Technical tree climbers have a growing number of mechanical SRT multicending tree climbing devices to choose from. SRT (single rope technique or static, fixed or stationary line climbing) has transformed recreational tree climbing, enabling climbers to ascend into and maneuver within the canopies, using the least amount of wasted energy.
In the last twenty years new climbing products and innovations like professional grade multicenders, or devices that combine ascending and descending functions into one device, within the SRT framework have become available. Choosing which device is best suited to beginners or advanced users depends on a number of personal preferences.
In case you didn’t already know, the main difference between single-rope-technique (SRT) and doubled-rope-technique (DdRT) is that with DdRT, you pull two times, or double the length of a moving rope, going up and around a limb and back down. The climber, controls both ends of the moving rope and has a 2:1 mechanical advantage. That makes it easier to lift oneself up a climbing line, but it only advances the climber half as far, when compared to SRT’s 1:1 advantage. Ascending SRT on a stationary climbing line, using a multicending device, together with a foot and knee ascender creates a Ropewalking climbing system. This puts a climber’s weight on both legs and not the upper body, enabling one to capture progress with each leg independently and literally be able to walk up the rope, almost like a ladder.
The Rope Wrench and the Hitch Hiker both use hand-tied friction-cords, aka: prusik cords, tied into rope-grabbing hitch knots. The effectiveness of either device can vary, based on the quality and type of friction hitch, the type of friction cord, as well as, its direct relationship with the climbing line and the climber. The friction cord’s diameter must be less than the rope’s diameter, in order to properly perform. Once the friction hitch is properly tied, dressed and set, these devices are as effective as the mechanical multicending devices, except for more sit-back that occurs each time the hitch knots are weighted. Most hitch knots also have a tendency to bind and can generally become more difficult to manage, when loaded.
Friction hitches or rope grabbing knots, although they can become tightly bound, are gentle on ropes and well suited for dissipating heat, compared to the metallic friction points, or way more abrasive teeth on certain types of hand, feet, knee or chest ascenders. These teeth, when shock loaded, can strip the cover off a rope. Friction cords are also economical and easy to replace, compared to the cost to replace or retool a worn out mechanical multicending device.
The Unicender, Rope Runner, BullDog Bone, ZigZag/Chicane and the Akimbo are completely mechanical multicending devices. They eliminate the use of friction cords altogether. These devices eliminate much more of the sit-back, common among hitch-knot users. Overall efficiency depends on climber’s size, rope width, type, make and condition of climbing line and even weather conditions, but they all seem to perform well with static 11.5mm to 12.5mm (or 1/2 inch) diameter climbing lines.
I began climbing with a Rope Wrench, using a dependable 5-wrap Michocan (aka: Martin) friction hitch/knot on a 28″ sewn eye-and-eye Bee-Line prusik cord and a Hitch-Climber pulley. While this device is dependable, keeping a close eye on the friction knot and adjusting it periodically to be sure it grabs and releases the rope when needed is always mission critical. Based on my weight, I tried a number of different prusik cords and hitch knots, until finding ones that were better suited to grabbing and releasing my weighted climbing line.
The Rope Wrench itself is incomplete without a hitch cord for the pruski’s hitch, a hitch tending pulley, 12″ stiff tether and a locking carabiner. The Rope Wrench itself is positioned on one end of tether, above the hitch knot, creating a bend in the climbing line. A hand spliced or sewn spliced Eye and Eye Prusik Cord connects the to the pulley and carabiner, creating an effect that is similar to a DdRT climbing system, but with the benefits of an SRT system. A tending device is also needed on ascent and usually attaches from the tether to either a chest harness, or an over-the-shoulder lanyard.
The Rope Wrench has the distinction of being the only multicender that’s for SRT climbing, only. However, the Rope Wrench and tether are mid-line attachable. When changing from SRT to DdRT, one would remove just the Rope Wrench‘s slic pin and detach the tether, while leaving the hitch tending pulley and prusic hitch in place. Just be careful not to drop the slic pin from the Rope Wrench, while up in a tree.
