Static and dynamic belay

If the leader falls, it is the belayer at the station who will catch the fall by handling the rope in a belay device. And there are two options how to operate the rope in the belay device, statically or dynamically. The part of the rope which is between the belay device and climber is called the “active part of the rope” and the part of the rope which is between the belay device and the wound coil of rope is called the “passive part of the rope”. For loading the rope, a static belay assumes a firm grip on the inactive part of the rope emerging from the belay device, and a hold on the rope in such a way that it does not slide through the belay device. This is suitable primarily for belaying a second, for belaying when climbing with a top rope, and during an effort not to extend the course of a fall if the faller is at risk of reaching a rock protrusion, shelf, or all the way to the ground when she falls. A dynamic belay assumes the retaining of a specific section of rope for sliding within the belay device. For the period of this slide, the falling force is converted into the work of the rope during friction against the belay device. The remainder of the falling force is then caught by the belayer with the hand gripping the inactive part of the rope protruding from the belay device.

This is suitable for catching a leader’s fall, and in all situations when a belay device is loaded abruptly and forcefully.

A dynamic belay does have a dark side, however, which is the extension of the length of the fall. When extending the length of the fall the faller can injure herself against the various rock protrusions, shelves, and ledges that can be found beneath her.

The relationship of loading forces to the length of extending a fall by allowing slippage.

The relationship of loading forces to the length of extending a fall by allowing slippage.

Optimal range of braking forces

A dynamic belay reduces the possibility of transferring falling forces to the protection points along the rope. You have two options for performing a dynamic belay, either with small braking force (an advantage) with long slippage (a disadvantage), or with great braking force (disadvantage) with small slippage (advantage). The requirements are antithetical, and must therefore be solved with a compromise. This is called the optimal range of braking. Experiments have determined that the optimal braking force ranges from 2.5 kN to 4.5 kN. In other words, this is the amount of force which the belay device must apply during slippage.

A good dynamic belay method should fulfil the following requirements:

  • reliability under any direction of loading
  • optimal braking range
  • functioning in a way that is compatible with human reflexes
  • simplicity and clarity (an apt term is “idiot-proof”)
  • the option of belaying without leather gloves
  • the option of use for both belaying leader and second.

This content is preview from e-book.

Title Part 3Mountaineering Methodology – Part 3 – Belaying and Rappelling

ISBN 978-80-87715-09-3

MMPublishing, 2013

Available for download from Apple iTunes (in the Books section).

For example U.S. store – link

Another countries – look on the page Download

See layout.

Another possibility is Google Play. This version is a simplified (as PDF).

Title Part 3 GPMountaineering Methodology – Part 3 – Belaying and Rappelling

ISBN 978-80-87715-14-7

MMPublishing, 2014

Available for download from Google Play.