Page 71 - Rappelling

Magic X rigging with two separate 5-foot lengths Self-equalizing three-piece rigging with a
of 7mm nylon cord—it’s self-equalizing and sling—nonredundant but very strong. To make
redundant. this rig redundant, simply tie an overhand knot
at the master point and add another quick link.
You’ll end up with three loops at the master
point, and a pre-equalized system.

Vectors Keep this in mind when you build rappel
anchor systems. If the angle between two anchor
A vector is a quantity that incorporates both direc- points reaches 120 degrees, you’ll load each anchor
tion and magnitude. Picture a tightrope walker at 100 percent. Strive to keep all the angles under
balancing out on the middle of a wire. If he weighs 60 degrees so you’ll be splitting the load roughly
200 pounds, the load at each end where the wire 50/50. A good rule of thumb is to always keep the
is attached will be roughly 1,000 pounds. Why is angles under 90 degrees. Also, avoid rigging a sling
this? When two anchor points are equalized, as the between two anchors in a triangular configuration
angle of the wire, sling, cord, or rope approaches (called the American Triangle), which, even at 90
180 degrees, the forces at the anchor points increase degrees, places 1.3 times the force at each anchor
drastically. When the angle is narrow, the load is dis- point. An American Triangle rigged at 120 degrees
tributed at around 50 percent to each anchor. would almost double the load at each anchor point!

60 RAPPELLING

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