The knowledge, ability and skill to employ multiple lines in tree care operations can provide climbing arborists with numerous advantages. For example, a secondary line can help with extra support, possibly bearing the weight of the load more equitably among numerous rigging points, but also can be very effective in actually moving large wood through the air to a designated and/or desired location, or landing zone.
This movement is achieved not only by careful planning and appropriate setup, but also through the use of various rigging devices or techniques to take in or feed out line as needed to achieve the desired or required movement.
The use of a secondary, or even tertiary, line in this manner often is referred to as a drift line. The use of additional lines enables tree crews to better and more securely stabilize loads where any sudden or abrupt movement might bring the load into contact with obstacles or hazards – or just in general be detrimental to the overall goal.
Multiple lines provide a large number of advantages in tree care operations, but as with many excellent tree care techniques, require a certain level of knowledge, gear and time to setup and employ effectively.
The most basic of scenarios that is well-suited to the use of multiple rigging lines is an operation in which there are “high value” targets beneath the tree, immovable obstacles or a very limited drop zone. Examples of these scenarios might include small fenced-in yards, valuable ornamental plants or even a glass greenhouse in the drop zone. Regardless of target and value, this is a situation where the use of multiple lines can not only make the job safer, but also more efficient.
While the situation described could certainly be dealt with using a simple single-line rigging/lowering system, it certainly would require taking small pieces, moving them around the targets/obstacles in some manner, and then the sweat equity to remove them from the drop zone, all of which add time and energy to the job and cut into the profit margin.
The availability of a second anchor point – either in another large lead within the tree being worked on, or, even better, in a tree off to the side of the primary anchor point – allows for the effective use of a secondary load or drift line.
The secondary, or tertiary, anchor point typically will be at the same general height as the primary anchor point, although this requirement is dependent on the situation and goal of the rigging plan. All anchor points – regardless of purpose or function – when using load and drift lines, should be composed of appropriate slings and blocks or pulleys. This reduces friction in the rigging system and allows for adjustability and the placement of rigging points at a spot where no natural branch union or feature may exist.
Tree care pros must be aware of – and do their best to avoid – a number of issues when using load and drift lines. One of the most common mistakes made when using the technique, and attempting to save time, is the practice of hanging a rigging line over a branch with a pulley or block attached to the end as a secondary anchor point. This is an excellent way to break gear and trees, often with catastrophic results due to the multiplication of forces created at the rigging point.
The use of a multiple-line rigging system, whether to better support a load or move it, is almost sure to require some form of mechanical advantage or device that can provide input force to the lines employed, and allow the ability to control them precisely. Gear such as Port-a-Wraps, Prusik minding pulleys, fiddle blocks, Good Rigging Control System, or a Hobbs are all certainly applicable and necessary in this application.
Load or drift?
The answer depends on the piece’s location along its desired path. Initially, the piece is caught by the primary rigging line, which is the load line at that point. The secondary or tertiary line(s) should be slack, as dropping a large load into a pre-tensioned line leading off to a distant anchor point most definitely should be avoided. Tension is then gradually placed on the piece through the chosen mechanical advantage system, in a sense pulling the piece in the desired direction. This use of the secondary line is a drift line. As the piece grows closer and closer to the secondary anchor point, the drift line takes more of the load, becoming the load line, and the original load line that is feeding out to control the piece’s movement becomes the drift line.
Load and drift line use can make many tree care rigging operations more efficient and safer, but only if the technique is used correctly and with a good knowledge base of the forces and dangers involved. It also is not a technique that is applicable in every situation, particularly due to the setup time required and gear/anchor points needed. So tree crews should be honest with themselves about whether they are just trying to make the technique fit the job, rather than using the best technique for the job.
Once learned and practiced, though, load and drift lines are an excellent tool for the mental toolbox when confronted with a removal with lots of obstacles, hazards or a limited drop zone.