Melting means just that - it will potentially fail far before that. Ever rapped in nylon shorts/pants and burnt a hole through them on your R thigh due heat - I have. Imagine this hapening to the sling when you fall on it.

As with all these things, its a probablistic risk management issue. Its not going to kill you straight up. You could do it 99 times and be OK, but...

You want a big guns report, try this one. Very comprehensive assessment of ascending rigs, industrial descenders, knots, knot failure, edge protection, etc., etc. Everything down to the effects of pidgeon crap on fixed ropes.

http://www.hse.gov.uk/research/crr_pdf/2001/crr01364.pdf

Hope this helps. Email me if you need more info.

Macca

With regard to your comment about not girthing nylon/nylon or nylon/spectra in a potential shockload situation, I'm not sure I understand the basis for your advice.

Why would the melting point of nylon or spectra affect the integrity of a girth hitch using either/both materials when shock loaded? (I'm thinking about cases like, for example, a fall taken onto a dynamic rope clipped with a biner to a spectra sling, which in turn has been girthed as an extension directly to the factory sewn nylon sling on a BD cam.)

I would expect the girth hitch to cinch down tight when it takes the hit, but I wouldn't expect this small amount of movement alone to raise a friction/heat concern.

Obviously, in a situation where there is significant running of one piece of nylon or spectra over another, friction/heat is a major worry, but I don't see it happening in a girth hitch in this scenario.

What am I missing?

- Bill

p.s. Your article really is excellent, by the way - I've also bookmarked it. Haven't yet read the other article you referenced, so perhaps it has my answer?

(edited for typos only)

Macca

I guess you can hope that instead of the hitch itself sliding, the entire factory sewn sling will slide through it's attachment point on the cam, as providing a less resistant avenue to move the hitch to the dependant point. Argues for a bit of thought about the positioning of the bar tacks on the factory sewn sling to facilitate this, however.

Hmmm.... interesting, and much appreciated!

However, I use all sewn spectra slings - Blue Water and BD. The Blue Waters have a breaking stength of 27Kn and the BDs have a breaking strenth of 22Kn. 30% reduction leaves you with 18.9Kn for the BWs and 15.4Kn for the BDs.

As you know, those figures are way above what your gear is rated for. So my thought is that a girth hitched sling is not a geniunely dangerous weakpoint.

As a result, when I climb on gear I use girth hitches all the time. I'll use a girth hitch directly to a cam sling to extend it, and the cam's racking biner is all I need for my rope connection. Saves biners and so I carry fewer. That equals saved weight - a helpful point for us munchkin-sized climbers!

Two points, however:

First, I would never girth hitch a sling directly to a wire (or anything else sharp). I think I remember reading tests that show girth hitching directly to a wire as not actually being too bad (again, don't hold me to this, I'll see if I can find the reference), but the cut potential just looks too scary to me.

Second, the force on a single piece of pro and the force on the "power point" on your anchor are two different things. In an anchor's power point, the 30% strength reduction could be more of an issue. So although I do use girth hitches in anchors, I make sure my anchors are multiply redundant to avoid any concern.

My 2 yen worth.

Primary knot failure (as opposed to cuts, heat or abrasion) happens where the rope/webbing bent through the tightest angle. You can therefore affect how strong a girth hitch/lark's foot is by how you rig the angle of pull - if you are pulling back so the free end is being bent around tightly by the standing bight it will be much weaker.

The other MAJOR issue here is that anything tied around a very small diameter item such as a wire is at risk of cutting under load, so take care.

Strength reductions (CMC rope rescue manual - statistically significant testing)
double fishermans 21%
ROPE
Fig 8 19%
Fig 8 loop 20%
Fig 8 loop foillow through 19%
Double fig 8 loop 18%
In line fig 8 loop 25%
Butterfly 25%
Bowline 33%
Overhand on bight 15% (!)
Overhand double loop 26%
WEBBING
Water knot 36% (!!)
Overhand loop 35%
Fig 8 loop 30%
Fig 8 loop follow through 26%

Macca (reputation to keep up)
www.asott.nsw.edu.au

I am looking for any assistance possible. I am busy doing my Bachelors degree in Emergency Medicine. Part of this degree is a Rescue Research Elective. I have chosen a topic that I feel you could shed some light on for me. I would like to research the breaking strength of the Alpine Butterfly vs. the In-line Figure of Eight on 11mm and 13mm (12.5)static nylon kernmantle rope. I will be using a loadcell to do this. I am looking for any advice you may have to guide me through this process. All the literature you read gives you different figures so I am curious to see what I come up with. My e-mail address is milbauer@iafrica.com and I would really appreciate the help.

Thanks a million.

