Releasable Rigging - does it have a place in caving?

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Releasable Rigging - does it have a place in caving?

Postby Anonymous_Coward » Mar 15, 2011 5:54 pm

A common practice in canyoneering, especially in class C canyons (moving water) is to rig releasable. Also known as a contingency anchor, releasable rigging allows for the person on rappel to be lowered from above. This is especially helpful in two situations. One is when the drop length is unknown or unseeable from the top. A person can be lowered from above in order to efficiently set the proper rope length. The second situation is when someone is stuck on rope, especially in a waterfall. The stuck rappeller can be easily and quickly lowered to the bottom.

There are many ways to set up releasable rigging. One of the simplest is with a contingency eight block, pictured below:

Image
this photo was shamelessly stolen without permission from canyonquest.com via Google images

The photo shows how it is rigged. In practical use, the eight would be locked off until needed using a bight of rope from the non-rappel end. The rest of the rope below the eight is stored in a rope bag. In the event of a lower, you unlock the eight and begin lowering. The extra rope feeds out of the bag until the patient is on the bottom. This is the fastest way I know of to get someone out of a waterfall and prevents any need for a dangerous pick-off or any additional rigging. What it does require is rope double the length of the drop and some sort of rappel ring to lower through on the anchor. What kind of cave trips carry this kind of equipment? Well, TAG pull-down through trips do for example.

As mentioned, there are other ways to rig releasable including munter hitches on carabiners and many other ways that you are probably thinking of in your head right now. The group I canyon with has adopted the contingency eight for its simplicity and versatility. The main advantage I see with the eight is that the rope can be pulled after the last rappel as is. No re-rigging is necessary for the pull. Everyone rappels single-strand on the opposite side from the block. The last person either throws the rope bag or brings it down with them. The rope is then pulled on the eight/bag side.

My question to the caving community is this: Why do we not use this technique on wet, pull-down trips? Is there any reason not to? Should we adopt this technology for all dangerous waterfall drops?

Recent events have caused me to question the appropriateness of hard-rigging in a waterfall. What are your thoughts?
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Re: Releasable Rigging - does it have a place in caving?

Postby Scott McCrea » Mar 15, 2011 6:13 pm

I think it is a grand idea. However, I can't visualize how it works. I'll have to try it this weekend.

So, the locked off 8 is "blocked" against the screw link when the rope is loaded, right? Any trouble unlocking the 8 while it is loaded? Can you still operate the 8 even when it is blocked?
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Re: Releasable Rigging - does it have a place in caving?

Postby Anonymous_Coward » Mar 15, 2011 6:53 pm

Scott McCrea wrote:So, the locked off 8 is "blocked" against the screw link when the rope is loaded, right? Any trouble unlocking the 8 while it is loaded? Can you still operate the 8 even when it is blocked?


Yes, the eight is blocked against the ring when loaded.

There is a certain way to lock the eight that helps prevent problems unlocking. Basically you follow through the big hole and then twist the bight before securing it over the small end of the eight. The twist helps prevent trouble unlocking. It is hard to explain, I'll look for a photo.

Yes, the eight is operated while blocked against the ring. We usually use two people on the lower control when they are available, but a one-person load can be easily controlled by a single operator. Bonny routinely lowers me and has no trouble keeping it under control by herself.
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Re: Releasable Rigging - does it have a place in caving?

Postby Scott McCrea » Mar 15, 2011 7:05 pm

Cool. I'll try it this weekend. We are doing a vertical training session at a quarry--a perfect place to give it a shot.
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Re: Releasable Rigging - does it have a place in caving?

Postby chh » Mar 15, 2011 7:17 pm

Since the 8 is not clipped to a harness, during the cycles of people getting on and off rope on the other side, are you ever concerned about the bights coming off the 8 if it's not properly attended to especially with a stiff rope? I doubt it would do so under load. That'd be the one thing I could think of, though it might not be an issue. Maybe clip a biner through the two holes in the 8 and around the bight of rope before the lock off? That wouldn't mess with the friction at all I don't think, but it would prevent the bights from comming off, if that's a concern. I've never thought of using the blocking part of this particular type of anchor as the lowering device. Something cool to think about for sure. :kewl:

Is is faster than a locked off munter? Maybe, maybe not, but it may be smoother. If someone were really stuck under a heavy waterfall, there would be that much more force on the lowering device. You sometimes have to pull pretty hard to get the bight in a mule knot to pop through, especially with a heavier person, or after a lot of cyclic loading, like people climbing/rappelling on it all day. Could be this would make the transition smoother, and hence, faster.

