Girth hitching/knotting slings

[Shawn B]

Check this out if you use the new skinny slings. I personally never girth hitch the skinny slings or cordelette. I have knoted two double length skinny slings with a figure 8 for a bolted anchor but no more. Jim Ewing (Sterling ropes) now suggests to never girth hitch period for a top rope anchor. Too much cyclical loading and unloading. I have seen some people girth hitching cordelette to webbing and never did like it or feel it was right.


--------------------------------------------------------------------------------
Below is an email from John Sherman, aka Verm, that has been arriving in my email box all weekend. Many people have been asking for my thoughts and comments.
I can not say for certain what caused this failure without the proper tests. My educated guess is that John is correct in his assessment that the sling most likely cut itself.
I personally have several of these new skinny slings and feel perfectly safe using them. However, I recommend that people avoid using them in any way other than between two carabiners. Doubling up is fine but avoid using them knots or hitches. Another concern I have is with them being used as a direct connection to a belay or rappel anchor because people typically girth hitch the sling to the belay loop of the harness when they do so.
As with any piece of life safety gear, know its limitations.

"Dyneema sling failure under very low load when girth hitched 10-19-06

On Oct 19th I experienced a partial rappel anchor failure when a Dyneema sling used as part of the anchor broke at the point where it was girth hitched to a wider Spectra sling. The anchor was set on Oct 15th, 30 feet back from the top of the cliff and used only for rappels and was never subject to any sudden impacts. The anchor was equalized for the direction of pull with the girth hitched point of failure on one side. In theory this part of the anchor should have only been subject to half the loads, however because the equalization point was a clove hitch it is possible that one side could have taken the full load (body weight only) if the angle of the rope changed. The rappel line was a static rope and I was using a Grigri as my rappel device. Where the rope ran over the lip of the cliff it was padded with a piece of carpet. Every morning the anchor was inspected for soundness (especially any cha-cha by rodents) and seemed sound. When loaded, the Dyneema sling was suspended in mid-air with absolutely no contact with the rock to cause abrasion. The anchor was rappelled on a total of seven times (sling failed on 7th rap). As we were cleaning routes, the time of rappels varied from about 10 minutes to one hour. There was a small amount of rain on the 17th and possibly some showers on the 18th, however the rappel line felt dry on the 19th. The failed sling was in use less than one year and showed no signs of damage prior to this incident. The girth hitch feels quite tight after the break. When the sling finally failed I was partway down a slab with multiple points of contact between the rope and the rock to reduce the force on the anchor. I was stationary at the time and suddenly dropped a foot when the sling broke. The point where the Dyneema failed was Dyneema pinching Dyneema and not in contact with the Spectra (see photos). The Dyneema sling that broke was an 8mm Mammut runner. The sling it was girth hitched to was a 5/8” Misty Mountain Spectra runner. The broken ends of the Dyneema feel soft, not fused.

What factors might have increased the load beyond body weight?

* Pendulums across the face – 10 foot lateral swing at most, 30 feet below the point the rope ran over the top of face.
* Extra force applied when prying loose blocks of with a prybar. In theory this force could not exceed the amount I could deadlift. In this situation I don’t beleive I ever exerted more than 100 pounds of additional downward force on the rope.
* Sudden drops onto rappel line after it was unweighted when standing on ledges. At times the rap line was partially unweighted, but because I am nervous/careful when it comes to ropework I always sucked up the rope through the Grigri before reweighting it.
* Extra weight of bolting gear, prybar, etc – 40 pounds at most.


I don’t believe any of the above factors is significant, especially since all of these take place below the lip where the friction of the rope on the lip would reduce the load on the anchor.

At times the sling may have been stored in the same pack as a Bosch battery. Is there any evidence that NiCad cells emit anything that can damage Dyneema?

At present my best guess as to why the sling failed is that when girth hitched tightly such a small diameter sling can cut through itself (the sling suffered a very clean break). In this incident I can imagine that the girth hitch received numerous small tugs under low load (body weight and less) and this might have caused a repeated microscopic nipping or sawing action that eventually cut through the whole sling (the wider Spectra sling it was girth hitched to also had some fibers cut at the point of contact with the Dyneema). I am trying to contact the equipment manager from Mammut to have this sling failure expertly analyzed. Until then I suggest that Dyneema slings should never be girth hitched or otherwise knotted.

John Sherman"


Jim, thanks for passing this along. I was wondering if you could share your thoughts on the following uses of the Dyneema slings:

In an alpine draw, girth hitched to the rope biner to prevent rotation.
We know that knots and hitches always reduce the strength of cord and webbing. High tensile, high modulus, materials in particular have problems with this. Personally I feel that using these skinny slings girth hitched as a runner is fine since it's not being cycle loaded, however, I am still cautious about it; avoid using in potentially high force falls and particularly as a runner or draw that is going to see repeated falls while working a move.


Quote
In equalizing a multi-point anchor, using a figure-eight.
A big honkin' fig 8 is fine but still be aware of repeated cycle loading. Probably wouldn't happen as a multi-pitch belay anchor but would as a top rope anchor.


Quote
In "extending the rappel", girth hitched through the tie-in points instead of the belay loop.
Until I see tests that prove this is safe I would avoid it. Again, girth hitching is bad and I think the potential for repeated loading on a focused point is high, as it might be as a rappel extender.


Quote
With the popularity of the skinny Dyneema slings I see them being used in those scenarios quite often (and use them myself). Just to clarify for my hard head, do you recommend that people use Spectra or nylon slings instead for those applications? Thanks again. Tom

Avoid sling to sling girth hitches in all materials when they are part of an anchor, any anchor. As for a personal direct connection to a belay or rappel anchor I think generally it's not the best scenario but I don't think you will die.

It's important to note that in Verm's rig he had a set up that put multiple small loads on a focused point. How many of those small loads will never be clear but sure I'd say that was the single biggest factor. Unless it was chemical contamination............

My motto:
Nylon, the new miracle fiber.

[granite_grrl]

I was going to copy the links for this discussion, but it looks like you put in more detail than I would.

Read about it here on Super Topo:
http://www.supertopo.com/climbing/thread.html?topic_id=269434&f=30&b=0

Or here in RC.com
http://www.rockclimbing.com/topic/121517

[The Mitt]

Man I used to do that all of the time.

Mitt

[Fred]

I've stoped girthing my skinnies. I double them up around the tree and just put two lockings in em. When the tree is too big I use a cord with tied figure eight and if I'm leading an easy route and get to the top and don't have a big enough loop I use my climbing rope as an anchor and gri-gri off that.

[The Teth]

After reading this and the stuff John posted earlier, I agree with this guy’s motto: “Nylon, the new miracle fiver.” We can get lighter, we can get stronger (under ideal conditions), but Nylon is still by fare the most reliable.

Teth

[john]

there are some new inconclusive preliminary studies supported by BD suggesting the differences between useful life of nylon and spectra are not a great as previously thought. If you follow all the above info and links associated on supertopo where the info was first put up I dont think you will be as "for nylon" all things considered. You have to read it all though.