T3WP as progress capture?

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T3WP as progress capture?

Postby NZcaver » Mar 31, 2012 8:25 pm

This subject came up recently, and frankly it has me a little baffled. Apparently some cavers and responders are being taught to always use tandem 3-wrap Prusiks for progress capture on the haul line, just like you see on a T3WP belay.

Like this:

Image\

Apparently their rationale for progress capture always being T3WP is that it's your life support line. I was also informed the only NFPA certified cave rescue technician course in the nation teaches it this way.

I admit I'm more used to the standard 3-wrap Prusik progress capture I see used everywhere in haul systems, including NCRC:

Image

Call me curious, but I'm trying to figure out why anybody would require tandem Prusiks for progress capture.

My understanding is the reason for the second Prusik (furthest from anchor point) is to catch a severe shock load by backing up the first Prusik which may slip/glaze when sudden, high force is applied. Perfect for the belay line, but a little redundant/inefficient for the main line which presumably has a team of people hauling on the end anyway. Tandem Prusiks on both main and belay do make the systems more interchangeable, but the need to switch roles during a raise or lower seems pretty unlikely.

Comments from any of you other cave/technical rescue people out there?
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Re: T3WP as progress capture?

Postby Stridergdm » Mar 31, 2012 10:21 pm

I'd say it's a case of overkill.

The question about the NFPA certified course though has me wondering. I'm going to drop a question to someone about that.
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Re: T3WP as progress capture?

Postby Stridergdm » Apr 1, 2012 7:59 am

Ok, talked to my source on NFPA and he claims there's no such thing as a NFPA certified cave rescue course.

So take that for what it's worth.
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Re: T3WP as progress capture?

Postby snoboy » Apr 1, 2012 9:29 am

NZcaver - I think you're on the right train of thought. The reasoning for two prusiks on the TTWPB is to distribute the heat and loading. If memory serves me correctly, a single TWP will catch a rescue fall, but it will glaze the prusik and the line possibly fusing them and making further progress difficult...

I think you will see some more application of this (two prusiks on capture) as more teams adopt mirrored systems. Then it is not there because it's needed for capture, but it's there to make either line functional as a belay. There are actually some significant advantages to this ability to swap the roles of the ropes during the evolution.

As an aside, I believe NFPA does not certify, they just set standards. A provider may be able to teach a course that follows the NFPA rope standards, and is oriented to cave rescue.
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Re: T3WP as progress capture?

Postby NZcaver » Apr 1, 2012 3:32 pm

Thank you both for your input.

snoboy wrote:I think you will see some more application of this (two prusiks on capture) as more teams adopt mirrored systems. Then it is not there because it's needed for capture, but it's there to make either line functional as a belay. There are actually some significant advantages to this ability to swap the roles of the ropes during the evolution.

Interesting point, and something I suspected as being a possibility. But I'm still scratching my head about what significant advantages there would be in swapping roles of the rope systems during a properly managed haul. I'm wondering if this is an attempt at an idiot-proof solution to a problem that doesn't really exist.

As an aside, I believe NFPA does not certify, they just set standards. A provider may be able to teach a course that follows the NFPA rope standards, and is oriented to cave rescue.

I'm thinking this might be the case. The certification comment came from a person whose background and experience level I am not familiar with. Might be a simple slip of terminology, like some students that assume they are 'certified' when they complete NCRC training.
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Re: T3WP as progress capture?

Postby Stridergdm » Apr 1, 2012 7:05 pm

snoboy wrote:NZcaver - I think you're on the right train of thought. The reasoning for two prusiks on the TTWPB is to distribute the heat and loading. If memory serves me correctly, a single TWP will catch a rescue fall, but it will glaze the prusik and the line possibly fusing them and making further progress difficult...

I think you will see some more application of this (two prusiks on capture) as more teams adopt mirrored systems. Then it is not there because it's needed for capture, but it's there to make either line functional as a belay. There are actually some significant advantages to this ability to swap the roles of the ropes during the evolution.


