Dynamic rope used in caving…Split from Possible new knot!

[Chads93GT]

This topic has been split from Split from Possible new knot! - Moderator

I still don't understand why dynamic ropes arent used in some instances when caving. Afterall. climbing in cave's is no different than climbing outside. Sharp edges that can cut your rope in half don't discriminate. Wether its on El Capitan or inside the TAG caves......................

[shibumi]

Yeah, they are going to need a new spine.

I still don't understand why dynamic ropes arent used in some instances when caving. Afterall. climbing in cave's is no different than climbing outside. Sharp edges that can cut your rope in half don't discriminate. Wether its on El Capitan or inside the TAG caves......................

Dynamic ropes ARE used in caving... ...when taking a fall on the rope is anticipated.

Otherwise, dynamic ropes can actually be more dangerous for SRT than static. The reasoning is simple:
dynamic ropes have more stretch. Why is this dangerous you ask? When you are climbing you are creating
bounce in the rope. This bounce is not only annoying (as is climbing 50' to get off the ground a 200' pit), but
where the ropes have a rub point it can accelerate wear, even in well padded ropes. Additionally, dynamic
ropes can lead to resonance building up as one climbs, further increasing the dynamic loading on the rope.
Dynamic ropes also, by necessity, have a softer sheath weave which allows dirt and grit to penetrate much
more readily. And lastly, the added cycling of the ropes vastly increases internal wear in the core, especially
when aggravated by dirt.

A dynamic rope is designed to be used to absorb energy in high specific impulse loads (falls) SRT is predicated
on AVOIDING high specific impulse loads.

As far as I am concerned, the annoyance factor alone is worth not using them for normal SRT.

[Amazingracer]

Agreed with Shibumi.

Only place you see me using dynamic ropes are for my cowstail and QAS attachment. Other than that I like to stay the heck away from them. In fact the static the better for me, thats why Im a huge fan of PMI's Talon rope.

[JoeNurse]

Of course since I don't think i'll be pulling up any 2000 #'s + of material in one haul, I think I'll use my knot for repelling and rigging, since I've been doing that anyway and it hasn't failed me "knock on wood"! :

It isn't the application of a static load that makes the knot strength important. I can't even think of a situation where I might need to hang #2000 on my rope. However, when a rope is shock loaded, the force to which it is subjected is magnified enormously. For instance, if a 200lb caver takes a 15 foot fall on a 75 foot piece of pit rope, the shock load is 12.25kN or #2754

I think if a 200lb caver takes a 15 foot fall on pit rope, they're going to have issues other than just the shock load on the knot!

True...if the knot survives, almost all of that #2754 will be transferred to the caver

If the knot fails, it will transform much of that energy in the act of breaking resulting in a greatly reduced fall injury. However, the following act of decelerating from terminal velocity to nil instantly will result in a much greater landing injury

[Chads93GT]

im talking about real climbing in a cave, where you have the chance to take a 15 foot whipper off of a wall you are trying to traverse. I am NOT talking about using a dynamic rope to ascend out of a pit. I know the dangers of ascending on a dynamic rope ;)

[Tim White]

Me and everyone that know that does aid or technical climbing in a cave DOES in fact use dynamic rope.

[shibumi]

im talking about real climbing in a cave, where you have the chance to take a 15 foot whipper off of a wall you are trying to traverse. I am NOT talking about using a dynamic rope to ascend out of a pit. I know the dangers of ascending on a dynamic rope ;)

Then I have no idea what you are talking about, because everyone I know who aid climbs in a cave uses a dynamic
rope.

[Chads93GT]

If thats the case, then I guess I totally don't understand how someone can take a 15 foot fall on a static rope in a cave. I guess the vertical caving in missouri sucks ;)

edit: and what I mean by that is I don't understand how someone could take a 15 foot fall on a static rope, unless they were aid climbing and not using a dynamic rope. In missouri we don't have a lot of vertical. mostly pits 60-150+ deep, but nothing fancy. We just drop in, and ascend out when we are done. Can someone explain that? Thanks

[wyandottecaver]

well, since this is a bit off topic I'd suggest you contact folks by PM if your interested in a exhaustive list of failure modes. they generally involve user error or bad luck. I'll briefly cite some quick examples.

you anchor your rope on a BFR (big freakin rock) but redirect it around a beefy looking stal 15-20 feet away to get a better drop point out of the water. The stal ends up being rotten and snaps while you and your buddy are tandem frogging out. You drop X feet until the BFR catches you...and then stuff (including you) starts breaking as described above.

You are rappeling against the wall with your trusty figure 8 when you knock a snake on a ledge off into your coveralls you had halfway unzipped to cool down. This scares the bejeebus out of you and you go into almost freefall as you grab for the snake. Your belayer is flirting with the cute newbie girl down below and doesn't notice your situation until 20 feet of almost freefall later. As he panic pulls the slack out you suddenly stop.

