Note - This post discusses techniques and methods used in vertical rope work. If you do them wrong, you could die. Always practice vertical rope techniques under the supervision of an experienced climber, and ideally in a progression: from flat ground, to staircase, to vertical close to the ground before you ever try them in a real climbing situation.
Rappelling with a monster pack or haulbag can be frustrating and frightening. The weight on your back can flip you upside down or waste your abdominal muscles fighting to stay upright.
Here’s two possible solutions.
1 - Rig a simple chest harness with a 4 foot sewn runner and a carabiner. Clip the loaded strands of the rope through the carabiner. This will help keep you upright. This technique is preferred if the rap is low angle. (This may be stating the obvious, but be sure and rig this before you start to rap!)
2 – Rather than wear the pack on your back, let it hang from the rappel carabiner from an extended rappel. (Do NOT hang a heavy pack from your belay loop!)
(Note: hanging the pack from the rappel carabiner is generally recommended for steep, high angle rappels - using this technique on a blocky slab will generally cause the pack to get hung up as you move down the rock.)
Rig for an extended rappel.
Girth hitch a double length / 120cm runner on the pack’s haul point. Be sure this sewn loop on your pack is solid; use both shoulder straps if you have any doubt.
Clip the pack runner to your rappel carabiner with a locking carabiner.
You are now ready to rappel. The extended rap setup gives you more control and some distance from the pack. Note that the pack weight is never hanging off your body, but from your extended rappel carabiner.
If you have multiple raps, girth hitch another sling and carabiner though the pack so you can easily clip it to anchors along the way.
In big wall climbing, you can take this one step further, by clipping your rap device directly onto your haulbag. You clip to the haul bag and then sit on the haul bag. This is known as “riding the pig”, and is the only safe way to make rappels with a ridiculously heavy haul bag. This obviously requires a haul bag with extremely stout tie in points (equivalent or greater in strength to your harness) and you would definitely NOT want to do this with a normal backpack!