uh, I´m not sure if I can explain it all in English…I learned it all in German and then in Dutch, so English… But just come for a visit and I explain it all.
But…ok, what I know is the reason you use a double rope or halbzeil halftouw or half rope (=all the same).
Are: -you can climb easier with a group of 3 (less important)
– you have less friction on bad belay points, like in ice or alpine.
– you still have a rope when you ruin one of the two due to sharp rocks or your axes/crampons
– it is more dynamic, so softer/safer falling
– you have a backup of the other rope if your belay point fails (like your screw/nut/cam pops out)
This all will change if you clip both in one belay point. Unless the Fangstos (or how do you call this in English) is very low. That says on the card with your rope. If this is below 6kN I believe, you can use your 1/2 rope also as Twin rope (the sign of the two circles)
But if you clip both ropes in one and you have a Fangstos of 8kN or more (never buy a rope with a Fangstos of more then 12kN, they´re just ueseless after a couple of falls). You have to realize this:
– the friction on both ropes in one quickdraw will be a lot. It might ruin your rope, and it blocks the dynamic falling
– the stiffness makes the fall harder on your body and all other equipment like the screw and the quickdraw.
So there are 1. max. pressure on your body (10kN)
2. max pressure on the belay point (screw/bolt) 3. mex pressure on the draw. 4. max pressure on the rope string.
If the rope, the draw, the bolt and you can hold the fall (like short falls on overhanging or vertical rock and your fangstos of your rope is low, then just clip in both.
If you want to be more sure and safe, like in iceclimbing or alpine routes, and the falls are one dubiues screws or nuts, your screw can pop out, or whatever, please just clip in or string of rope. (unless your fangstos is very low). But then it says it on the rope pack, or websites as earlier metioned (also see petzl.com or mammut.ch or whatever your rope brand is.)
I maybe don’t say it completely clear in English. I might be better with examples in German or Dutch…but then you have to learn German/Dutch first
Ow yes, on the rope pack you also see the rope takes norm falls with 55kg (mostly, sometimes 65kg or more) a norm fall is a factor 2 fall and the 55 is not 80kg or 110 because of a ancient fault in how to count the falls. For an explanation about that…another time.