Mooring Warps - Size Guide

General guide for determining the size of your mooring lines

Important Decision Factors:

  • Displacement to Length ratio i.e. is your yacht relatively light or heavy for her length?
  • 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 major factor.
  • Exposure: e.g. fetch, tide and chop.

Moorings can be broadly divided into three categories:

  1. Shoreside e.g. Jetties, pontoons (fingers), piers, 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 – also known as a single or simple mooring is generally a single anchor or weight laid on the sea bed and connected to a buoy on the surface. A mooring that is attached to a series of anchors or weights on the sea bed (also known as a trot) is still a swinging mooring if the connection is individual i.e. allows swing, Swinging refers to the fact that a yacht secured to a single point will be able to turn full circle in either direction according to the wind and tide. The buoy can be identifiable as a yacht’s home or as a visitor mooring Sea bed mooring points vary from purpose designed anchors to concrete weights according to local conditions. The sea bed anchor is normally 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 and 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 led 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 very popular for dinghies and tenders which can be therefore be moored at a distance from the shore but easily pulled back in for embarkation.

There are two major factors in determining the adequate rope diameter for your individual 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 General Use Mooring Lines (Shoreside):

  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 it is greater than displayed in your column in the table, 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 set up 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 certain directions which afford relatively little protection.
  6. Decide whether an upgrade would enhance your mooring convenience
  7. Add anti chafe measures and/or compensators for peace of mind and less replacement costs
  8. Bear in mind that the overall strain can be shared by a number of correctly deployed mooring lines - more mooring ropes should result in less load on each warp and consequently less shock impact on your deck fittings.

N.B. 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.

Benchmark Guide for Multipoint Mooring Lines for Yachts up to 16 metres LOA

Yacht Length Overall< 6 metres6-8 metres8-10 metres10-12 metres12-14 metres14-16 metres
Aproximate length in feet< 20 feet20-26 feet26-33 feet33-40 feet40-46 feet46-53 feet
Displacement in Tonnes1 tonne2.5 tonnes5 tonnes9 tonnes13 tonnes16 tonnes
3 Strand, Dockline, Octoplait Polyester8/10mm10mm12mm14mm16mm18mm
Anchorplait, Handy Elastic, 3Strand Nylon8/10mm10mm12mm14mm16mm18mm
Moorex12 Polyester, 3 Strand Polyproylene12mm14mm16mm18mm20mm

Benchmark Guide Mooring Lines for Yachts over 16m LOA

Yacht Length Overall16 - 18 metres18 - 22 metres22 - 26 metres26 - 30 metres30 - 36 metres
Aproximate length in feet53 - 60 feet6- 72 feet72 - 85 feet85 - 98 feet98 118 feet
Displacement in Tonnes20 tonnes25 tonnes30 tonnes40 tonnes70 tonnes
3 Strand Polyester18/20mm20/24mm24mm--
Dockline18/20mm20/24mm24mm--
Octoplait / Anchorplait18/20mm20/24mm24mm--
Handy Elastic18/20mm20/24mm24mm28mm32mm
Super Yacht Mooring 01300 (Dockline)--24mm28mm32mm

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

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

  • Single Point generally means a Swinging Mooring
  • 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 it is greater than displayed in your column in the table, 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. Have a good look at the mooring configurations on neighbouring yachts with a critical eye and judge whether your set up 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 (or Double) Point Mooring Strops

Yacht Length Overall< 5 metres5 - 6 metres6 - 8 metres8 - 10 metres10 - 12 metres12 - 14 metres14 - 16 metres
Aproximate length in feet< 16 feet16- 20 feet20 - 26 feet26 - 33 feet33 - 40 feet40 - 46 feet46 - 53 feet
Displacement in Tonnes0.6 tonnes1 tonnes2.5 tonnes5 tonnes9 tonnes13 tonnes16 tonnes
Strop Diameter14mm16mm18mmm20mm24mm28mm32mm

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

  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 it is greater than displayed in your column in the table, 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

Benchmark Guide for Rope / Chain / Rope Bridles

Yacht Length Overall6 - 8 metres8 - 10 metres10 - 12 metres12 - 14 metres14 - 16 metres
Aproximate length in feet20 - 26 feet26 - 33 feet33 - 40 feet40 - 46 feet46 - 53 feet
Displacement in Tonnes2.5 tonnes5 tonnes9 tonnes13 tonnes16 tonnes
Anchorplait / 3 Strand Nylon14mm16mm18mmm20mm24mm
Chain8mm10mm10mmm12mm12mm

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