Dagmar Muhlbauer
Paramedic from Sunny South Africa

http://www.chockstone.org/TechTips/JoinRopes.htm#Fisherman

http://www.bwrs.org.au/research/

Cheers,
D

What do you disagree with here? I'm curious. Testing (several sources) has shown that an abnormal figure eight is prone to "rolling" and may have accounted for the fatality in Zion last year (Spaceshot). Seems like their testing supports the conclusions of quite a number of folk. UIAA, UIAGM and AMGA all support the use of the overhand knot (aka euro death knot) as the knot of choice for joining two ropes together for rappel?

>....anyway, you might find it an
>interesting read and may get some value out of it. It is a
>test report done by a SAR group from Australia that states
>emphatically that the "Abnormal Figure 8" is not safe to
>join rap ropes....they say the simple overhand is better
>.....but I think they base it on the chance that the knot is
>tied loosely and is not packed right - but it is interesting
>reading.

See also http://www.xmission.com/~tmoyer/testing/ which comes to a similar conclusion. Was also a german guide who posted testing by Edlerid on wreck.climbing.

But, not the same as what this feller wants.

Posted, "I would like to research the breaking strength of the Alpine Butterfly vs. the In-line Figure of Eight on 11mm and 13mm (12.5)static nylon kernmantle rope."

I'm assuming he'll be testing the loop strength of each. Fixturing for this test will be a bit different than for testing rappel knots. I'd make sure I used a very highly rated steel carabiner (or a large diameter pin well above the rated rope strength) for the loop end. For the other end, make sure to use a wide and large diameter cylinder. You'll want to wrap the rope probably a minimum of three times around the cylinder. See Tom Moyer's website above, as he had some cylinders custom built for rope testing of this nature. He's also very emailable, if you have any questions.

Will also depend on how you test the figure eight (ie, which direction you pull if from). Nice if you pulled from each "side". Won't matter as much for the butterfly (hence, why its a better knot than the figure eight for a loop in the middle of a rope). Be interesting to see your results.

Please keep us posted of all testing results!!

Thanks,

Brian in SLC

I disagree with the statement that the "abnormal figure 8" (AF8) is not suitable as a rap knot.

All the samples of AF8 that were tested rolled back at least once, but the loads for the roll-back ranged from 2.78kN to 6.84kN with a mean of 4.92kN - more than adequate for my typical rap situations.

I.e. if using the knot for rapping only, I am not expecting to be loading the knot higher than about 2.5kN...certainly not into the 4.6kN range (1st roll back for one sample) nor into the 11.5kN range (2nd roll back for that same sample).

Based on the loads they applied, I feel totally comfortable using the AF8 for all my rap situations. However, I always pack the knot tightly with long tails (>14"), and lately my partner's and I have been using either a simple overhand backed up with another overhand, or an AF8 backed up with a simple overhand - for those situations where it is unlikely to be getting our rope stuck.

I'd also like to point out that they tested only static lines. Part of my brain wonders how much of a difference (if any) a dynamic line would have made. Would the knot "choke" better, would it slip more, etc,...?

Cheers,
D

Why? Becuase this is the standard ropes that rescue teams in the US must use. Rescue teams are anal about loads, load shifting and safety factors ans so spend endless amounts of time and effort defining just what the effects of xyz will be on an assembled rescue rig.

Not nearly as much work done on dynamic ropes or climbspec tube tape.

Macca

so to continue in the question vein:

1) When placing a T-slot anchor or burying a snow stake horizontally as a deadman, which of these do people use? (a) a sewn sling girth hitched around the middle of the stake through the holes (b) a bit of tape tied with a tape knot threaded through the holes.

I guess I've used both depending on what was handy at the time and I'm curious to see if there's any consensus on the safest way to do this. Personally I reckon the anchor will lift from the snow before either knot/sling will fail. What do you guys think?

2) When tying a third person into the middle of a rope do they (a) clip in to an Alpine butterfly with a locking carabiner or (b) tie in with a rethreaded figure 8 or clipped overhand knot on a loop of line extended from an overhand knot tied on a long bite.

I'd never used method (b) and don't like it that much as the Alpine Butterfly is a nicer knot for loading along the rope from front to back. I reckon the overhand knot on the bite is ghastly for loading in three ways... but a guy I climbed with uses this method and prefers for the middle climber to be tied in rather than clipped in. Any thoughts?

Alan.

PS... glad you guys liked the NZ photos I will put some of the better ones (which inevitably weren't taken when I was dangling off mountainsides) online as time permits.

I think it depends what you are going to use (and abuse) it for. If just bailing, then I'd probably just girth hitch a sling on. If fixing for return jugging, might use a carabiner to attach the two.

