What did I just read?

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Re: What did I just read?

Postby Cody JW » Mar 22, 2013 9:18 pm

I remember hearing that open face ascenders were more prown to twisting off . I remember about the time when ropewalkers went from using only Gibbs to using Petzl or cmi that issue or possibility of that issue came up. . NZ, I know you have done at least one NCRC . Do rescue personnel prefer to use Gibbs on a haul system ?? If so, is it because they do not twist off like an open face ascender like Petzl, Jumar and CMI ? Or is the load rating higher on gibbs?
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Re: What did I just read?

Postby Stridergdm » Mar 22, 2013 10:08 pm

Cody JW wrote:I remember hearing that open face ascenders were more prown to twisting off . I remember about the time when ropewalkers went from using only Gibbs to using Petzl or cmi that issue or possibility of that issue came up. . NZ, I know you have done at least one NCRC . Do rescue personnel prefer to use Gibbs on a haul system ?? If so, is it because they do not twist off like an open face ascender like Petzl, Jumar and CMI ? Or is the load rating higher on gibbs?


On a haul system? Your hand grip. If you're discussing a rope grab, prusik or rescucender.
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Re: What did I just read?

Postby NZcaver » Mar 23, 2013 2:35 am

Cody JW wrote:NZ, I know you have done at least one NCRC . Do rescue personnel prefer to use Gibbs on a haul system ?? If so, is it because they do not twist off like an open face ascender like Petzl, Jumar and CMI ? Or is the load rating higher on gibbs?

As Greg said, the PCDs and haul cams on rescue systems are usually Rescucenders or Prusiks. With excessive force, both *usually* tend to slip-and-grab without damaging the rope or device. Rescue personnel over here (US) prefer to avoid toothed cam ascenders for hauling any rescue loads because when overloaded they tend to strip the sheath of the rope, not twist off the rope. However in some countries, toothed cam ascenders are commonly used in cave rescue haul systems with single person rescue loads.

The old Gibbs ascenders you mentioned will cut the rope in two when too much force is applied. With this application it's not so much the amount of force that is relevant, but the mode of failure (harmless slipping to reduce peak force, versus catastrophic failure). All this is more relevant to rescue haul systems than personal climbing systems.
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Re: What did I just read?

Postby paul » Mar 23, 2013 4:55 am

NZcaver wrote:However in some countries, toothed cam ascenders are commonly used in cave rescue haul systems with single person rescue loads.


We do, in the UK.
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Re: What did I just read?

Postby Mike Hopley » Mar 23, 2013 5:44 am

"Always maintain two points of contact" is a simplified rule of thumb. It's obviously false, unless you believe that a descender should be backed up by a second point of contact. Nevertheless in many situations it is a good rule.

Ascenders can accidentally come off the rope when they are unweighted. This is very rare, but does happen. When climbing rope, your ascenders are alternately weighted and unweighted. For this reason you must have a minimum of two points of contact when climbing rope.

Ascenders never come off the rope when your weight is hanging on them. You couldn't force them if you tried. Hanging from just one ascender, under static tension, is safe; climbing rope attached to only one ascender is not.
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Re: What did I just read?

Postby Extremeophile » Mar 23, 2013 9:58 am

NZcaver wrote: do you know of documented examples where modern toothed-cam ascenders (e.g. Petzl) have twisted off a rope in normal SRT use in a frog system?

I'm not aware of any specific examples in SRT using a frog, but I have heard of it happening in rock climbing. It's obviously much more likely in a traverse situation than in a direct vertical pull situation, but there are definitely many traverse lines underground and other places such as J hangs and many rebelays where the rope isn't always perfectly vertical. With changeovers or crossing knots there are also times where you weight and unweight attachment points, which is an opportunity for things to get twisted or cross-loaded. Again, I don't think trusting one ascender provides an adequate safety margin, and I don't think there are scenarios where it is necessary. The 2 seconds that might be saved isn't worth the additional risk, even in time critical pick-off maneuvers.

I am not necessarily advocating the use of single point ascender attachments during changeovers.

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Re: What did I just read?

Postby Extremeophile » Mar 23, 2013 10:08 am

Mike Hopley wrote:Hanging from just one ascender, under static tension, is safe; climbing rope attached to only one ascender is not.

I usually refrain from using the word "safe". I see safety as a continuous spectrum, not a yes or no judgment. Using one ascender attachment obviously has a lower margin of safety than two points of attachment. I believe the margin of safety is too low to endorse its use.
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Re: What did I just read?

Postby Extremeophile » Mar 23, 2013 10:17 am

paul wrote:
NZcaver wrote:However in some countries, toothed cam ascenders are commonly used in cave rescue haul systems with single person rescue loads.


We do, in the UK.

I definitely think the use of toothed ascenders, Traxions, and Grigris in cave rescue, especially small party rescue, should be further evaluated in the US. Some of the standard methods seem to be overly complicated and slow in order to avoid some possible but unlikely side effect. But that's a topic for another thread.
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Re: What did I just read?

Postby Stridergdm » Mar 23, 2013 12:22 pm

Extremeophile wrote:
paul wrote:
NZcaver wrote:However in some countries, toothed cam ascenders are commonly used in cave rescue haul systems with single person rescue loads.


We do, in the UK.

