In reply to jezb1:
> I'd hope all of them. I do, and obviously when teaching I make it clear you always should.
> Most people I see abbing use a prussik.
> Seems silly not to.
Curiously the local caving club, despite being extremely serious about safety...Don't consider it worth while to backup an abseil (aside from firemans style when someone's learning), despite doing a lot of abseiling.
I've read of a few accidents of people just coming off the end of the rope (be it abseiling or lowering), though I only recall two of people losing control of abseils:
- One without a backup
- One with a backup, off the leg loop, who is thought to have relied on it and have rotated his body sufficiently that the prussic hit up against the abseiling device and not hold any more.
I'm not saying its only happened twice in history, but rather, that its a relatively rare event.
I used to always backup abseils, but it added a notable amount of faff. Now, not so much.