>I guess I've used both depending on what was handy at the
>time and I'm curious to see if there's any consensus on the
>safest way to do this. Personally I reckon the anchor will
>lift from the snow before either knot/sling will fail. What
>do you guys think?

Shite, them slotted pickets can be bomber!

>2) When tying a third person into the middle of a rope do
>they (a) clip in to an Alpine butterfly with a locking
>carabiner or (b) tie in with a rethreaded figure 8 or
>clipped overhand knot on a loop of line extended from an
>overhand knot tied on a long bite.
>
>I'd never used method (b) and don't like it that much as the
>Alpine Butterfly is a nicer knot for loading along the rope
>from front to back. I reckon the overhand knot on the bite
>is ghastly for loading in three ways... but a guy I climbed
>with uses this method and prefers for the middle climber to
>be tied in rather than clipped in. Any thoughts?
>
>Alan.

Clipped into Alpine Butterfly. If you've ever held a hard crevasse fall, and need to escape the belay, you won't need to cut the rope. Way faster to just unclip the rope, rather than try to undo a weighted knot, that is probably wet and/or frozen too. Situation might be time critical.

Nice pics, btw, keep 'em coming!

Brian in SLC

>Shite, them slotted pickets can be bomber!

Indeed! I've not seen a properly placed one fail. Hope I never do! Have had a picket placed vertically fail spectacularly though... no damage done. Kind of guessed it wouldn't hold so tested it before trusting it... and kaboom... flying picket.

>Clipped into Alpine Butterfly. If you've ever held a hard
>crevasse fall, and need to escape the belay, you won't need
>to cut the rope. Way faster to just unclip the rope, rather
>than try to undo a weighted knot, that is probably wet
>and/or frozen too. Situation might be time critical.

Yes, this is a good point I'd not thought of. I haven't yet had the experience of holding a fall with a climber in the middle of the rope. (Actually, this last trip was the first time I'd ever climbed with three on a rope at all.) Mind, if the person in the middle does go over too, maybe they'd prefer to be tied rather than clipped with a single biner. Then again, the anchor for the rescue is probably clipped with a single biner (although hopefully backed up with another anchor) so it should be fine for the climber.

Alan

Email them at:
climb@bdel.com

or call 011 (801) 278-5552 and see if you can talk to their testing lab.

Matt

Would be either Paul T or Kolin P. They have done some pull to failure type testing on ropes.

Brian in SLC

Check out kolin's web site. Lots of footage of his wife pulling down.

wwww.kolin-and-ellen.com

matt

Book marked that dude along time ago...his Denali video is super, feller is talented.

Ellen sent 13c at the VRG...yeeeouch! Got a decent photo of her catchin' air on a .12 back up in their homeland (Grassi or Cougar Creek er something outside Canmore)...

Fun bunch of folk here in the briney pond village...

Brian in SLC

Note that it covers nylon slings only - he didn't test spectra.

Note also that in the girth hitch test, sling-to-sling, the nylon slings lost 26% of their strength. This is pretty much in line with what I would have expected (I guessed 30% in my first post), but I still think there's another source somewhere with more extensive data about this. I'll post if I find it.

Anyway, here you go:

******

this was on rec.climbing:

Test Report - Sewn Slings on Wire Stoppers - Suicidal or Acceptable

Tom Jones - tom@jrat.com, www.canyoneeringusa.com

Thanks for Black Diamond for providing materials, information and
testing facilities for this test. All conclusions are my own, and
do not represent the opinion of Black Diamond Equipment LTD.

(c) 2002 Nolan Jones. Permission is granted to reproduce only in
it's entirety, including this copyright notice.

Introduction:

The question comes up from time to time - how strong is a sling
thrown through a wired stopper? Some say - really weak - never do
it. Some say - it's not so bad. So I decided to run some tests
and find out.

Black Diamond Wired Stoppers come with 3 sizes of cable: #s 1 and
2 use 1/16" 7x7 galvanized cable; #s 3, 4 and 5 use 3/32" 7x19
galvanized cable; and larger sizes use 1/8" 7x19 galvanized cable.
I concentrated on the larger two sizes. BD was kind enough to make
up samples of just the swaged cables.

Black Diamond Nylon 11/16" or 18mm runners are similar to slings
in common use among climbers. These are probably a little stronger
than average, and were chosen for testing largely because I had a
bunch of new ones from the same batch that I could use. All results
should be scaled down based on the rated strength of the runners
you are using.

WARNING: evaluation of these tests requires experience and judgment.
I do not recommend using slings on wires - but for the expert
climber it MIGHT be a reasonable alternative IN SOME CIRCUMSTANCES.

