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10/02/2024
Prevention | Maintenance & Technology
MOORING CORRECTLY:
MATERIAL SCIENCE FOR MOORING LINES
The selection of materials for mooring lines is pivotal, as they directly impact the safety of both your boat and others. The emphasis here lies on specific properties, which may differ from those required for bulkheads. Mooring lines should exhibit high elongation, commonly referred to as "stretch," along with a high breaking load and resistance to wear. Moreover, they should be easy to handle, a quality sailors term as "lean." Polyester and polyamide are the most prevalent materials for mooring lines, although polypropylene may also be suitable for certain applications.
1. WHICH MATERIALS ARE SUITABLE FOR MOORING BOATS?
A. POLYESTER (PES)
Polyester, often abbreviated as PES and also referred to as Dacron, is renowned for its durability and strength. It boasts resistance to UV rays and excellent abrasion resistance, making it a popular choice for marine applications. However, one drawback of polyester is its limited stretch, necessitating the use of shock absorbers, especially when used in combination with this material.
B. POLYAMID/PA
Polyamide, commonly abbreviated as PA and also recognised as nylon, boasts significantly more stretch than even the highest-quality polyester cordage. This characteristic renders polyamide particularly well suited for scenarios involving sudden loads. However, nylon is susceptible to UV radiation, necessitating regular inspection and maintenance. Additionally, there are ropes available on the market that incorporate both polyester and polyamide fibres, harnessing the strengths of both materials for enhanced performance.
C. POLYPROPYLENE (PP)
Occasionally, mooring lines crafted from polypropylene (PP) are also available. However, polypropylene lacks sufficient resistance to light and abrasion. Therefore, it should only be employed when buoyancy is an absolute necessity for the line.
2. WHICH RIGGING CONSTRUCTIONS ARE SUITABLE AS MOORING LINES FOR BOATS?
The construction of the cordage is just as crucial for determining its properties as the material itself. "Construction" refers to the technical arrangement of the fibres. Here are some commonly recommended constructions for mooring lines:
A. TWISTED ROPE
Twisted cordage, also referred to as laid cordage, consists of three strands, known as "carding elements," twisted around each other. This construction is advantageous for its ease of splicing and stretchability. However, it is not highly elastic and may be prone to forming kinks.
B. SQUARELINE/SQUARE MESH
In the Squareline construction, four strands are braided together, resulting in a highly flexible and stretchy cordage. This construction is easy to cover and stow, and the cordage does not kink. However, it may be prone to pulling threads.
C. CORE-SHEATH BRAID
This structure corresponds technically to that of sheet cordage, resulting in a highly robust and flexible cordage. The elongation varies depending on the material used but is typically slightly less than that of a squareline.
Beware of potential confusion between sheet and mooring ropes, as they share a similar construction.
3. HOW TO CHECK THE ROPE FOR WEAR AND HOW OFTEN DOES IT NEED TO BE REPLACED?
The safety of a boat relies heavily on the integrity of its mooring ropes. Consequently, regular inspection for signs of wear is crucial.
Rope is a material prone to wear. Cutting corners here means cutting corners in the wrong place.
A. VISUAL INSPECTION
Ropes should undergo regular inspection for visible signs of wear, including abrasions, tears, or fraying. Special attention should be devoted to areas where the cordage comes into contact with edges or cleats (referred to by sailors as "shamfilt"). It is not advisable to simply turn the lines around, as this merely relocates the weakened area to another part of the rope.
B. CHECK BY TOUCH
By running your hands along the mooring lines, you can detect any bumps or thickening that might suggest internal damage, particularly in the case of core-sheath braiding. Any section displaying such anomalies warrants closer examination. When in doubt, it is better to replace the mooring line altogether.
C. REPLACEMENT DATE:
The service life of cordage varies depending on factors such as usage, weather conditions, and maintenance. As a general guideline, it is advisable to replace cordage every two to five years, even in the absence of visible damage. This helps minimize the risk of unexpected issues arising.