In reply to beardy mike:
> Diameter of rope is absolutely no indicator at all of the stretchiness of the rope. Impact force gives you soem measure, but direct comparison is difficult as the tests for a half rope are done with a 50kg weigh as opposed to an 80kg force so resultant impact force is bound to be higher. Stretch has to do with the tightness of twist of the core. Most skinny doubles for example have a higher or equal impact force to fatter ropes.
I am aware. However in practice every single half I have owned has been more stretchy than any single I have owned.
> As for lighter to the other poster? What a load of cobblers. A 10mm Mammut Galaxy (a fat single) is 68g/m whilst an 8mm double is 42g/m but you need 2. So their thinnest ropes are still 1/3 heavier than a pretty fat single. The only way you'd be able to claim it's lighter is if you were carrying one and doubling it over, and even then the weight that you are dragging is still the same as using two!
That's exactly the comparision being made; two halves and a doubled single (i.e. two strands of either whilst on the route)
> Pretty much only reasons for double ropes (in rock climbing atleast) are as follows (fully expect someone to come and put me in my place with a few more seeing as I've been a bit bolshy):
> Drag - if the route wanders you can reduce friction caused through runners by clipping alternate ropes, or directing them your ropes up seperate lines to make use of geometrically divergent placements. That said if you extend sufficiently well, you'll have no problem on a great many routes.
> Reducing impact force - by placing gear in parallel, i.e. putting pieces in very close to one another and clipping one rope into one piece and the other rope into the other, you are halving the impact force on the pieces reducing the chance of a placement failing, or if it does having a second which will see a reduced impact due to the other having taken some of the force.
> A fall onto double ropes where the force is not at least partially spread between pieces does absolutely nothing to reduce impact force unless the rope you are using in preferance to a single rope is more stretchy. Or the person magically loses weight
> And abseiling more than 25m.
30 m, we live in a world of 60m ropes
> In response to the OP, bring either a double or a thin triple rated single as you will be able to climb just about anything in England with it. The only time you migh need a second rope is on particularly wandering pitch, or if you need to do a full length abseil, which frankly is not that common. If yu have baggage restrictions and are buy ropes specifically fo the job, it's the most versatile option - get a 60m one and you can still do 30m pitches - that's longer than most crags in the peak district.