Why a 6-Foot Fall Can Be More Dangerous Than a 100-Foot 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.
Common scenario: You are working a sport route when you clip directly in to your high bolt with a long quickdraw or sling clipped to your belay loop. Common practice, right? 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 you pull back onto the rock, crank a move, and fall. But, oops you forgot to unclip from the draw.
The fall onto the quickdraw, 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 hurts, 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.”
In both situations you fell prey to shock loading, and although your falls were short, both were fall factor 2—the severest possible [read “What the Hell Is a Fall Factor Anyway?”]. 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 carabiners) 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 most lead falls. In the first example, when you neglected to unclip from that quickdraw, you removed your dynamic rope from the protection chain. Since quickdraw, carabiners and slings 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 like damaged goods.
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.
Shock loading is among climbing’s most insidious, and potent, hazards. It awaits, lurking, for you to screw up. 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, we 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.
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.
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, and always use a locking carabiner in situations where proper carabiner orientation is questionable.
“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, a former gear engineer at Black Diamond and now at Blue Ice. “When the forces get high enough, something has to give. It’s just physics.”
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.
Points to Remember
- Quickdraws, slings and daisy chains, for practical purposes, don’t stretch.
- 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.
- Keep the dynamic capacity of the rope active in the protection system at all times.
- 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.
- 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.