Emergency backup ascenders, Petzl Tibloc?

[David_Campen]

A rescue manual I read ... has said they do not recommend prusiks as a PCD because they do not work in all rope conditions, as a last resort yes.

Which rescue manual is this?

[hank moon]

1) The rope was not... just me and all my vert gear.
2) Uhhh.... The standard Petzl SHA? (sorry, don't know model # and name) originally purchased app 20 yrs ago, above incident occured about 8 yrs ago, and even today all but one tooth are still in good shape (spring too) and the one tooth has been slightly filed to remove the "bend" in it.

Cob, thanks for the info - this was needed to give a better answer. So, the rope wasn't slimed, just your gear. Petzl ascenders of that vintage were somewhat different than they are today and I have experienced slippage with older models, too. Haven't slipped yet with any of the newer ones <knock>.

By cut... I mean as discussed in this thread (refer to previous posts for "tearing of the sheath" comments)(when I read that I had a vision of a sheath torn, exposing the core on one side for a length of???) As to whether it is "severed" or just "damaged" is beside my point, which is that a "damaged" rope should not be used again. Not even by the guys below you (even tho technically it is still strong enuf). True?

The damage from a slipping TIBLOC is normally just fuzzing of the sheath, not actual cutting or coreshot. I suppose with a very thin-sheathed rope, you might get a coreshot after several slippings in the same spot, but not sure. I've never had a TIBLOC slip during an actual ascent, but it's very easy to get it to slip this way for all y'all who want to shred up a rope just for fun:

Attach TIBLOC to rope anchored overhead, put foot sling on TB biner, foot in sling, then grab rope below TB, pull it up 6" or so (TB will slide up rope), then weight the footloop suddenly while holding the rope (making a U-bend around the TB 'biner). You should get some fine fuzzin' that way. If you do it repeatedly in the same spot, you will probably get a coreshot.

I am most definitely NOT an expert, and do not pretend to be. You obviously have more vert knowledge in your little finger than I have in my entirety. So did Ken. So did Joe Ivy. But then all that knowledge didn't help Joe much, did it?

Joe Ivy's belay system was ill-conceived and untested. Not sure what you're trying to say here - I'm no more an expert than you or anyone else - just got my experience.

So Hank, I answered your questions, how about you answer mine? I ask again: Why would one use an ascender, especially in a rescue situation, that has been reported by others (not me, I have never used a tibloc) to damage rope? Especially when a Petzl rep (you) does not refute those statements? Enquiring minds want to know...

Personal gear selection is...personal. I cannot comment on why one would base a personal choice on someone else's word. I carry TIBLOCS and have used them several times, though not in a life-threatening emergency. I have also used tape slings and Prusiks to accomplish the same things. However, TIBLOCS can do things Prusiks cannot, such as slide easily down the rope after having been loaded. I sometimes use this property when passing knots on skinny rope.

[cob]

The damage from a slipping TIBLOC is normally just fuzzing of the sheath, not actual cutting or coreshot.

this is what was unclear, and unrefuted by anybody. As I explained before when I heard the damage reports... this sounds MUCH more like a pulling of the sheath that occurs when a bent tooth is at work...

Attach TIBLOC to rope anchored overhead, put foot sling on TB biner, foot in sling, then grab rope below TB, pull it up 6" or so (TB will slide up rope), then weight the footloop suddenly while holding the rope (making a U-bend around the TB 'biner). You should get some fine fuzzin' that way. If you do it repeatedly in the same spot, you will probably get a coreshot.

Now I see HOW it happens...

Joe Ivy's belay system was ill-conceived and untested. Not sure what you're trying to say here

yes it was, and my point was that knowledge can breed complacency, which seemed to be happening in this thread, (to paraphrase) "the tibloc tears the sheath, but I can deal with it."

- I'm no more an expert than you or anyone else - just got my experience.

Ok Hank, ON THAT ONE I DRAW THE LINE! Liar.... I know better than that...

To close Hank, I very much appreciate your direct and concise answers. I have to admit that your COB remarks got my goat a bit, not in a personal way but as an "avoidance" of the questions I was asking, which seemed pertinent to me. I knew Joe Ivy (not well, he and I were only underground together once, but we did share a few fires and more than a few "war stories" I would not call him a friend... more like a close acquaintance) and I have a tendency to bring his fate up when I see complacency creeping into peoples attitudes about vert work. As one who has never had any fear of heights, complacency is something I fight constantly (even after a free rappel) and I am probably too sensitive too it.

tom

[cob]

I have also used tape slings

Ok Hank, now you got to earn it... educate me: What is a "tape sling"?


tom

[fuzzy-hair-man]

A rescue manual I read ... has said they do not recommend prusiks as a PCD because they do not work in all rope conditions, as a last resort yes.

Which rescue manual is this?

Life on a Line (Part 1, page 46)

OK, I went and found it, the manual doesn't mention using prusik knots for a PCD(well not that I found) at all but it introduced the french prusik saying:

Although this book in general aviods the use of autobloc knots, a rigger should be able to tie and use them where appropriate. Underground on wet and muddy ropes very few autoblocks work at all well, and the classic 'prusik' knot is next to useless. The French prusik is however very good at gripping on moderately muddy ropes.

[Stridergdm]

Reviewing the thread, yes, it looks like there wasn't enough clarification made that 'normal use" and loads, a Tibloc won't cut the rope. A shockload could.

Having said that, why do I care them?

