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


Dec 24, 2012, 11:20 AM

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Registered: Oct 13, 2005
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Re: [milesenoell] Rappel accident, 60' fall
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milesenoell wrote:
If that's the case then let me venture the question: How likely is a correctly rigged autoblock to fail?

Good point. At the same time, it's one thing to say that a bowline is correctly tied. Or a double fishermans is correctly tied. An autoblock has variables (some listed below) that necessitates something more than "is this the config I am used to seeing?"

(above, I'm probably saying things that you already include in "correctly rigged" - just want to be explicit.)

In my limited experience with an autoblock, it seemed to be a kind of balancing act between too loose to catch and too tight to be smoothly slid down by the hand. The consequences of too loose are obvious. For too tight, it's both an annoyance and a distraction during the rap. Maybe this balancing act is why some in this thread have emphasized testing the set up to see if it seems to catch (albeit in the config of a given pre-rap test) - to get the balancing act just right.

Assuming the ATC didn't push the autoblock down during this fall, perhaps the failure here has to do with one or more of the following - any of which will reduce the chance that the autoblock is going to grab on its own:

* the number of wraps around the rope being too few (perhaps combined with the ends of the cord not being held in close proximity or crossed (akin to kleimheist)?);
* the relative diameters of the cord to the rope; the author of the video indicated the rope was a 9.0 mm rope; the coils of an oversized cord will not cinch down on a relatively small diameter rope as readily as a cord of lesser diameter;
* the type of rope; Blue Water Canyon Line spec info indicates it has a 100% Technora Aramid sheath for excellent cut resistance (relatively slick?);
* edit to add: too short of a cord may cause the biner to be in contact with the rope - perhaps that could hinder the autoblock from grabbing on its own; perhaps this in itself is a good reason to wrap towards the ATC and then clip back on the opposite side of the girth hitch.

Is there something else (again, assuming the ATC did not push down the autoblock)?

Bill L

(This post was edited by billl7 on Dec 24, 2012, 11:24 AM)

Edit Log:
Post edited by billl7 () on Dec 24, 2012, 11:21 AM
Post edited by billl7 () on Dec 24, 2012, 11:24 AM

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