Many assume that a rigging plate will keep things better organised and provide some separation between components. There are many ways to configure parallel devices but the main consideration should be the ability of a single operator to manage two devices comfortably. This is demonstrated clearly in the following short video.ĭual main rope rescue: Three teenage boys with 8mm ropes. The backup belayer provides appropriate redundancy to ensure there is no single person of failure in the system. Operation of a dual main lowering system – notice the three hands on both brake strands. Their secondary task is to clear tangles and warn the main operator as knots or other obstructions approach. Their primary task is to ensure the brake strands are managed and, in the unlikely event that the main operator loses control of the lowering devices, hold on tight.
In this image, the second person simply tails both the orange and blue ropes and maintains a small amount of slack in the strands running forwards to the primary operator. This person acts in the same way as a bottom-belayer by providing a fireman’s belay should the operator lose grip with their brake hand. Many rock-climbing instructors are very familiar with the use of an extra person, or backup belayer, behind the primary belayer. I touch briefly on this consideration in the free article: Redundancy in Rope Systems. Backup BelayerĪ common and valid criticism with having a single operator controlling both lowering devices is that THAT person is a single point of failure in the system. In the RopeLab member report Members: Matching Tension with Mirrored Systems, I discuss the effectiveness of using two Petzl IDs operated by a single operator and found that, even with attempts to mismatch, the tensions never deviated outside 60/40 – 40/60. It is common to observe big swings from 90/10 to 10/90 between the two as the operators attempt to match each other’s rate of lower. Systems like the one shown above, while functional, make it very difficult to match the tension in the two ropes.
Matching Tension Dual main system using CMC Rescue MPDs for lowering Instead I would like to focus on the implementation of dual main lowering systems for rope rescue operations. Much has been written by others about the relative merits of each of these systems and I will not discuss them further here.
Dual main implies that our two rope system sees both ropes loaded and capable of task completion should one of these ropes ‘disappear’. I am deliberately choosing to stick with the simplest of terms here and ‘ dual main‘ covers all bases. Single main/single backup systems normally see the task undertaken using a main rope with another backup rope on standby should the main fail. There is a growing awareness of the benefits of dual main over the more traditional single main/single backup rope systems.
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