By Michael “House” Tain
There are no shortage of rigging situations and scenarios 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 understanding 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 detail, 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 efficiently. 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 efficiently 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 efficiently.
[First-level subhead, bold] Forces
Lifting is almost always going to involve putting some pretty extreme forces on the various anchor points that may be involved; 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 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 anchor point, pulling it horizontally and vertically. Both scenarios involve forces that may very well be manageable given the correct 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.
[First-level subhead, bold] 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 “balance” 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 enough. Care should be taken to select the proper diameter of spider leg, typically 1/8 inch smaller than the rigging line being used (1/2-inch rigging line = 3/8-inch spider leg), as this will create the required “grip” in the hitch while not “gripping” too much as would a significantly smaller diameter spider leg.
[First-level subhead, bold] Location, location, location
As in all things, location is very important in lifting, but particularly important is the location of the anchor point relative to the piece being lifted. The type of lift being carried out is going to dictate the location of the anchor point; and, as always in tree care, the structure and the strength of the tree itself. The use of some type of block or pulley is required in lifting operations, for although it may be possible to lift a branch or piece through a natural crotch, the friction involved is going to be extremely hard on the tree and rope involved and require much more energy/force to lift. A branch that is being balanced is going to require an anchor point that is almost directly over it and centered over the load to avoid any swing or lateral movement. If a swing or lateral movement is not a problem, then the anchor point can be off to the side; but the use of some form of control line to lessen the swing is recommended. And, of course, all personnel involved need to be prepared for the branch’s movement after separation. A scenario that is going to take a horizontal branch/piece and lift it to vertical prior to separation requires an anchor point as much directly over the intended cut as possible. In this scenario, having the anchor point in a different location changes the forces/vectors on the branch being lifted and can lead to problematic outcomes.
[First-level subhead, bold] You want me to lift what?
This might be the statement made by most branch managers if instructed to provide the lifting force in a branch lifting operation; and rightfully so. The input force required in most lifting rigging scenarios is going to require far more than any Johnny B. O’Doughnuts is going to be able to generate. Thus, lifting operations require the use of winches, mechanical advantage systems, or Hobbs/GRCS type systems. Regardless of which system is used, it should be set up so the operator can “hold what they got” without any slippage of the load. This is obviously no problem with a GRCS or Hobbs, but the use of mechanical advantage systems or fiddle blocks may require the thoughtful placement of a Port-a-wrap or other friction management device prior to the lifting action beginning. Additional thought and planning need to go into what is going to happen to the piece once lifted. If it will simply be lowered, then the GRCS or Hobbs will neatly transition to that action, but, once again, other systems might require pre-lifting setup. If the piece is to be “drifted” or otherwise moved laterally, the system to carry out that action needs to be in place and “good to go” prior to lifting for a smooth, safe transition.
[First-level subhead, bold] Precision is key in cutting
While precise clean well-matched cuts should always be the goal in any chain saw operation, it is of particular importance in lifting operations. The forces and mass involved — not to mention the hazard/target the limb or piece is being lifted from — mean that sudden abrupt movements can be hazardous to life, limb and target. A balanced piece — one that is intended to stay horizontal as being lifted — requires a fairly simple cut: an undercut beneath the branch, then the finishing cut on the top, as matched up with the undercut as possible. Finishing cuts with a straight hand saw in lifting operations will help climbers avoid dancing with a large, rapidly moving piece of wood and a running chain saw in their hands. A branch that is being lifted to the vertical plane should be viewed as a tree to be “felled” upward. This requires a face notch on the upper surface of the branch with a back cut below. The notch width and angle of opening will dictate when the branch separates, given the presence of good wood fiber, so operators should consider the face notch placement carefully. In general, one cut of the face notch should be perpendicular to the branch, and the other slightly less than parallel to the ground (but branch orientation will dictate specific angles). The operator should recognize that the goal is for the piece to be vertical prior to the notch closing/hinge breaking; and attempt to cut the face notch accordingly. Once again, a straight hand saw is the safest way to complete the cut. In either scenario, a small amount of pre-tensioning of the system will be useful to prevent the saw binding during cutting operations, but care must be taken not to preload the system so greatly that premature separation or violent movements occur while the operator is in the danger zone.
As mentioned, the lifting technique in rigging operations can be quite simple or very complex, dependent upon the needs of the tree, site, and job requirements. But the basic tools, techniques, knowledge, and methods discussed here can begin the process of helping tree crews add this useful technique to the rigging compartment of their respective mental toolboxes.
[ital>Michael “House” Tain is a contract climber, splicer, educator and writer associated with North American Training Solutions<ital] www.northamericantrainingsolutions.com [ital>and Arbor Canada Training and Education<ital] www.arborcanada.com. [ital>He is currently located in Lancaster, Ky., and can be reached via e-mail at<ital] email@example.com.