In reply to Nathaniel Gjöderum-Larsson:
There's been discusion on this in the past and some argue that the load on the gear would be more than using doubles, but to my mind it's the same as using them as singles (bar the weight), so I'd have no issue.
In reply to Nathaniel Gjöderum-Larsson: I've spent lots of time climbing on stupid combinations of old fluffy fat ropes, and new thin half ropes, and old stiff half ropes, etc. No problems, it can just be a bit annoying.
after seeing a presentation on this type of thing from the BMC tech guys i'd not use them as it'll put a lot more load on your gear. if your gear is always bomber then you'd probably not have a problem other than a slightly more abrubt stop if you fell off. if your gear was marginal then you'd increase the chances of it ripping out as well.
Agreed. When I did a multi-pitch sport climbing course in Verdon with the UCPA a few years back we used singles as half ropes. I asked why, my instructor replied "why not?". To him, it was just a more redundant and flexible system, and it proved it's worth when we abbed in one morning and only at the bottom did we realise one of the guys forgot to bring a rope with him. One pair climbed on a single and the other two pairs climbed on the two ropes as normal.
> My girlfriend owns a 9.4cm (60m) single and I'm thinking of buying another single the same size. Would we be able to use these two ropes at the same time as doubles when climbing trad?
Yes but it's very heavy.
Personally I'd suggest either a 60m half rope if your interest is trad (fold it for 30m pitches, combine with the full for longer pitches if you really must) or a 70m lightweight full if your focus is sport. Or save the money for something nice, keep using your girlfriend's rope.