Dynamic Directionals (a type of offset) are useful in adjusting the main line and belay from above the rescue page or in some cases, from across a gap or chasm.
The use of this system usually requires a fair amount of horsepower, at least a mechanical advantage of 6:1 or 9:1, but not always. As seen in a few of our Horizontal Rigging courses, a 5:1 was perfect.
For gaps, a minor dynamic directional anchor may not require a belay for the point of horizontal influence, however the belay option may be put into use based on the decision that the dynamic directional is indeed a critical safety element of the overall operation. The key question you must ask is, if the dynamic directional were to fail, would the the pendulum effect of the main line cause serious injury to the rescue load?
Note: The Dynamic Directional may also be controlled from the mainline side by utilizing a change of direction pulley at this location.
For more on Dynamic Directionals, see Rigging Lab Academy and our Horizontal Rigging Course.
As always… rig safely and once the foundations are understood… be creative!
Peace on your days…
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