Product Design
Each and every product developed at Sterling is designed using our total quality management three part process. This process begins with the planning stage in which we outline the product objectives and requirements. Here we seek input from customers, market managers, and our research and development staff. Next we begin prototype development and testing. The rope is engineered through fiber and construction analysis, then assembled. The prototype is tested in-house to meet our standards and then sent for field-testing. Field-testing is carried out by our select group of Product Development Testing Personnel (PDPT Team) where it is put through the rigors of practical use. Depending upon the feedback from the PDPT Team and our in-house testing, we will make minor adjustments to the design of the rope as necessary. Once it meets our customer's or our own requirements, the product is sent out for third party testing and certification to the necessary standards.

Construction
Rope construction is a balancing act with many considerations; elongation, impact absorption, great handling, strength, and durability must all be considered. Rope's overall performance cannot be quantified in test numbers. Ropes prove themselves in the field and on the rock. There are several important phases of construction.

4a. Twisting
Twisting begins by balancing the fiber. Twisting creates the strands that make up the core and sheath. We twist the fiber in the core to add mechanical elongation and determine strength. We twist our sheath yarns to aid abrasion resistance, obtain uniformity and enhance the handling performance of the rope.

There are two directions of twist, "S" twist and "Z" twist.

Incorporating two directions of twist gives the rope balance. This balance translates into a high performance rope with even load distribution and consistent reliability, that won't cause a climber or rescuer to spin when they load the rope by climbing or falling on it.

Twisting of Core and Sheath Yarns

Core yarns: receive two levels of twist. The first twist dictates the rope's level of elongation. It also affects the overall strength of the rope. The second twist combines several yarn bundles producing a finished core. The level of second twist greatly affects the overall hand and knotability of the finished rope. It is important to remember that the core of a kernmantle rope is upwards of 80% of the total strength of the rope and also handles the majority of impact absorption in static and dynamic ropes. Dynamic ropes have high levels of twist in the cores, acting like a spring when shock loaded, increasing the elongation and impact absorption. Conversely static ropes have much lower twist in the cores creating a rope with much less elongation.

Sheath yarns: Sterling's innovative Better Braid Technology(tm) is incorporated all our sheath yarns. Better Braid Technology(tm) utilizes the most advanced twisting machinery, leading to awesome abrasion resistance and a rope that runs smoothly through gear. What is crucial to sheath twisting is aligning the load bearing direction of the yarn with the longitudinal axis of the rope. This takes advantage of the fiber's tensile strength as well as reducing the abrasion of the sheath as it runs over obstacles.

In other words, sheath yarns are S- and Z- twisted, then braided into the sheath so the fibers of the sheath are aligned in the direction of load and abrasion for maximum strength and minimum snagging.

Next time we will continue with the topic of Braiding in Rope Design and Construction.

Until next time, be safe and always dress your knots!

STERLING ROPE and AHS Rescue