Wednesday, December 25, 2013

Via Ferrata Tethers--Some Good Ideas, But Not for Sailing

Via ferrata trails, literally iron ways in Italian, are climbing trails equipped with rungs and safety wires that allow fit but unskilled personnel to move quickly and safely over difficult terrain. Though they date back into the 19th century, they are best know from their use during World War I, moving troops through the mountains.  Since then they have expanded to thousands of tourist routes in Europe and the United States. Since tether technology is the focus of this post, I'll leave history research to the reader; the internet is great for that.

The climber is protected falling all the way by a pair of tethers that follow a safety wire to the side of the rungs. Periodically, the wire is fixed to the face, and this is the challenge; these points are generally  10-20 feet apart, allowing for  serious falls before the tether takes, and requiring the tether to absorb a great amount of energy, more than a dynamic rope alone can handle. Dynamic ropes are rated for a fall factor of 1.8, whereas a via ferrata fall can be fall factor 5 or more.

The solution is a more extensive energy absorption system, including either friction through an aluminum plate or a tear-type energy absorber, like a Screamer.

Why wouldn't these make useful sailing tethers?
  • The allowable impact force is much greater, since the load is taken on a seat harness rather than a chest harness; the human tail can take a lot more force than the ribs. Sailors need a softer catch.
  • The falls are really much greater. A sailor will never see an impact beyond fall factor 1; the ISO drop testing required by the ISAF rules is based on a FF1 with a 100Kg mass.
  • The end clips on via ferrata tethers are applicable and gaining popularity. The West Marine tethers are now Kong Tango via ferrata biners (pictured on tethers to right), and I like them very much. Fast on and off, one-handed even when cold and wet, locking, light, and fit over most handrails too. Because they are aluminum, they do require periodic lube and rinse. Mine have held up very well, like new after 2 seasons.
  • Harness attachment. Sailors like a quick release on the tether, something that can be removed under load. Climbers opt for a locking biner, since no possibility of accidental release is acceptable. Most often the tether is cow-hitched to the harness.
  • Length. Sailors like dual lengths (2-3 feet and 4-8 feet) while climbers are restricted to 2 matching arm's length tethers; they never want the clip to move out of reach (if it snags below you this is a real drag).
Certainly there are some ideas here, some worth adapting, but the application is different.


Note on recalls. Because of the extreme nature of the falls and untrained nature of many users, there is some history of failures, most often fatal. In general, the causes have been:
  • Fall too great. Anything of 10 feet is trouble and over 15 feet is beyond the equipment rating. The via  ferrata trails generally recognize this, placing tie points ever 10-15 feet, but risk is often part of  climbing; if it looks too scary, go down.
  • Worn friction rope. Some designs rely on a rope slipping through a plate with many holes. If the rope wears through use--tour groups use them daily--the rope slides more easily and insufficient energy is absorbed. This type has gone out of production because they are too difficult to inspect.
  • Poor or worn stitching, or any other construction fault, though this type of failure can result from too long a fall.
ALL via ferrata falls are bad, far more dangerous than falls on a climbing rope. They feel safer but are not. The impact forces are high and there is much to hit on the way down.


  1. Thanks Drew, much appreciated. Another question I had was whether it would be useful to have the jack line attachments have some energy absorption capability (think rubber snubber on a rode). Happy Holidays.

  2. Jacklines and energy absorption. I wrote a long post on this subject here ( In a nut shell, there seem to be 3 points:
    1. There are very few recorded injuries and failures related to sailors clipped to jacklines. Unless the lines are very short and made of steel cable, there is generally enough stretch in the system to control forces. Rope or webbing are fine for boats under 40 feet.
    2. More stretch could be bad, increasing the chance of going over the side.
    3. The greatest injury risk has proven to be getting rinsed the full length of the deck. More of a Volvo Ocean Race issue.

    How much stretch is allowable depends on deck layout. I have a catamaran and run the lines well inboard. This allows for a stretch line, which is good, because I have a big tramp which allows for long slides. On a narrow boat I would use polyester line, but probably not Amsteel; too much impact load.

    Jackline attachments need to be VERY strong as the tight rope effect multiplies forces. Even for casual sailors, the 5000-pound figure is a minimum. For larger competitive boats, 10,000 pounds is a better design value, easily managed with today's fibers; this is significantly because it is more likely for a fully crewed boat to have 2 sailors on the jackline.