For more than 30 years, Arbor Age magazine has been covering new and innovative products, services, technology and research vital to tree care companies, municipal arborists and utility right-of-way maintenance companies
Issue link: http://read.dmtmag.com/i/319014
22 Arbor Age / June 2014 www.arborage.com B y M i c h a e l " H o u s e " T a i n A ttaching another line, a piece of gear, or even a fl oating anchor point to the middle of an existing line is a scenario that arises on a fairly regular basis in the tree care in- dustry; and is also a situation that can not only be problematic to carry out, but downright dangerous if done improperly. "Poor outcomes" can range from the fairly minor (a desired rigging line falling free from the ascending line and "monkey knot" just as it reaches the climber) to the catastrophic (a poorly chosen midline knot or attachment method failing under the stress and force of a rigging/pulling operation leaving ropes and large woody debris fl ying in unintended directions). [As an aside, a "monkey knot" is where one does not know the correct knot/hitch; and "monkeys" around until some form of knot/hitch is created.] There are a variety of knots, hitches, and midline attach- ment methods available — some quite simple and others more complex. But regardless of which method is used, it is imperative that, in the interest of safety and effi ciency, the tree crew involved have the necessary knowledge and train- ing to make the correct choice. Strong and easy Although the tree crew should choose their midline attach- ment method based on strength and ease of use, they should also keep in mind that these two factors may often affect one another. Strength, whenever a discussion of knots and hitches is involved, is primarily about how much strength will be lost in the line through creating a hitch or knot. As is well known among tree folk and cordage connoisseurs everywhere, the bends created in a line when tying a knot cause strength loss (generally the sharper or more acute the bends, the more strength is lost). Ease of use is a fairly simple concept to comprehend — if a chosen midline attachment method takes a great deal of time to put in place, and can only be removed through the use of a fi d or sharp-edged im- plement, it is pretty clearly not that easy to use. There are midline attachment methods that may take longer to "set up," thus reduc- ing their ease of use factor; but if the particular method creates the minimal strength loss needed for the scenario, the additional time is well spent. Knowledgeable and well-trained tree crews are constantly balancing these two factors throughout their daily work; and making choices that make the most sense for strength and ease of use. Some examples of midline attachment methods that are extremely easy to use are mechanical ascenders or other similar devices. The downside is that under extreme loads many ascenders will begin to tear the cover of the rope, thereby causing strength loss; so perhaps they are best suited for very minor loads or the climbing applications for which they are designed and intended. A Bowline on a Bight is a knot that is fairly easy to tie midline, but its sharp bends create signifi cant strength loss, and it can involve some effort to untie after heavy loading — thereby proving itself lacking in both strength and ease of use for midline attachment of heavy loads. Mountaineers present The Alpine Butterfl y is not only fairly easy to create once practiced, but has a moniker guaranteed to bring a grin to nature- TRAINING & EDUCATION TRAINING & EDUCATION Midline Attachment Methods When you need a spot for that midline knot