There is for example a local cave with a nice T-crack that we worry about getting people stuck in if they slip in.

Part of my cave pack is a sling, some biners, a couple of tiblocs (and I'd have to check I think my mini-Traxion.

For something like the scenario I find like there, I want something where I can rig a foot-loop or two that the trapped caver can slip a foot (or arm or whatever into) and I can take up an inch or two at a time. Since it's probably him/her and myself in the crack, I'd like something that will basically autotend. A prusik won't. A Tibloc probably will. No shock load and probably not even a full body weight.

As for the question of prusiks for PCD. You can get people into long debates over that. NCRC curriculum teaches the use of 2 triple-wrap prusiks. (generally people use a double-wrap on personal systems.)

Part of the theory is that a 2TWP will slide under severe load rather than break. Practice, well "it varies".

Hope that helps some.

(and hopefully you can make NCRC next Spring. Always lots of fun!)

[Rastus]

Is there anything more to be said that isn't an assertion of personal preference on the basis of individual experience?

[NZcaver]

Is there anything more to be said that isn't an assertion of personal preference on the basis of individual experience?

Yes - personal preference can also change as a result of the experience of others, if you keep an open (but somewhat critical) mind.

Personally, I like to see things broken - in a controlled environment, of course - to better understand uses and failure modes with my own eyes. But then I don't have enough money to throw away by breaking all my gear, so I let other people do it (manufacturers, NCRC, etc).

[Evan G]

Cob wrote

What is a "tape sling"?

Cob it is a climbers reference, it is just a sling make out of webbing and bar tacked.

[NZcaver]

Now that we are(hopefully) past the misinterpretations (apologies all around ) we can get back to the educational mode.

#1: It needs to be tended even with a prusik minding pulley?

#2: As I recall.... Ken used his rescuecenders for the haul line (they would slip if too much force was applied?) and prusiks for the PCDs (as I recall, he DID say it was just his thing)

#3: In another post you said you had seen where prusiks had torn the sheath from a rope??? This is news to me (not being sarcastic, seriously, I have never heard that). I thought the main advantage of a prusik was it could NOT damage the rope (in that way at least).

#1 - IF your PCD is below/forward of the haul cam, it will generally need to be tended - otherwise it won't capture the progress effectively. You could possibly weight it down or rig a bungy cord to pull it forward, but that could be difficult in some locations and/or might get tangled in the main line.

#2 - If your PCD is by the first pulley (above the haul cam), then it should be fairly easy to rig in a way it doesn't need tending. This is where a Prusik is commonly used (in conjunction with a PMP - Prusik-minding pulley), like you described.

#3 - Regarding Prusiks - I was (and still am) fairly sure that in one round of testing several years ago a Prusik did some sheath damage. However, looking through my photos I can't find evidence of that. But in the interests of full disclosure, I did find a shot that shows an 8mm Prusik which has slipped when overloaded - like it's supposed to.


Photo by Susan

Check out how tight that Prusik hitch is! The red nylon from the cord has actually infused into the rope as it slipped.

Well, I digress. I suspect my recollection of sheath damage was with something like a smaller diameter Prusik (say 6mm) being overloaded on an 11mm rope and failing to slip. But I could be wrong, and I can't find any photographic evidence - sorry.


Incidentally - have you all received your September NSS News? I just opened mine to read on the plane yesterday, and right there on page 4 is an excellent article by Clem Akins entitled "Self-Rescue 101: Avoiding a Callout". Although it doesn't mention the Tibloc specifically, it does detail many of the techniques and issues we've been discussing here.

[NZcaver]

Cob wrote

What is a "tape sling"?

Cob it is a climbers reference, it is just a sling make out of webbing and bar tacked.

Just to expand on this, in many other countries (UK, Australia, NZ etc) tubular webbing is known as tube tape. Therefore, you can make a sling (aka loop) by tying it with a tape knot (aka ring bend, water knot, or overhand bend). As kver33 mentioned, there are also pre-sewn tape slings available - something climbers might use as "runners" or "quickdraws" when doing traditional or sport climbing.

Clear as mud?

[Evan G]

Clear as mud?

Perfectly said NZ, now where is my spachla

[hank moon]

I have also used tape slings

Ok Hank, now you got to earn it... educate me: What is a "tape sling"?
tom

Tape = webbing in UK and OZ. I sometimes use it when short of breath

[cob]

OK guys, education session not quite over:

A "tape sling" is tied *onto the rope* in the same way as a prusik?

rastus said:

Is there anything more to be said that isn't an assertion of personal preference on the basis of individual experience?

individual experience is a wealth of knowledge I mine whenever possible... Because my own is so limited (yeah I been around the block a time or two, but collectively WE have been around the block a thousand times or 2). I always want to hear others experiences. They just might save my life.

tom

*= edit

[hank moon]

OK guys, education session not quite over:

A "tape sling" is tied *onto the rope* in the same way as a prusik?

3 common hitches w/tape sling:

Autoblock (aka French Prusik):
http://www.virtualinks.com/pics/knots/auto01.jpg
http://www.virtualinks.com/pics/knots/auto02.jpg
http://www.virtualinks.com/pics/knots/auto03.jpg
http://www.virtualinks.com/pics/knots/auto04.jpg


Klemheist
http://en.wikipedia.org/wiki/Klemheist_knot


Bachmann
http://storrick.cnchost.com/VerticalDev ... KnotA.html

A Prusik doesn't work very well with tape.