[ QUOTE ]
[ QUOTE ]
...but I am keen to expose as much of the facts as possible to help others make an informed decision.
[/ QUOTE ]
OK, so here is some info, with very little additional comment.
From L2s paper (double quotes "....." indicate the text is repeated verbatim from the paper):
In the ‘Doubled Rope Drop Tests’ for a ‘fall factor 2’ fall, the forces “…are very high and appear to be likely to cause damage to the climber” (p.33). In the ‘Single Rope Drop Tests’ for a ‘fall factor 2’ fall, “The recorded forces were almost 50% (on average) lower than the doubled rope ‘fall factor 2’ falls” (p. 35).
The above are for falls of ‘fall factor 2’. For falls of ‘fall factor 1’:
For the ‘Single Rope Drop Tests’ for ‘fall factor 1’ falls, it is stated “Both cord types held the fall with similar results to the doubled rope drop test for falls of ‘fall factor 1’” (p. 34).
"Maximum peak force recorded"
---for falls of 'fall factor 1' with a single rope: 700Kg
---for falls of 'fall factor 1' with a doubled rope: 892Kg
"Minimum peak force recorded"
---for falls of 'fall factor 1' with a single rope: 624Kg
---for falls of 'fall factor 1' with a doubled rope: 641Kg
NB--various combinations of friction hitches, split tails, and climbing lines were used, and these were not always duplicated from one type of test to another.
Most of the paper seems to consider that the climber is tied-in to a limb and is working the canopy. In a few places the paper specifically mentions working on a spar and in the ‘General Conclusions’ it states “…when topping down a pole…the lifeline should be chokered (either doubled or single) around the stem at waist height in order to avoid a factor 2 fall” (p. 38).
[ QUOTE ]
No slack, no force, no worries.
[/ QUOTE ]
I'll buy the beer.
[/ QUOTE ]
Hmmm...As you know, I checked this out Mahk, and what I'm talking about wasn't recorded in the research. I can't remember why, but I do remember running the tests. Should be a good one for those with dynamometers to play around with to see what they find. I'll get round to it one day.
Heres how I set up the test:
-Run 1/2" single braid 16 strand tree rope through 2No. maillon rapides as anchor point in tree, attached to dynamometer.
-Run out 14 metres of rope and tie as a doubled rope system with VT (Use two seperate krabs for each end of line to avoid krab failure).
-Clip both ends of rope as you would to climb, to a 100kg load; there should be around 7metres distance between load and TIP.
-lift load until 50cm of slack are in both legs of rope.
-release load and record.
Obviously, this will have to be set up to avoid the load impacting the ground.
This should show, that, even though its a factor 1 fall, the fall forces can be exceptionally high with a DdRT, if such slack is allowed in the system. Fall factors are concepts that explain seriousness of a fall with Single rope techniques. The actual forces in a factor 1 fall with DdRT could be way too high if loops of slack creep into the system. If it doesn't, I obviously got my wires crossed; I've had several knock-out blows to the head since then (metaphorically speaking).
Tut! The Guiness is stale! My round!
