Early nylon ropes were made of a "twisted" or "laid" construction, in which small nylon filaments were bunched into four or five strands and then twisted together to make the rope. These ropes are made of drawn nylon yarns, which means fibers are strengthened and stiffened while the semi-crystaline molecules of the nylon become stretched. Heat is used for this process.
Today's standard is kernmantle nylon ropes, which are specifically designed for climbing. Kernmantle ropes are made of two parts: the core and sheath. Standard dynamic ropes are 11 mm in diameter and 50 meters (165 feet) long, with a stretch of 6 to 7 percent (of its length). Climbing ropes are commonly made in diameters of 8mm to 12mm.
The inside of kernmantle rope is made of braided or parallel nylon filaments. These form the core and make up approximately 70 percent of a rope's diameter.
The outside of kernmantle rope (the sheath) is made of smoother, colored nylon strands that are woven. This construction offers more stretch.
Static and Dynamic
Nylon ropes not constructed in a kernmantle design are not suitable for climbing and are called static ropes because they do not stretch. All nylon ropes used for climbing are called dynamic because they stretch. The stretch in climbing ropes is necessary to safely buffer a climber's fall and prevent the climber from getting whiplash or a more serious injury.
Article Written By Naomi Judd
Naomi M. Judd is a naturalist, artist and writer. Her work has been published in various literary journals, newspapers and websites. Judd holds a self-designed Bachelor of Arts in adventure writing from Plymouth State University and is earning a Master of Fine Arts in creative writing from the University of Southern Maine.