Chapter 17 · Knots, ropes, and lashings
Types of rope
In this section (5)
| Material | Advantages | Disadvantages | Use it for |
|---|---|---|---|
| Nylon (includes paracord) | Very strong; stretches and absorbs shock loads; resists mildew and rot | Stretches a lot (bad for tensioning); loses some strength when wet; needs protection from the sun | General use, lashings, kit rope |
| Polyester | Stretches little; keeps its strength when wet | Absorbs shock loads less than nylon | Tarp lines (ridgeline), clotheslines, cargo tie-down |
| Polypropylene (cheap yellow or blue rope) | Floats; cheap; unaffected by many chemicals | Degrades in sunlight; slippery: knots can come loose | Water rescue lines, temporary use |
| Natural (manila, sisal, cotton) | Good grip; knots hold firm; does not melt | Rots if stored damp; weaker and heavier; manila shrinks when wet | Log lashings, use near fire, when there is no other |
550 paracord
Military paracord (type III) is nylon, with a woven sheath and 7 to 9 inner strands, and has a minimum breaking strength of 550 lb (about 2,400 N). Much of the cord sold as "550" or "paracord type" is a weaker imitation: if it does not say it meets the military specification (MIL- C-5040H type III), do not count on that figure. The inner strands can be used separately as sewing thread, emergency fishing line, or fine twine.
Real strength: what the label does not say
- Knots weaken. Depending on the knot, the rope loses roughly 20% to 55% of its strength. Rule of thumb: assume a new knotted rope holds, at most, half of what the label says.
- Safety margin (design factor). The Cordage Institute recommends that the working load be between 1/5 and 1/12 of the breaking strength. For anything that supports or protects a person, use 1/12: lifting an adult requires a rope with about 1 ton of breaking strength. Even then it is not suitable for climbing (see the warning at the end).
- Old, wet, dirty, or damaged rope loses strength. Nylon can lose up to 20% when wet.
- Jerks multiply force. A load that falls or swings can break a rope that held it still.
Rope care
Cutting and finishing the ends
- Mark the cut with tape. Wrap the rope with adhesive tape and cut through the middle of the tape: both ends stay bound.
- Synthetic (nylon, polyester, paracord): melt the end with a lighter until it seals. Do it with ventilation and do not touch the melted plastic: it burns and sticks to skin. When it is just warm, smooth it with a metal surface, not with your fingers.
- Natural: it does not melt. Finish with a whipping: wind thin thread tightly about ten turns near the end and tuck the end under its own turns; or use tape.
- Without tools: tie a simple figure-eight near the end so it does not fray.
Coiling and storing
- Butterfly coil (for a backpack). Take the rope by the middle and pass it from side to side over your hand or shoulder in long bights, alternating sides. It does not twist or tangle when you pull it out.
- Finish it off. With the two ends, make several tight wraps around the center of the coil, pass a bight through the top, and tuck the ends through it. You can carry it on your back.
- Short rope or cord. Coil it around your hand in a figure eight (between thumb and little finger) and finish with a few wraps and a half hitch.
- Store it dry, in the shade, without tight knots, and away from chemicals. Mark the length with tape at the end.
