Whether they are aware of it or not, the vast majority of climbing arborists use dynamic climbing systems on a daily basis to carry out their chosen passion and profession: the care of the large, relatively immobile, woody denizens of the world. Though most tree care professionals may use the dynamic system the majority of the time, they are also familiar with elements of the other climbing system varieties. The typical tree care climbing system falls into one of three types: static, dynamic or hybrid.
A static system is one in which the rope or individual parts of rope do not move during ascent, descent or work within the canopy, and though traditionally used mainly for ascent/descent, is becoming more commonly used for work within the canopy through the use of tools like the Unicender or systems like the F8 Revolver. This lack of rope movement means the rope is static or stationary, thus the name.
In a dynamic climbing system, both parts of the rope move as the climber ascends, descends or works within the canopy, and this dynamic movement gives this type of system its name.
A hybrid system is simply one that combines elements of both the static and dynamic systems, and typically consists of a dynamic system for canopy movement “piggybacked” upon a static system.
As previously mentioned, dynamic climbing systems are probably among the most common in use in the tree care industry, and many may feel they know it intimately enough as is, but as with any system there are inherent advantages and disadvantages, and a knowledge and understanding of these pros and cons cannot fail to help tree crews make better choices about which system is best for individual situations, scenarios or needs.
The forces involved with climbing systems, particularly at the anchor or tie-in point (TIP), can be difficult to understand at first glance, but as this is the point that keeps a climbing arborist up in the air avoiding that sudden stop, an understanding of what forces are going to be experienced by the TIP will help climbers make good choices, and hopefully ones that keep them aloft.
As can be seen from the accompanying diagram, different systems, and how they are used, place different forces at the TIP. For example, a 200-pound climber tied back into themselves with a climbing hitch in a dynamic system will only put 200 pounds of force on their anchor, discounting bounces, falls, etc. Yet, should that same climber detach their climbing hitch and ask their ground crew to heartily haul them up into the canopy by pulling on the running end of the line, the forces at the TIP have at least doubled to 400 pounds, or twice the climber’s weight. How is this possible? Simply put, when the climber is a part of the dynamic system, attached back to the climbing line by their hitch, their weight is split between the two parts of line, so each part of the rope sees 100 pounds, allowing the TIP to experience 200 pounds total. When the climber is detached from the system, they become a load on the end of the climbing line, one that weighs 200 pounds, which means that the crew has to pull down on the other part of line with at least 200 pounds just to keep the load aloft. Now each part of the line is experiencing 200 pounds, the full weight of the climber, leaving the anchor point to struggle with a total load of 400 pounds, or twice the climber’s body weight.
This phenomenon of physics is also part and parcel of the mechanical advantage of using a dynamic system for climbing. When a climbing arborist is using a dynamic system, discounting friction and other factors, they only have to move or thrust one-half their body weight upward at a time due to the load being split between both parts of the line. The advantage of having to move less weight is slightly offset by the fact that the climber will have to move more rope, and makes dynamic systems a good choice for short ascents and working within the tree, but a poor one for long, high-entry ascents.
A certain amount of friction allows tree care professionals to do what they do, after all, knots, hitches and splices all need friction in order to function properly and stay in place. However, friction at the TIP in dynamic climbing systems can not only be frustrating, but over the course of the day, exhaust a climber’s physical strength and resources, not to mention damage the tree that is being cared for. The use of friction management devices such as the Rope Guide, Friction Saver or simply appropriately strong webbing with pulleys or carabiners at the TIP will greatly assist movement through the canopy, retain the climber’s energy and protect the tree’s cambium when using dynamic climbing systems.
This technique, typically used with a Tautline or Blake’s hitch, is the traditional method of ascent in the tree care industry, particularly in North America. It is most often used when the climber can securely place both feet against the trunk, although with a great deal of additional exertion it can be used when hanging away from the stem in “dead” air. Thrusting upward with hips/pelvis, the climber simultaneously pulls down on the running end/climbing hitch side of the rope. This movement lifts the climber up as far as possible, and the hitch is then advanced to retain what has been gained in one smooth motion. A micro-pulley beneath the hitch attached in a fixed spot to the standing part of the working end of the climbing line will advance the hitch automatically, as will the double Blake’s hitch method developed by Martin Morales. In Morales’ method, a second Blake’s hitch is tied around the standing part of the working end of the line, and this “stationary” hitch then advances the first Blake’s hitch as the running end of the line is pulled down.
Pulling oneself up hand over hand by the climbing line feels more natural and seems less complex to many climbers, but having to pause often to advance the climbing hitch and tend slack lessens the efficiency of this technique. A small pulley beneath the climbing hitch allows a crew member to tend the slack for the climber, letting them climb hand over hand safely to their heart’s content, or until they run out of tree. Very little pressure is required by the person on the ground, as they are not pulling the climber into the tree, they’re simply advancing their hitch for them. A short split bridge/tail works best in this slack tending system, and is often used with closed climbing hitches such as the Michoacán.
The modified footlock is a technique in which the climber uses the weight of their body and the strength of their legs to ascend the climbing line. Often used away from the stem or trunk, the modified footlock is less strenuous than body thrusting in midair. The standing part of the line should fall between the climber’s knees and over the top to the outside of either foot. The other foot then comes beneath, bringing the line up on top of the first foot, standing on it and pinning the rope. The higher the climber brings their knees, the more height they will gain with each “lock.” In addition, focusing on keeping the knees spread apart will make the lock more secure by putting more pressure on the feet. As the climber stands using the muscles of their legs, they advance their climbing hitch, typically a Blake’s hitch, up the line.
This technique, much like the secured static line footlock, can be quite challenging and requires a fair amount of practice to master. Mechanical options that allow the use of this technique with less practice are the Petzl Pantin or CMI Foot Ascender, small-framed ascenders that fit on either foot and grip the rope when pushed downward, thus eliminating the need for a footlock. This can also be accomplished by forming a Prusik with a separate piece of cordage around the standing part of the line as a foothold, however, unlike the Pantin or Foot Ascender, the Prusik will have to be manually moved upward after each “lock.” Once again, due to the nature of a dynamic climbing system, a great deal of rope has to be moved to ascend, thus the modified footlock technique is best suited to short ascents.
Dynamic climbing systems, when properly set up and understood, can provide climbing arborists with a great deal of precision and control when moving throughout the canopy, increasing efficiency, along with safety, as the business of tree care goes on. Yet, as with so many available systems, techniques and methods, a dynamic climbing system is not the only choice, nor is it the best one when confronted with a long ascent or other specific challenges. A professional, regardless of their chosen field, will adapt and improvise to the situation at hand, choosing the safest and most efficient course, dynamic climbing systems are just one more choice to have in the mental toolbox.