Considered by many as advanced operations because highlines deviate in many ways from standard rope rescue rigging practices, building and using highlines requires a clear understanding of sound rigging principles and a working knowledge of the force vectors involved.
Some Key Concepts to remember:
- Know when highline systems are needed and should be used during a rope rescue.
- Know and understand the guidelines for tension and highline Track Line
- Understand the potential forces involved in a highline and the rigging safety measures taken to control them.
- Know the steps in constructing a highline.
- Now how to construct and operating a Reeving System.
Highline operations are one of the most dangerous and most difficult vertical rescues. Highline rescues invoke the use of advanced rigging skills, performed by advanced technicians. Under no circumstances should a highline be attempted solely on the instruction of this book. Anyone interested in performing a highline must have intermediate skills, and seek advanced training through an accredited school of rope rescue. This section of this chapter gives only a general overview of this extremely complex subject of highlines. For a fuller understanding of highlines RescueRig offers rigging courses for advanced level technicians.
Highlines are almost always a last resort option. The good side of highlines is that it is a viable option; the bad side is that there are numerous reasons why not to do one. If over tensioning and rope abrasion are the archenemies of rope rescue operations, than consider these two evils the devil incarnate to a highline.
By its very nature, highlines go against most conventional rules of safe anchor building. In most cases, we try to keep the angle between multi-point anchors 90% or less, at 120 degrees the force at each anchor equals the weight of the load. With highlines, you are looking at a vector angle of 150 degrees and up. This alone will multiply (with the rescue load in the middle of the trackline) the weight of the load anywhere from 2 times at 150 degrees to 11 times at 175 degrees at each anchor!
A Checklist To Always Keep In Mind
Because of this tremendous stress highlines put on the anchors, here are some key principles that must be included in the construction of highlines:
- Anchors must be bombproof.
- Full strength of the trackline must be utilized by eliminating all knots, and all sharp bends.
- All knots on the control lines must be bypassed.
- Maintaining a pulley tension system to the highlines utilizing a “slipping clutch” (or safety fuse) in the form of system prusiks. (8mm, 3-wrap)
- Incorporate a carriage system supporting the load.
Stages of Highline Operations Checklist
Highline operations consist of five major stages, they are:
- Spanning the Gap
- Construction of the high directionals
- Construction and Tensioning of the Trackline
- Construction of the tagline/belay systems
- Construction of the carriage
- Break down.
Construction and Tensioning of the Highline
There are immense forces generated at each end the highline, because of this it is imperative that all knots be eliminated from the highline, and that the highline not be over tensioned.
The highline must be one continuous rope and the opposite side must be anchored with a high strength tie-off.
The control side of the highline is typically finished off with an integral 3:1 MA. (Ganged systems are sometimes used, especially for bundled 2 and 4 rope highline systems.) This MA should include tandem prusiks at the ratchet pulley (This is the only time tandem prusiks should be incorporated in a mechanical advantage.) When pre-tensioning the highline, use only one person to pull on the equivalent of a 3:1 MA. Post tensioning of the highline the maximum number of haulers is dependent on the weight of the rescue load, the length of the highline, and the amount of desired percentage of sag.
Here is a 50 second run through on not just a Single Track Highline, but just to wet your whistle… a bit more.
Peace on your days…