Page 219 - Bài 1 ok_Neat

end till it rests on the "neck" of the Figure Eight. The
bottom small hole is clipped to the rescuer or anchor. The
“rescue eight” design (Figure 49) incorporates protruding
ears, which prevent the rope from sliding up to the top of
the device and forming a Girth Hitch during a rappel, which
immediately stops further descent. A very significant
drawback of the Figure Eight is that it twists the rope during
use. Although the Figure Eight can be double wrapped
during setup to increase friction, it however cannot be
varied during an operation, which limits its overall
usefulness. Figure 49- Figure Eight
Descender. CMI Rescue
Eight
ASCENDERS

Prusik Hitch- The original and simplest ascender
device is simply a hitch which is applied to a host rope
for upward travel. Dr. Karl Prusik of Austria first
described the use of this hitch in 1931. The versatility
of the Prusik Hitch (Figure 50) continues to make it a
mainstay in rescue rigging. Prusiks do have their
weakness in that they can be rigged improperly. The
need to properly tie and tend Prusik Hitches cannot
be overstated
Figure 50- Prusik Hitch

Mechanical Ascenders- For long ascents
mechanical ascenders outperform Prusiks.
Handled ascenders (Figure 51) are designed to
be easily attached to and removed from a fixed
rope, providing an efficient personal rope
ascending tool. Mechanical ascenders are
rated by manufacturers only for one-person
loads. Several commercial manufacturers offer
handled and non-handled models. Handled
ascender models include Petzl Ascension, CMI
Ultrascender and ISC Ultrasafe Hand Ascender. Figure 51- Petzl Ascension Ascenders
Non-Handled varieties include CMI Ropewalker, (Pair- right and left). © Petzl.
Gibbs Ascenders and Petzl Croll.

65 | Pa g e