Single Rope Technique (SRT) Climbing

Issue: 
January-February 2012

Although SRT has been used exclusively in fields such as caving and mountaineering, its applications in the arboriculture field have been limited. SRT has been used by some arborists for decades for safe, efficient ascents into the canopy, utilizing an array of cammed ascenders and foot loops. Typically after ascension, the climber would then transfer to a traditional climbing system such as the doubled rope technique (DdRT). Recently, arborist specific SRT tools have become available that create a system that can both ascend and descend and make it possible for a climber to “work the tree.”

Some of The Benefits of SRT

•  1:1 power ratio. SRT is a static system meaning there is no load sharing or mechanical advantage as there is with DdRT. For every foot you lift yourself, you ascend one foot. This also means that a 180 lb. climber must lift 180 lbs. Fortunately, the use of hand and foot ascenders in SRT distributes the lifting to major muscle groups such as those in your legs.

•  No need to isolate TIP (tie in point). As only one leg of rope is used in SRT, the rope must be tied off or anchored. Unlike DdRT, isolating the TIP isn’t necessary with SRT as long as a rope is secured in a strong union or unions. The fall of the rope can then be secured to the base of the tree using a trunk anchor that can significantly save setup time. Please note: when trunk anchors are used, 2x the load is applied to the TIP. Isolating and girthing the TIP with a mid-line knot is one way to alleviate the double loading issue. A strong understanding of vector forces is necessary.

•  Friction and redirects. Since the SRT climbing line does not move, only the hitch, this means there is constant friction at all times no matter how much contact there is with the trees trunk and limbs. This allows the potential of near infinite redirect possibilities to position yourself perfectly for whatever task needs to be completed without having to wrestle with friction. 

These were the main factors that drew me to try SRT. My lead climber had been using the technique for several months with a previous company and after a demonstration to test its safety and efficiency as well as aerial rescue scenarios, I decided to try it out. I had been resisting using SRT for ascent for some time as I considered it gear intensive and time consuming as it needed to be replaced with a DdRT system after ascent. The SRT climbing tool I am currently using is the Singing Tree Rope Wrench. The rope wrench works by creating a bend, and in turn friction, in the SRT line above the hitch. This system shares the load of the climber between the rope wrench and the hitch. This load sharing makes the hitch react similar to how it would in a traditional DdRT system.

Advantages

•  Setup. Both the trunk anchor and the aerial TIP via girthing the tip are extremely easy to setup. Although trunk anchors vary, little equipment is necessary. Pictured is the SRT trunk anchor for all climbers at Logan Tree Experts. This system is quick to setup, has several backups for controlled lowering, and a backup in case of emergency or aerial rescue. By having the SRT line threaded through several high unions, you can also share the double load that occurs with a trunk anchor. For the aerial TIP I use a three-ring bowline which keeps my girth secure and provides an easy “break” when it is time to retrieve. 

•  Ascending. Without question, SRT ascension is quicker, and if using the right system, less labour intensive than DdRT. I’ve been using a modified microfrog system replacing the chest ascender with the rope wrench. This makes a quick transfer from an ascending to a climbing system by disengaging and removing the hand ascender and disengaging the foot ascender. 

•  Working the tree. Moving around a tree on an SRT system requires a shift in thinking and procedure. It takes time getting used to multiple redirects and where and when to set them. I find you tend to climb the tree more and rely on the rope less. Clipping back on your foot ascender or adding a hand ascender even for short ascents is recommended and will lessen fatigue. 

Disadvantages

• The gear. Ascender compatible rope is necessary as the toothed cams can damage rope and should not be used with cover dependant ropes. Generally, SRT systems require a large length of rope. For example, in a simple retrievable aerial TIP, a rope three times the height of the TIP is necessary. 

• Cut potential. When using a trunk anchor, beware of where the fall of the rope is at all times to avoid accidental contact with a hand saw or chainsaw as the fall can sometimes be hidden on the backside of a tree. As the rope is loaded with the full weight of the climber, even a slight graze with a sharp object could be disastrous. Lanyard in at all times when cutting.

• Limbwalking. When no significant redirect is available for limbwalks, they can be a little difficult climbing SRT. I find feathering line in or out a little laboured and I find more weight is put on the limb. I currently have a quick 3:1 system that I install in situations where I have to “think light.” 

• Responsiveness. I don’t find the responsiveness of SRT quite the same as DdRT. I hope this will change as I experiment with different product combinations, i.e. ropes and hitches. 

• Ergonomics. Ascenders must be used with this system for ascents. Although it is possible without them, it is extremely arduous and will cancel any benefits of using the SRT system. Most SRT ascender rope is smaller diameter, difficult to grasp, and hard on the arms, especially on a 1:1 power ratio. 

In conclusion, SRT, like all new climbing systems, is a work in progress. No climber is alike therefore climbing systems are modified to accommodate a climber’s particular need while still maintaining and increasing safety and efficiency. I believe that SRT will continue to evolve and grow in our industry. It will not replace DdRT, as this system still has many benefits. SRT will simply be another tool in the toolbox to create safety and efficiency in the tree. 

For more information on SRT, there are several good books and articles including: On Rope, by Smith & Padgett; The Tree Climbers Companion, by Jepson; and Single Rope Technique, by the Victorian Tree Industry Organization. Since climbing SRT is relatively new, most books and articles focus on SRT ascent, but they still provide great information on equipment, anchors and TIPS as well as invaluable knowledge on vector forces.  

About the Author

Matt Logan is owner/operator of Logan Tree Experts based in the Peterborough/Kawartha area. He is an ISA Certified Arborist/Tree Worker ON931-AT as well as a Certified Tree Risk Assessor CTRA721 and trainer for ArborCanada.

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