Mooring Warps Size Guide

General guide for determining the diameter of your mooring lines

These are the Important Decision Factors:

• Displacement to Length ratio, i.e. is your yacht relatively light or heavy for her length?
• Monohull or Multihull - catamarans may be subject to additional windage and torsional stress
• Mooring Configuration, e.g. alongside, stern to, fore and aft, or on a swinging mooring. N.B. the number of warps that share the load is a significant factor.
• Exposure, e.g. fetch, tide and chop.

Moorings can be broadly divided into three categories:

1. Shoreside, e.g. Jetties, pontoons (fingers), piers, and harbour walls, but could also include any convenient tree or rock.
   • Mooring alongside a fixed structure (along her length) with several lines to share the load and restrain her movement
   • Mooring stern to (perpendicular to the shore) with stern mooring lines to the shore and utilising anchor lines deployed beyond her bow to maintain her angle to the shoreline
2. Permanent Anchor Mooring: permanent attachment to the sea bed at a single fixed point or as part of a series.
   • Swinging Mooring – a single mooring is generally a single anchor or weight laid on the sea bed and connected to a buoy on the surface. A mooring attached to a series of anchors or weights on the sea bed (also known as a trot) is still swinging if the connection is individual, i.e. allows swing. Swinging refers to the fact that a yacht secured to a single point can turn full circle in either direction, according to the wind and tide. The buoy can be identifiable as a yacht’s home or a visitor's mooring. Sea bed mooring points vary from purpose-designed anchors to concrete weights according to local conditions. The sea bed anchor is typically attached to the mooring buoy with a chain known as the riser. A yacht is generally attached to the mooring buoy with a substantial, chafe-protected mooring rope commonly referred to as a strop or a bridle.
   • Pile Mooring: poles driven into the bottom of the sea bed or river bed in a regular line, with their tops protruding the surface to a serviceable height. A yacht positions herself in line between two piles and deploys mooring lines fore and aft to a heavy steel ring on the pile (which may slide up and down with the tide).
3. Running or Travelling: a fixed anchorage on the seabed with a block attached. A long line is reeved through the block, and each end leads back to the shoreline, where it is spliced together to form an endless loop. A rope is attached to the running rope to act as a riser. This type of mooring is prevalent for dinghies and tenders, which can be moored at a distance from the shore but easily pulled back in for embarkation.

There are two significant factors in determining the adequate rope diameter for your mooring requirements:

• The risk factor created by leaving your yacht unattended in all weathers.
• The number of lines that are deployed to take the expected load.

1. Selection process for the diameter of General Use Mooring Lines (Shoreside):

1. Find the column below that best represents your Boat Length Overall.
2. Compare your displacement with the tonnage listed.
3. If the displacement is greater than displayed in your column in the table, or the yacht is a multihull, consider moving across to the next column to increase the diameter.
4. Have a good look at the mooring lines on neighbouring yachts with a critical eye and judge whether your setup should be the same or whether you can make improvements
5. Take local conditions into account - some marinas are notorious for excessive movement (wave motion) when the wind is strong from a specific direction affording relatively little protection.
6. Decide whether an upgrade would enhance your mooring convenience
7. Add anti-chafe measures and compensators for peace of mind and fewer replacement costs
8. Bear in mind that several correctly deployed mooring lines can share the overall strain - more mooring ropes should result in less load on each warp and, consequently, less shock impact on your deck fittings.

NB. Consider upsizing your Stern Mooring Lines when moored stern-to (Mediterranean style) because the strain on the ropes will be considerably greater than when your yacht is moored alongside a pontoon.

Consider doubling up your stern-to mooring lines for Mediterranean Style Mooring as a precaution, especially when leaving your yacht unattended for any length of time.

N.B. LIROS Super Yacht Mooring Line Article 01300 is the LIROS recommended dockline for yachts over 22 metres LOA 

2. Selection process for a Single Point or a Double Point Mooring Configuration (Permanent Mooring):

• Single Point generally means a Swinging Mooring - N.B. Anchorplait/Octoplait 8 strand is recommended to prevent cockling
• Double Point could be, e.g. Fore and Aft between piles

1. Find the column in the table below that best represents your Boat Length Overall.
2. Compare your displacement with the tonnage listed.
3. If the displacement is greater than displayed in your column in the table, or the yacht is a multihull, consider moving across to the next column to increase the diameter.
4. Take advice on local conditions and check the benchmark size from the table below against other similar sized boats moored in your area.
5. Look at the mooring configurations on neighbouring yachts with a critical eye and judge whether your setup should be the same.
6. Consider whether you can make any improvements in terms of mooring convenience and anti-chafe measures.

Benchmark Guide for Single Point Mooring Strops e.g. permanent home buoy swinging mooring
including Fore and Aft (double point) Mooring

3. Selection process for a Rope/Chain/Rope Bridle (Visitor Mooring):

1. Find the column below that best represents your Boat Length Overall.
2. Compare your displacement with the tonnage listed.
3. If the displacement is greater than displayed in your column in the table, or the yacht is a multihull, consider moving across to the next column to increase the diameter.
4. Consider the application for your bridle - Will it be used as a single or double mooring point or as an anti-chafe mechanism to protect your regular lines
5. Consider the nature of the application - the chart is conservative and aimed at an overnight visit; consider upgrading to the next column for a more permanent arrangement or on an exposed mooring

Benchmark Guide for Rope / Chain / Rope Bridles

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