Careful with that belay loop

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One of the gyms I climb at has this article up on the wall:
Todd Skinner's hands were cut up and he was tired after a hard day of climbing, but he was a happy man standing high above Yosemite Valley on what is known as Leaning Tower.

...

They talked about their plans for the next day, then Skinner began rappelling down from a ledge part way up the 2,000-foot face. Five minutes later, he was dead.

Skinner, a 47-year-old former rodeo cowboy and world-renowned rock climber, fell more than 500 feet to his death Monday after the nylon loop used to attach the climbing rope to his harness broke. The accident has sent shock waves through the climbing community, where Skinner's outgoing nature was almost as legendary as his courage and skill on some of the world's most dangerous rock faces.

...

The part that broke, called the belay loop, is designed to be the strongest part of the climbing harness, but Hewett, 34, said Skinner's harness was old.

"It was actually very worn," Hewett said. "I'd noted it a few days before, and he was aware it was something to be concerned about." Friends of Skinner said he had ordered several new harnesses but they hadn't yet arrived in the mail.

On Monday's climb, Hewett said the belay loop snapped while Skinner was hanging in midair underneath an overhanging ledge.

For those who don't climb, a little explanation may be in order. Your basic climbing setup is that you've got two guys, one climbing and one belaying. They're both wearing harnesses and are attached to each other by a safety rope. The idea here is that the belayer leaves a relatively small amount of slack in the rope so that if the climber falls, he only falls a short distance.

The climber typically has the rope tied directly onto his harness, since it's a fixed point. Your classic harness is just a waist belt with some leg loops and you tie in through both of them. Simple.

However, since the distance between the climber and the belayer keeps changing, the connection at the belayer's end is more complicated. The rope is threaded through a belay device which is a gizmo that lets the belayer apply a lot of friction to the rope without much force. The idea here is that while the climber is climbing the belayer can adjust the length of the rope but of the climber falls the belayer can lock the rope.

The belay device and the safety rope are attached to the belayer's harness by a carabiner (a metal ring with a gate one one side to let you open and close it). For a variety of reasons, people are concerned about having the carabiner through the waist belt and the leg loops (a lot of people argue that this cross-loads the carabiner thus increasing the chance of failure--this isn't an issue for the climber because rope is flexible). In order to avoid this, most modern harnesses have a belay loop. This is just a sewn nylon (or spectralink) loop that goes through the waist belt and leg loops (right where the rope would go). You clip the carabiner for the belay device into the belay loop. In the picture below, the belay loop is the green thing.

If the climber falls, you suddenly have a lot of force on the rope connecting the climber and the belayer. This force is on the climber's harness at the tie in point and on the belayer's harness at the belay loop--and of course on the waist and leg loops because the belay loop goes through those. Thus, the belay loop creates an additional point of failure, but this typically isn't a problem because they're enormously strong--Black Diamond rates theirs at 15 kN (3372 lbs).

What appears to have happened in this case (see this article) is that Skinner had been using a daisy chain—more webbing—through his belay loop and that the rubbing of the two pieces of webbing had abraded the belay loop. This can also happen if you tie in via your belay loop, which is why it's recommended that you tie in directly through the waist and leg loops, which have abrasion resistant material on the outside, which the belay loop does not. Note that this isn't an issue with belaying since the carabiner causes less abrasion of the belay loop.

One thing that's weird here is that belay loops are massively overbuilt. According to the article I pointed to above, even if you remove 90% of the material in a BD belay loop, the breaking strength is 777 pounds. If you're rapelling, or hanging as this article suggests, the total force is merely your own body weight and most rock climbers weigh far less than 700 lbs. Either the belay loop was truly damaged, which is something you would expect to be so obvious that you wouldn't use it at all or we need to account for some other source of failure.

One more observation: as I said earlier you attach the belay device through your belay loop and the force of the fall is transmitted to the belay loop through the belay device. A fall from a reasonable height will load the belay loop substantially more than just the body weight of the climber. Given that Skinner and Hewett were at the top of the climb, it seems likely that Skinner was belaying off that same loop, a practice that would have left even less margin of error than we now know was already inadequate.

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It seems plausible that in rappelling past the overhang, Skinner could have ended up swinging towards the wall, thus loading the system with more than body weight, though probably not by a significant factor. I'll be interested to hear the results of the official investigation.

This, like Lynn Hill's fall on an incomplete figure-8, will make a good story to tell when I'm trying to impress upon new climbers the importance of safety checks.

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