Trends are phenomena that sweep through our culture constantly. Some are new and original, others a rendition of those that came before. Then there are those that resurface. The rediscovery of something that had previously come and gone. The tree world is no different.
However long you’ve been in tree care, you’ve likely seen at least a few trends. You may have been in the business long enough to remember when rigging ropes ran right on raw bark and no one batted an eye. Yes, good old-fashioned aerial friction, before ropes were double braided, before hardware was king. Its resurgence is upon us, although with a modern take on the tried-and-true method.
Friction
Before such hardware as blocks, pulleys, portawraps, or Port-A-Wraps, and other various lowering devices, work still had to get done. We know all too well that portions of trees needing to be rigged quickly exceed the weight a person can handle directly. Friction is our friend. But how do we create it without nice, smooth, aluminum bollards for wrapping?
Those newer to the industry may not remember repeatedly gathering coils of three-strand rope from the ground and walking it around the trunk. The trunk wrap was standard practice for quite some time. This simple, low-tech solution provided exactly what the ground personnel needed – the necessary friction to control the force generated by a rigged piece.
Problems with trunk wrapping
The savvier, production-minded climbers of that day knew that, although wrapping the trunk was an invaluable item in the toolbox, it had its shortcomings. It was slow having to add and subtract wraps. The amount of friction was difficult to modulate. It could mark up the trunk terribly (a big issue if the tree was being retained). And it completely tied up a ground person, no pun intended.
Advantages of taking wraps into the canopy
Taking wraps up into the canopy, however, opened up a whole other world of possibilities. One benefit was that the shorter end of rope was easier to wrap. Wrapping a small-diameter limb as opposed to a trunk meant slightly more friction control, and the trunk of a tree to be retained was left unmarked. But possibly the biggest advantage came after the load was arrested. The ground person could transfer the lowering duty to the climber (if they were near the wrapped area) to free up a set of hands on the ground for processing.
In addition to benefits in productivity, and maybe the reason for its modern reimagined resurgence, is what happens with the forces in one’s rigging system. In a frictionless environment, an overhead rigging point can see double the weight of a load at a static standstill. This is because you have the weight of the load and the input force of the counterbalance to hold it, which must be at least equal to it. When there is friction at the overhead rigging point, it assists the holding of the load by resisting the pull of gravity on the load. The input force does less work to achieve the counterbalance.
What does it all mean?
So what does all of this mean? Well, in theory you could decrease the forces at the rigging point, or points, by adding friction to them. Just natural-crotching the rope creates friction that in theory lowers the forces at the points, but adding canopy wraps takes it a step further.
Canopy friction is very useful in general. But even more so on a compromised tree or any situation where you want to keep forces at a minimum, lest you break whatever fragile situation you’re dealing with.
Rope construction matters
I should take the time to point out that the commonly used ropes of that day were three-strand. Natural fibers at first, then synthetic and on up to 12- and 16-strand as time went on. This is important to note, because their construction is much better suited to handle the friction of natural-crotch rigging.
The smaller, higher count of strands in the modern-day, double-braid ropes makes the ropes more easily damaged by running over raw bark. Also, the double-braid ropes share the load between the cover and the core. If the cover is damaged and weakened by friction, the core must do a disproportionate amount of the work.
Generally speaking, double-braid ropes are best suited for use with smooth-surfaced hardware. Here, they can better maintain their shape when loaded and be safer from damaging abrasion and heat from friction.
Using modern hardware with old techniques
So how did an old-school technique, the basis for which is rope on wood, regain interest in an age of aluminum and high-tech rope construction? How could we create friction in the canopy with these modern tools and not damage either of them? The same way we achieve friction on the ground on modern-day lowering devices. Bending, wrapping and even providing pressure to the rope can apply the necessary friction we seek to achieve.
There are several products on the market today that do this in the aforementioned various ways. Generally, they are constructed of aluminum, which effectively dissipates friction-generated heat. This property, combined with their smooth surfaces, makes them safe to use with our modern double-braid ropes.
One of the main benefits of creating friction with smooth, aluminum hardware over raw bark is consistency. The rough surfaces of various limbs or crotches of different sizes can change drastically. The number of wraps needed to handle loads of similar size would not be the same if you went around a larger limb versus a smaller one. With hardware designed to create aerial friction, you get the same ride every time. Many of these devices also have adjustments or settings so you can regulate the amount of friction applied.
Is the investment worth it?
So, is it worth it? Should you invest in an aerial-friction device to get smooth, consistent friction in the hopes of reducing forces at your rigging points? Should you dust off an old hank of three-strand and run it through some crotches? Or wrap it around some limbs or stubs up in the canopy? Or should you not bother with either?
Well, in my opinion, it really depends on the type of work you do and size/type of crews you run. On a smaller crew, the option for the ground person to arrest the load, then pass it off to the climber because the friction is being controlled up top, can be quite useful. Or, if you’re in very tall and/or skinny trees, the theoretical dampening effects of aerial friction may be greatly appreciated by the climber who has to squirrel out there.
Maybe neither of these scenarios apply to you. It could be that once in a great while you get a sketchy canopy needing to be rigged. And some force reduction at the rigging point(s) might make things safer. Whatever the case, any new tool has a learning curve and should be practiced in non-critical situations to familiarize everyone with it.
Lawrence Schultz is an ISA Certified Arborist and an ISA Certified Municipal Specialist working as a contract climber in the San Francisco Bay area of California.
This article was based on his presentation, “Creative Applications for Tight-Quarters Rigging & Aerial Friction,” during TCI EXPO ’22 in Charlotte, North Carolina. To listen to an audio recording created for that presentation, click here or go to TCI Magazine online at tcimag.tcia.org. Under the Resources tab, click Audio. Or, under the Current Issue tab, click View Digimag, then go to this page and click here.