The Tests:

Of course, we can't test every combination. So here's what I
decided to test:

A. Data on the #2 stopper establishes the base strength of the
1/16" cable. B. Data on the #5 stopper establishes the base
strength of the 3/32" cable. C. Data on the #8 stopper establishes
the base strength of the 1/8" cable. D. Data on Camalot slings
establishes the base strength of the webbing loops.

Base Data:

1/16" cable: Average 724 lbs, Minimum 566 lbs, Rating 450 lbs, N
= 131. 3/32" cable: Average 1747 lbs, Minimum 1409 lbs, Rating
1259 lbs, N = 220. 1/8" cable: Average 2970 lbs, Minimum 2607
lbs, Rating 2248 lbs, N=190. Slings: Average 5781 lbs, Minimum
5393 lbs, Rating 4946 lbs, N=236.

But, we're not going to be real sophisticated here, we'll just use
the average.

1/6" cable = 724 lbs. 3/32" cable = 1747 lbs. 1/8" cable = 2248
lbs. Sling = 5781.

New Test Data - all tests use 4 samples. All strengths in pounds.

T1: Test actual batch of slings.

Average = 5880. Minimum = 5733.

Conclusion: this batch of slings a little stronger than average.

T2: Test slings, girth hitched together (as they normally are in
the field), not neatly dressed.

Average = 4363. Minimum = 4084.

Conclusion: girth hitching sling to sling loses 26% of the sling
strength. Given the high initial strength, the hitched system is
still strong enough for most climbing uses.

T3: 1/16" cable with sling girth hitched to it.

Average = 936.5. Minimum = 911

Conclusion: compared to 1/16" cable average of 724 lbs - Sling is
stronger when girth hitched to sling than when run over the head
of a tiny stopper.

T4: 3/32" cable with sling girth hitched to it.

Average = 1301.5. Minimum = 1269.

Conclusion: compare to 3/32" cable average of 1747 lbs. Loss of
strength of 26% on the cable.

T5: 1/8" cable with sling girth hitched to it.

Average = 1709.0 Minimum = 1624.

Conclusion: compare to 1/8" cable average of 2248 lbs. Loss of
strength of 28%.

T6: 1/8" cable with sling doubled through it (rather than girth
hitched).

Average = 3211. Minimum = 3054.

Conclusion: compare to 1/8" cable average of 2248 lbs. No loss
of strength.

T7: 3/32" cable girth hitched with 3/32" cable (stopper to stopper
extension).

Average = 1520. Minimum = 1439.

Conclusion: compare to 3/32" cable 1747, loss of strength of 13%
- better than the sling.

Comments: The data is screwed up a little bit because the actual
stoppers are tested with the aluminum stopper at the top and a 10mm
pin at the bottom. These commonly break at the top, where the
cable folds tightly going into the stopper. Thus, in these tests,
we can achieve "stronger than average results" because we are
running the tests differently.

Overall conclusion:

Yes and No.

1/16" cable (really small stoppers)

You probably would not think of tossing a sling through these,
because the placement and the cable are so small and weak to begin
with. Looks like the sling does not make it any worse, but this
is of little utility, since this is an aid piece anyway. Not strong
enough to rappel off of.

3/32" cable (small stoppers 4, 5 and 6)

I think these are usually considered pretty strong, but not truck.
Girth Hitching the sling through gives you significant loss of
strength, to down below the rating on the #5 Stopper. May be OK
for rappelling and low-impact falls, but not for general use.

1/8" cable (large stoppers)

These are usually considered truck. Tossing the sling through
results in a strength of 1709 lbs (loss of 28%). Sketchy still,
even on the large size. OK for rappelling and low-impact circumstances,
but not for general use.

Girth Hitch vs. Doubling the sling through:

Doubling through WINS big time. Yes, it takes twice as much sling,
but it is definitely significantly stronger.

Wire Cable hitched with Wire Cable (Stopper to Stopper extension)

Stronger than the sling, but not that strong. Makes for a stiff
unit, negating what is often the prime reason for extending the
piece in the first place.

Conclusive Overall Conclusions:

Girth Hitching a NYLON sling through reasonable size Stoppers is
OK for low-strength operations, but should be treated with caution.
Doubling the sling through, especially on the smaller sizes, is
acceptable. Extending with cables suffers from some of the same
problems, though to a lesser degree.

Spectra Slings - No comment, not tested.

And of course, everyone will draw the line differently. Protecting
a 60' runout and no biners to spare? Sure, it's better than nothing,
but I'd try to double the sling through at the very least. For
setting a rappel? Acceptable I guess, in the larger sizes, but
repeated use might eventually cut the webbing.

Using smaller webbing than the BD 18mm nylon slings? Exercise more
caution.

That's my story, I'm a stickin' to it.

(signed) Tom Jones aka Jrat aka Ratagonius Utahness