Page 22 - Des Pawson "Pocket Guide to Knots & Splices"
P. 22
Equipment
small braided cords. It was rarely used It is fractionally weaker than nylon and
at sea except for fishing nets. As cotton holds its strength when wet. It resists
is prone to rot, the fishing nets needed rot and chafe. It is the material of
frequent dipping in some form of choice for many yacht ropes as it has
preservative, such as the tannin derived little stretch, and can even be bought as
from barks of various trees, tar, or special prestretched ropes that have
chemicals like copper sulphate or c even lower stretch.
opper naphthenate.
Polypropylene was developed in the
Nylon was the first synthetic material 1950s. Though not as strong as nylon
that was suitable for making rope. and polyester, it is considerably cheaper.
Developed in the mid-1930s, at first it It was the availability of low-cost rope
was very expensive and also very made from polypropylene that really
stretchy. Slowly the scientists were able marginalized the production of natu¬
to reduce both its cost of production ral-fiber rope. Polypropylene is light in
and the degree of stretch. Today’s nylon weight so it will float, making it useful
rope is very strong, more than two and for rescue ropes and short mooring
a half times the strength of hemp. It still ropes. It must be noted, however, that
has some stretch in it, but this makes it polypropylene does not resist abrasion
especially good for use where there well and, even though today’s
may be sudden shock loads applied, polypropylenes are treated with ultra¬
Pocket Guide to Knots & Splices
such as mooring ropes, tow ropes, and violet light inhibitors, UV rays still
climbing ropes. As a heavy monofila¬ cause the rope to break down far
ment yarn, nylon is also used for most quicker than polyester or nylon. To
fishing line. Nylon ropes lose about counter the natural stiffness and slip-
5-10% of their strength when wet. periness of the straight polypropylene
Nylon rope wears very well, it is yarn, it is processed and produced in a
resistant to chafe and to mildew and number of forms. Monofilament
rot. polypropylene rope is the most resist¬
ant to chafe. Multifilament is much
Polyester, also known as Dacron or softer and easier to knot and handle.
Terylene, was developed in the 1940s. Staplespun, where the fibers have been
20
