Tree folk are confronted on a daily basis by the need to move something, usually awkward woody debris, from one place to another in an efficient manner. Often this involves a great deal of “sweat equity” with crew members physically carrying branches, logs and wood to the truck or chipper, typically with a fair amount of physical effort, energy expenditure and negative verbal commentary.
Slide lines, also often called zip or speed lines, offer another option for this debris movement. They’re an option that, though gear- and set-up-intensive, can be quite efficient, not to mention easier on a tree crew’s back and morale.
Slide line use may be dictated by the worksite – for example, if there are hazards or obstacles immediately beneath or around the tree being worked on – or they simply can eliminate a long, tedious route of dragging debris to the truck or chipper. Slide lines often are used in concert with other techniques, such as balancing, lifting, knotless rigging and spar pole removal. Regardless of the application, the complex nature of slide lines and the forces they generate require an understanding of multiple factors to ensure their safe and efficient use.
Sometimes the “old school” method of just buckling down and sweating away at hauling that brush will be the safest and most efficient method. But, given the right situation, a knowledge of slide lines can get the job done safely and efficiently with energy savings all around.
Which line for sliding?
As is so often the case in tree care operations, one of the first questions to be answered in slide line use is which type of rope to use. Factors such as strength, elongation or stretch, and melting point all need to be considered, as they can have significant impacts on how well the slide line operation will go.
As an example, a line with more elongation will absorb energy more readily than a more static rope, but will require a great deal more input force, or pulling, to make it taut to “slide” loads down.
In turn, this requirement for more input force will require more time and energy, thereby making the use of the slide line perhaps not the quicker, more efficient choice it was meant to be.
Conversely, a very static line, or one with little elongation, will not stretch much when loaded, but will transmit all the input force to the anchor points of the slide line, possibly creating another area of concern.
Only as strong as what it’s tied off to
The anchor points to which the slide line is tied or secured also must be evaluated in the use of this technique. The line carrying the load will have a lot of tension and force on it, both from the initial input force to make it taut and the weight of the load being transported. These factors will be transmitted directly to the anchor points at either end of the slide line.
Of particular concern is the anchor point aloft, especially when the point chosen is in the same tree to which the climbing arborist is attached, as it can create a bending moment that can cause failure in the tree itself. A better option is to anchor the upper end of the slide line into a separate tree, thereby avoiding any additional forces on the tree being worked on, although this might not be possible. Should a second tree be unavailable, or simply poorly positioned, the correct use of appropriate redirects can reduce the forces involved while anchoring the slide line adequately.
In addition, the lower anchor should be adjustable, so that tension can be applied and removed.
When tight is too tight
The slide line itself should never be under tension when the load to be transported is brought to bear on it. Dropping a load into a taut slide line is a sure recipe for an emergency room visit accompanied by a trip to an arborist retailer to replace broken ropes and gear.
If the situation/scenario requires dynamic rigging, or a load that needs to drop a certain distance, a secondary line and rigging system should be used to control and absorb that force, after which the load is attached to the slide line for transport.
The slide line is then put under tension and the load sent along its journey to its intended destination.
There are many ways to tension and loosen the slide line, such as fiddle blocks, tensioning kits with Prusik minding pulleys, or a device such as the Good Rigging Control System, all of which can be fairly user-friendly. Using trucks, skid steers or ATVs to tension slide lines is a very poor choice, as it can easily result in broken gear, trees and even climbers or crewmembers.
Control is key
Except for extremely small or light loads, some form of control line should be employed to control the speed of “sliding” on descent; without one, even loads that are thought to be extremely small or light will appear to be traveling fairly rapidly to the crew at the receiving end. In addition, loads “sliding” down without any control line will increase the heat input on the slide line, perhaps making the melting point an even more important consideration. When properly set up, the control line need not involve any additional rigging, and can simply be the rope that was used to “catch” the dynamic load prior to the slide line being tensioned.
Consideration also should be given to the manner in which the control line will be “controlled,” as relying on a crewmember’s grip strength when sliding a 250-pound log toward the brand-new chipper may be a poor choice. A Port-A-Wrap or other friction management device might be a better option.
Traveling and carrying
A traveler or carriage is the item to which the load is attached, which “slides” down the line to its final destination. Many pieces of arborist gear can be used in this application, but with a wide variety of performance levels.
The simplest carriage might be some form of carabiner or snap, but users should keep in mind that the friction generated will not only slow the load’s travel but create a great deal of heat input in the slide line. Any number of pulleys are available, from single to multiple sheaves that will travel quite smoothly and generate less friction, but users should evaluate any pulley used for the necessary strength and appropriate design for the load involved.
Having multiple travelers or carriages on hand not only will assist in moving larger or longer loads, but will make the process more efficient as the climber can prepare the next shipment while the previous one is being removed from the slide line.
Slide lines aren’t required in every situation, but, when used appropriately, they can save a great deal of time, energy and money. Once added to an arborist’s mental toolbox, they can make seemingly endless brush hauls slip and slide away.