The Rope Wrench, when used in combination with the ZigZag or the Chicane/ZigZag, offers a hitch cord alternative, while providing the mechanical strength and consistency needed for SRT climbing systems. Unlike other multicenders, the ZigZag is not mid-line attachable and that may be challenging when advancing and or alternating between climbing lines. The tests in the following video confirm the integrity and strength of the the ZigZag and proves how it’s relatively safe to use a ZigZag in place of a hitch cord, with a Rope Wrench in an SRT system.
The Rope Tek Hitch Hiker 2 is a personal favorite and possibly the best multicending device ever. It’s noted for its overall strength, simplicity and for being compact and efficient when used at different climbing angles. Unlike the Rope Wrench, it uses an friction cord that’s threaded through a dog-bone like metal bar, secured with fisherman’s stopper knots on both sides. A steel carabiner and the dog bone add friction to the Hitch Hiker 2’s climbing line when weighted, enabling the prusik knot to grab consistently and release smoothly when required.
A Hitch Hiker 2 does not include an optional tending attachment that’s needed for ascending. So one must improvise and somehow attach the Hitch Hiker to a chest harness or an over the shoulder lanyard. One can easily be homemade with wire or a piece of throw line. A short 5″ rope with two sewn eyes, or a holster made of molded plastic is also available.
Installing the hitch cord on a Hitch Hiker is a bit more tedious than other devices, but the friction and stopper knots are simple to learn and once the friction knot is properly dialed in, it’s an efficient, compact, rugged and economical multicender.
Both the Hitch Hiker and the Rope Wrench are mid-line attachable. Because prusik cords are economical, easily available and rope-friendly, both of these devices are very popular multicending contenders for hitch knot users. They both require some getting used to, in terms of getting the prusic cord’s hitch knot properly tied, dressed and set. The Hitch Hiker is the least expensive to own and operate, compared to other multicenders and it’s built like a tank.
As shown in the above video, Climbing Innovations is now selling a variation of the Rope Tek Hitch Hiker 2, using a Tree Quickie, in place of the original steel carabiner. The Hitch Hiker X no longer has riveted bumps on it’s sides, leaving smooth surfaces on both sides for the Tree Quickie to move more freely. For this reason, I found it impractical to use the Tree Quickie in place of the carabiner on my Hitch Hiker 2. However, I’ve tried using a piece of rubber tubing on the friction knot and it works beautifully.
When friction knots are properly tied, dressed and set using either the Rope Wrench or Hitch Hiker, they perform adequately with minimal sit-back. A friction cord under load and heavy use will eventually wear out, causing it to lose integrity, mainly due to heat build-up and friction. Friction hitch/knots are not recommend solely for use as a primary repelling device on SRT, unless its being integrated into one of these two devices. In this regard, without this augmentation, the hitch knots themselves can become tightly bound and more difficult to responsibly manage.
While many commercial grade friction cords are heat rated for climbing, excessive friction may cause scorching on the cord itself. By rubbing it back and forth against tree bark, it is possible to scrape off the excess scorched material, but friction cords do wear out.
The Unicender is a compact, fully self-contained and mid-line attachable ascending and descending device. It works well on both SRT and DdRT climbing systems. There’s a slight transitional bump or jerkiness that happens when transitioning to and from ascent to decent, but getting used to that is easy. Wrapping the rope around the Unicender on descent is strongly advised, rather than pinching the two outside arms together with your hand and holding on for dear life. The later option is dangerous under any condition and should be avoided.
The risk of an object or falling limb striking the Unicender’s upper arm, or any multicending device, may cause an unintentional or accidental release from the climbing line. This may occur as a result of falling debris or improper use and while it may only have a temporary effect while the pressure is being exerted, then the device should re-engage. However, the end result may potentially cause an unintended fall and/or a shock-load to you and your climbing system.
Based on the high friction demand placed on the Unicender, especially due to factors that may include an unwashed climbing line causing abrasion, and through normal wear and tear will eventually take it’s toll. Equipment of this caliber is usually dependable for maybe three years, depending on each individual’s climbing characteristics.
I’ve climbed on my Unicender many times with no slippage, but I am seeing some signs of friction wear on the anodized finish. Although the Unicender has no replaceable parts, there are two options to address signs of excessive wear. For about $200, versus the $300+ replacement cost, you can get the device restored and refurbished through Rock Exotica. In comparison, the Rope Runner has wearable bollards and other components which can easily be replaced with available replacement parts. This may be the one of the most notable differences between the various mechanical multicenders.
