Forums: Climbing Information: Accident and Incident Analysis: Re: [billl7] Rappel accident, 60' fall: Edit Log


Dec 26, 2012, 2:57 PM

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Registered: Oct 13, 2005
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Re: [billl7] Rappel accident, 60' fall
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To look at how sensitive the french-prusik autoblock might be to number of wraps, I did some testing. I tried to be as close as practical (for me) to reproducing their rope and cord diameters:

* 9.2 mm Sterling Nano vs. their 9.0 mm Blue Water Canyon Line;
* 6 mm perlon accessory cord vs. their unknown dia cord although ratio of cord to rope looks about right for 6 mm in their images,

Edit: The scope of the testing was increased from that shown below. All current results are shown here.

To summarize: five wraps of the autoblock would stop a drop of a 34 pound weight (via bathroom scale). Four wraps would not stop the same drop, albeit with travel limited to about 2 feet. Each autoblock config was tried 5 times to check reproducability - results were reproducable. And for each drop I would lock off, push the autoblock down about an inch, and then let go.

Interestingly, both configs could hold the weight if the autoblock was pre-tensioned.

This was with 22 1/2 inch stretched-out loop (~45" circumference). loop girthed to leg loop behind buckle (Petzl Adjama), wrap towards load, clip leg loop rear-ward of the girth. It was probably a longer loop than Matt's and would require extending the rap device to avoid interference.

Can provide more details of the tests if folks are interested.

Bill L

(This post was edited by billl7 on Dec 26, 2012, 8:04 PM)

Edit Log:
Post edited by billl7 () on Dec 26, 2012, 4:48 PM
Post edited by billl7 () on Dec 26, 2012, 4:49 PM
Post edited by billl7 () on Dec 26, 2012, 8:04 PM

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