Ok guys I’ve addressed this before and I kind of knew this would be coming around again….. Amsteel or Amsteel blue both have a melting point of below 300 degrees. One is listed at 290 and the other at 296 so the temps aren’t different enough that one is “better” at friction handling than the other. However since most guys using amsteel are full burying the splice, the hitch will bite down incredibly hard, the slick nature of dyneema along with the urethane coating and it will reduce its friction against itself and dissipate it fairly quickly. So while friction and melting is a concern it’s not the major concern. The major concern is its lack of stretch. The rope has less than one percent stretch at 30% of its MBS. This problem is 2 fold when using it as a tether. The first problem is that because it doesn’t stretch amsteel is not great at dynamic loading. Some people climb above their tethers. Some people spin on the platform for weak side shots. Equipment fails ect ect ect…. There have been many dynamic tests ran where nylon runners out perform dyneema runners for mountain climbing. Nylon runners with 4000 lbs break strength often hold without failure to that force or above when dynamically applied, where as dyneema (the material amsteel is made of) routinely breaks at much lower forces than it’s rated for when dynamically applied. This problem becomes two fold as material degradation comes into play and the fact that we girth hitch the tree. A girth hitch reduces the strength of rope by approximately 40%. So your rope is 40% weaker than it’s mbs, and then you use it a full season it’s weakened by abrasion, sunlight (slightly) and friction. You take it out for season 2 and you suffer a fall, do you trust the reduced strength of that rope to catch you when it already doesn’t like to be shock loaded?…
Which leads me to the second point, most climbing ropes even static ones have around 3.5% elongation or more at 10% of their breaking strength. Some ropes like 10mm protac have closer to 6 or 8%, and dynamic will have greater than 20%. Why is this important? Some have suggested elongation is what you use to rate the ropes safe work load….. this is completely wrong. Elongation is important because the rope stretching, reduces force by acting like shock absorbers. The more stretch your rope has, the less force making it to your saddle and your body.
So why use it for bridges? Well it’s simple bridges are basket configuration. They are attached on both sides so force is applied at two locations. This essentially makes the rope 1.5 times stronger than it is when being used as a tether. A tether is a single point of force applied directly to one location.
Ok so a lineman’s rope acts like a bridge in that it has two points of contact. Yes this is true and you could use amsteel as a lineman’s rope. Except that proper use of a lineman’s rope is you hold the ropes at a point close to the tree, you lean in slightly to remove the tension then you lightly flip your wrists to advance the rope up the tree. Amsteel even double buried is too flimsy and flexible, not to mention the diameter is a little small to safely and reliably flip the rope as you should. So while it’s strong enough to use (if it’s at least 1/4” because you’re gonna have a smaller diameter cord for your friction hitch) it’s not firm enough to handle so you’re stuck reaching around the back of the tree to advance your lineman’s rope. This is improper use and bad form both of which could lead to you falling down the tree or pinching off your fingers while they are under the rope. My opinion is don’t do that. There are safer and better options for both lineman’s ropes and tethers. And there are better places to save on weight and money.