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www.arborage.com Arbor Age / September 2014 11 increases or "spikes" in the pounds/kilonewtons/choose a unit of measurement involved. While this makes it easier to estimate how strong the system needs to be and choose appropriate equipment and anchors, it also means the folks involved need to be mindful of creating different — and possibly harmful — vectors of force. A "straight" lift — one in which the anchor point is fairly close to directly over the load — will generally create the greatest force at the anchor point, typically twice the load being lifted. But this force — dependent on the form of the tree — will also be distributed in the best way possible, through the vertical plane of the trunk. A "vectored" lift — one in which the line exits the anchor point at an angle toward the object being lifted — lessens the load at the anchor point, but creates a bending moment on the tree or lead acting as an an- chor point, pulling it horizontally and vertically. Both scenarios involve forces that may very well be manageable given the cor- rect gear and set-up, but it is imperative that the crew members be aware of the existence of the different forces, and evaluate the tree/anchor points involved accordingly. Balance in all things Although it may not always be required in lifting operations, the ability to balance limbs or pieces (keep them in the same position/orientation as they are attached to the tree) can be extremely useful at times. There are a variety of ways to "bal- ance" a limb, but one of the easiest and most versatile is the use of spider legs. Spider legs are a rope tool typically spliced out of 12-strand hollow-braid cordage with a large spliced eye on one end. This large eye is used to create a hitch on the rigging line, a Prusik, Klemheist, or other appropriate one, and the non- spliced end of the spider leg attached to the limb or piece to be balanced. The hitch can then be adjusted up or down on the rigging line to provide the proper tension prior to cutting to keep the piece in the desired position once free. Spreading branches may require multiple spider legs to fully support and balance them, but it is always better to have too many than not here is no shortage of rigging situations and sce- narios in the day-to-day work world of the tree care industry — from the basic-but-challenging spar pole rigging system to the complex, gear- intensive, multiple-technique slide line process over varied targets. And although each situation requires a certain basic knowledge and under- standing of different methods and techniques, the safe use of the technique of lifting a branch or piece over/off a hazard/ obstacle demands not only extreme care and attention to de- tail, but also an extensive knowledge of the forces and vectors involved and being generated. Lifting in rigging operations is most likely a skill that will not be used every day, but one that, once understood and mastered, can be applicable and extremely useful in a wide variety of simple to complex tree care operations. At the simple end of the spectrum is a tree crew confronted with a fenced-in backyard takedown and the prospect of hauling all that woody debris out piece by piece, or setting up some form of lifting/transfer system to move out the debris in greater volume and more effi ciently. Conversely, the spectrum's complex end might involve a large, spreading branch immediately over a house or wire with little room for error or drop; and the application of a lifting system removing it safely and effi ciently in one piece. At either end, and through the remainder of this spectrum, an understanding of the forces, techniques, and methods of lifting rigging systems can help tree crews accomplish their mission more safely and effi ciently. Forces Lifting is almost always going to involve putting some pretty extreme forces on the various anchor points that may be in- volved; and crews should examine their chosen anchor points accordingly with a critical and discerning eye. A lifting system, if set up correctly, should present only a static or non-dynamic load to the components and anchor points involved. This means that there should be no "drops" into the system, creating sudden The GRCS winch in action. Photo by O. Sisk The climber's view of an obstacle/hazard from which a branch might need to be lifted. Photo by T. Harbourt h n c sp in o r T