SRT Rope Recommendations
DdRT is a technique specific to Arboriculture and if one is asked to recommend a rope to a beginner a simple explanation can be given. 16 Strand is robust, holds nearly all its strength in the cover (so is easy to inspect), can bend around natural anchor as well as rings and pulleys, is easily spliced and has a long history of use with hitch based systems.
The other choice is Double Braid, nearly always with 24 strands in the cover, with size ranging from 10mm to 12.5mm. Double Braid works best in pulleys as the cover and core must be in balance to maintain optimum strength, it has
a workable bend ratio, runs well with mechanical devices because of its high cover strand count, is splice-able and has a good ‘hand’ for knotting (as does 16 strand). Both ropes remain relatively soft even after much use.
Both ropes are made with 100% polyester or with nylon added (for the European market), the nylon allows some stretch and keeps peak loads from falls at a minimum.
For arborists new to climbing there is still a bias toward DdRT technique and therefore most
climbers will crossover to SRT with their DdRT ropes, this is OK but with a large caveat.
Key words so far are: 16 Strand, Double Braid 24 strand - Polyester - Polyester/Nylon (EN1891)
The video was filmed at ShopK several years ago and the outcome is this: toothed ascenders work
best with parallel cored ‘access’ ropes as the ‘rips’ were controlled to a maximum 22cm with over
90% of strength bearing core strands remaining. Double Braid ropes are scary, the one rope that
didn’t use a stopper knot ran for 270cm. 16 strand is also uncontrollable, the drop being over
100cm. This is of key importance in the first step to understanding which rope is best for SRT and
it leads to the first question: What is the interface? Toothed cam, Smooth cam or Hitch, as each
have a pronounced difference in application and worst case scenario (like in the above video).
European manufacturers state parameters of use and recommendations dictated by test criteria.
The Petzl RIG (smooth cam descender) and Ascension (toothed cam ascender) are recommended to be used with a 10-11.5mm diameter EN1891 type A rope.
The popular climbing rope from TEUFELBERGER
Thanks to its unparalleled feel and its exceptional performance, Tachyon
is ideal for use with the latest mechanical systems.
Lengths: 35 m, 45 m, 60 m; available with one or two [slaice]® rope
Standard: EN 1891A, ANSI Z133-2012
Plait number: 24
If one went by recommendation alone then Tachyon would seem a good choice for both tools being that rope diameter and testing criteria are compatible, not to mention that Teufelberger state that Tachyon is “ideal for use with the latest mechanical systems” though configured to a tooth ascender system is far from perfect (down right dangerous).
Teufelbergers Braided Safety Blue is also an EN1891A rope but its diameter is 12.7mm, size is OK for the Ascension but not for the RIG, construction is dangerous for the Ascension due to over extended slip distances and badly configured for the RIG due to its large diameter (and softness).
KMIII is also EN1891A certified, is available in a choice of diameters (task dependent) has a cover strand of 32 (8 more than Tachyon and double that of Safety Blue) and is a parallel core so will perform safer with the toothed ascender because of a smaller drop distance (fall scenario) and will maintain good workability and shock absorption capability with the RIG because it does not exceed its maximum recommended diameter. The higher strand count in the cover gives the KMIII good abrasion resistance and great performance as more strands equals smoother cover which in turn equals a more reactive performance.
Out of the three choices of rope KMIII is obviously the better choice for SRT with an ascent/descent made up of Ascension and RIG though for Arborists the definition of SRT is different, it has taken a side step away from caving and industrial-access-SRT practice because of its ‘three-dimensionality’ (climbing on a pendulum).
More key words: tooth cam, smooth cam, hitch, abrasion resistance, shock absorption,compatibility, strand count, ascender, descender.
SRT’s historical story is ancient, rope was probably one of the first tools used by man, to tie things together or perhaps take advantage of a natural form like a vine to access into a tree or up a cliff.
In 1938 E.I. duPont deNemours and Co. introduced Nylon to mountain soldiers and sailors. It was a remarkable change from natural fibres, was strong for its size, didn’t rot and was easy to inspect for damage. After the (second world) war nylon became popularised due to its elasticity, abrasion resistance and strength against sharp bends and became the go to rope for life-support. Rope construction at that time was laid which caused some complications.
