Some discussion erupted on youtube about this video. I’d like to point out a few things here, on my website: first of all the series is aimed at the general public and it has to condense in 3 minutes practical information easy to absorb by audience with little technical knowledge.
The contentious point was my saying “factor 1 falls are normal”. Probably saying “fall factors of 1 or less” would have been better and then “fall factor 2 or more” etc “BUT the general public operates with two concepts: Fall 1 factor and fall 2 factor. It was clearer and easier to point out the “good” one as opposed to the “bad” one by using the two already familiar concepts.
The accompanying point, however, is linked and it states that when falling (in a normal sport climbing scenario for example) we are always closer to factor 1 fall than we think. In the case of a fall only the length of rope between the penultimate and the ultimate runner will be fully loaded so regardless if you have 15 m of rope to the climber and he only falls 2 m <<only in theory>> (!) you’d have a 0.13 for example fall factor. It is how the rope travels between the belayer and the climber, the edges it runs over, the friction with the biners and the way the quickdraws are set that affect how much of the rope takes the actual force of the fall and it is always closer to 1 than the so called ‘theoretical fall factor’ which is considered the Ff = height of fall / lenght of rope.
Some Lanex (Tendon) engineers looked into this in 2006 https://isbweb.org/images/conf/2009/data/pdf/241.pdf then Bedogni and Manes from CAI much more in detail in 2011: http://www.caimateriali.org/fileadmin/user_upload/pdf/sdarticle.pdf
The take away points are simple:
- don’t think that just because you have a lot of rope between the belayer and the climber and a short fall you will get a low fall factor. It’s how that rope travels that matters and the friction in the system as well as your belay device
- falling in the air on a rope won’t cause it to break even if has been under normal wear and tear. Your body or slings in the safety chain will give in first before the rope breaks
- From Kukuzca to Michele Caminatti and beyond the rope broke due to the rubbing against an edge. Diameter (as one is tempted to believe otherwise) is of less importance. The real things to take into consideration is the combination of: weight of the climber + the type of edge the rope runs through + the distance the rope travels over the edge and eventually (+ if the rope is wet)
- An increase/doubling in weight on the rope (from 80 Kg to 160 Kg in a lower off test – rope under tension on a sharp edge) reduced the rope resistance by 600% while a 1.1 mm increase in diameter of the rope increases its cut resistance only by 20%.
So keep your rope away from edges by extending the runners, keep the rope dry, try to place your runners as in line as possible so it is more of the rope that catches the fall, use tube-style / munter-hitch for belaying over grigri and the such.