12:31 pm

ek wrote:I am curious about using a tensionless hitch on a rock. Since rocks tend not to be rounded, I was always taught that rocks should be rigged with a loop knot in the rope (e.g. bowline, rethreaded figure-eight, double bowline a.k.a. bowline tied on a bight), or with webbing. Is this not so?


There is that word again...always. :tonguecheek:


If the rock does not cause a risk of damaging the rope due to sharp edges, etc., then why not use a tensionless hitch? (or as NZ said if the rotational torque is not going to twist the rock out of the ground)
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Postby ek » Dec 19, 2007 12:54 pm

I was always taught that. That's not quite the same as having been taught it was always so... :tonguecheek:

Tim White wrote:If the rock does not cause a risk of damaging the rope due to sharp edges, etc., then why not use a tensionless hitch? (or as NZ said if the rotational torque is not going to twist the rock out of the ground)

Good point--I will keep this in mind.
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Postby Tim White » Dec 19, 2007 1:16 pm

ek wrote:I was always taught that. That's not quite the same as having been taught it was always so...

:exactly:
I know, but so often those of us who always teach something over and over have a tendency to lead others to think that it should always be done that way.

ek- great discussion going on here...this is how we all learn!
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Postby wyandottecaver » Dec 20, 2007 7:32 pm

I often use tensionless rigs on rocks. The most extreme example is on an in-cave pit where there were no "bomber" rocks close to the pit edge. I ran the rope along the cave floor for about 50' to a BFR at the far end of the room. I had taken the "slack" out of the rope but a small loose bend remained just before the rig point. Several people did the 100' pit. When I derigged, the bend was still there. Just the friction of 50' of rope laying on the floor was enough "anchor".

This works in reverse too. Try hauling 1 or 2 people up and over a pit lip with multiple ropes (such as from Z rig systems) going over the lip. They say gravity works, and so does friction!
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Postby Wormster » Dec 21, 2007 12:04 pm

I *thought* the way to rig safely was:

Backup anchor on GBFO tree / rock

Separated 2 part* pitchhead (minimum)

*y hang on your preferred knot bowline of fig 8

that way IF you come a cropper and your y hang fails you have your backup to get you out of trouble.

having just one anchor point on a pitchead strickes me as very dangerous and somewhere approaching dawinism.

just my 2c's worth.
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Postby ek » Dec 21, 2007 1:35 pm

Suppose there is a huge rock feature that's not going anywhere. Consider the following rigging options:

(1) Tie around the whole thing.
(2) Put two bolts in and attach the rope to those.

Few would dispute that claim that correctly placing two bolts of modern construction in good, solid rock and rigging off both of them with a load sharing anchor that minimizes extension is a very acceptable way to rig. Option 2 fits this description and is redundant. Option 1 is not even redundant. Which is safer?

Suppose you are considering backing up your huge rock feature tie-off with another huge rock feature tie-off. Would you really put two more bolts in, if you were rigging with bolts? Would you even use them if they were already there?

I would rather hang my life off a single bomber anchor point--that is, one with no substantial chance of failing (e.g. a large living tree that has survived previous caver rigging, rescue rigging, and hurricanes; a huge boulder; a large, solid rock feature that's been there a real long time), than *any* number of anchor points that *should* be good enough...but maybe, just maybe, aren't (e.g. bolts, rock and ice protection; boulders that are probably attached and probably heavy enough, probably; small trees). When rigging off the latter kind, I always have at least two--if rock or ice protection, at least three. But I prefer one of the former kind if available.

The doctrine of looking for a single, bomber anchor point first is by no means accepted everywhere, and in many situations there is no such anchor point, but to say that using one is "somewhere approaching Darwinism" is to ignore a long and rich history of caving in the United States in which people have done this and experienced no problems. Not only has this practice not been eliminated over time, but it is taught to and used by rescuers.

