Selection
How to Select a Mooring Rope
8 min read
Rope selection goes wrong when it starts from the catalogue. It should start from the ship. Here is the order that produces a line that fits the vessel rather than the invoice.
Step 1 — Establish the design load
Start with the ship design MBL from the vessel's mooring documentation and the LDBF band required by the mooring management plan. This gives you a target break force before any product is discussed.
Step 2 — Choose the fibre
Fibre choice is a behaviour choice, not a strength choice, because you can reach almost any strength by changing diameter.
| Fibre | Choose it when |
|---|---|
| HMPE | High load, weight and handling matter, ship must be held tight |
| Polyester | Abrasion and cost matter, moderate elongation acceptable |
| Nylon (polyamide) | Shock absorption is the priority — tails, surge berths |
| Polypropylene | Buoyancy and low cost matter — messengers, workboats, harbour work |
| Mixed / combination | A compromise between cost, strength and elasticity is wanted |
| Steel wire | Permanent drum storage and severe steel-on-steel abrasion |
Step 3 — Choose the construction
Construction affects handling, splicing, torque and abrasion resistance. Three-strand is cheap and easy to splice but rotates under load. Eight-strand plaited is torque-neutral and handles well on drums. Twelve-strand braided is standard for HMPE. Double braid gives a durable cover over a strength-bearing core, which is useful when abrasion is the main enemy.
Step 4 — Fix the diameter and length
Diameter follows from the target LDBF and the chosen fibre and construction — not the other way round. Then check two physical constraints: the winch drum must store the length at that diameter, and the fairlead and bitt geometry must accept it. A line that meets every strength requirement and does not fit the drum is a failed purchase.
Length comes from the mooring arrangement, not from convention. Common stock lengths of 110 m, 200 m and 220 m exist because they suit common arrangements, not because they suit yours.
Step 5 — Specify terminations and tails
- Eye length, measured for the bitt or hook it will actually go over
- Thimble or soft eye, and whether the eye needs a protective cover
- Chafe protection position — fairlead contact zone and eye
- Tail material, length and connection method if a tail is used
- Tagging and line identification for the line record
Step 6 — Specify the documentation
Decide before ordering what the line must arrive with: manufacturer certificate, break load test certificate stating the test standard, material and construction data, batch traceability, splicing details and, where required, classification society certification. Requesting these after delivery is significantly harder than requesting them in the purchase order.
The information a supplier actually needs
- Vessel type and name, and IMO number
- Ship design MBL
- Required diameter, construction and length
- Quantity, eye size and chafe protection requirement
- Whether tails are needed, and their specification
- Certification requirement and the society if applicable
- Delivery port and required date
Frequently Asked Questions
- Only if the previous specification was verified against the ship design MBL. Like-for-like replacement propagates any original mistake for the life of the vessel.
Need this applied to your vessel?
Send us the ship design MBL, the required diameter, construction and length, the delivery port and the date. We will come back with a line configuration and the documentation it will carry.
Request a quotation