LIROS specify their minimum break loads in Dekanewtons (DaN)
Kg force is a more recognisable illustration of strength, so you can convert the LIROS DaN values as follows:
1 Dekanewton = approximately 1.02 kg force
Therefore, the strength for any given diameter will be higher in kg than in daN, e.g. 11800daN = approximately 12036kg
Plain white LIROS Octoplait Nylon article 01058 with only LIROS tracer yarns is also available.
3 Strand Nylon will suffice if the mooring setup will not allow the boat to swing through 360 degrees in the tide.
The selection process for a mooring strop on a swinging mooring:
Find the column in the table below that best represents your Boat Length Overall.
Compare your displacement with the tonnage listed.
If the displacement is greater than displayed in your column in the table, or your yacht is a multihull, consider moving across to the next column to increase the diameter.
Take advice on local conditions and check the benchmark size from the table below against other similar-sized boats moored in your area.
Look at the mooring configurations on neighbouring yachts with a critical eye and judge whether your setup should be the same.
Consider whether you can make any improvements in terms of mooring convenience and anti-chafe measures.
Permanent Mooring Warps, Strops and Bridles:
Single Point generally means a Swinging Mooring
Double Point could be, e.g. Fore and Aft between piles
Benchmark Guide for Single (or Double) Point Mooring Strops
Yacht Length Overall
< 5 metres
5 - 6 metres
6 - 8 metres
8 -10 metres
10 - 12 metres
12- 14 metres
14 - 16 metres
Approximate length in feet
< 16 feet
16 - 20 feet
20 - 26 feet
26 - 33 feet
33 - 40 feet
40 - 46 feet
46 - 53 feet
Displacement in tonnes
N.B. Use only Anchorplait for swinging moorings - 3 strand lines may 'cockle' when the 'swing' turns against the lay of the rope.
Cockling (unravelling against the lay of the rope)
Cockling occurs when a fixed three strand construction warp is forced to rotate against the direction of the twisted lay, opening up the strands until they distort into 'ears' This will eventually be the case if a yacht continually swings around its mooring 'the wrong way'.
You can sample this with a soft piece of small diameter three strand rope - Twist it tighter, and the rope construction tightens - Twist it the other way, and the strands will soon de. Then the rope will go entirely out of shape, compromising the performance of the warp, with the distinct possibility of failure through rupture.
Video Demonstration of Rope Cockling
This may not look like it can happen in a large diameter strop. However, when a large diameter nylon warp dries out after contact with seawater, the fibres shrink, and the lay of the rope tightens. The result is a stiff rope akin to an iron bar that doesn't look like it could unravel. Still, it certainly can in conditions where the force of the rotational twist in the unlaying direction is both strenuous and persistent.
Cockling cannot happen with Anchorplait, no matter which way the rope is twisted.
Look after our splicing as well as your rope: The three strand splice will be in danger of unravelling if the strop isn't used correctly because once the rope has distorted as far as physically possible without rupture, the rotational force can be transferred to the splice with disastrous consequences.
When you have chosen the rope construction and the diameter, you can get an instant quote online, including all the splicing and finishing, anti-chafe and compensator options.
Jimmy Green Advisory on Twin Strops for Multihulls:
For wide-span catamarans and trimarans, it will be prudent to use two separate strops shackled together to make a V shape. Another short strop could also be deployed at the apex of the V to make a Y shape.