Page 13 - Cliff Jacobson - Outdoor Knots

Polyethylene. Inexpensive, slippery, slightly elastic, unaffected by water,
available in colors, and it floats—popular for towing water-skiers.
Polypropylene. Similar to polyethylene but less slippery and more elastic (a
better rope). Abrasion, ultraviolet light, and heat are major enemies of plastic
(polypropylene and polyethylene) ropes. Not all polypropylene cordage is the
same. Some types (notably baler twine) have ultraviolet inhibitors and can hold

knots without slipping.
Polyester (Dacron) is the material for sailboat sheet and mooring lines and
every place you need a rope that is dimensionally stable and resistant to
ultraviolet light. Unlike nylon, polyester rope retains all of its strength when wet
(see table 2), which is the reason sailors like it. You can get prestretched
polyester rope for special applications that require extreme dismensional
stability.
Natural-fiber ropes. Except for cotton, which is still used for sash cords and
clothesline, natural-fiber ropes such as manila, sisal, hemp, and jute have almost
gone the way of the passenger pigeon. Natural fibers have a nice hand; they coil
well and hold knots tenaciously. But they rot easily and for their weight aren’t
very strong. For example, the tensile strength in pounds of new manila rope is
roughly 8,000 times the square of its diameter in inches. Thus, new ⅜-inch