How to find the right mooring line for your boat

How to find the right mooring line for your boat

Mooring lines are used to secure your boat to jetties, pontoons, quays or anchor buoys. Whenever your boat is not in use, mooring lines ensure that your vessel is held safely and securely at the mooring. So, it's important that your mooring lines can reliably hold the weight of your boat and are of good quality. Here, we tell you what you need to look out for when choosing mooring lines.

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What makes a good mooring line?

An important feature of a good mooring line is a high degree of elongation. If the mooring line doesn't have a certain degree of elongation, the movement of the boat caused by wind and waves puts unhindered force on the cleats or grommets on which the rope is fastened to. A mooring line absorbs this kinetic energy, which not only prevents possible damage, it also makes the time spent on board more pleasant. Similarly, a mooring line must have a high breaking force to be able to secure the boat, even in stormy weather and heavy swell. The necessary breaking force depends on the size of the boat. We recommend always being generous when considering breaking force, as even slight chafing will weaken the rope considerably - and there are plenty of places where mooring lines can chafe, such as on fairleads, chocks etc. Mooring lines should therefore be robust. They should also have good flexibility and grip, so that managing the lines, coiling and making knots or splicing is easier. Finally, UV resistance is important. Mooring lines which are left permanently at the berth should not be allowed to become porous or brittle.

What kind of rope constructions are used for mooring lines?

Three different rope constructions are used for mooring lines:

  1. Twisted rope: With twisted rope two or more strands are twisted around each other. This type of rope is stretchable, can be easily spliced and is cheap to buy. However, it isn't overtly flexible and kinks can develop after some time.
  2. Square braid: Square braided ropes, also called square lines, are very supple and have the best stretchability of all fender lines. The rope is easy to tie and stow and does not chink. The only disadvantage of square braid is that the rope tends to string.
  3. Double braid: This rope is particularly robust and supple. Elongation depends on the material, but is usually lower than with square braids.

What material for mooring lines?

The most commonly used mooring lines are made of polyester, polyamide, also known as nylon, and polypropylene. All three materials have their advantages and disadvantages.

Polyester mooring lines

Polyester mooring lines are particularly UV-resistant. Furthermore, in terms of breaking strength, shrinkage and abrasion resistance, polyester lines are superior to those made of polyamide or polypropylene. The material is also relatively cheap, high grip and only absorbs a little water. The only disadvantage of polyester mooring lines is that they are not particularly stretchy. So, you should either use very long mooring lines or a snubber. For a particularly good quality line, we recommend purchasing polyester mooring lines with square braiding. These provide excellent grip, are very elastic and completely free of kinks.

Polyester mooring lines
Polypropylene mooring lines

Polypropylene mooring lines

Polypropylene is the lightest of all textile fibres. It absorbs practically no water and is floatable. As a result, mooring lines made of this material are less likely to be caught on the boat propeller when manoeuvring in the harbour. Polypropylene is also very resistant to chemicals. Unfortunately, these ropes are much less UV-resistant, more prone to abrasion, have a lower breaking force and are generally less durable than mooring ropes made of other materials. They should only be used if you need a floatable line (i.e. for towing) and, if possible, only in sheltered berths. As a precaution, order with a larger diameter than necessary.

Polyamide mooring lines

The advantage of polyamide mooring lines is that they yield up to 10% more stretch than polyester ropes. They are the most elastic of all materials used in the manufacture of mooring ropes. For many years, polyamide ropes quickly became very stiff and hence unmanageable. This is because polyamide absorbs a lot of water. In the meantime, however, polyamide lines have now been much improved by manufacturers.

Polyamide mooring lines

Which diameter for mooring lines?

The right diameter for mooring lines depends on the size of the ship. For yachts with a length of ten metres and a displacement of four to five tonnes, mooring lines with a diameter of 12 to 14 mm are suitable. To determine the necessary diameter of mooring lines for your boat you can use the following table for help:

Boat length in metres Polyester Bavaria & GeoSquare Polyamide Hempex
6 m 10 mm 8 mm 8 mm 14 mm
8 m 12 mm 10 mm 10 mm 16 mm
10 m 14 mm 12 mm 12 mm 20 mm
12 m 16 mm 14 mm 14 mm 22 mm
14 m 18 mm 16 mm 16 mm 26 mm
16 m 22 mm 18 mm 18 mm 28 mm
18 m 24 mm 18 mm 20 mm 28 mm
20 m 26 mm 20 mm 22 mm 32 mm
22 m 28 mm 20 mm 26 mm 32 mm

How long should mooring lines be?

As regards the length of mooring lines, it is recommended to have four lines on board, two in the length of the boat as stern lines and another two approximately twice the length of the boat width for the bow to moor as 'med style' or 'stern to berth' with pillars or lead lines or four boat's length lines to moor bow and stern plus springs. This way you will be well equipped for various ports and moorings. Furthermore, one or two longer lines are recommended to be kept on board, which you can use as manoeuvring or towing lines or as a shore line for lying in a packet. These lines may be at least twice the length of the boat.

Why splice mooring lines?

A spliced rope has a significantly higher breaking load than a knotted rope. It is recommended to have mooring lines that are precisely made to measure, above all for your regular berth. But a spliced thimble or eye can also be quite useful when sailing. The rope can be attached directly to the ring on the pier or the harbour wall, or it can be coiled and secured by belaying pins without reducing the breaking load of the rope with a bowline. We can supply prefabricated mooring lines with various eye diameters, simple or reinforced stainless-steel thimbles, leather sheathing for reinforcement or spliced-in dampers. You can, of course, also have us configure a mooring line of your choice and have it manufactured according to your specific requirements.

Which accessories for mooring lines?

Which accessories for mooring lines?

So that your mooring line is at hand at when you need it, we offer various hooks and rope holders. Depending on the model, the hooks can either be fixed on board, for example to the bow or stern pulpit, or they can be installed at the jetty, so that you can easily reach your mooring lines at fixed mooring points and manage them easily.