With every passing year, the gear available to us in the arboricultural industry continues to evolve and change. In spite of all the latest advances in our tools, the old-school ways often still work and are a key component to understanding the new tools and how they are used. Even with the evolution of climbing equipment, we now see many of the old principles back in play.
Let’s take a look at old-school, natural-union rigging and what it created –
friction! This same principle is in play with the new rigging rings that are becoming more and more prevalent in the industry. A rigging ring creates consistent friction aloft, just as a port-a-wrap or bollard-type lowering device would at ground level. It’s easy to create artificial unions with these rigging rings by using a variety of sling configurations. The ability to create anchor points anywhere the tree can support them – not just at the branch unions – really opens up rigging possibilities.
Slings
Let’s take a closer look at the slings that are used to create the anchor points. Slings come in a vast array of materials from lots of manufacturers, but the four main configurations are the dead-eye sling, multi-rig sling, whoopie sling and loopie sling. Each one of these sling configurations has pros and cons and uses that allow the aerial worker to customize the rigging setup for each situation.
The dead-eye sling is a configuration that has a spliced eye at one end of the sling and just a finished end at the other. This allows the user to tie the sling on with a variety of knots and hitches: timber hitch, cow hitch, running bowline, closed clove, multiple half hitch and other secure configurations. Depending on the situation, the dead-eye sling can be configured close to the material being rigged or set up as a floating redirect out in mid-air. This allows for many different variations and solutions to complex rigging operations.
The multi-sling with a ring is a configuration that has many different attachment holes to place the ring or block through so you can then cinch to the tree material for rigging. This allows for quick setups, but it has some limitations. One of those limitations is the inability to easily create a tight rigging setup, where the rigging device (ring or block) has as little “flop” as possible. Flop is when the rigging device isn’t snug against the sling and the material it’s secured to. There is the ability to use a multi-sling with a ring as a floating anchor, but since there is no easy way to create a tight squeeze on the tree with the sling configuration when not loaded, it can create dynamic movement and potential shock loading that could create a catastrophic sling failure.
The whoopie- and loopie-sling configurations are very similar in principle but have some slight differences. The whoopie is a double-eye sling that has one eye that is adjustable through use of a “bury,” which is material inside the sling that works like a Chinese finger trap. When bunched together, this material allows the sling to slide and be adjusted. But when spread out, it prevents the sling’s adjustability.
The loopie is the same design, but instead of two eyes, it’s one large, round sling with adjustability in the size of the loop. Both of these configurations allow attachment of the sling to the tree by using a girth hitch and possibly a doubled half hitch on a spar, where you can slide the sling over the material versus wrapping the sling material around the tree material.
Friction devices
Now that we have looked at the different sling configurations, let’s take a look at some of the options for rigging equipment you can use with them. First and foremost is probably the port-a-wrap. This device is a cylindrical tube of steel with an attachment point for the sling. It also has “ears” (brackets) to keep the rigging drop from sliding off on the load side. And on the running end, it has a set of ears to allow the ground worker to lock off the load line in the event the climber or crew need to keep the load static, i.e., while leaving the rigging line to perform another duty.
This device comes in a multitude of sizes and colors from several manufacturers. The best way to learn the difference between the different sizes is by field work and practicing with small weights of material and different-size rigging lines to learn the friction points and number of wraps needed to create the friction desired. Too many wraps can be dangerous, because it prevents the rope from moving through the system and decelerating the load. Instead, the wraps lock the load off and can create dynamic forces on the components, which could result in failures of the rigging components and/or injury, or worse, for the worker aloft.
Rigging blocks, although they look like pulleys and share similar characteristics, have one major difference. A pulley is designed to be used only when the load is under the pulley (positive position). A block, on the other hand, allows the user to place the rigging tool below the load (negative position) and then “catch” the load while it is simultaneously being lowered.
Rigging blocks, more commonly called impact blocks, have a double-sheave design and rounded edges that are soft material, so they are friendly on the side plates. This allows the block to be secured with soft material such as a rigging sling. Once secured, a rigging line is run through the large sheave, which carries energy and does not create friction, or creates only minimal friction. This design allows the energy to be dissipated throughout the entire length of rigging rope, between the load attached and the friction device at ground level. The rigging block carries the energy by allowing the line to stretch and move versus with a rigging ring, which we will discuss next.
There are a few things to remember about rigging/impact blocks. The bend radius created by the moving sheave needs to be in line with manufacturer’s recommendations for both the rigging block and the rigging line. Usually a 4:1 ratio is correct, but always consult with the manufacturer’s user guide. Also, with rigging blocks it’s important to ensure the ratings for the sling material and configuration you are using it in are going to be at least equal to the rated working load limit (WLL) of the rigging block. As with any tool, ensuring equal or close-to-equal ratings is key to keeping the system intact and not creating a weakness in the system.
Rigging rings were first introduced by David Driver, creator of the X-Rigging Ring (to the best of my knowledge, though possibly they were in use before David made them famous), and take the principle of friction created by a smooth surface, like the port-a-wrap, and place it aloft. The rigging ring functions very similarly to how a natural union would in rigging by allowing the worker aloft to distribute load and friction throughout the system instead of just translating it to a friction device at ground level.
The learning curve can be rather steep when using rigging rings, mostly due to ground workers not accounting for the friction the ring will create. They place too much friction at the ground-based friction device, and the load becomes locked off and creates the potential for a dynamic load, or shock load.
Rigging rings come in a variety of sizes and from multiple manufacturers. Just like our slings and other rigging tools, always consult the manufacturer’s recommendations on what other rigging tools they are compatible with, and always pair a sling with the rigging tools that have a similar WLL. We don’t want to be placing an extra-
large rigging ring with a WLL of, say, 5,500 pounds with a 1/4-inch sling with a WLL of 500 pounds. This creates too much potential for overloading the system.
Conclusion
With all the new tools and techniques, it’s best to learn low and slow, and most of all with small, lightweight pieces. Until you become comfortable, I encourage you to rig small and learn the way each tool reacts to different setups, so you gain not only experience but also confidence while remaining safe. No one ever died from rigging too small, but many arborists have lost their lives from rigging too big and either exceeding the WLL of their tools or having the tree material they are rigging from be the weak point, creating a catastrophic failure.
Please don’t take this or any other education as your only form of training on any tool or technique. Read your user’s manual and TCIA’s Best Practices for Rigging in Arboriculture, learn from others with experience and try never to “learn the hard way.”
Travis Vickerson, CTSP, QCL, is vice president of operations with Chippers, Inc., an accredited, 21-year TCIA member company with offices in Vermont and New Hampshire.
Click below to view a video demonstrating the rigging tools discussed here.