Theoretically additional security is achieved by backing up a bomber anchor point that is guaranteed to be stronger than the rope and individually good for catching falling two-person rescue loads. Rescuers don't do that because time (and to a lesser extent, gear) is a resource. (Granted, there is a separate belay, but my understanding is that it is acceptable to have the belay use a separately rigged anchor on the same bomber anchor point as is used by the haul line.) Preservation of time and gear may not be essential in sport caving, but I would ask whether or not it is really worthwhile to exceed standards for rescue rigging in one's sport rigging.

Furthermore, even in sport caving, I would say that *simplicity* is a resource. You arrive at the drop and it is not even rigged--the most simple configuration. But that is unsatisfactory, because this simple state does not permit safe negotiation of the drop. So then you rig something, and use up some simplicity. The more you rig, the more simplicity you use up. The more simplicity remains, the easier it is to look at the anchor or anchor system and know that it is correct and what can and cannot safely be done with it. I think an anchor that minimizes risk of catastrophic failure while preserving as much simplicity as possible is practically the safest option.

(Also, I would dispute the claim that how you rig your caves is genetic. :tonguecheek: Furthermore, I suspect that the extreme, life-threatening stupidity of some is actually essential to the survival of the species and thus will never be eliminated evolutionarily. But I'm not an evolutionary biologist, and that's :off topic:.)
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Postby paul » Dec 21, 2007 2:31 pm

Wormster wrote:I *thought* the way to rig safely was:

Backup anchor on GBFO tree / rock

Separated 2 part* pitchhead (minimum)

*y hang on your preferred knot bowline of fig 8

that way IF you come a cropper and your y hang fails you have your backup to get you out of trouble.

having just one anchor point on a pitchead strickes me as very dangerous and somewhere approaching dawinism.

just my 2c's worth.


I know somebody has already answered, but from a fellow UK caver. if you have a "bomb-proof" anchor, there's no need for a backup.

Artificial anchors such as spits and P bolts are not 100% bomb-proof and therefore should always have a backup and where there isn't enough rope to absorb the shock if the anchor fails, there must be two anchors arranged in a "Y" so that neither will be shocked if the other fails.

Have a look at the two alternative surface pitches at Alum Pot in the Yorkshire Dales. Both can use a tree as the belay (providing you take care to pad any rub points) and these trees are not going anywhere so a backup would be pointless, as would a Y hang.

Another reason to have even a bomb-proof anchor rigged with what appears to be a back-up would be to provide a traverse line to allow the approach to be safe-guarded by clipping into that rope.
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Postby ek » Dec 21, 2007 3:42 pm

paul wrote:Another reason to have even a bomb-proof anchor rigged with what appears to be a back-up would be to provide a traverse line to allow the approach to be safe-guarded by clipping into that rope.

Good point. Similarly, one might rig a load-sharing anchor off two bomber anchor points to make the rope run down from some point between them, if dong so would help make negotiating the lip or drop easier, or reduce rope abrasion.
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Postby wyandottecaver » Dec 21, 2007 5:46 pm

The other unsaid equation is that as ek said simplicity is easier to do right. I can't count the times where we were making a simple rig complex for fun or practice and ended up creating a dangerous situation that we only found while double or triple checking (which we always do with complex rigging). Also, the odds of a truly bombproof anchor (giant rock away from an edge, big solid tree) failing are simply negligible. However, the odds of making a mistake getting your angles right and your gates shut and the waterknot secure are quite a bit higher :)
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Postby NZcaver » Dec 21, 2007 7:52 pm

Good point, Wyandotte. There is a LOT to be said for Keep It Simple and Safe (KISS). On the other hand, it can be a concern when some cavers always keep their rigging "dumbed down" to the simplest Sling the Rope Down (SRD) option. They're not really doing themselves or others any favors. Especially when an occasion arises which may require more technical rigging, and nobody knows how - or even worse just fudges it.

Whether simple or complex, just make sure the rigging is safe and it works. Then factor in a little efficiency of time and material, environmental impact, and caver ergonomics etc, and determine yourself which balance you need to strike on a cave-by-cave basis. Just like the old saying goes, practice, practice, practice. Then keep learning, discussing and practicing some more. As long as the discussion doesn't get in the way of the actual caving too much :wink: there's nothing wrong with learning new tricks.
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