TYPES OF ROPES USED ONBOARD SHIP

ROPE

Definition of Rope:-

Thick strings, yarn, metal wires, fibre that are twisted together to form a strongerline is called rope.

TYPES OF ROPE

Mainly three kinds of ropes used onboard they are,

1) Vegetable or natural fibre ropes.

2) Synthetic fibre ropes.

3) wire/ metal ropes.

                                                       Vegetable or natural fibre ropes

            Vegetable or natural fibre ropes are mainly classified into five types.

Manila

Manila is obtained from the abaca (wild banana) plant.

largely grown in the Philippine Islands,

It is exported via the port of Manila, from which it acquires its name.

Manila rope is not as durable as hemp, but is most certainly more pliable and softer.

It is gold-brown in colour.

It swells when wet.

This it is considered by far the strongest natural rope made.

It is very expensive and its availability will depend on the political climate.

Used extensively where the safety of life is concerned.

Sisal

Obtained from the leaves of the plant Agave sisalana, a large plant of the cactus family.

The sisal rope is hairy, coarse.

It is white in colour.

It is not strong compared to manila.

When wet, it swells up more than manila, as the water is absorbed more quickly, and it becomes slippery to handle.

It is extensively used in the shipping industry either in its own state or mixed with manila fibres.

A good sisal being similar in strength to a low grade manila.

The cost of production is better suited to the ship-owners, and the supply is more reliable than manila.

Coir

Coir is obtained from the fibres of coconut husks.

It is a very rough, coarse and hairy rope.

It is very light and floats, possessing great elasticity.

It is often used as a towing warp or mooring spring, because of its buoyant and elastic properties.

The coir fibres are short, brittle and thick.

These features produce a stiff non-flexible rope, difficult to manage.

Hemp

Hemp is obtained from the stem of the plant Cannabis sativa.

 This was accepted as the best rope in the marine industry from the early developing days of sail.

The hemp fibres are a light cream in colour when supplied to the rope manufacturer.

They have a silky texture and are of a very fine nature: hence the extra flexibility of the hemp rope compared to a sisal or manila.

The advantage of hemp rope is that it is impervious to water and does not shrink or swell when wet. For this reason it was extensively used for the rigging of sailing vessels, and roping sails.

Cotton

Cotton Ropes are not used on ships because of their water absorption property that makes them very heavy when wet.

Synthetic Fibre Ropes

Nylon

This is the strongest of all the man-made fibre ropes.

It has good elasticity, stretching up to 30 per cent and returning to its original length.

It is used for such functions as shock-absorbing when coupled with a mooring wire: the nylon forms a rope tail which takes the heavy shocks as a vessel ranges on her moorings.

It is also used in a combination tow line – one section steel wire and one section nylon rope.

Nylon ropes are light to handle, twice as strong as an equivalent sized manila and give the appearance of a smooth slippery surface.

They are impervious to water, have a high melting point, 250°C, and in normal temperature are pliable, being suitable for most forms of rigging.

The disadvantages of nylon ropes are that they do not float, and in cold climates they tend to stiffen up and become difficult to handle.

Nylon is expensive, but its life may be considered to be five times as long as its manila equivalent.

Polyester

A heavy rope compared to the nylon and not as strong.

It is considered to be more resistant to acids, oils and organic solvents than its nylon counterpart, while its strength remains the same whether in a dry or wet condition.

It is used for mooring tails and mooring ropes.

Polypropylene

This is probably the most popular of the man-made fibres at sea.

The ropes are cheap, light to handle, have the same strength whether wet or dry, and they float.

They are used extensively for mooring ropes and running rigging.

The melting point is low compared to nylon, 165°C.

It is resistant to chemical attack by acids, alkalis and oils, but solvents and bleaching agents may cause deterioration.

It neither absorbs nor retains water, and because of this fact has recently been used for the inner core of wire ropes, the advantage being that inner corrosion in the wire is eliminated.

The wire would still need to be lubricated externally.

Wire / Metal Ropes

A steel wire rope is composed of three parts – wires, strands and the heart.

The heart is made of natural fibre, though recently synthetic fibre has been used when resistance to crushing is required.

With the many changes in the marine industry the needs in wire rope have altered considerably from the early production days of 1840.

Then the first wire ropes, known as selvagee type ropes, were constructed of strands laid together then seized to form the rope.