5.1 Natural, Synthetic & Wire Ropes: Care, Coiling & Splicing

Introduction to Shipboard Cordage & Wire Ropes

Cordage and wire ropes are fundamental tools of everyday seamanship on merchant vessels. A General Purpose (GP) Rating handles ropes across mooring operations, anchor handling, cargo lashing, gangway rigging, pilot ladder deployment, life-saving appliances, and aloft/overside maintenance. Selecting the proper rope material, understanding its mechanical limitations, maintaining it against environmental degradation, and mastering splices and terminations are core competencies evaluated on the DG Shipping GP Rating exam.

Modern merchant ships deploy three broad categories of cordage: natural fiber ropes, synthetic fiber ropes, and steel wire ropes. Each material presents unique tensile strength, elasticity, density, abrasion resistance, and safety considerations.

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1. Natural Fiber Ropes: Materials & Maintenance

Natural fiber ropes are manufactured from plant fibers twisted together. While largely superseded by synthetics for primary mooring hawsers, natural ropes remain widely used for boat falls, heaving lines, gantlines for bosun's chairs, stage lashings, fenders, and cargo slings because they do not melt under friction and provide excellent tactile grip.

Common Natural Fibers

Care and Storage of Natural Fiber Ropes

Natural fibers are organic cellulose materials subject to bacterial decay, fungal attack (mildew and rot), and chemical destruction:

1. Drying Before Stowage: Never stow a natural fiber rope while wet or damp. Wet ropes coiled in dark, poorly ventilated lockers generate internal heat and ferment, causing rapid rot and loss of tensile strength. If wet with seawater, rinse with clean fresh water to remove hygroscopic salt crystals, then hang in loose flakes in a shaded, well-ventilated space until bone dry.
2. Ventilation & Elevation: Stow ropes on raised wooden gratings or slatted shelves at least 100 mm off the deck plating. Ensure the rope locker is well-ventilated, clean, and dry to prevent condensation.
3. Chemical Contamination: Keep natural fiber ropes completely clear of acids (such as battery electrolyte), alkalis (caustic soda hold cleaning wash), boiler flue gas wash water, paints, solvents, and petroleum oils. Contact with battery sulfuric acid destroys vegetable fibers within minutes.
4. Abrasion Protection: Fit canvas or leather chafing gear where lines pass through hawse pipes, fairleads, or over sharp gunwales.

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2. Synthetic Fiber Ropes: Types, Properties & Hazards

Synthetic fiber ropes are produced from continuous extruded polymer filaments. They have replaced natural fibers for primary mooring lines and heavy towing hawsers due to their superior tensile strength, rot resistance, and durability.

Primary Synthetic Polymers

• Polyamide (Nylon):
  • Strength: The strongest conventional synthetic fiber line, possessing approximately 2.5 times the breaking strength of grade-one manila rope of equal diameter.
  • Elasticity & Snap-Back: Exceptional elasticity, elongating up to 40% before catastrophic rupture. This high stretch enables nylon to absorb immense dynamic shock loads (ideal for towing springs and anchor rodes). However, when stressed near its breaking limit, it stores elastic potential energy. If it parts, that energy can drive rapid, potentially fatal snap-back.
  • Water Effect: Nylon absorbs water (up to 5% by weight) and loses 10% to 15% of its tensile strength when saturated, though it regains full strength upon drying.
  • Melting Point: Approximately 250°C (482°F).
• Polyester (Terylene / Dacron):
  • Strength: Roughly 2 times the strength of manila, nearly equal to nylon.
  • Stretch & Stability: Low elongation (only 12% to 15% at break). It does not stretch dynamically like nylon, providing precise positioning control.
  • Environmental Resistance: Outstanding resistance to ultraviolet (UV) sunlight degradation, cyclic abrasion, acids, and atmospheric weathering. Retains 100% of its strength when wet.
  • Shipboard Uses: Running rigging, mooring tails, crane cargo runners, and topping lifts.
  • Melting Point: Approximately 260°C (500°F).
• Polypropylene:
  • Buoyancy: Lightest conventional synthetic fiber with a specific gravity of 0.91, meaning it floats on water (seawater density is 1.025). Flotation helps handlers see and recover the line, but floating rope can still foul a propeller. Keep slack lines clear of propulsion equipment.
  • Strength: Roughly 1.5 to 1.7 times the strength of manila.
  • Low Melting Point: Polypropylene has a very low melting threshold of 165°C (329°F). Friction heat generated when surging polypropylene turns on a rotating capstan or warping drum quickly melts and fuses outer fibers, creating a hard, glazed surface that slips unpredictably.
  • UV Degradation: Unstabilized polypropylene degrades rapidly under solar UV radiation, turning brittle and powdery. Maritime polypropylene lines must be manufactured with UV inhibitors or carbon black additives.
  • Slipperiness: Low coefficient of friction. Knots and splices slip under heavy strain unless secured with extra tucks.
• High-Modulus Synthetic Ropes (HMPE / Aramid):
  • Modern commercial tonnage increasingly deploys High-Modulus Polyethylene (HMPE, e.g., Dyneema, Spectra) and Aramid (e.g., Kevlar, Technora) mooring lines.
  • HMPE matches or exceeds the breaking strength of steel wire rope of identical diameter at roughly one-seventh (1/7th) the weight, floats on water, and exhibits near-zero elongation. However, it requires dedicated anti-chafing sleeves and cannot tolerate high radiant heat.

