Shrinkage of Ropes with use
How much do ropes shrink as we use them? There is no standard test for this, so it becomes very hard to say. I think/guess/observe/no-really-it-is-a-guess about 5% in the first few trips, and not much past that. For my Imlay Canyon Gear ropes that are 100% polyester, sheath and core, thus perhaps more resistant to shrinkage than other ropes. But what is really true? Could we actually collect some data and find out?
OK, let's do that.
June 20, 2016 - pulled a brand new 120' Canyon Fire off the shelf. Actual length = 121 feet (1452 inches)
June 21, 2016 - Imlay Sneak route with 3 ropes used randomly. 5 people. 27 rappels or so total, so used on approximately 9 rappel, mostly single strand. Wet.
June 22, 2016 - Rope mostly dry. Measured length = 118 feet, 8 inches (1424 inches) ==> measured shrinkage = 1.93%
Unfortunately, this rope sustained a core shot 20 feet from one end, and is now a 98 foot rope. (sigh)
Coreshot
Alas - next time for sure... I will work on it with a new rope, and probably track this shortened rope too.
Tom
gear to get you started
We applied the Sheath-Heavy design that worked so well for the Canyon Fire to our 9mm rope, to get a somewhat bigger, somewhat stouter and better-handling rope — Canyonero! The sheath is 52% of the rope, so there is 8% more sheath than core. It is firmly woven for longest life, and uses 100% polyester to minimize water absorption. A nice handling, long-lasting static rope that works great, especially for heavier canyoneers and for Class C canyons with harsh rock, as in Ouray, Colorado.
The Canyonero is longer lasting (than the 8mm and 8.3mm) for 10% more weight. We also gave it a few more core strands, so it has a rated strength of 5000 lb.
2025 color is Red, White and Blue
NOW with 5% more, all lengths, to account for shrinkage. (e.g. a 200 foot cord is actually 210 feet)
Our cord is Polyester sheath and Polyester core which absorbs quite a bit less water than nylon cords. It is quite a bit more static, so you won't be fighting the stretch. Works better! After using a very pretty but very stretchy nylon accessory cord as pull cord for a couple of years, I figured it was time to make some 100% Polyester pull cord for superior performance.