...the claim that 12g is equal to 12kN for the average climber is clearly false.

If they wanted to minimize the possibility of injury to the average climber (not some worst case scenario), they'd set it at around 9kn, if not lower.

...the human body can actually handle 12 kn for very brief periods of time...

First, we need to define what "rope failure" actually is. No, I dont think anyone has ever completely severed a rope in half from "too big" of a lead fall (aside from failure due to sharp edges or chemical alteration). However complete sheath failure, resulting in serious injury, has occurred. When rappelling a 11mm static rope in Yosemite this happened to me:

[img]http://img853.imageshack.us/img853/7739/img0203tp.jpg[/img]

The rope deshethed as my belay device hit a worn section of the rope. I slid down the rope until the sheath jammed in my belay device, stopping me. A few of the core strands failed as my Trango Cinch attempted to jam the core strands, but failed to. The rope could have failed and if it had, my death/ injury would have been a result from rappelling on an excessively worn rope, which seems to meet your qualifications. Someone in Hawaii had the same thing happen to her a few years back. She was rappelling on a rope and the sheath failed sending her 60 feet to the deck. The rope did not completely fail, however, because belay devices grab onto the sheath of the rope, she just slid down the core strands to the ground. I did not have that problem because in my case, the sheath failed in the belay device, not after the belay device. Had the sheath severed after it passed through my belay device, it would have been pinching the detatched sheath instead of the core strands and I would have likely decked (think of trying to rappel by holding onto the rope through a banana peel)

Dang. Damned. Crap. That is basically the repetitive nightmare that I keep having, and why I asked this question. Would the moderator please delete USNavy's post and I'll pretend I never read this.

Isnt there something on this website that lets me block USNavy's posts?

Seriously tho, how old was the rope and how bad was the wear?

I believe the 12g number originally came from military parachute jump injury statistics. Granted, for a given fall and rope a lighter person will experience a higher peak deceleration. But how deceleration and body mass scale with respect to injury rate is not obvious, at least not to me.

The figure I have heard and seen referenced in regards to falling is 12kN. The military parachuting experiments showed that organ displacement occurred at 12kN. I have not heard g-forces referenced in relation to these experiments.

In the following article, the researchers found that lumbar vertebrae suffered fracturing at an average of 6.5kN, though they state that spinal muscle and connective tissue would likely cushion and reduce peak impact forces in a real-world situation. In the study the majority of the specimens fractured at less than 9kN of peak load, though one set (21yo male subject) exceeded 15kN before breaking.

http://www.ncbi.nlm.nih.gov/.../janat00240-0080.pdf

Has a rope ever broke with no extenuating circumstances? More specifically, has a climber ever taken a fall and had the rope break because the force of the fall exceeded the breaking strength of the rope.

Typical extenuating circumstances that dont apply to this question:
--Rope cut by sharp edges in gear or rocks.
--Rope exposed to chemicals.
--Manufacturer defects like the disintegrating petzl ropes.
--dan osman.

And by rope, I mean a modern dynamic kernmantle rope.