As part of a very large group You are tandem ascending near the top of the pit on one of 2 mainlines but the guy 20' above of you is having trouble with the lip.. You decide to just switch over to the 2nd line that is within reach and now unused since the guy on that rope just yelled off rope. A quick tug reveals no slack and you switch over and get ready to ascend. Unfortunately the reason your tug didn't get any slack was because 2 people were standing on the rope up top talking. Feeling pressure on the rope they figure someone on the bottom is getting on and step off. They don't notice the 15' of slack on the ground the last climber dragged up with him until it zips down the pit giving you a nasty surprise.

[Chads93GT]

perfect explanations , makes sense.

[ek]

It isn't the application of a static load that makes the knot strength important. I can't even think of a situation where I might need to hang #2000 on my rope. However, when a rope is shock loaded, the force to which it is subjected is magnified enormously. For instance, if a 200lb caver takes a 15 foot fall on a 75 foot piece of pit rope, the shock load is 12.25kN or #2754

Do you have a citation for that? What kind of extremely static rope are you talking about?

You're describing a fall of factor 0.2. For a fall of factor 1 (e.g. falling from the anchor, all 75 feet onto the 75 foot rope), the standard for semi-static ropes requires the peak force not exceed 12 kN for a 100 kg (i.e. 220 lb) load (see Alpine Caving Techniques). This is the standard single-person industrial load (the standard single-person sport load is considered to be 80 kg). Fall 15 feet onto a 75 foot nylon caving rope (i.e. a semi-static rope), and the peak force is going to be way less than 12 kN.

Granted, make the rope old and/or wet and its elasticity reduces. But still not so much that the impact of a factor .2 fall would produce serious injury. Whatever kind of rope you're describing, it's not a nylon rope certified for caving use. This seems perhaps more plausible for a polyester rope.

Theoretically, it's safe to take a fall of factor 1 onto a nylon cave rope. Actually...maybe not so much. 12 kN is considered to be the highest the body can withstand in a full-body fall arrest harness. A caving harness isn't designed for insane falls, and (without a suitable load-bearing chest harness being attached) it is prone to flipping you over backwards even in relatively small falls due to its low attachment point. Plus there's the age/water saturation issue, which causes a rope to be less elastic than when it's new and dry. But there's no way that with a nylon cave rope you would (as Chads93GT says) "need a new spine," unless perhaps the rope is far overdue to be retired.

Let me put this another way. A fall of factor .2 onto 75 feet of rope (which would be a 15 ft fall) is equivalent, in terms of severity and peak force, to a fall of .2 onto 25 feet of rope. Well, that's a five foot fall. So suppose we have a drop in a cave that has a rebelay 25 feet below the top anchor. Suppose then that the rebelay anchor fails as the caver approaches it from below. Well, there's your factor .2 fall.

[Amazingracer]

im talking about real climbing in a cave, where you have the chance to take a 15 foot whipper off of a wall you are trying to traverse. I am NOT talking about using a dynamic rope to ascend out of a pit. I know the dangers of ascending on a dynamic rope ;)

Ah yes, sorry for the misunderstanding. Thats a logical use for dynamic :)

[knudeNoggin]

You think someone grabbing a carabiner and accidentally unclipping it is impossible?

Yes, practically. This is a far-fetched scenario, which, as I said, is likely
impossible--period--in many situations, where the drop is not near enough.
AND that a **tensionless** hitch, having no tension at this point,
needs no securing there. Now, I don't advocate taking things so far,
or always ensuring enough wraps for it (though OnRope1's MythBuster
re this aspect suggests that the usual course is to overwrap for a TH), but
it should be the case that considerable friction hence resistance is built
up and the wraps won't be pulled out.

These two situations should absolutely be equated--failure of the carabiner in either results in catastrophic anchor failure followed by serious injury or death.

Then you've seriously botched the TH in not wrapping enough!

The friction in the loop knot finishing a tensionless hitch that has slipped (or been non-ideally rigged) is perpetual.

Well, let's leave at friction is what makes most knots work.
Citing rope-on-rope issues here is just plain silly, period.
Arborists will get noticeable wear in sliding on friction hitches,
slip-then-grip. But, here, no--NOT a valid consideration in the
deliberations on whether to tie off with the rope sans 'biner.
(Yes, you did try to diminish it, but needed some boost in that,
and would've been better off not mentioning it at all.)

But just because I disagree with you, does not make articulation of my ideas stupid or worthless.

Oh, goodness, no no no. That "rope-on-rope" tickled an old peeve about
some myths. There have been a good many things re cordage use that
get spoken enough times, or by authoritative-enough figures, that they
are swallowed hole, without thought. Rockclimbers have gone gung-ho
over the fabled "cordelette", nevermind that it wasn't tested; now, only
after one of its principal proponents has reviewed and actually tested it,
we can see that it was more a back-up than load-sharing/equalizing
anchor structure. And there was much hype about how Dyneema,
thin ("dental floss") webbing slings were very dangerous and would
cut through themselves if "girth hitched" (another knot-name issue),
and interpretations of one infamous John Sherman broken-sling
case were crazy, but fit the hype and ... have taken much shooting
in order to be (maybe not?) shot down (with a test report from
sling-maker Mammut (since good sense & analysis wasn't working)).