Comparison Table of Cordage Fibers

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3. Steel Wire Ropes: Construction & Lay Terminology

Steel wire ropes are engineered for heavy lifting, cargo handling, standing rigging, and mooring on dedicated winches where extreme tensile strength, minimal stretch, and resistance to abrasion are essential.

Construction Anatomy

A wire rope consists of three basic components:

1. Wires: Individual cold-drawn high-carbon steel wires of designated tensile strength (e.g., 1570, 1770, or 1960 N/mm²).
2. Strands: A predetermined number of wires laid helically around a central wire.
3. Core: The central foundation around which the strands are helically laid.

       CROSS-SECTION OF A 6x19 WIRE ROPE
                    [Wire]
                  o o o o
                 o o o o o
             [Strand]  [Strand]
                \      /
          [Strand]- (CORE) -[Strand]
                /      \
             [Strand]  [Strand]

• Wire Rope Designation ($6 \times 19$, $6 \times 36$, etc.):
  • The first numeral indicates the number of strands in the rope.
  • The second numeral indicates the number of individual wires in each strand.
  • A $6 \times 19$ wire rope has 6 strands, each containing 19 wires (totaling 114 structural wires around the core).
  • Flexibility Rule: Wire ropes with fewer, thicker wires (e.g., $6 \times 7$ or $6 \times 19$) offer high resistance to surface abrasion and dragging wear, but are stiff. Wire ropes with many finer wires (e.g., $6 \times 36$ or $6 \times 41$) are supple and flexible, designed to flex repeatedly around sheaves and drums without metal fatigue.

Core Construction: Fiber Core vs. IWRC

• Fiber Core (FC): Made from natural sisal or synthetic polypropylene. The fiber core acts as an internal sponge saturated with neutral, acid-free petroleum lubricant, releasing grease internally as the rope flexes. It cushions the outer strands and provides high flexibility. Not suitable for high-temperature areas or multi-layer spooling winches where high crushing loads occur.
• Independent Wire Rope Core (IWRC): A miniature steel wire rope (typically $7 \times 7$) running down the center instead of a fiber core. Provides maximum structural resistance against crushing, flattening, and distortion on winch drums under multi-tier spooling, increases overall rope breaking strength by 7% to 10%, and tolerates high radiant heat (e.g., engine room cranes, cargo grabs).

Lay Types: Ordinary Lay vs. Lang's Lay

The "lay" refers to the direction and manner in which the wires and strands are wound:

• Right-Hand Ordinary Lay (Regular Lay):
  • The strands are laid around the core to the right (clockwise), while the individual wires within the strands are twisted in the opposite direction (to the left, counter-clockwise).
  • Characteristics: Outstanding structural stability. Resists unlaying, untwisting, and kinking; easy to handle and splice. Standard for cargo runners, crane falls, mooring wires, and general shipboard hoisting.
• Lang's Lay:
  • The wires in the strands and the strands around the core are twisted in the same direction.
  • Characteristics: Wires contact sheaves along longer diagonal arcs, providing superior resistance to bending fatigue and outer wire abrasion. However, Lang's lay ropes unlay and spin rapidly under free-hanging loads and kink very easily. Ordinary non-rotation-resistant Lang's-lay ropes require both ends to be restrained against rotation. Use the rope construction and lay specified for the equipment; guided elevators and mine winding are examples, not its only applications.

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4. Rope Handling, Coiling, and Care on Deck

Improper handling of cordage during breakout and stowage introduces permanent kinks, snarls, and mechanical defects that destroy rope integrity.

Breaking Out a New Coil

New coils of natural or synthetic fiber ropes arrive from ship chandlers tightly wrapped in burlap or plastic bands, packaged from the factory:

• Uncoiling from the Inside: A new coil must always be broken out by reaching inside the central tunnel (the eye) of the coil and pulling the bitter end out in a counter-clockwise (anti-clockwise) direction. This ensures that the rope pays out smoothly without forming kinks or cockles.
• If the rope uncoils clockwise from the inside and begins throwing kinks, the coil must be rolled over onto its opposite face so the line pays out counter-clockwise.
• Turntable Method: Alternatively, the coil can be mounted horizontally on a revolving turntable or spindle, allowing the line to be drawn from the outer perimeter as the drum rotates.