For someone like myself who climbs strictly for recreation, or much less than someone like a tree care professional who regularly hauls cutting and rigging equipment into the trees, the Unicender remains a top contender because of its overall user-friendliness, being mid-line attachable, compactness and especially for being fully self-contained, with no removable parts.
I’m curious about how well all these devices perform in side by side comparisons, with regard to friction, heat retention and dissipation, namely on descents that are 200′ or longer. Changing over to a descender from a multicending system is no longer necessary, but when rappelling from heights that may reach 200′ or more, a climber may opt to use a Petzl Rig, or another similar type of mechanical positioning or descending device that may incorporate an anti-panic feature, or be designed more specifically for longer, heavier, and/or more controllable descents. Always keep in mind, these devices are all subject to the same laws of physics, friction and heat retention.
Friction and heat build-up can scorch and actually start to melt a polyester covered climbing line, especially if a climber is ripping around and not being attentive enough to their gear. A scuba-diver is subject to embolisms when ascending too quickly, whereas a descending climber depending on a friction knot and or mechanical device may overheat and melt a polyester climbing line when rappelling too quickly for a long duration.
Richard Mumford at ClimbingInnovations.com has designed a Unicender accessory to mitigate friction, known as the Drum and it looks like it makes things a lot better for Unicender users because of the way it helps improve both friction-management, reduces wear and tear and provides for an easy lock off. Richard demonstrates its installation and use in the following video.
How the Drum may effect the overall performance of the Unicender, for better or worse, is uncertain, but it does alter the original design in an attempt to make it more durable and functional. I’m not aware of any formal response from the inventor Morgan Thompson, or Rock Exotica who manufacturers the Unicender, with respect to them possibly sanctioning the Drum, or any such modifications to the original design.
The Rope Runner, as demonstrated below, uses a mechanical hitch, very similar to the Rope Wrench, but without any friction cord. It has two auto-locking removable slic pins and a steel carabiner to guide the rope through the device, but is otherwise fully self-contained. With proper care, this device will never wear out. Replacing warn our slick pins, nuts, and the spring from becoming overly worn, keeps this device fully functional and far extends its estimated life expectancy.
Aside from being slightly more bulky and priced about the same as the Akimbo, but slightly more than other multicending devices, it appears to be a top choice for a mechanical multicending device, especially for production climbers. The device requires the use of a tending device, which is not included and tending systems may vary, depending on the climber’s climbing style and preference. A climber must somehow augment the Rope Runner, so it can connect to a chest harness or an over-the-shoulder lanyard.
On a personal note, I know a successful competitive tree climber who prefers using the Rope Runner with a worn down upper slic pin, but was hesitant to replace it, due to the added efficiency and control it provided him.
Singing Tree, makers of the Rope Runner sold the RR’s rights to TreeStuff, who were then bought out by SherrillTree. According to Kevin Bingham, the inventor of the Rope Runner, the Rope Wrench and founder of Singing Tree, the original Rope Runner is well suited for commercial use, because of its component based design that vastly extends its longevity, when properly maintained.
Whether there will ever be a Rope Runner 2 is doubtful. The Rope Runner 2, unlike the original Rope Runner, would presumably have no removable parts. That defeats the advantages of the original Rope Runner’s ability to provide ongoing manageability through the replacement of it parts, versus replacement or refurbishment of the entire device.
Initially I discovered the BullDog Bone with a buy-and-use-at-your-own-risk disclaimer, available through a private party who makes and sells these. The BullDog Bone is similar to the Akimbo’s fundamental design and while this is a highly regarded multicending device. A search on the TreeBuzz forum using the keywords, “BullDog Bone“, may provide access to the individual who sells these.
Like the Unicender and Rope Runner, the BullDog Bone is a fully mechanical, self contained multicending device that has the appearance of being a top contending option, but the BullDog Bone isn’t a mass marketed product and for that reason, it falls outside of my personal comfort level when it comes to testing and researching new products of this magnitude. If it were to become available on a retail level, my ability to compare this to other similar products would be less biased.
