Can You Decrease Fall Factor?
Instead of taking the maximum fall factor, should you let the belayer feed out more rope, resulting in a longer fall but lower fall factor?
Let’s assume you are on an overhanging climb high above the ground (no groundfall potential). You are 10 feet above the belay with 10 feet of rope out and no pro between you and the belayer. You will fall 20 feet on 10 feet of rope, resulting in a factor 2 fall. Instead of taking the maximum fall factor, should you let the belayer feed out more rope, resulting in a longer fall but lower fall factor? If the belayer pays out an additional 10 feet of rope (20 total), you will fall 30 feet on 20 feet of rope, resulting in a factor 1.5 fall.
First, a big squeeze to all you clones and masochists who e-mailed questions hoping to con me into giving you the free pair of Scarpa Techno X rock shoes I promised per the “Send a Question to Gear Guy” contest in November. Tanner, you have won. As for the rest of you, keep the queries coming—one of them will win yet more free stuff.
Tanner posits an interesting alternative to a worst-case roped fall, and one you likely haven’t thought of, since the human instinct is to reel in rope and shorten the fall.
But Tanner is spot on: More rope relative to the fall distance will decrease the fall factor and impact force. This is because the rope is a spring. The longer the spring, the more it can stretch and absorb. The nuances of fall factors and impact forces would fill Einstein’s chalkboard, but practically, you will notice that when you fall low on a route with little rope out that you rattle a few fillings, while when you fall higher with more rope out the catch is nice and cushy.
Tanner’s example of a factor 2 fall right off the belay is, however, as unlikely as winning at PowerBall because even a half-dim leader will clip a piece of pro at the belay, reducing the fall factor. This is why the UIAA/CE certifies ropes using a 1.77 fall factor for drop tests instead of a fall factor of 2.
Even so, a fall factor of anything over 1 is severe. Do what you can to avoid the possibility. “Don’t fall” is always a good mantra. Fiddling in some kind of gear even if it is mank can reduce the impact force. Other tactics to minimize the impact force are to have the belayer give a dynamic belay by jumping as he feels the leader come onto the rope.
Black Diamond, in one of its QC Lab Reports, notes that the benefits from letting a rope rest between falls—a common sport-climbing practice—only marginally reduces the impact force. Switching ends or even ropes is the best way to keep your cord springy and impact forces lower. Next!
This article appeared in Rock and Ice issue 232 (February 2016).