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Karl Lew

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Black Diamond Girth Hitch Test

In response to gathering interest from the denizens of rec.climbing, the following information was provided by Chris Harmston, Quality Assurance Manager for Black Diamond Equipment. The test was conducted at BD facilities on samples of sewn BD nylon and spectra runners. Many thanks to Chris and all the gang at Black Diamond.

To appease the unit gods, this information is available in kN or lbf.

kN S1 S2 S3 S4 S5 AVG STD SD3 KNOT
11/16 Nylon Supertape sewn loops. 26.6 24.8 25.1 25.2 25.3 25.4 0.7 23.3 100%
5/8" Spectra 27.9 27.8 26.7 26.9 27.9 27.4 0.6 25.6 100%
Nylon Girth Hitched to Nylon 15.7 17.8 19.4 16.6 19.1 17.7 1.6 13.0 70%
Spectra Girth Hitched to Spectra 18.9 19.6 19.7 17.2 19.6 19.0 1.1 15.8 69%
Nylon Girth Hitched to Spectra 18.1 17.4 18.8 16.4 18.2 17.8 0.9 15.0 70%
Spectra Girth Hitched to Nylon 19.0 18.6 18.1* 19.3 19.2 18.8 0.5 17.3 74%
S1...S5: samples; AVG : average; STD: standard deviation; SD3 = AVG - 3*STD; KNOT: % avg loop strength
* Spectra sling broke

Chris concludes:

  1. These are variable systems. Multiple data points are needed in order to be able to state real trends between groups.
  2. 11/16" Nylon Runners are 93% of the strength of 5/8" Spectra loops.
  3. Girth Hitching reduces the strength of the material by 30%.
  4. Girth Hitching strength is more or less independent of what it is attached to (at least for this test). Note the similar strengths between Nylon hitched to Nylon or Spectra and Spectra hitched to Spectra or Nylon.
  5. If you must link two runners a carabiner is stronger. If you must use a girth hitch then put the girth hitch on the web that has higher strength. Or use a longer runner altogether.
Karl speculates:
These tests also suggest that the girth hitch loads slings asymmetrically, with the girth hitch sling taking the major hit. Observe the spectra sling that broke in the last set of samples.

continued...