The Akimbo became available, as of January 25, 2019. It is both SRT and DdRT friendly, aesthetically pleasing, compact, adjustable for use on static climbing ropes favoring certain ropes between 11.5mm and 13mm diameters. It uses no external locking pins and it doesn’t rely on a friction cord. It uses two adjustable bollards, to assure better conformity with different size climbing lines. The tending system is unique and includes a wire gated hook. This may take a bit of time for climbers to get adjusted to and hopefully come to appreciate.
In the following video, the Akimbo’s creator, Jaime Merritt, shows a couple tending methods, using a climbing lanyard. My preference is the Petzl Torse Croll Harness, a lightweight adjustable webbed suspender-like 1″ strap that attaches the the Akimbo’s wire-gated tending system using a micro-carabiner, or something similar. Having the ability to control tension when remaining attached to the wire gate tending system gives me more mobility, especially when I pause for a rest during a long ascent.
Finding the proper bollard settings is required every time a climber uses their Akimbo and different climbers may have different settings on the same or similar ropes. Using ropes under 11.5mm on the Akimbo may cause slippage and Rock Exotica has published their list of approved weight rated ropes, some with a 220lb weight limit, and some with a 286lb weight limit. The Akimbo’s approved rope list appears on Rock Exotica’s web site and is expected to grow over time as more ropes get tested and new ropes become available. My personal experience when trying several non-approved ropes has been less than favorable when it came down to not being able to dial into functionally safe and usable bollard adjustments. For that reason, I bought a new 150′ hank of Drenaline by Teufelberger, which runs great for me. I now enjoy the Akimbo on an approved rope and feel more secure and confident doing so.
Perhaps the Akimbo will someday evolve and include self-adjusting bollards that work on a broader variety of rope sizes, or maybe a non-breakaway tending point. Despite the set up time, hard to see bollard pin settings and the unique learning curve, the efficiency and compactness of the Akimbo, when used properly, puts it in a class of its own.
I initially began climbing with the Rope Wrench and then upgraded to the Unicender, once I became better trained and understood the fundamentals of climbing. I still prefer the simplicity of the Uni, the efficiency and ease of installation, over that of more temperamental hitch cords, or the Rope Runner. In foul wet weather a Hitch Hiker 2 is my preference. I suspect I’ll be using my new Akimbo the majority of the time, from now on.
I’ve gone full circle. Over time, I’ve come to appreciate and deeply respect the overall benefits of rope-friendly friction cords, in comparison to less rope-friendly mechanical ascending products that flatten and/or use teeth like cams to grip the climbing line. I’m also comforted knowing how we all can totally rely on each of these multicending SRT devices, when used responsibly and safely, in accordance with the manufacturer’s guidelines.
Given the diversity of static climbing ropes, it’s becoming apparent that certain ropes perform better than others, depending on the specific multicending device. The Akimbo is geared toward ropes in the 11.5mm-13mm range, while other multicenders also work on smaller diameter ropes. Of all the available static climbing ropes, some devices may or may not work properly, so be sure you are buying a rope that is properly suited to your climbing system/s.
In conclusion and based on feedback from others, I recommend the Unicender, Rope Wrench, Hitch Hiker or the Rope Runner for daily production work. The Akimbo and the ZigZag/Chicane are now viable options, especially for more experienced climbers. The Rope Wrench is a good starting point for beginners, because of how it acclimates a climber to using a hitch based system, with minimal mechanical augmentation.
Unicender always remains a strong option, being how it’s so simple and efficient. While the Akimbo may be the most light weight and fun to use, it has finicky settings and is only for use on recommended ropes, with specific weight limits. The ZigZag/Chicane is a non-mid-line-attachable, mechanical replication of the Rope Wrench, and that’s a nice alternative to using more finicky hitch cords, not that a custom Zig/Wrench isn’t doable too.
Seasoned and old-school climbers may prefer the Hitch Hiker or Rope Wrench, when the weather sucks, but will likely use a mechanical multicender when the conditions are optimal. The Rope Runner has replaceable components which make it well suited for production climbers, but the adjust-ability, compactness and efficiency of the Akimbo makes it the most promising multicender to emerge on the scene.