I don't see any reason why it would work differently in a cave than in a canyon. And yes, I do think releasable rigging has a place in certain caving scenarios.
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Re: Releasable Rigging - does it have a place in caving?

Postby Extremeophile » Mar 15, 2011 10:33 pm

Andy, have you ever had to use the releasable block in a canyon, or only for practice? If so, what was the circumstance? I was generally under the impression that this was more commonly used by guides with less experienced clients in case they run into trouble. Professionally guided canyons seems to be much more common than professionally guided caves.

I'm a fan of 8mm polyester ropes for canyons, and I like the increased security of rappelling on double strands, but then you give up the release-ability. I've used biner blocks with a pull cord in canyons, but I definitely feel more secure on a double strand. I'm not sure a block type anchor has the strength or security I would want for ascending. I guess you could back it up though.

I like the concept of keeping any excess rope at the top of a rappel rather than getting coiled up in a whirlpool or sitting in mud at the bottom. It has many more possible uses when its at the top. The big problem when you can't see the bottom is determining whether you've lowered enough rope to reach. I guess lowering someone on a releasable block is one way to set the correct minimum length, but I prefer to control my own descent. I could imagine as many or more problems allowing someone else to lower you down a waterfall. It might be alright if you can see the person (which is harder in a cave), but if you can see them all the way to the bottom then you can probably set the rope length without lowering them.

I guess my general thought is that this might make sense for pull-down trips, which are the same mechanics as canyoneering, but I'll probably stick with traditional rigging for fixed ropes.
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Re: Releasable Rigging - does it have a place in caving?

Postby Extremeophile » Mar 15, 2011 11:47 pm

Anonymous_Coward wrote:Bonny routinely lowers me and has no trouble keeping it under control by herself.


I definitely wouldn't let my wife lower me... too many conflicting impulses. :yikes:
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Re: Releasable Rigging - does it have a place in caving?

Postby Anonymous_Coward » Mar 16, 2011 10:11 am

chh wrote:Since the 8 is not clipped to a harness, during the cycles of people getting on and off rope on the other side, are you ever concerned about the bights coming off the 8 if it's not properly attended to especially with a stiff rope? I doubt it would do so under load. That'd be the one thing I could think of, though it might not be an issue. Maybe clip a biner through the two holes in the 8 and around the bight of rope before the lock off?


This is an excellent point you bring up. The block can be safety-ed off by clipping a biner through the small 8 hole and then around the webbing on the anchor. I have never seen the bights loosen or try to come off the 8, but this safety prevents it. Also it prevents catastrophe if someone was to rig into the pull side instead of the intended rappel side.

I should mention that we use 9 and 8mm rope which works quite nicely for this. 11mm would be clunkier, and may require a larger figure 8 for ease of use.

chh wrote:Is is faster than a locked off munter? Maybe, maybe not, but it may be smoother.


I think it is. The unlock procedure is less prone to binding, the operation is smoother, and there is somewhat less twist to the rope than with a munter. It is definitely faster to rig. Also once again, the assembly can be pulled as-is, without need for a re-rig to pull. The 8 rig is also easier to teach and to learn than the munter mule assembly.

Derek Bristol wrote:Andy, have you ever had to use the releasable block in a canyon, or only for practice? If so, what was the circumstance?

Derek, I have thankfully not yet had to use the releasable in an emergency situation, but I think that is its greatest potential use for caving. It is just such an easy, pre-planned way to get someone out of a waterfall. It is also a quick-fix for hair in the rack, unconscious on rope, etc.

We have only used it for real to set rope length. As you mentioned, there is no real need to lower someone when you can see the bottom. In that case, we just lower the rope until you see it hit the ground or water surface, raise it back up about a foot, and block it at that level.

For those that may not be on the same page, the reasons that setting rope length is so important are two-fold. First, you may be rigging a 100 foot drop with a 200 foot rope. It is critical not to waste rope on the rappel side so that you won’t come up short on the pull side. If the pull side is short, it is not the end of the world but you will have to spend time tying something else onto the pull side to make it long enough. The second reason is to make sure there is an easy, safe disconnect from the rope at the end of the rappel. Especially in water, we prefer to slide off the end of the rope rather than fumble around disconnecting while treading water risking getting tangled in the extra rope. It is also obviously not a good idea to be attached to a rope in a hydraulic.

