Rope and Cordage
Knots and Rope Work
Course 1 · Chapter 2 · Rope and Cordage: Fibres, Construction and Care
A knot is only as good as the rope it is tied in. Different fibres grip, stretch, float and rot differently, and the way a rope is built changes how it handles. This chapter covers the common fibres, the two main constructions, how to look after rope, and how to stop a cut end unravelling.
Fibres
Rope is made by twisting or braiding fibres. Natural fibres were the only choice for most of history; synthetic ones now dominate. The notes below are general characteristics, and individual products vary (check the maker's label).
| Fibre | Type | General character |
|---|---|---|
| Manila / sisal / hemp | Natural | Good grip, little stretch, rough on the hands, rots if stored wet |
| Cotton | Natural | Soft and easy to handle, weaker, rots if left damp |
| Nylon (polyamide) | Synthetic | Strong and stretchy, absorbs shock, sinks |
| Polyester | Synthetic | Strong, low stretch, good in sunlight |
| Polypropylene | Synthetic | Light, floats, cheap, weakens in sunlight, can be slippery |
Laid and Braided Rope
Laid (twisted) rope
Fibres are twisted into yarns, yarns into strands, and (usually three) strands are twisted together in the opposite direction. The counter-twist is what holds the rope together. It is easy to splice but can kink and untwist.
Braided rope
Strands are plaited rather than twisted. It tends to be smoother, kinks less and handles well, but is harder to splice. Many modern ropes have a braided cover over a core.
| Feature | Laid | Braided |
|---|---|---|
| Splicing | Easy | Harder, needs a method for the rope type |
| Kinking | More likely | Less likely |
| Feel | Coarser, grippy | Smoother |
| Inspecting for damage | Strands visible | Core is hidden by the cover |
Strength and Stretch
Rope is described by diameter, material and a breaking strength, with a much lower working load limit recommended for everyday use so there is a margin for wear, knots and shock. The breaking strength is for a new rope in a straight pull, and, as Chapter 1 explained, knots reduce it. Stretch matters too: a stretchy rope such as nylon absorbs sudden loads, while a low-stretch rope is better when you need a firm, steady line.
Care and Inspection
- Keep it dry and aired. Coil loosely and hang to dry before storing, especially natural fibres.
- Avoid chemicals and heat. Fuel, acids and strong cleaners can weaken fibres. Friction heat can melt synthetics.
- Protect from sunlight. Prolonged ultraviolet light weakens many synthetics.
- Avoid sharp edges. Pad corners or use a sleeve.
- Inspect before use. Look and feel along the length for cuts, flat or stiff patches, fuzzing, discolouration and a core that feels uneven.
- Retire it when in doubt. A damaged rope is demoted to light jobs or thrown away.
Whipping the Ends
A cut rope end frays quickly. A whipping binds the end with a small cord so it stays neat. Synthetic rope can also be sealed with careful heat, which fuses the fibres, but whipping works on all types and is the traditional method.
- Lay a loop of thin whipping twine along the rope with the loop's end sticking out past the rope end.
- Wind the twine tightly around the rope and over the laid-down loop, working towards the rope end, for a length about equal to the rope's width.
- Pass the free end of the twine through the loop.
- Pull the other end of the twine so the loop is drawn under the whipping and disappears.
- Trim both ends of the twine neatly.
Not Yet Verified, and Sources
- Source. Written from general knowledge of rope and cordage; no specific source was read, and nothing is quoted from a text.
- Marked (check). Fibre characteristics for particular products, safety standards and labelling, and the lay-direction convention. Check the maker's information and local standards.
- Illustrations. The 1200-unit and factor-of-6 figures are invented.
Exercises
Choose a suitable fibre from the table for each: a washing line left outdoors all summer, a rope that must float on a pond, and a rope that must absorb a sudden jerk. Give a reason each time.
Find a rope or cord at home. Say whether it is laid or braided, guess its fibre from the feel, and inspect it using the care checklist. Write down what you found and whether you would trust it for a heavy load.
A rope has a breaking strength of 900 units and a recommended safety factor of 5. What is the suggested working load? Then whip the cut end of a piece of cord using the steps above, and list what went wrong or right.
Quick Reference
- Natural: manila, sisal, hemp, cotton: grip, rot if damp
- Synthetic: nylon (stretchy), polyester (low stretch), polypropylene (floats)
- Laid: twisted strands, easy to splice. Braided: smoother, kinks less
- Working load: breaking strength divided by the safety factor
- Care: dry, clean, out of sunlight, away from edges, inspect first
- Whipping: binds a cut end, length about the rope's width