The other day we were waiting in line for a popular 200 foot single pitch climb in the valley and the party in front of us was using two 70 meter ropes they had joined together with a double fisherman's as a top-rope. I had never seen or heard of this being done before and I can think of a couple of reasons why I wouldn't be comfortable doing this myself:
- Amount of rope stretch in 140 meters of dynamic rope
- Amount of rope drag on less-than-vertical routs when using 140 meters of rope
- The knot getting caught in a constriction or on a ledge
- Increased rope-abrasion where the knot is tied, since the rope rubbs on the rock when the rope is weighed with a climber during lowering
- Not being able to belay a climber all the way to the anchor, since the knot is going to interfere with the ATC if the climb is not exactly the length of the rope tied to the climber, potentially rendering the retrieval of the anchor dangerous, or endangering a novice climber who doesn't notice that the rope is not advancing any more as they make forward progress.
I can also think of a couple of reasons why there are certain situations where this minght be the smaller of two evils:
- An unexperienced climber does not have to rappel
- In a situation where the weather is fickle, no-one has to belay from the top, expediting the process of getting everyone off the rock faster, at the expense fo leaving the anchor at the top
- When climbing with several novice climbers, the most knowledgable climber can stay at the ground to help with tying in and crowd control at the base of the climb.
- Reducing the wait on popular routes (This is more of a convenience...)
Does anyone know if using two ropes as a top-rope is condoned or discouraged by professional guides? Also, has anyone heard of any accidents or close calls that have happened when using two ropes in this manner? Does anyone know of any testing that has been done on this technique?
Feel free to add benefits or disadvantages that I have missed.