Most of all, setting rope length is efficient, and in canyoneering efficiency translates into safety. We have not done all that many class C (moving water) canyons, but we are often in a race against weather. Like Derek, I “prefer” to control my own speed on descent. However, sometimes that preference can translate into wasted time for the whole team. Example: On a 100 foot drop with at 200 foot rope, I estimate rope length, set a biner block and rappel. At the bottom, I discover there is 20 feet of rope on the ground. In order to pull the rope, the rope length must be reset, or the last person down will have to stop and tie on more rope to the pull side. Either way, a few minutes are eaten up. When there are six people on the team, and 15 drops to negotiate, and a thunderstorm moving in, every second counts. So, while I prefer to control my own descent, I am perfectly comfortable being lowered when I trust my team. That way I can go down attached to the end of the rope with a munter mule, and pull the rip cord when I am right at the bottom. Boom, instant perfect rope length. No time wasted.

I should mention here that our group uses more of a caver mindset of everybody on the team should be capable of every aspect of rigging, lowering, pulling, etc. I do not care for the guide-client mentality. We also use micro-racks which are plenty secure on single-strand skinny rope. Single-strand is not always appropriate for the ATC-figure eight crowd, especially on long drops.
Well, I have rambled much too long about why we use releasable rigging for rope length, which is something of a sidebar for this discussion. I think its greatest application is that it is pre-rigged for rescue purposes, which I thankfully have not needed it for yet.

One more thing Derek. Why do you think the block would not be sufficiently strong for ascending? I am not arguing, just wanting to learn if you know something I don’t. I have ascended on this rig a few times now.
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Re: Releasable Rigging - does it have a place in caving?

Postby Extremeophile » Mar 16, 2011 2:44 pm

One of my first technical slot canyons was Keyhole in Zion NP. We descended in the middle of a snow/rain storm and there was a huge volume of water rushing through it. We learned that if you throw 100' of rope down a 15' rappel into a waterfall that within about 60 sec you end up with 85' of rope tied into the worst knot you've ever seen. In the first deep pool we spent about 45 minutes untangling the mess as the water level was rising around us. It was a good learning experience.
Anonymous_Coward wrote:One more thing Derek. Why do you think the block would not be sufficiently strong for ascending? I am not arguing, just wanting to learn if you know something I don’t. I have ascended on this rig a few times now.

I definitely don't know anything you don't.
Maybe it's the fact that a biner or eight block is a hitch rather than a knot. Or maybe it's that I haven't seen pull tests on this type of anchor. My "feeling" is that there are possibly more modes of failure with this type of anchor, e.g. maillon failure, webbing failure, pinch point between maillon and eight, rope slipping on eight, etc. In canyoneering I've rappelled off meat anchors (aka other canyoneers), dead-men (not other canyoneers but buried rocks), knot chocks, hooks, rotting logs, and other unreliable objects. The shorter the distance and the softer the landing the less robust the anchor needs to be. In caving and climbing I've generally learned that an anchor always needs to be beyond reproach, i.e. capable of holding any worst-case load with a 4-5x safety factor, and that's generally because anchor failure means death.

Going to a releasable anchor for caving would require using webbing or cord to connect individual points together (bolts, natural anchors, trees, etc.) into a master anchor, and then rigging off the master point, rather than using the rope to connect each individual anchor. This is standard practice in other vertical pursuits so I don't see a problem with it. I think the concept of a releasable anchor for caving is worth further discussion. Since most caving parties don't carry figure-8s maybe some new techniques need to be developed using the gear we already carry.
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Re: Releasable Rigging - does it have a place in caving?

Postby Anonymous_Coward » Mar 16, 2011 3:22 pm

Derek Bristol wrote:I definitely don't know anything you don't.


Having spent some time with you Derek, I seriously doubt that!

Derek Bristol wrote:Going to a releasable anchor for caving would require using webbing or cord to connect individual points together (bolts, natural anchors, trees, etc.) into a master anchor, and then rigging off the master point, rather than using the rope to connect each individual anchor.