I definitely think the use of toothed ascenders, Traxions, and Grigris in cave rescue, especially small party rescue, should be further evaluated in the US. Some of the standard methods seem to be overly complicated and slow in order to avoid some possible but unlikely side effect. But that's a topic for another thread.


The NCRC in addition to the week-long seminar (which I encourage all cavers to take) offers a small party rescue class which does discuss such usage in small party rescue. There's definitely a place for such usage.
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Re: What did I just read?

Postby Carl Amundson » Mar 23, 2013 11:01 pm

Extremeophile wrote:
paul wrote:
NZcaver wrote:However in some countries, toothed cam ascenders are commonly used in cave rescue haul systems with single person rescue loads.


We do, in the UK.

I definitely think the use of toothed ascenders, Traxions, and Grigris in cave rescue, especially small party rescue, should be further evaluated in the US. Some of the standard methods seem to be overly complicated and slow in order to avoid some possible but unlikely side effect. But that's a topic for another thread.

The Traxion is a great device for a single load haul system. A pulley with a progress capture, what's not to like.
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Re: What did I just read?

Postby driggs » Mar 24, 2013 12:00 am

junkman wrote:The Traxion is a great device for a single load haul system. A pulley with a progress capture, what's not to like.


The MSRP! :yikes:
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Re: What did I just read?

Postby paul » Mar 24, 2013 8:51 am

junkman wrote:The Traxion is a great device for a single load haul system. A pulley with a progress capture, what's not to like.


The problem with these sort of progress capture/pulley systems is that they are easy to set up and use when taking in rope but problems may occur when not knowing how to release them when under load and then lower down a caver. There have been at lease two fatalities in the UK where a Traxion or MiniTraxion was being used with a safety line and this sort of thing happened.

In one case an exhausted caver was unable to climb a ladder with a waterfall nearby. He was being safe-guarded with a lifeline through a MiniTraxion and his caving mates could not release the device and lower him back down, leaving him hanging exhausted in the full flow of the water until he became unconscious. Unfortunately he died and was on a 20 foot pitch some 10 minutes from the cave entrance. See incident 325 on http://www.derbyshirecro.org.uk/call_outs.html.

In the other case a caver was being assisted in a cave in high water levels with a tied on rope, again passed through a Traxion/MiniTraxion. They slipped into the stream and the device could not be released, Again the caver died.
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Re: What did I just read?

Postby wyandottecaver » Mar 25, 2013 7:33 am

Jumping back in here going back to body type and frog/mitchell. I love a mitchell hanging in a tree or wide open pit. For 90% of the actual caving I do, not so much. Overhung lips, snaggy walls, heavy goopy mud, dragging the thing around... It's a pain. Of course I drag a dedicated adjustable QAS around and wouldn't leave home without it...so go figure :roll:

As for changeovers and attachment, the key is to make sure you can actually do it at all under sub-optimal conditions. If that means briefly going to 1 point of contact I'm ok with that. Of course doing it where you maintain 2 points is always preferred. The bottom line IMHO is you should always weigh the risks. If your hanging in a tree with your buddies you can afford to be snobbish about technique. If your hanging in a waterfall and not going anywhere, it's time to get out of there any way you can.
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Re: What did I just read?

Postby Extremeophile » Mar 25, 2013 11:14 am

wyandottecaver wrote:If your hanging in a tree with your buddies you can afford to be snobbish about technique. If your hanging in a waterfall and not going anywhere, it's time to get out of there any way you can.

I hope you're not saying that advocating for good vertical technique is being snobbish.

Maybe a better option than relying on a single ascender would be finding ways to stay out of waterfalls while on rope.
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Re: What did I just read?

Postby Stridergdm » Mar 25, 2013 11:43 am

wyandottecaver wrote:Jumping back in here going back to body type and frog/mitchell. I love a mitchell hanging in a tree or wide open pit. For 90% of the actual caving I do, not so much. Overhung lips, snaggy walls, heavy goopy mud, dragging the thing around... It's a pain. Of course I drag a dedicated adjustable QAS around and wouldn't leave home without it...so go figure :roll:

As for changeovers and attachment, the key is to make sure you can actually do it at all under sub-optimal conditions. If that means briefly going to 1 point of contact I'm ok with that. Of course doing it where you maintain 2 points is always preferred. The bottom line IMHO is you should always weigh the risks. If your hanging in a tree with your buddies you can afford to be snobbish about technique. If your hanging in a waterfall and not going anywhere, it's time to get out of there any way you can.


There's a good book out there, Deep Survival that I recommend everyone read. He discusses some of the things that help people survive "bad things". One of them is a lesson that I think applies here. People tend to revert to what they were taught (almost always a good thing) but also often make the mistake of trying to fit reality to their idea of it. The classic cartoon of "Well according to this map, we're on that peak over there" is an example of it.

This applies to SRT. KNOW your techniques cold. Be able to do a "proper" changeover in your sleep. 99 times out of 100, this will be the right move. But, I have to agree. If you get into that 1 out of a 100 situation and you can't do a "proper" changeover (here to mean always having two points of attachment), don't necessary try to adopt reality ("2 points is impossible for some reason") with your idea of reality ("I must have to points of attachment"). Go with reality, change your concept of what things SHOULD be and do what it takes to save your life.
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