The combination of increasingly thinner ropes and slicker belay devices has led to the potentially dangerous problem of climbers finding they cannot exert enough control on the speed of their decent. When you combine this problem with a heavy load, say a large climber or heavily laden climber, and the descent can become terrifying and potentially terminal unless preventive measures are taken.
These techniques are also useful if abseiling on thicker ropes when heavily loaded such as in a rescue situation (both climbers on one belay device) or when descending with large rucksack or haul bag.
When deciding whether or not to use some of the increased control techniques you must judge the type of descent ahead of you. The worst scenario is a free hanging abseil because all your weight is on the device meaning you’re more prone to feeling exposed and out of control and therefore panicky plus it’s harder to remedy the situation once you begin. In these cases always opt for caution and increase the control.
An abseil down a less then vertical wall places slightly less weight on the device, plus it feels less committing as you can walk your feet down the wall. Sorting out problems is still very difficult once you begin so again if you think your device and rope combo need some help then don’t risk it.
A slabby decent puts a much smaller weight on the device, often to such a small extent that it feels as if it’s only there for balance. Minimal friction is required, commitment is small and any problems can be easily rectified. The only time to go for maximum control is when descending with a very large load. Always remember that friction and control will be at its highest at the start of the descent due to the weight of rope below. If you don’t feel happy in the first few feet, stop, pull yourself back up while you can and sort it out, because if you feel out of control now, things will only get worse.
The double HMS
The beauty of this system is that it not only increases control over the rope by adding friction to the rope, but also allows greater heat dissipation and increased security due to the fact that you’re hanging from two screwgates instead of one – and so is the best technique to employ on most abseils. To do this simply clip both bites of rope through two HMS krabs (with gates opposed if you want maximum safety). If you don’t have a spare HMS handy then you can use a snap gate karabiner instead. If this is the case it’s usually best for the rope to run over the karabiners back, rather then through the top or bottom of the krab as is usually the case.
With your belay device/ropes clipped into your HMS take the live rope and clip it back into the hms, letting the ropes run around the spine (not the gate). This introduces more friction without too much complexity, but can also lead to slight twisting of the rope (varies with rope construction). Extreme care must be taken not to have the rope running over the gate for obvious reasons!
One of the simplest techniques is to use your legs to increase friction. This can be applied at anytime, and although uncomfortable is very effective, needs no equipment. The most common technique is to run your live ropes over and around your thigh. Once around is usually enough to stop any movements, making it necessary to feed the rope over your thigh. Passing the rope over the outside of the thigh, rather then between the legs, works best. A subtler way to apply friction is too to just let the rope pass over your foot and ankle. The friction can be increased by pressing your other foot down on the rope, a little like sliding down a gym rope. A little less friction can be achieved by passing the ropes between your legs, and letting them run beneath your thigh. With this technique it’s best to hold with both hands, with one below the device (this also holds down your prusik and the other by your leg. The beauty of this technique is that you can easily rap the rope completely around the thigh if you need to gain more friction.
With any technique using your body you must take great care not get tangled up, go too fast or loose your concentration and let the rope slip off you. They also don’t work very well if running over bare skin!