Samson developed a double braid (then called 2-in-1) which overcame some problems of laid rope but added more too. The 50-50 strength construction and soft braided cover meant that the climber could be faced with a huge loss of strength when subject to abrasive wear and a break in the sheath would allow the climber to shoot down the core braid (like in the video above).
In 1966 Bluewater developed a hard, tightly braided cover that was woven over a core of parallel strands. The tightness of the cover gave the rope great abrasion resistance and strength was retained to nearly 100% in the core fibres. From here SRT rope history is diverse with many companies developing ropes that considered and enhanced safety and efficiency.
Speeding up toward present day, Arboriculture has refined its own ropes, systems and climbing techniques, primarily for DdRT climbing and through companies like Yale, Samson and New England (now Teufelberger).
SRT was left on the side lines, to deal with access and other straight up and down duties with tools borrowed from industrial access and caving and it wasn’t until 2004, when Morgan Thompson introduced the Unicender mechanical device, that it became viable to consider SRT for Arboreal climbing (for those that don’t know it is problematic to make a hitch work on a single line). Not only could ascent and descent climbing be achieved with one tool and with a top to bottom passage through the device to facilitate the most ergonomic vertical climbing but arboreal three-dimensionality could be explored with ease. SRT was an instant game changer for those who rigged climbing systems in trees. By this stage double braid ropes were ubiquitous with forward thinking arborists and parallel core was left to access duties, which was fine in a way because the Unicender and subsequent devices (Rope Wrench, Hitch Hiker, Rope Runner and Compact Bulldog Bone) all have a smooth interface, and as the main point of attachment meant that a shock load into the rope would not have issues of ripping the double braid’s cover. Toothed devices can be fitted into the double braid system as non-tethered and non-life-supporting ‘aids’. Arborists had taken a fork in the road with SRT and it was the beginning of a semantic change that would affect system design and performance. SRT, always known as Single rope technique would change to Stationary rope technique and begin to take a life of its own as a bonafide working system.
As it stands today for European Arborists there are two certified devices for Stationary Rope Technique, ISC’s Rope Wrench and Taz’ LOV2. For those that know each device it is easy to see how different the devices are, the former excelling at 3-dimensional movement and the latter fitting in great to access and other up-and-down duties.
Key words: nylon, laid, parallel strands, access line, aids, working line, Unicender, 3-D climbing.
16 Strand, Double Braid and Parallel Core.
Ropes for SRT
The ropes profile changes considerably as the strand count increases, 16, 24, 32 (left to right). The double braid tends to flatten but performs moderately well, much more than the 16 strand that doesn’t flatten as much but is too bulbous for toothed ascenders to grip well on, even when used as aids. Both these ropes have a soft hand (knots well) and because of this have a slightly ‘squidgy’ feeling when used with SRT. All ropes are certified to EN1891A so when used for SRT will stretch much more than is needed for safety, they become a nuisance. The double braid should be run through pulleys and should avoid natural anchors. It’s soft cover braid means increased friction if set on natural anchors, increased friction means more wear and tear on the tree, rope and climber. The parallel core ‘access’ line shown performs well for up and down ascents and aspects of it show up in the new generation of climb lines from Teufelberger and Yale.
Two ropes at the head of SRT development are Teufelberger’s Drenaline and XStatic. They both have strength retaining parallel cores, tightly woven covers, non-flattening cross-section, high cover strand count, minimal stretch (but still EN1891A). The X-Static’s hard hand means low friction to tree and climbing device, it truly glides, but means that knots are more difficult to tie. Drenaline has a special factory made termination for DdRT climbers and a soft hand that holds knots well. SRT climbers tend not to need life-support eyes and a simple stitching pattern with small diameter cord can be used for installation and retrieve purpose. Both ropes are too large a diameter for the LOV2 but work well with Rope Wrench and other devices (mentioned earlier).
Final key words: strength retaining parallel cores, tightly woven covers, non-flattening cross-section, high
cover strand count, minimal stretch, soft hand, hard hand.
Firm profile, parallel strands and stitched loop.
Hiro, Sekine and I all climb for the same company and so tend to be influenced by each other, you can see a
trend in our choice of equipment and how it is configured. Toothed cams are used as aids (foot and knee
ascender). Up until early this year we all used double braids for our working lines, this has, positively I think,
changed now to parallel core lines.