That is my thought. It's not so much for the "haul" side but more for the "let's flip things around as quickly as possible."

snoboy wrote:As an aside, I believe NFPA does not certify, they just set standards. A provider may be able to teach a course that follows the NFPA rope standards, and is oriented to cave rescue.


Correct.

I suspect the speaker misspoke or misunderstood the situation.
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Re: T3WP as progress capture?

Postby shibumi » Apr 9, 2012 11:18 am

Jansen, I don't know the specifics of the folks you were talking with, but that misunderstanding seems to be VERY prevalent as every year we have people come into L2 wanting to do it that way when I know they weren't taught that at L1 and I know they didn't get training elsewhere. It only takes a few people to perpetuate that down before it starts becoming "standard" among some training organizations.
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Re: T3WP as progress capture?

Postby NZcaver » Apr 9, 2012 5:54 pm

shibumi wrote:Jansen, I don't know the specifics of the folks you were talking with, but that misunderstanding seems to be VERY prevalent as every year we have people come into L2 wanting to do it that way when I know they weren't taught that at L1 and I know they didn't get training elsewhere. It only takes a few people to perpetuate that down before it starts becoming "standard" among some training organizations.

Interesting. It's a mystery, Anmar. Perhaps some people are so enamored with the T3WP belay, they feel they must use a tandem set anywhere the system calls for a Prusik?

It was suggested that I might want to consult On Call to better understand the use of tandem Prusiks. :shock: Hmmm. I don't have my copy with me, but off the top of my head I can't recall it detailing the use of the T3WP for progress capture on the main line.
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Re: T3WP as progress capture?

Postby Stridergdm » Apr 9, 2012 10:04 pm

NZcaver wrote:
shibumi wrote:Jansen, I don't know the specifics of the folks you were talking with, but that misunderstanding seems to be VERY prevalent as every year we have people come into L2 wanting to do it that way when I know they weren't taught that at L1 and I know they didn't get training elsewhere. It only takes a few people to perpetuate that down before it starts becoming "standard" among some training organizations.

Interesting. It's a mystery, Anmar. Perhaps some people are so enamored with the T3WP belay, they feel they must use a tandem set anywhere the system calls for a Prusik?

It was suggested that I might want to consult On Call to better understand the use of tandem Prusiks. :shock: Hmmm. I don't have my copy with me, but off the top of my head I can't recall it detailing the use of the T3WP for progress capture on the main line.


"On Call", you should be referencing the NCRC Manual of Cave Rescue Techniques :-)
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Re: T3WP as progress capture?

Postby NZcaver » Apr 10, 2012 3:08 am

Stridergdm wrote:"On Call", you should be referencing the NCRC Manual of Cave Rescue Techniques :-)

Indeed. I have that one too, also buried in storage. Clearly I have a weakness for ancient history.
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Re: T3WP as progress capture?

Postby tagkycaver » Jun 20, 2012 6:00 pm

I was in a SAR training a few years ago where we performed drop tests/holding tests for sudden rescue loads; T3WP held every time (fused some though) whereas single knots and lots of other stuff frequently failed.
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Re: T3WP as progress capture?

Postby Stridergdm » Jun 21, 2012 11:50 pm

tagkycaver wrote:I was in a SAR training a few years ago where we performed drop tests/holding tests for sudden rescue loads; T3WP held every time (fused some though) whereas single knots and lots of other stuff frequently failed.


Agreed on capturing a fall, but that's not the point of a progress capture, which is what is being discussed here. (your mainline in theory should never be capturing a fall since it should normally be loaded.)
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Re: T3WP as progress capture?

Postby NZcaver » Jun 22, 2012 1:03 am

Stridergdm wrote:
tagkycaver wrote:I was in a SAR training a few years ago where we performed drop tests/holding tests for sudden rescue loads; T3WP held every time (fused some though) whereas single knots and lots of other stuff frequently failed.


Agreed on capturing a fall, but that's not the point of a progress capture, which is what is being discussed here. (your mainline in theory should never be capturing a fall since it should normally be loaded.)

:exactly:
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