How do you choose mooring ropes for a ship?

Which materials are used for mooring ropes?

The common mooring fibres are polypropylene, polyester, polyamide (nylon) and HMPE (also called UHMWPE), alongside steel wire and mixed wire-and-synthetic lines. Each trades stretch, weight, buoyancy and resistance to sun and chafe differently, so no single material is best for every mooring.

In general terms, polypropylene is light and floats but has limited UV and abrasion resistance. Polyester has low stretch and is often described as the best all-round fibre, with good UV and abrasion behaviour and little change when wet. Nylon is very elastic and absorbs shock loads, but it loses strength when wet. HMPE is very strong for its weight, has very low stretch and floats, but costs more and is used mainly where its low stretch is needed. Wire barely stretches and resists abrasion, but it is heavy, needs lubrication and can fail under sudden loads. Mixed lines usually have a wire core under a synthetic cover.

How do the materials compare?

The table gives general tendencies from manufacturer and trade guides. Exact values depend on the construction and the maker, so use it to shortlist, not to specify.

What do 3-strand, 8-strand, 12-strand and double braid mean?

These terms describe how the fibres are put together. Three-strand rope is twisted (laid) from three strands and is easy to splice and elastic. Eight-strand (plaited) rope lies flat and resists kinking. Twelve-strand is a single braid, flexible, and often used with high-strength fibres such as HMPE. Double braid has a braided core inside a braided cover and generally feels smoother and stretches less than laid rope.

Which one suits a given winch drum, fairlead or bollard depends on the vessel's mooring arrangement and the supplier's recommendation. Laid rope can partially untwist under load, which is one reason braided types are common on larger vessels.

Do you order by diameter or circumference, and what is MBL?

Rope size is stated either as diameter in millimetres or, in the traditional imperial convention for larger rope, as circumference in inches. Always confirm which one a data sheet or old stores list uses before ordering, because the two figures are not interchangeable.

Minimum breaking load (MBL) is the force a new rope is expected to withstand before it breaks, as stated by the manufacturer. Do not take a value from a catalogue summary or a general article. Read it from the manufacturer's data sheet and, for a specific line, from its certificate. The OCIMF Mooring Equipment Guidelines (MEG4, 2018) go further for tankers and similar vessels: they define terms such as Ship Design MBL and Line Design Break Force, and ask for certificates traceable to the individual line. Nylon is a special case because wet and dry strength differ, so the test condition on the certificate matters.

What are OCIMF MEG4 and ISO 2307?

MEG4 is a publication of the Oil Companies International Marine Forum. It sets recommended minimum requirements for mooring systems and gives guidance on purchasing, testing, inspecting and retiring lines and tails. Its recommendations are aimed mainly at tankers and terminals, but its terminology is widely used when ordering lines.

ISO 2307:2019 is a standard for fibre ropes. It describes how to determine properties such as linear density, diameter, lay length, braid pitch, elongation and breaking force. It is a test-method standard, not a rule about which rope a ship must carry. Ask the supplier which standard or test method the quoted figures follow.

What are eye splices, soft eyes, tails and chafe protection?

An eye splice is a loop formed by tucking the rope's own strands back into the rope. A soft eye is a loop without a metal thimble, so it is lighter and kinder to the fitting it goes over. A tail is a shorter, usually more elastic length added at the ship end of a high-strength line to absorb shock. Chafe protection, such as a sleeve or cover, is placed where the line touches a chock, fairlead or sharp edge. Specify the eye type, protection and any tail with the length when you ask for a quotation.

How is rope sold on a ship stores list?

In the IMPA Marine Stores Guide, ropes sit in section 21, Rope & Hawsers. The typical unit of measure for that section is the coil (CL), so a line may be quoted as a coil of a stated length rather than per metre. Check the coil length against the data sheet before comparing prices, and say clearly if you need a cut length with spliced eyes.

How do you request a quotation for a mooring rope?

State the material, construction, diameter or circumference, length, the minimum breaking load you require (from the mooring design), the eye and chafe requirements, and the certificate you need. Browse Rope & Hawsers items in the catalogue, review what an IMPA code tells you, and read how to prepare a ship stores RFQ. When ready, add lines to the RFQ cart.