The purpose of this entry is to promote a public posting of rope specifications and to present these two questions as follows: 1) Are there specifications on rope rigging that include application conditions for the use of nylon versus polyester ropes? 2) Most importantly, what are you climbing with?
It’s common knowledge that the arborist and recreational tree climber prefer a polyester rope over nylon. The polyester rope has a high melt point and is more abrasion resistant than the nylon rope commonly used in rock climbing. There are several more technical details that indicate the polyester rope is the right choice in tree climbing. Polyester has less progressive strength loss as the heat of friction increases. Another critical issue is presented when nylon absorbs water. Wet nylon softens to a point equal to baking it at 158 degrees F. This is why you wet your nylon fishing line while making a knot. The water softens nylon and makes the knot seat. If the dry techniques found in cliff climbing are employed, then a nylon rope can function safely. Nylon is the stronger roper under ambient, dry load conditions. The rope used in a climb is a lifeline, and the correct rigging conditions mean everything in keeping it safe. Thus it’s amazing that specifications on rope rigging aren’t readily available – if they even formally exist.
The community websites on tree climbing and the online rope distributor/manufacturers promote the use of polyester rope for the double rope technique in a tree crotch. The professional literature doesn’t. In Jepson’s “The Tree Climber’s Companionâ€, there’s a curious absence of a discussion on the vastly different properties that exist between polyester and nylon ropes. Jepson refers only to the generalized specifications of ANSI Z133.1-2000 on page 12 of the 2nd edition. Jepson’s book defaults to the compliance of load specifications and regular inspections as the guide for safe rope use. Unfortunately, it’s not the full story. Moreover, the US Department of Agriculture published “National Tree Climbing Guide†does provide limited notes on the technology of rope, but it leaves one with a few facts without context. Without additional background on the technical aspects of ropes, one can incorrectly conclude that a Nylon 6,6 grade rope is superior to all ropes under all conditions of tree climbing.
As a side note, the USDA “National Tree Climbing Guide†is a blend of information found from Jepson’s book and “On Rope†by Padgett. I recommend that you download it and retain it as a reference though clearly it goes beyond the realm of the recreational tree climber. This 86 page document is downloaded in two PDF files. http://www.fs.fed.us/treeclimbing/policy/pdf01672802pt1.pdf
http://www.fs.fed.us/treeclimbing/policy/pdf01672802pt2.pdf
The mountaineering associations aren’t satisfied with the performance of nylon rope. The biggest concern is the significant loss of properties when nylon is wet. They’re hoping for a new technology to replace its well noted load strength under dry conditions. A mountaineering report is as follows: http://216.239.41.104/search?q=cache:jUGYk-PLuKIJ:www.alpineclubofcanada.ca/services/safety/wet%2520ropes%2520text.rtf+glass+transition+of+rope&hl=en&start=1&ie=UTF-8
The arborist found the correct type of rope – polyester. If this isn’t specified, then this entry serves to promote a written specification in ANSI and future notations by the professionally published literature. Would you climb on a rope baked to 158 degrees F? You find the same weakened properties when your nylon rope is wet. This issue doesn’t exist with a polyester rope. Ropes don’t come with written warnings of all conditions that degrade their performance. A specification with wide publication would resolve that for the tree climbing community.
Your insight on specifying a rope for tree climbing is welcomed! What are you using and how are you using it?
Regards,
JimK