I am getting the sense from your post that you are developing some degree of antipathy toward me, which I hope is not the case, ...

Oh, please, no ... . The benefit of the Net is getting ideas to many
minds, and after some good shaking about, what remains ought to
be firm *stuff*--the weaknesses shaken out. Why, now that we know
your middle initial, and you make a BINGO! on an infamous knot,
you're gold! (But I have modifications to that knot, mind.)

I have, in a practice environment. It is hard. You have to hold up the tensionless hitch to prevent it from collapsing and unwrapping, while simultaneously tying a bend.

Well, here again it seems that this hitch just isn't given the wraps
it needs, if this is hard. If you have tied off with a slip-free hitch
(such as Highwayman's), you can join ends and then release, as
you note. And a hitch is more easily adjusted than esp. a Fig.8.

I am going to "fight" this, and argue that "on a bight" should mean the same thing as "in a bight", and that "with a bight" means something different.

Don't overlook "in the bight", while you're at it. (And some popular
versions using "bite".) It is one major uphill battle to make headway in
knots nomenclature, and ...

any more than you telling me that I should remain silent because the Force is against me is an argument.

that wasn't an argument but wise counsel (or a threat!).

The bowline with a bight is tied with a bight as its tail, and is therefore

... already begging the question of good sense in nomenclature.

a two-loop, directional bowline that may be tied in mid-rope,

"directional" and "mid-rope" are synonymous--let's not loosen THIS nomenclature.

is non-jamming, but

... might be non-holding: beware trying the nip of multiple strands,
I've seen such things fail to hold. (In this case, it would be the non-eye
loading (end-2-end) that is suspect.)

... because it is tied with, but not on a bight.

Well, partly "with", and I don't swear by Ashley, just use him as
both a good start and a commonly known one. Quite odd that he doesn't
show the 3-eye one, but ... .
"The figure-eight on a bight, ..." can be well seen as tying a Fig.8 with
a bight; it has this recognition, implicitly but with different diction,
when called "double Fig.8"--a use of "double" sometimes applied to
the offset bend (rope-joiner), with the Overhand. Naming's a mess.

Similarly, the overhand on a bight and figure-nine on a bight.

You'll do well to consider how DISsimilar these cases are to that of the BOAB:
that in these just-cited the entire named knot is tied <you-chose-preposition>
a bight in entirety, unlike the like-named Bowline (where the finish comes
not with "rabbit going around tree" but a clever, use the bight-end, "backflip"
to lock).

It's not clear to me whether or not you're criticizing the term "triple bowline on a bight," but I'll go ahead and defend it just in case.

I'm not sure I was, but I'm happy to oblige! --and I do

The "triple bowline on a bight" is a correct name for this knot (at least in the same sense that "bowline on a bight" is a correct name for the double-loop knot commonly used for Y-belays in caving that, like Ashley's "bowline with a bight", is tied with but not on a bight).

Whoa, WHAT? Check that: TB **on**... is correct because it is NOT tied **on**, but >>with<< ?!
I object to this use of "triple", more than "on"/"with"; and it's what I call "with"
--the full bowline, tied with a bight of rope, doubled throughout.

Both are made correct by widespread usage and acceptance,

Boo, I'm a pre- not de-scriptionist linguistically. (I have a Webster's 2nd to
restrain the (quite long overdue for revision) 3rd New.) The Net spreads
nonsense like wildfire.

and definition in works that are considered canonical. This is matter of correctness of language.

Do you tie any "Larksfeet"? --or "Larksheads"? (Or "Girth hitches"?)

it may even result from mistakes and poor thinking, but they have come into use. ... See Alpine Caving Techniques for the term "triple bowline on a bight."

I won't surrender to that. But knot naming is a very hard problem,
and there will be plenty of confusion throughout. One doesn't even
have to cross fields, but many do, and that only compounds confusion.
With a KISS, small set of knots, each field can have some pretty distinct
names; start crossing borders, and you end up in some conflict; and
consider the vast number of uncommon but workable knots, and you
are in no-person's-land.

But it's a very unique name--no other knot is called that.

Okay, now it's "<intensifier> unique", and oft' heard "more/extremely critical":
the modifiers just destroy the sense of the words, which are either/or & not
halfway. But that's an old battle beyond the caves & climbing & cordage.

Finally, I'm unclear about what you meant by the first "no" in "No, and no it should NOT."

That I didn't want to use that bowline, but a hitch.
But, yes, w/o ends (and that, for me, is "in the bight").

And I wanted to swat that notion about there being no bunny-ears
Fig.9, but that can come later; there is more than one way to
do that, and I think another way avoids problems Merchant cites.
(For that matter, the Fig.9 itself can be drastically reoriented,
a la Ashley's #1425/525.)

*knudeNoggin*

[gdstorrick]

Post deleted.

[ek]

Aren't UIAA drop tests conducted with static masses (i.e. not bags of fluid) and rigid anchors attached to the rope knotlessly by capstans?