Introduction to Ropes

There are many materials used today to make rope; synthetic fibre, natural fibre and wire. The most popular is nylon, a synthetic. It is strong, holds up well to the weather and stress, and coils without kinking. Line is also made from natural fibres like cotton and hemp (manila), and other synthetic fibres such as dacron, kevlar, and polypropylene.

Synthetic lines are lighter and stronger and more rot-resistant, generally, than natural fibre ropes. Synthetic lines are slipperier than natural fibre ropes so be sure to check your knots to make sure they are secure. Synthetic lines should be cleaned with fresh water and detergent, kept out of sunlight, inspected frequently for chafe, and stored dry.

Polypropylene

Polypropylene line is the least expensive of the synthetic lines, however, it deteriorates quickly from ultra-violet rays and wear. It is not a good line for dock line because its hard surface tends to slip from cleats and can cause cuts if it runs free through your hands. It floats, so it is good for rescue lines. It is also appropriate for dinghy painters, short mooring pendants or other applications where you want to be able to see the line on top of the water. Not for use as dock, anchor or towing lines.

Nylon

Nylon rope has a lot of stretch (up to 40%) and is very strong for its size, allowing it to absorb shock loads well. However, when it is wet it can loose up to 25% of its strength. It wears well, resists mildew and rot, and does not float. Nylon three-strand is the preferred line for towing and dock lines since it stretches sufficiently to dampen the shock of wave action and wind against your cleats. Just make sure it does not stretch too much for the situation in which you use it.

Polyester

Polyester rope wears better than polypropylene, is almost as strong as Nylon, and retains its strength when wet. It does not stretch as much as Nylon and does not float. Polyester (such as Dacron) is used for sailboat running rigging, anchor rode, towing lines and other applications where you don't want line stretch to interfere. It will, however, chafe easily so check it often and protect as necessary.

Natural Fibres

Natural fibres such as manila, sisal, hemp and cotton will shrink when they get wet and also tend to rot or become brittle. Manila is still used today on large ships and is the best natural fibre for mooring lines, anchor lines. Manila has a minimum of stretch and is very strong. However, it has only about one-half the strength of a comparable-sized synthetic line. They do sink in water which may be a possible advantage for diving.

Natural fibre line should be uncoiled from the inside of a new coil in order to prevent kinks. Always whip or tape the ends of natural fibres to keep them from unravelling. When natural fibre lines have been in salt water you should rinse them in fresh water and allow to dry thoroughly. They should then be properly coiled and stored on grates above deck in a dry, well-ventilated place to help prevent mildew and rot.

Rope construction

Rope is constructed in two basic ways, laid and braided, although there are variations on the theme.
 

Triple strand line

The first is "3 strand" line. The direction of twist is called the lay of the rope. Three strand twisted line can be "laid" right or left, and should always be coiled with the lay of the line. This rope is described as S-laid (left-laid) or Z-laid (right-laid) according to whether the twist follows the line of the center part of the letter S or Z. Most three strand rope is Z-laid (right-laid) If you hold a length of 3 strand right-hand laid twisted line at arm's length and eyeball it, you will see the wrap of the line twisting to the right.

The construction of stranded line, whether natural or synthetic, is much the same. Individual fibers are twisted into yarns, the yarns are twisted into strands and the stands are twisted into line. Right-laid is twisted clockwise and left-laid is twisted counterclockwise. The fibers are twisted in the same direction as the strands, however the yarns are twisted in the opposite direction. This right, left, right for right-laid line helps give strength, keep the line from kinking and hold its shape.

Braided line

The other construction type is braided line. This type of line does not stretch to the degree that twisted line does, and is more difficult to splice. However, it goes through a pulley or block very well because of its rounded shape, and is stronger than its equivalent-sized twisted line. Braided line also tends to snag when used as docking line if the pilings are rough.

A variety of braided lines are available:

• Braid on Braid has a braided core inside a braided sheath - will stretch less, and has less flexibility, than a hollow braid.

• Multibraid is braided with 2 pairs of Z-laid and two pairs of S-laid strands – it is flexible and does not kink.
• Parallel Core has a braided sheath over a core of straight or lightly twisted yarns – it is very strong.
• Hollow Braid has no core – is very flexible but can flatten during use. It is only found in small sized rope.

When coiling a rope, always commence at the end which is made fast so that any twists or kinks can be chased along and run out at the far end. It is particularly important to ensure that load is never applied to rope when there is a kink in it as this will almost inevitably damage and weaken it. Nearly all laid ropes are right handed and should be coiled clockwise to ensure smooth running out.

Sizes

Modern ropes are measured across the diameter in millimetres. Old ropes used to be measured around the circumference in inches.

Uses the rope must be chosen for its suitability. A rope for a 25Kg shot weight would only need to be 3mm but would be difficult to haul, so 12-15mm would be more appropriate.

A line is a rope used for a specific purpose e.g. shot line.