Energy efficient SRT tree access is becoming more and more popular in tree work, largely driven by developments in SRT access hardware. Unfortunately, investment in hardware is only one part of the equation - the other aspect to consider is your choice in rope.
The ideal ascent rope has a couple of important requirements over and above the usual features associated with climbing lines: a tight-weave, outer sheath to reduce slippage and 'picking' of the rope on toothed ascender cams, a thinner diameter (usually around 11mm) to run smoothly through the mechanical device and a lightweight, low elongation core typically made from high mod fibers like Dyneema, Technora and Spectra.
The access line does not necessarily have to conform to the EN 1891A standard because SRT ascent (when performed correctly) produces almost no slack or the opportunity for sudden dynamic loading. If you do opt to use a non-rated access line it cannot be used as a climbing line under any circumstances.
Tree climbers tend to prefer access lines close to the characteristics of steel wire which makes most EN rated lines less attractive (the one exception is Treemagineers Tree Access). A good example of a rope with steel-wire-like characteristics is Globe 5000 from Teufelberger but the price frightens off most punters. What's needed is a high-tech access line at a reasonable price.
Yale Certified rope experts, John Canning and the late Scotty Sharpe worked in conjunction with Yale Cordage to produce Blue Tongue Access Line to meet the requirements of Australian SRT access climbers.
Blue Tongue Access Line has a blended core of Technora and Spectra covered in a rugged 24-strand polyester sheath. The construction of the rope produces very little stretch - only 0.18% at 250kg - yes, that's less than 180mm over 100 meters. In comparison the EN 1891 static elongation requirement can be up to 5%. Low stretch means all the climbers energy is concentrated on going up!
The Technora component in the core of Blue Tongue Access Line provides a high degree of heat resistance (Technora has a char point of 482° Celcius). The Spectra component helps to reduce weight without sacrificing strength or elongation.
Blue Tongue Access Line is 11mm in diameter and weighs in at 2.7kg per 30 meters with an average strength of 4545kg. Treetools should have this new Yale rope in-store mid December.
Remember, this is not a climbing line - it must be used for access only!