A key component of daily tree care operations is being able to lower large pieces and parts of woody debris with a fair amount of control and accuracy. Although all climbing arborists secretly dream of an endless stream of “freefall” jobs where the property owner will take care of the brush, the reality is that many removals, and even mildly significant pruning jobs, involve some obstacle or target that must be avoided. As gravity seems to be the law no matter where a tree crew works, and wood can generate a fair amount of damaging velocity from rather insignificant heights, rigging, and the control that should be a part of it, is part and parcel of the tree care industry’s daily existence. Knowledge of how to acquire, and the ability to build, systems that provide rigging control not only will assist in avoiding damage to property, but increase the safety and efficiency of the work site. After all, an energized conductor beneath a branch to be removed is not only an obstacle that has to be undamaged, but also a palpable threat to the climber and crew if not avoided safely and under control.
Additionally, a growing awareness through research and training has made many in the industry aware of the forces trees are exposed to during rigging operations. Some of which, if improperly handled/controlled, can have catastrophic physical results for both tree and crew. In years past, and on many work sites currently, the method for gaining control over a large piece of woody debris descending at a high rate of speed was to take wraps around the tree or an adjacent tree, thereby generating the required friction for some measure of control. This technique, though still useful at times, has a number of disadvantages, including friction generation that varies with species due to bark differences, ground personnel that must be experienced and knowledgeable enough to take an appropriate number of wraps, and the dizzying number of times a ground worker has to circle the tree to put on or take off wraps. One of the simplest, lightweight and most economical tools available to provide rigging control is the Port-a-Wrap, designed and developed by working climbing arborists Scott Prophett and Norm Hall. This safe and efficient lowering device not only provides consistent friction with attendant strength regardless of tree species, but also is simple enough for efficient use with a minor amount of instruction and training. However, as with anything new to the gear bag, it must be used correctly to reap its full benefits, while avoiding improper use and situations that could lead to its failure.
Attaching the Port-a-Wrap to the trunk of the desired tree is a simple and straightforward process requiring only an eye sling of proper length and knowledge of appropriate rigging sling attachment knots. The use of connecting links of any type to attach the sling to the Port-a-Wrap is not recommended in any rigging situation; and particularly not in a situation involving dynamic loading where the connecting link could become cross or side-loaded during movement and subsequently fail. Rather, the best and safest way to attach the sling to the device is by girth hitching the sling around the larger or longer of the U-shaped brackets beneath the barrel. Rigging slings with larger eyes that are large enough to pass all the way around the Port-a-Wrap will make this girth hitching process even easier, and avoid the possible weakness of a connecting link. A cow hitch with a better half is an excellent choice for securing the sling and device to the tree, although in the event the sling is too short, a timber hitch may be used. If additional eye slings are available, they can be tied to one another with a double sheet bend, creating a longer single sling, allowing for the use of the cow hitch. If the timber hitch is used, ground personnel should make sure it is loaded correctly after every load to ensure the timber hitch’s coils have not gotten too close together.
Setting the rigging line
In order to prepare the Port-a-Wrap to lower a load, a bight of the rigging line is fed through the smaller angled “U” on top of the barrel, around and under the forward end of the barrel itself, and beneath the protruding pin, between the pin and the “U,” thus securing the line in place. At this point, the operator should pull down on the part of the line leading up to the load and up on the part of line exiting the device. This will assist in removing slack from the line and rigging system, and though not eliminate the Port-a-Wrap sagging at the instant the piece or branch is cut free, will lessen the severity somewhat. The line is then passed completely around the barrel behind the “U” until the number of desired wraps and attendant friction is created. More wraps around the barrel obviously mean more friction, but personal experience has shown that the most common mistake among new users is too many wraps rather than too few. Two to three complete wraps will provide total control for all but the most extreme loads. The ground person can then stand out of the landing zone at almost any angle from the device as the two pins on the end of the barrel of the Port-a-Wrap direct the line into the barrel correctly. These pins also provide a place to “cleat” off the line, keeping the load from moving in the event of a static load or to enable ground personnel to cut some pieces off a large load while stable. The barrel should be filled with wraps in this application to provide enough friction to prevent the “cleat” to become overtightened to the point where the only option for removal is a knife.
The goal when lowering a load with the Port-a-Wrap, as with any rigging control device, is to lower the load smoothly and safely with a minimization of forces at the anchor point, which is typically quite near the climber aloft. This is not accomplished by snubbing the piece or load off and bringing it to an abrupt stop. In fact, that is the worst thing that can happen in regard to forces experienced by the anchor point and the climber. By using the proper amount of wraps on the Port-a-Wrap, the operator is able to gradually slow the piece, bringing it to a stop where required by obstacles and the level of the ground beneath the tree. This gradual deceleration will allow the elongation of the rope to absorb some of the generated forces, dissipating their severity at the anchor point. In cases where circumstances or obstacles dictate snubbing the piece off, all personnel involved should be aware of the possible forces that are going to be generated, examine the tree and gear for expected survival of such forces, and plan accordingly.
The Port-a-Wrap is most commonly used in rigging systems to control the descent of loads, but with a little imagination and common sense it has a wide variety of applications in other facets of rigging or tree care. The smaller version can be used as a personal descent device in place of a figure 8 on long descents, though gear used once for rigging should never be used for climbing after its rigging use. The device also works well in applications involving lifting, pulling and/or mechanical advantage to take up and hold the slack generated by the fiddle blocks or other system, or to create an adjustable “floating anchor” in tree pulling situations.
The Port-a-Wrap III, as well as earlier versions, are made by Buckingham Manufacturing, and are available in a number of sizes, materials (including steel and aluminum) and coatings from a variety of arborist retailers. Their safe working load (SWL) is dependent on model and material, but is generally in the 2,000-pound range for the larger models. A newer version has recently come on the market that is made overseas for SherrillTree. This is called the Port-a-Wrap IV, and is available in medium and large sizes in steel and stainless steel with a working load limit (WWL) of 2,000 pounds. This version also includes a cap at the end of the barrel intended to protect the bark and trunk of trees not being removed during rigging operations. The size of the device, regardless of manufacturer, will dictate what diameters of rigging line can be used with it, so operators should take that into consideration when selecting one. Personal experience has shown that the Buckingham Port-a-Wrap III and earlier versions are strong, durable and well-built. Hopefully the newly released Port-a-Wrap IV will live up to the legacy of its forefathers, and exhibit the same tendencies.
Rigging operations in tree care are, by their nature, dangerous undertakings, involving attempting to move large weights in a controlled fashion, while ropes, gear, trees and climbers are all possibly experiencing extreme forces. The Port-a-Wrap is an excellent tool in these undertakings, one that once understood and used correctly cannot help but increase the safety and efficiency of tree crews everywhere during rigging operations, and whose versatility will prove useful in a wide variety of applications. Simple, strong and easy to use, the Port-a-Wrap is definitely a tool that keeps on giving.
Editor’s note: This story was originally published in May 2010 and has been updated.