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Red River Gorge - Spring 2012
Red River Gorge - Spring 2012

Hot to Climb Safe: The Dangers of Short Static Falls

04-Jan-2013
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Chris McNamara employing proper daisy-chain technique by keeping the sling clipped overhead and using the rope below him to catch a potential fall. Photo by <a target="_blank" href="http://www.coreyrich.com/">Corey Rich</a>Common scenario: You are working a sport route when you clip in directly to your high bolt with a quickdraw attached to your belay loop. Resting on the draw, you suss and brush the holds, then rest some more until you feel strong again. With fresh blood pumping through your forearms—and nary a word to your belayer—you pull back onto the rock, crank a move, and fall.

CRACK!

The jolt back onto the bolt, into which you are still quickdraw-tethered, stuns you. You only fell two feet, but your neck is stiff and your innards feel like they’ve been kicked by a mule. “Lower me,” you say. “I don’t feel so hot. I think my kidneys exploded.”

Another common scenario: You are leading a pitch on a big-wall aid route. It’s dicey, so for extra security you always keep one daisy chain clipped to a lower piece. As you ease onto a high placement, an antique RURP, it pops ... and dings you in the forehead, drawing blood. That smarts, but it’s nothing compared to the rude awakening you receive when you drop onto your daisy chain. That impact feels as if it will snap you in two. But just as that begins to happen—SNAP—your daisy chain breaks and you cartwheel 20 feet down the wall until the rope catches you on a lower, bomber cam.
Though you only fell three feet onto your daisy chain, your back is going rigid and your guts are alarmingly astir. There’s also the acorn-sized knot and ooze of blood on your forehead. “Lower me,” you tell your belayer. “I think it’s your lead.”

What happened?

In both situations you fell prey to shock loading, and although your falls were short, both were fall factor 2—the severest possible. To calculate the fall factor, divide the distance you fell by the amount of rope (or in this case, the length of the draw plus biners) that caught the fall. Fall 50 feet on 100 feet of rope, for example, and the fall factor is 0.5, i.e., not too bad. Fall 100 feet on 50 feet, however, and the fall factor is 2—heinous.

Believe it: Short falls directly onto a quickdraw, sling or daisy chain are more severe in terms of impact forces than any lead fall. In the first example, when you neglected to unclip from that quickdraw, you removed your dynamic rope from the protection chain. Since quickdraws and carabiners don’t stretch, your two-foot fall, rather than gradually being decelerated by the rope, was stopped instantly by the draw. Add to that the fact that you fell two feet on a one-foot quickdraw (fall factor 2), and it’s no wonder you feel likedamaged goods.

That impact feels as if it will snap you in two. But just as that begins to happen—SNAP—your daisy chain breaks and you cartwheel 20 feet down the wall

In the second, aid-climbing example, you did essentially the same thing. Rather than boinging onto the dynamic rope, you shock-loaded the daisy chain, which, unable to stretch, simply blew apart when pushed beyond its load-bearing capacity. And, as in the first example, you cranked off a fall factor 2. Jingus.

Shock loading is among climbing’s most insidious, and potent, hazards. It awaits, lurking, for you to screw up. Shock loading is why, with a lightweight hammer and a short bit of cable, you can funk out welded pins, or break carabiners. Even a small mass moving at high speed and abruptly stopping will generate tremendous energy.

An object going from quickly moving to deathly still may be the hangman’s friend, but it is a climber’s enemy. To ferret out this foe, Rock and Ice conducted a series of drop tests using common items on your rack—quickdraws, runners (nylon and Spectra) and daisy chains—in the aforementioned scenarios. For the quickdraw test, we replicated a fall onto it at its maximum extension (about 12 inches) above the protection. The resulting 24-inch drop sounds tame, but shock loads peaked at 1,600 pounds force, much higher than you’d expect from a mere plop onto a draw. Draw drops from six inches above the pro impacted the anchor with 1,200 pounds of force.

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Though the forces from the quickdraw falls didn’t approach the gears’ load limits, they were quite tangible—the crash-test dummy (yours truly) walked away with a sore back—and are high enough to pull or even break marginal gear placements or funky bolts, such as old quarter-inchers or desert spinners.

Right! Using a daisy chain as a keeper cord, letting the rope catch the fall. Illustration by <a target="_blank" href="http://jercollins.com/">Jeremy Collins</a> For the sling and daisy-chain drops, a 165-pound weight volunteered to take my place. The caveat to comparing “live” drops to “dead-weight” drops is that the human body is gelatinous (some more than others) and has moving parts that absorb energy. A climbing harness also has some load-absorbing capacity. Replacing the body in a harness with a dead weight will increase the forces in any drop test. Nevertheless, this test indicates how equipment, when overloaded, will behave in the real world.

The results of the sling drops were startling. Brand-new, 22-inch-long  Spectra (a polyethylene fiber also manufactured under the brand name Dyneema) runners, CE-rated to nearly 5,000 pounds, broke at the end of their 44-inch falls, grim testaments to the forces you can achieve when you fall directly onto a sling. Interestingly, nylon runners, even old, faded ones scrounged off desert towers, subjected to the same test, did not break, although the shock loads surpassed two tons, far beyond the maximum 2,697 pounds force allowed by the UIAA for single ropes.

