There are a wide variety of situations and scenarios in daily tree care operations where the ability to create an attachment point midway in a line is extremely advantageous. Each scenario presents different challenges to tree crew personnel, and the ability to identify those challenges and make appropriate choices from the available midline attachment methods can help ensure safer and more efficient operations.
Strength/ease of use
The two primary factors that must be considered when choosing midline attachment methods are strength, or more correctly, the amount of strength loss created by the chosen method, and the ease of use of the particular method. As an example, mechanical ascenders are easy to use as a midline attachment, however, their tendency to tear the fibers of the rope under extreme loads makes them an unwise choice in many applications. Some knots, such as the bowline on a bight, are fairly secure as midline attachment methods, yet the strength loss they create in the rope through their sharp bends and the difficulty involved untying them after heavy loading advises against their use in certain situations.
Alpine Butterfly: The alpine butterfly, an easily tied midline attachment knot with mountaineering roots, does create some strength loss in the rope through its sharp bends, but has shown in testing to create less strength loss than the traditional bowline variations. One method of tying it is to make three turns around the palm of the hand, from thumb to fingertips. The turn closest to the thumb is passed over the other two turns to the fingertip end, followed by the next turn, adjacent to the thumb, in the same manner. The turn now closest to the fingertips is then brought back through the other two, forming the loop for attachment. Both ends of the standing part of the line are then pulled in opposite directions to dress and set the knot. The alpine butterfly may be loaded on both ends of the line and in the midline attachment loop created, all simultaneously if required by the situation.
|From left, quick hitches with the bight through the loop from above, and with the bight through the loop from below.|
TripleBowline/Blackwater/Lineman’s Loop: This knot, whose name seems to vary widely with geographic location, is also an easily tied midline attachment knot that creates less strength loss than the traditional bowline variations. An additional advantage to this knot, gained from field use and experience, is that it is easier to untie than many of the other knots after extreme loading. One method of tying it is similar to the alpine butterfly and, in fact, starts in the same manner. Three turns are made around the palm of the hand, from thumb to fingertips. The turn closest to the thumb is then passed over to the middle, between the other two turns. The turn closest to the fingertips is now taken to the “new” middle, between the other two turns. In the final step, the turn now closest to the thumb is also taken to the “new” middle, and pulled through, forming the loop for attachment. Both ends of the standing part of the line are then pulled in opposite directions to dress and set the knot. As with the alpine butterfly, both ends of the line and the midline attachment loop may be loaded if required by the situation.
Eye and Eye Methods: The use of an eye and eye or two-eyed bridge/tail to create a midline attachment point can be quite advantageous when minimal strength loss and adjustability are desired. Any of a variety of climbing style hitches may be used, though additional wraps are taken to increase the amount of friction or grip provided by the chosen hitch in this application. A fairly simple and secure one is a variation on the Valdotain tresse, or Vt. As many turns as possible with the given eye and eye are taken in an upward direction on the line. The two ends are then brought together and held secure at the bottom of the turns, as the top turn is rolled down over the other ones, creating the braid or tresse in the Vt. This Vt variation also has the added advantage of being much easier to adjust or move after loading than a traditional Prusik hitch.
Directional Quick Hitch: The quick hitch is an easily tied and untied simple slip knot in the standing part of the line. Though not suitable for heavy loads and all applications, its use is quite valuable in sending a variety of equipment aloft, preventing rigging lines from passing through a block or pulley inadvertently, or even snaring a forgotten friction saver out of a tree. It is formed by creating a loop in the line and then passing a bight through it, either from above the loop or below it. Particular attention should be paid to how the quick hitch will be loaded when deciding from which direction to pass the bight through the loop. A bight from beneath the loop will allow for easy release from below, while a bight from above allows for upper release. In either case, the hitch is easily untied with a simple tug in the appropriate direction.
|From left, the steps in tying an alpine butterfly.Three turns around the palm, turn closest to thumb over to the fingertips, next turn over to the fingertips, through the middle, and tied, dressed and set.|
Slipped Sheet Bend: This knot, a slipped variation of the sheet bend, is useful when sending additional ropes aloft. Its security and simplicity make it an efficient knot to have in the mental toolbox. It is tied by forming a bight in the upper line, then passing the end of the rope to go aloft through and around the back of the bight. A sheet bend would be finished with the end of the line to go aloft passing beneath itself, but in this slipped variation, a bight is formed and passed underneath. This allows for quick, easy, one-handed release by the climber in the canopy.
These few simple secure midline attachment methods are a good beginning for tree crews deciding how to safely and securely employ the middle of their ropes and lines. Their use and application is only limited by their users’ imaginations and, as always, a desire for an appropriate safe efficient method.
|From left, the steps in tying a triple bowline/blackwater/lineman’s loop.Three turns around the palm, turn closest to the thumb to the middle, turn closest to the fingertips to the “new” middle, turn closest to the thumb to the “new” middle and through, and tied, dressed and set.|
Michael (House) Tain is a contract climber, splicer, educator and writer associated with North American Training Solutions/Arbor Canada Training and Education, currently located in Lancaster, Ky.