In reply to Cheese Monkey:
> (In reply to Ian Parsons) Yeah I know about tying it off with a triple. Theres no possible way for the bowline to come undone, I'm just more concerned about overall strength.
Ah - I think I've just worked out what you mean. As long as you end up with the two ends joined with a triple fisherman's, then yes - the bowline, fig-8 or whatever is captive so can't come undone; it may slip a bit but unless that has the potential to generate a melting level of heat - which I would think unlikely given the short lengths involved - that shouldn't be a problem. As far as knot strength is concerned you're quite right in comparing it with clipping back into the rope loop when belaying, and while the alpine butterfly, for instance, is specifically used in various situations to prevent the "incorrect" loading of alternative knots, it's quite common - when threading and knotting a single cord one-handedly, for example - to connect the two ends of a sling with an overhand tied in both strands together which gives a similar configuration; the usual worry in this case, as with the joined ends of abseil ropes, isn't that the knot might break but that you've left long enough ends to prevent the knot "unrolling" and coming undone, which can't happen if those ends are securely joined. Clear as mud!