Attribute the nylon slings’ durability to the material itself. Nylon, even when it is made with a static weave, as with a runner, has some elasticity. Spectra, though it is 15 times stronger than steel, “is as static as static can be,” says Scott Newell, President of Blue Water Ropes, the first manufacturer to market Spectra slings. “Spectra is incredibly strong, but only as long as you apply the load gradually.”

Note that some of the tests were discounted because when the weights fell, the carabiners rotated—causing minor-axis loading—and their gates failed. Such failures reveal the element of chaos caused when rope, sling, carabiners and body fly through space, and only confirm that you should always tie in to the rope instead of clipping in with a carabiner, which can minor-axis load and break. Carabiners that were properly oriented at the beginning can rotate into weaker orientations—pay attention to your carabiners’ minor-axis and gate-open strengths (see wire-gate carabiner chart, page 90), and always use a locking carabiner in situations where proper carabiner orientation is questionable.

The broken Spectra slings, while surprising, aren’t an indictment of the material–not nearly enough sling diameters and lengths were tested to arrive at any firm conclusons. (Look for a more detailed comparison of Spectra, nylon slings and daisy chains in next issue’s installment of Climb Safe.) We do know that Spectra is stronger for its weight than nylon and doesn’t absorb water, a benefit for mountaineering, ice and alpine climbing. The broken slings do graphically illustrate the limitations of a material when it is misused, and show that nylon slings are more forgiving, though they, too, are not designed to absorb energy. Of all the components in the protection chain, only the rope is meant to stretch.

“Using your daisies or slings to catch falls is asking your system to fail, because there is nothing to absorb energy—you have excluded the dynamic abilities of the rope,”

The forces generated in the daisy chain drops varied depending on which “pocket” the weight was clipped to. A sewn 54-inch nylon daisy chain with the weight clipped to the chain’s middle pocket (allowing a 54-inch drop) peaked at 2,200 pounds force, at which point the pockets began blowing. Four pockets ultimately ripped before the fall was stopped. Ditto when the weight was clipped to a pocket a third of the way down the daisy. The action of the daisy chain  zippering from pocket to pocket slowed the fall dynamically.

When the weight was clipped to the end of the daisy chain, however, and dropped from its full 54-inch extension, both of the daisy chains subjected to this punishment broke cleanly in two. Thus, beware using daisy chains as your primary belay-anchor attachments.

“Using your daisies or slings to catch falls is asking your system to fail, because there is nothing to absorb energy—you have excluded the dynamic abilities of the rope,” says Bill Belcourt, who works in Black Diamond’s equipment-design department. “When the forces get high enough, something has to give. It’s just physics.”

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But if micro-falls onto static slings, draws and daisy chains are so severe, and climbers routinely misuse gear this way, the question remains: Why haven’t we seen a rash of such accidents?
Thankfully, the load-absorbing capacity, slight though it may seem, of the human body, harness and other links in the system builds in a fudge factor that somewhat softens shock loading—but don’t count on it. In some cases, shock-load accidents do happen, but are chalked up to other causes. For example, when we fall onto a daisy chain, which shock-loads the placement, which rips, we blame the accident on “pulled pro.” In other cases, the cause is clear. Recently, a climber fell onto and snapped a daisy chain. He then fell farther, breaking his leg. At least two other daisy-chain falls have resulted in ruptured spleens.

 Wrong! Using the daisy chain as a tether in lieu of the rope can cause bone-jarring falls, gear failure or worse. Illustration by <a target="_blank" href="http://jercollins.com/">Jeremy Collins</a>  Lastly, many of us have simply been dodging a bullet. Time to change our ways. After witnessing carabiners, slings and daisy chains explode in what I previously considered minor falls, I’m rethinking the way I aid-climb: Instead of clipping a daisy chain to a placement and keeping it attached until after I’ve climbed above the piece, I’m going to clip the rope to that piece and unclip the daisy before I climb past it. Then, if I fall, I can ride on down the easy way.

POINTS TO REMEMBER

1. Quickdraws, slings and daisy chains, for practical purposes, don’t stretch.

2. Any fall directly onto a draw, sling or daisy chain creates a very high fall factor—much higher than if you took the same short fall onto the rope. In some cases, the fall factor is 2, the highest (worst) attainable, and one large enough to have serious repercussions.

3. Keep the dynamic capacity of the rope active in the protection system at all times.

4. When you lead aid pitches, use a system where your daisy chains function as keeper cords only for overhead attachments. Don’t clip them to placements in lieu of the rope, even when the attachment is temporary.

5. Mix up nylon and Spectra slings, using the more dynamic nylon slings whenever there’s a chance you could accidentally fall directly onto an anchor, such as at belays.

6. Use nylon, not Spectra daisy chains, for rock climbing, where the benefits of the non-water-absorbing Spectra are lost.

7. When you rest on a piece connected to your harness via a draw or sling, remember to unclip from the pro before you climb again. Do not work a move while clipped directly to a piece of pro.





 

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