Page 181 - J. C. Turner "History and Science of Knots"

172 History and Science of Knots

Flowing Hitches
A hitch is defined as a knot attaching a rope to an object. With an ordinary
hitch, the knot, rope and object are held in place, stationary relative to one
another. With a friction hitch, the rope and the knot are stationary relative
to each other, but the two together move past the object (the standing rope).
I give the name flowing hitch to a group of knots in which the knot and the
object are stationary relative to each other but the rope moves, flowing through
the knot. Obviously, the knot must be very simple to allow the rope to flex its
way through it. Indeed, the definition of a knot must be somewhat strained
to include some of these structures as knots. The best known example is the
round turn taken round a bollard or the like when paying out a rope under
load.
Climbers and cavers use other simple flowing hitches to provide friction
when abseiling down a rope. Even the Classic Abseil technique (Fig. 8) can
be considered a flowing hitch; but today descenders are commonly used, me-
chanical devices intended to provide the friction of the rope during abseiling.
Pre-war systems of abseiling, such as the Classic, involved wrapping the rope
round parts of the body to provide friction during a descent. This was not
too uncomfortable when wearing clothing suitable to alpine conditions, but
decidedly warming when wearing clothes for a hotter climate. A descender al-
lows the rope to be removed from contact with the body; the braking friction
derives from the movement of the descender along the rope. Early descenders
consisted of karabiners in various configurations, of which the simplest is the
Twisted Hitch (Fig. 45). A karabiner is attached to the body harness usually
by another karabiner. The rope, often doubled, is anchored at the top and
then taken in one or, for greater friction, two round turns (up to three turns
when using a single rope) round the back of the karabiner [4] [10, p. 141],
and is grasped in the gloved hand below the descender before dropping to the
bottom of the pitch. The other hand helps to keep the body in balance by
lightly holding the rope above the karabiners. Friction can be varied by the
tightness of the grasp and the descent can be stopped by bringing the lower
rope up beside the upper, and then either holding the two ropes together or
fastening with an appropriate knot.
Several other arrangements of karabiners have been devised, some with
accessories, but most modern abseiling is done with purpose-built devices,
forcing the rope through a more complicated curved path. Some provide means
for varying the friction through a wide range, some have automatic safety
devices which stop the descent if the grasping hand is released. Probably the
most popular device is the Figure Eight Descender (Fig. 46) made in several
configurations [4][10, p. 140][27, p. 123]. This has two apertures of different
sizes, allowing use to be adjusted to the circumstances [30, p. 127]. Care must