The use of rope has been recorded for over 20,000 years. The
early use of vines and roots led to a more sophisticated weaving
or braiding of other natural materials. Today's construction
includes man-made fibers or metals that are used in manufacturing
a cylindrical line of specified lengths. The unique aspect
of rope is that it can be used only in tension, due to the
flexibility of the fibers. Its tensile strength is dependent
on both the type of material and its style of manufacture.
Rope has a limited useful working life so constant monitoring
of size and condition is important. In the case of a natural
fiber rope, five years is considered its working life, after
which it should be cut up into short non-usable pieces and
discarded. Improper storage and exposure to moisture can cause
rope to fail prematurely.
Rope is and has been made from natural materials such as hemp,
sisal, cotton, grass or any other fibrous material that can
be twisted or braided together. There is now a strong trend
towards the use of synthetic materials such as nylon, polypropylene,
Kevlar® and others. Lengths of material are twisted
together into yarns, the yarns are re-twisted into larger
lines called strands, and the strands are twisted together
into a rope. Because twisted rope can unwind, strands can
also be braided or plaited together for greater durability.
Wire rope or cable is made in much the same manner from metal
wires. Wire cables sometimes have synthetic or natural fiber
cores to give them greater flexibility.