The reason there's so much confusion is that there are 3 different, and often conflicting things you are trying to do:-
1) stop someone hitting something, lock it off, giving high forces. If you're falling off overhanging rock, you will slam in
2) give a soft catch (mostly on poor trad gear). Letting the rope slip (or jumping up if you're light) limits loads, and slightly reduces slamming in on steep routes
3) Reducing slamming in- in a simple world it's best done by giving a metre of slack rather than by giving a soft catch. The lower you are when the rope comes tight, the less the angle of the rope and the less inwards force.
![](/upload/userfiles/mikllaw/fall333.jpg)
This gets less clear cut when you consider that a soft catch also reduces the vertical force F which drives the horizontal component.
Which combination of slack (3) and soft catch (2) actually works best depends on many factors, climber and belayer weights, rope stretch and drag, climb angle. Both work better than locking off (1). |