On the contrary, it could be a webbing interface on just one bomber anchor. But you are correct that in most cases it would be a 1" webbing interface connecting two bolts, two rocks, one jug and one rock, etc. The point being that there would be webbing and a ring left behind. This is already the case in many TAG pull-down caves. That's why I think this could be easily adopted at least in wet, pull-down caves. It was a trip through Sinking Cove and McBrides last spring that got me thinking along these lines. I was able to convince the McBrides crew to try out the rope bag/biner block method and all agreed that it worked quite well. I think I'm safe in saying that the entire team that day thought it superior to the double-rope/toss n' go method that is usually the case in TAG. When I started thinking releasable was when we rapped the big drop in McBrides in high water. Crossing the lip was like getting hit in the face with a fire hose. Granted, I was the last one down so releasable wouldn't have helped me. (an important point to remember in this discussion, releasable does nothing for the last rappeller) But, standing at the top feeling rope weight to see if the previous caver was off rope, it would have been nice to be able to lower them had they gotten stuck. All the other rescue options would have been hell in that waterfall.

Derek Bristol wrote:This is standard practice in other vertical pursuits so I don't see a problem with it. I think the concept of a releasable anchor for caving is worth further discussion. Since most caving parties don't carry figure-8s maybe some new techniques need to be developed using the gear we already carry.


Agreed. There are other options like munter-mule if you don't need the pull-down capability. However, if you do want that capability without having to re-rig, figure eights are cheap, light, and nobody's rope gets twisted unless there is a life-threatening emergency. It would be an easy thing to add to the kit. Hell, I'm not a climber or a canyoneer, just a regular old caver and I've got two or three eights laying around the gear room already.
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Re: Releasable Rigging - does it have a place in caving?

Postby chh » Mar 16, 2011 7:52 pm

Anonymous_Coward wrote:This is an excellent point you bring up. The block can be safety-ed off by clipping a biner through the small 8 hole and then around the webbing on the anchor. I have never seen the bights loosen or try to come off the 8, but this safety prevents it. Also it prevents catastrophe if someone was to rig into the pull side instead of the intended rappel side.


Obviously this doesn't work for the last person down either. They just have to make sure they don't suicide rig it :big grin:
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Re: Releasable Rigging - does it have a place in caving?

Postby wyandottecaver » Mar 16, 2011 7:59 pm

I have used releasable rigging on vert training sessions. The one thing I wonder, is if your already committed to hauling the extra rope, why abandon the safety for the last guy? Couldn't you just quickly reverse the setup so that the last guy raps the "safety leg" and the group below could feed the former main line if needed? The main drawback I see is if the bottom crew cant redirect their line enough to prevent tangling.
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Re: Releasable Rigging - does it have a place in caving?

Postby Extremeophile » Mar 16, 2011 11:39 pm

Anonymous_Coward wrote:It was a trip through Sinking Cove and McBrides last spring that got me thinking along these lines.

I definitely think I need to do a little field research at Sinking Cove and McBrides. Those are my priorities for the next visit to TAG.
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Re: Releasable Rigging - does it have a place in caving?

Postby Anonymous_Coward » Mar 17, 2011 9:18 am

chh wrote:Obviously this doesn't work for the last person down either. They just have to make sure they don't suicide rig it :big grin:


Correct again. This is one example of why it is important to have everyone on the team on the same page when using somewhat complex rope techniques. Either that, or you have to revert to the the guide/client mentality and make sure the guide is the last one down. One thing that helps immensely in preventing the suicide rig is to leave the rope bag on top until the last rappel. Most people will rig to the rope that goes down the pitch instead of the one that goes up canyon into a bag.

wyandottecaver wrote:The one thing I wonder, is if your already committed to hauling the extra rope, why abandon the safety for the last guy? Couldn't you just quickly reverse the setup so that the last guy raps the "safety leg" and the group below could feed the former main line if needed?


Todd, unless I misunderstand you (and please correct me if I do), your idea actually requires THREE times as much rope as the pitch depth. If you're at the bottom, you can't lower the guy who gets stuck near the top unless you have another entire pitch length of rope on the bottom to lower with. In our 100' pit/200' rope example, you would need to tie another 100 footer on the former main line in order to still have some rope in your belay device when the patient reaches the bottom.
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Re: Releasable Rigging - does it have a place in caving?

Postby NZcaver » Mar 17, 2011 5:49 pm

Often in small party rescue training we talk about the the merits of cavers rigging their ropes releasable, with the spare rope left at the top rather than dumped at the bottom. A while back, Clem Akins published a small article in the NSS News about this too. I think it's a great idea, although we usually do the locked Munter, or perhaps use a tree as a belay spool (in an emergency). And of course a locked rack is often used as the anchor for vertical practice.

This is the first I've heard of the specific technique of blocking a figure 8 descender against a screw link or rappel ring. Thanks for sharing - I'll have to try it out some time.
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