The Biography of Modern Climbing Ropes
In the early to mid-1900s, climbing equipment
was so unreliable that the predominant ethos was that the leader “must not fall,” and the follower had better hang on, too. Of all the gear improvement in the last half-century, rope technology has done the most to transform the mentality of today’s climbers to not only accept leader falls, but often to expect them. What’s changed so radically from then until now?
Modern climbing ropes began with the production of high-grade nylon in the 1950s and 1960s, which replaced manila and hemp. Nylon ropes had the advantages of being significantly stronger and lighter than their earlier, natural fiber counterparts. Nylon ropes also absorbed more impact force, which put less stress on the climber and the gear.
Early nylon ropes included Goldline Rope, which was the most common climbing rope in the 1960s and early 1970s. Goldline was a ‘laid’ or ‘twisted’ rope, constructed with three strands of twisted filaments. It was stronger and lighter than earlier ropes, but had its drawbacks. Goldline, like any twisted rope, suffered from partial untwisting when loaded, thus spinning the suspended climber. More importantly, Goldline had no sheath to protect the fibers of the rope, which severely limited its durability. Finally, Goldline was stiff in hand and not dynamic (stretchy) enough to prevent serious shock-loads on gear and the climber during lead falls.
The problems with Goldline were solved once dynamic kernmantle ropes emerged for climbing in the late 1970s. Superior strength, easy handling, and consistent elongation and impact absorption made these the norm back then, and they’re still the ropes we climb on today. Kernmantle ropes have a twisted, parallel core (kern) wrapped in a tightly braided sheath (mantle). The core provides the majority of the strength (70- to 80-percent), while the sheath protects the core and gives the rope its feel. The polymeric fibers (synthetic chemical compounds) in kernmantle ropes have exceedingly high strength along their longitudinal axis (tensile strength) but a lower strength along their horizontal axis (flexural strength). This explains why the folding and bending of a rope in a knot significantly weakens a rope. But for climbing purposes this strength loss is negligible, because a rope that holds 5000-pounds without knots will still hold 3900-pounds with a figure-8 knot, for example.
The kern is a high-strength inner core of nylon threads made from twisted textile yarns. These fibers naturally shrink during manufacturing and must therefore be thermo-dynamically balanced, or heat stabilized. This process controls yarn shrinkage, limits sheath slippage, keeps the rope supple over time, and helps maintain elongation when it’s bearing weight or when it’s wet. The core fibers are twisted in two directions: S (counterclockwise) and Z (clockwise), which adds mechanical elongation and strength. The twisted strands of the core behave like miniature springs, lengthening as they absorb the energy of a fall. Incorporating both S and Z twists gives the rope balance, ensuring that the climber won’t spin radically when free-hanging on the end of the rope.
Sheath yarns are S and Z twisted then braided so that its fibers are aligned in the load-bearing direction for maximum tensile strength. The sheath has a fine, abrasion-resistant weave that repels dirt and slides smoothly over rough rock. Many ropes are also produced with a water-resistant sheath treatment and some companies also treat individual core fibers. Finally, the process of braiding the sheath around the core produces a finished rope that, once cut and labeled, is ready to catch falling climbers.
Modern rope construction ensures that today’s leaders can fall with impunity – at least, as far as the integrity of the rope is concerned. Indeed, today’s dynamic kernmantle ropes are often the strongest link in your chain of safety as a climber.
Cinnamon, Jerry The Complete Climber’s Handbook, 2nd edition, 2000.
Sterling Rope Guide to Rope Engineering, Design, and Use Volume 1
Heale, J.W.S., McKenna, H.A., O’Hear, N. Handbook of Fibre Rope Technology 2004.
Climbing Equipment, Wikipedia
Blue Water Ropes