QC LAB: DO ROPES NEED TO REST BETWEEN FALLS?

Our QC Lab posts aim to answer some of climbing's most common gear-related questions. In this edition we talk about whether or not you need to rest your rope between falls.

Before any piece of Black Diamond gear makes it on to the shelves, it spends months, sometimes years getting put through the wringer by our Director of Quality, Kolin Powick, and his team of Quality Assurance engineers. Through extensive and meticulous testing, both in the lab and in the field, KP and his team help ensure that you can count on your BD gear to be as durable, reliable and as strong as possible every time you head into the mountains or out to the crags.

Climber on belay

A few weeks ago I was at a local sport climbing cliff when one of my buddies came up and asked if I would mind him posing a "technical-sciency-engineering-like-type-question." He wanted to know why each fall he took while working his "proj" felt progressively more painful. I mentioned the old adage from Freedom of the Hills as well as numerous climbing magazines about letting your rope 'rest' between harsh falls, or even switching ends before trying that crux move again. This of course is to reduce the loads experienced, which can become especially critical when climbing on sketchy gear. The rope is the number-one piece that helps absorb energy in the system by elongating—and like stretching an elastic, it needs time to relax between loading scenarios so that it can absorb the maximum amount of energy the next time. My friend looked at me, obviously not having a clue what I was talking about.

He went on to ask if there was anything else he could do to reduce the pain his kidneys feel, and minimize the load the gear sees. My smartass answer was don't fall. No fall equals no load. But on top of that: ensure a dynamic belay, use a cord with high elongation, loosen your knot slightly after each fall (as the knot absorbs energy by tightening during a fall), let the rope rest between attempts, and use nylon slings and quickdraws which absorb a bit more energy than spectra/Dyneema (which doesn't stretch).

To try to put some numbers to it, myself and a few of the QA engineering guys and gals dreamt up a quick test plan and headed down to the drop tower for an afternoon. We figured we'd try to see what the difference in loads seen on the top piece of protection were when: