Mooring lines are the unsung heroes of boating, silently ensuring your vessel stays safely secured when docked or anchored. But with an array of materials, thicknesses and lengths available, selecting the right ropes can be daunting. Here, we explain the crucial factors to consider when choosing mooring lines for your boat. 

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Marlow Ropes has been the leading rope brand in the yachting industry for over fifty years, with a heritage in rope making going back over 200 years.

“Historically, we’ve found that mooring lines are the most over-looked ropes on any yacht. This is something we’ve always found baffling, especially when you consider that these are the most important ropes for securing your beloved boat. Sailors and boat owners often look at price first when buying mooring lines, which results in low quality, low durability and much shorter longevity. 

“At Marlow, we manufacture a range of mooring lines to suit all budgets – each with their own unique specification to suit the requirements that we often come up against. It’s worth sailors and boat owners being aware of the unique construction characteristics of the various mooring lines on the market.”  Paul Honess, Leisure Marine Director

STRENGTH IS PARAMOUNT 

The primary function of mooring lines is to withstand the forces exerted on your boat by wind, waves, tides and currents. These forces translate to breaking strength, the amount of weight a line can hold before snapping. The key is to choose lines with a strength that significantly exceeds your boat’s weight. Consult your boat’s manual or manufacturer for its displacement (weight) and factor in a safety margin of at least 3:1. 

MATERIAL MATTERS

• Nylon: Offers high elasticity, crucial for absorbing shock loads and preventing snapping. Bear in mind, it is known to degrade under UV exposure, resulting in reduced strength over time. 
• Polyester: Known for its strength, and resistance to abrasion and sunlight. It has a lower stretch than nylon, so consider using mooring shock absorbers for additional give. This is the most reliable material for mooring lines.  
• Polypropylene: A budget-friendly option with good buoyancy and moderate strength. Bear in mind, it stretches significantly and degrades quickly in sunlight. Only to be considered for its floating characteristics. 

MARLOW RECOMMENDS:  

3-strand Nylon  

Multi-plait Nylon  

3-strand Polyester  

3-strand Polyester Pre-stretched for greater strength and durability 

Marina Grande 

Blue Ocean® Dockline – sustainably manufactured from GRS certified rPET and available pre-spliced  

3-strand Nelson  

FINDING THE RIGHT SIZE

Mooring line diameter is directly linked to breaking strength. Use the breaking strength recommendations as a guide. Also, consider consulting a marine store professional for specific sizing based on your boat and typical mooring conditions. 

LENGTH MATTERS TOO

Mooring lines come in various lengths, with specific applications in mind: 

• Bow and stern lines: These should be at least half the length of your boat, ideally longer, to allow for mooring at different angles and absorb wave action. 
• Spring lines: Designed to prevent your boat from swinging excessively, these should be the entire length of your boat or even longer. 

DURABILITY

The marine environment is harsh, so consider factors that can degrade your mooring lines: 

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• Abrasion resistance: Friction against docks, pilings and other boats can wear lines. So look for materials with good abrasion resistance or use chafe guards at potential wear points.  
• UV resistance: Constant sunlight exposure weakens most mooring lines. So choose materials with good UV resistance or consider adding a UV protectant spray. Polyester is best, with nylon a reasonable second and polypropylene a distant third. UV stabilising techniques help, but don’t significantly alter the general comparable resistance values of each material. Counteracting UV deterioration should be a major consideration for yachts, especially in sunny climes such as in the Mediterranean and the Tropics. 

COMFORTABILITY CONSIDERATIONS

• Creaking mooring lines is a bugbear for many sailors and boat owners plus those living or working close by. It’s often not known what causes the dreaded creak – but chafe, caused by salt water, or the fibre quality degrading over time may be factors. The addition of chafe covers or a lubricant coating may help. Nylon shrinks when it’s wet, which can result in a tightening of the rope strands, thus creating a harder, stiffer rope. This may lead to creaking, but a stiffer rope may be of greater benefit for permanent single purpose warps. 
• Handling – Rope construction and diameter will make a difference to your comfort. Braided docklines, such as Marlow’s Marina Grande and Blue Ocean® dockline, not only look good but feel good too thanks to their flexibility and smoother finish. This makes them much easier to handle, especially in the stressful situation when coming alongside.  
• Coiling and hanking – For good rope maintenance, storing your mooring lines is vital to ensure their longevity and ease of use when it’s time to moor. A rope’s construction will dictate how it should be hanked. 3-strand ropes need to be rolled around your thumb to keep the lay in regular form. Whereas braided and plaited ropes should be formed into a figure of eight, to ensure twist is not imparted into the rope which puts undue pressure on to the fibres.   

INSPECT YOUR ENVIRONMENT

Mooring lines are a safety-critical element. Regularly inspecting them for signs of wear is good practice – replace them promptly when they show signs of deterioration. When in doubt, consult your local rigger or chandler for recommendations specific to your boat and mooring conditions.  

By making informed choices, you can ensure your boat stays securely moored, giving you peace of mind while you’re off enjoying the water. 

Mooring Rope Selection Guide

The Main Factors to consider in selecting your mooring rope

Stretch Factor – mooring lines need to absorb snatch loads and maintain the capacity to elongate and recover without suffering premature stress failure. Polyester has the required amount of working stretch for mooring and the ability to absorb surge loads can be enhanced with mooring compensators. Polypropylene stretches a little more than polyester. Nylon is the most elastic of the three materials, approximately 5-10% more elongation than polyester.

Strength and Durability – mooring ropes need to manage the substantial strain experienced in securing a yacht in your chosen configuration (the number of ropes that effectively divide the load) so relative diameter and break load are important factors. Nylon is initially the strongest mooring rope but it is a widely held belief that it loses 10-15% when thoroughly wet which brings it back to relative parity with polyester. Polyester has better UV resistance than nylon which means that it builds a small advantage each season resulting in a longer working life. Polypropylene is not comparable to the other two materials and should not be considered unless stepping up in diameter.

Abrasion Resistance – depends on what the rope is made from, how it is manufactured and to a lesser extent, the finished construction. Polyester and Nylon have comparable performance with Polypropylene, again a distant third. LIROS employ heat setting technology and special twisting techniques on the fundamental filaments and yarns to enhance wear performance.

Nylon shrinks when it is wet resulting in a tightening of the rope strands creating a harder, stiffer rope. This can be of benefit for permanent single purpose warps.

Comfort – rope construction and diameter make a difference to comfort, especially for more delicate hands. Braided Docklines are commonly regarded as the most flexible, luxurious handling rope for mooring. Octo (Anchor) plaited ropes are also flexible and comfortable to handle. 3 strand rope is generally regarded as less kind to the hands but is probably still the best all-round choice for most mooring applications.

Handling, Coiling and Hanking - rope construction dictates how you should hank a rope into a coil for stowing and throwing/heaving. 3 strand rope needs to be rolled around your thumb to keep the lay in regular form. Braided and Plaited ropes should be allowed to form a figure of eight shape, to ensure that you are not imparting twist into the rope.

UV Resistance – Everything degrades in the sun. The speed at which the deterioration occurs depends on what the rope is manufactured from. Polyester is best, with nylon a reasonable second and polypropylene a distant third. UV stabilising techniques help but don’t significantly alter the general comparable resistance values of each substance. Counteracting UV deterioration should be a major consideration for yachts in the Mediterranean and the Tropics.

Buoyancy - Polyester and Nylon both sink. Polyester is slightly heavier than nylon. Polypropylene floats. There are some applications where it is important that a line floats on the surface, but otherwise Polyester and Nylon are more durable fibres in terms of strength and resistance to abrasion and UV.

Summary - Polyester is the best all round fibre for mooring applications. Nylon has additional elasticity and can develop a harder finish which is of benefit for certain solutions. Polypropylene isn't really comparable and should only be selected to take advantage of the fact that it floats.

Single Purpose Mooring Lines

Single Purpose Mooring Lines are ropes made up to a specific measurement, spliced and finished to fit your home berth mooring configuration. These lines tend to be for more permanent arrangements, also known as Permanent Warps:

Mooring Strops and Mooring Bridles

Design Considerations and Plus Factors:

• You can select your preferred optimum rope for each purpose: base material (rope type), construction, diameter and exact length.
• Spliced loops to conveniently drop over cleats or bollards, remember to allow just enough extra to pull the loop to the furthest extremity of the horn, before it drops over and sits neatly around the cleat base. Spliced loops can be ordered with anti-chafe webbing fitted.
• Spliced thimble eyes for connecting shackles to rings, or other fixed attachments on the pontoon or harbour wall. Stainless steel connections reduce the chances of abrasion.
• Mooring Compensators threaded onto the lines before splicing, to add extra shock absorption where it’s most needed.
• Chafe Protection threaded onto the lines before splicing, to protect the most likely wear points.

Multi-Purpose Mooring Lines

Multi-Purpose Mooring Lines are generally longer lengths that can be deployed for varied tasks and tend to be for more temporary arrangements.

Design Considerations and Plus Factors:

• You can select one rope type suitable for all your mooring requirements. This may help the crew to become more proficient at critical moments.
• Spliced loops on one end can be very helpful when trying to secure your yacht in difficult wind and tide conditions.
• All non-spliced rope ends should be heat sealed and whipped to prevent fraying.
• Bow and Stern lines can be made off and doubled back to make a spring.
• Longer lines can be deployed to attach directly to the pontoon, when your yacht is outside several others on a visitors pontoon.

Rafting Out and Towing Warps

It’s generally good practice to have two long lines in your rope inventory for when you’re rafted out on a visitor pontoon. It is not advisable or the done thing to rely on your inner neighbours to keep you securely moored to the jetty, by simply tying up to next door’s cleats. You will create extra load on their lines and fittings which will not be appreciated and in any case, may expose their lack of strength and suitability.

It’s also a good idea to consider a towing line for emergencies. Stowage room and extra cost may lead you to designate an existing mooring or anchoring warp for this purpose. Just bear in mind that the rope ends need to be finished in a versatile manner so that the line is genuinely multi-functional. A towing warp needs to be long and fairly stretchy so is reasonably compatible with doubling up as rafting out, kedge or drogue warps.

Compare the three main choices of Mooring Rope Construction:

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