Climb Safe: Belay School – Why Dynamic Matters

I’ve always viewed trad- or ice-climbing falls as more serious than sport whippers. Heck, most of us, myself included, have become so accustomed to dropping onto bolts that we now fall more often than we send. The casualness has trickled down to belayers, who scratch their dogs and lounge in lawn chairs as their partners plummet earthward.

Turn that sport route into a thin crack or frozen pillar, however, and—whoa!—falling suddenly becomes a horrible prospect: What if that TCU rips, or ice shears? Even as a belayer, when I hear the cry of “Falling!”, I tense up and brace hard for the upward jolt.

Paradoxically, a good firm catch may be exactly the wrong move—an unyielding belay can double the impact forces on the top piece of gear, a critical consideration when leading on natural gear.

For this installment of Climb Safe, Rock and Ice Publisher Duane Raleigh and I field-tested impact forces during a common fall scenario—a nine-foot whipper with about 55 feet of rope out—using two belay techniques. For one set of falls, I belayed with a Petzl Grigri anchored securely to the ground (a static belay) while Duane hurled himself off the rock; for the next, I clipped the Grigri to my belay loop and, leaving myself unanchored,
jumped up at the moment of impact, yielding a dynamic belay.

The Field Test

For consistency, Duane logged six equal-length plummets while I heckled him from terra firma, alternating static and dynamic belays with the Grigri. We measured the impact forces on the top bolt. The details of each fall went like this: Duane (145 pounds) fell from 4 feet 7 inches above the quickdraw
for a total ride of 9 feet 2 inches (plus rope stretch), on 57 feet of rope; he spaced the falls four minutes apart to allow time for the rope to recover.
I, the belayer, weigh 200 pounds.

The engineers among you will quickly note that these falls equate to a pretty measly fall factor of .16 (out of a maximum factor of 2)—yet were still hefty enough to generate well over 1,000 pounds force on the bolt. To determine fall factors, divide the length of the fall (before rope stretch) by
the total amount of rope out. See Climb Safe, No. 131, for more details on impact forces and how they affect the leader, the belayer and the top piece
of gear.

Test Results

Static belay 1: 900 pounds force on the top piece of gear

Static belay 2: 900 pounds force

Static belay 3: 1,300 pounds force

Dynamic belay 1: 650 pounds force on the top piece of gear

Dynamic belay 2: 750 pounds force

Dynamic belay 3: 550 pounds force

Why Dynamic Belays Matter

As the numbers show, the falls caught with a static belay loaded the bolt with 900 to 1,300 pounds force, the difference likely caused by variables in the system, plus a tiring rope. The dynamic catches, where I “jumped,” letting the force of the fall tug me upward some five to seven feet, loaded the bolt with only 550 to 750 pounds. The third catch generated the lowest impact forces, likely because, by then, I learned to anticipate the fall and jump upward at the exact moment the rope came taut.

In plain terms, the dynamic belay reduced the load on the top piece of gear by up to 60 percent. Considering that many micro cams and small wired nuts have listed breaking strengths of 6 kilo­Newtons, or 1,350 pounds force, a dynamic belay could make the difference between your gear breaking or holding. Remember, the test falls were relatively mild at factor .16 (although rope drag likely increased the impact forces somewhat); it’s easy to get significantly higher forces as you increase the fall factor. In other words, the importance of a dynamic belay for ice and trad climbing cannot be overstated.

Choose the Right Belay Device

Does it matter if you use a vise-like belay device, like the Grigri, versus a tube-style device? Petzl (which manufactures the Grigri as well as a tube-style device, the Reverso) doesn’t recommend the Grigri for “adventure climbing,” nor for winter use, where the device could ice up. Certainly winter use is a no-no, but our field tests suggest that if you belay dynamically, belay-device discrepancies will play little if any role in overall impact forces on the protection.

But if the belay is static (such as when you’re belaying directly off an anchor, or tethered tightly to it), severe falls may benefit from the use of a
tube-style device. Under large loads, these can sometimes let a bit of rope slip through, creating a dynamic, if only slightly, catch.

The lesson? Use whatever belay device you’re comfortable with, as long as you can employ a dynamic belay. Note, however, that a dynamic belay isn’t always possible or can even be dangerous.

Rigging safe dynamic belays

There are many situations where a true dynamic belay is simply unsafe. Some sample scenarios: 1. When the fall can slam the belayer directly into the rock, or upward into a roof (ouch!). Lighter belayers should be particularly careful of this when belaying Clydesdales. 2. When the fall could yank the belayer upward into a quickdraw, which could pinch or disengage a belay device. 3. When the belayer is unanchored on a ledge, and a single misstep could send him plummeting. 4. A leader fall could drag the belayer directly into the line of falling ice, ice tools, etc. 5. A dynamic belay could send the leader falling farther than he wants, hitting a ledge or the ground. 6. Any number of possible scenarios—make sure you evaluate each belay accordingly.

A solution? Create a modified dynamic belay: Tie into a belay anchor so you don’t get yanked into the wall or lose your hold on the device, but give yourself some slack (no more than five feet) to absorb impact forces. When building the anchor, remember that the direction of pull will be directly toward the leader’s first piece, not toward the leader himself. For the softest possible catch (and to prevent being dragged across the dirt), the belayer
should position herself directly below the first piece of gear, ready to jump.

Remember to practice dynamic belaying in a safe situation before taking it to the real world—this is an advanced technique that could land your partner on the ground if you overdo it. Learn to recognize how much—if any—jumping is appropriate.

Even on multi-pitch routes with hanging belays, it’s possible to create a dynamic belay by tying into the anchor with several feet of rope. If you clip
in three feet below the anchor point, you’ll have a total of six feet of upward travel to help absorb the impact forces. (Beware of any overhead projections, and wear a helmet.)

Another good option is to clip into the anchor with one, or a series of, load-limiting quickdraws like Yates Screamers. These provide a dynamic catch when little else will. The dynamic belay isn’t always taught by climbing instructors, often because it is deemed too complex for novices. Nevertheless, for more experienced climbers looking to increase the chance that their gear will hold, it’s an effective technique to add to the quiver.