Coiling on Deck

• Right-Hand Laid Rope: Standard right-hand laid 3-strand ropes must always be coiled down clockwise ("with the sun" or in the direction of the hands of a clock). Coiling right-hand rope counter-clockwise introduces kinks and damages the lay.
• Left-Hand Laid Rope: Coiled counter-clockwise ("against the sun").

       COILING RIGHT-HAND LAID ROPE
               (With the Sun)
                   12
               .  - -  .
            /             \
          9       ( )       3  --> Clockwise
            \             /
               '  - -  '
                   6

• Faking Down (Flaking): When a rope must run free at high speed without fouling (such as a lifeboat painter, mooring messenger, or deep-sea towing line), it is laid down on deck in flat, overlapping figure-of-eight turns or straight parallel flakes along the deck plating. Faking down eliminates all rotational twists, ensuring the line pays out freely through chocks without throwing loops that could trap a rating's foot.
• Flemishing (Flemish Coiling / Cheesing Down): Coiling a line tightly and flatly onto the deck in a concentric, spiral circular mat from the center outward. Used solely for decorative neatness during port inspections when lines are not in active use.

Whipping Cordage Ends

The unlaid bitter end of any fiber rope will rapidly fray into an unusable "cow's tail" unless properly bound. Whipping secures the strand ends using waxed sail twine:

1. Common Whipping: A neat binding made by laying a bight of twine along the rope, winding tight turns over the bight toward the end, threading the twine through the loop, and hauling the loop halfway underneath the binding to lock it.
2. Palm and Needle Whipping: The most secure permanent whipping for working lines. The twine is stitched through the strands using a sailmaker's palm and needle, wound tightly around the rope, and "wormed" back along the grooves (contlines) between the strands with frapping turns.
3. Sailmaker's Whipping: Tied by unlaying the rope strands for a few inches, placing a bight of twine over one strand, relaying the rope, pulling the twine up through the strands, and finishing with tight reef knots between the strand crowns.

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5. Rope Splicing & Wire Rope Terminations

A knot reduces the tensile strength of a fiber rope by 40% to 55% because the sharp bends concentrate shear stress on outer fibers. In contrast, an engineered splice interlaces the rope strands along their natural axis, preserving 85% to 90% of original rope strength.

The Eye Splice in 3-Strand Fiber Rope

The eye splice creates a permanent loop in the end of a rope, commonly fitted around a galvanized steel thimble to prevent internal chafing.

• Step 1: Mark and unlay the length required by the selected splice instructions, allowing enough strand for all full tucks and any taper. Seize the base of the unlaid strands.
• Step 2: Form the loop of desired size, placing the three working strands across the standing part of the rope.
• Step 3 (The Tucks): Tuck the center strand under the nearest strand of the standing part, working against the lay (from right to left, "over one, under one"). Tuck the left strand under the adjacent standing strand. Turn the splice over and tuck the third strand under the remaining standing strand. Ensure all three strands emerge evenly spaced around the rope circumference at the same level.
• Number of Tucks and Finishing: Follow the rope maker's instructions for its material, construction and intended use.
  • Natural Fiber Rope (Manila/Sisal): Three full tucks are a basic seamanship eye-splice pattern. For lifting-appliance ropes or slings, ILO guidance specifies at least four full tucks against the lay, then securing the ends.
  • Polyamide (Nylon) and Polyester: COSWP specifies four full tucks, followed by one half-strand tuck and one quarter-strand tuck. Leave tails at least three rope diameters long and secure the tapered portions.
  • Polypropylene: Use four full tucks with tails at least three rope diameters long; this meets the ILO lifting guidance and COSWP's three-to-four-tuck guidance. Do not substitute the nylon taper automatically.

       THREE-STRAND EYE SPLICE — TUCK AGAINST THE LAY
                [Rope Eye]
                    |
        Each full round: tuck ALL THREE strands
        Over one standing strand, under the next
                    |
        Basic natural-fibre exercise: 3 full rounds
        Natural-fibre lifting eye:   4 full rounds minimum
        Nylon/polyester:             4 full + 2 tapered rounds
        Polypropylene:               4 full rounds
        Finish tails as specified; inspect before use.

Short Splice vs. Long Splice

Wire Rope Terminations: Bulldog Grips

Bulldog grips (U-bolt wire clamps) are used only where the application permits them. COSWP says to avoid them if possible and not use them on lifting or mooring wires, strongly vibrating ropes or plastic-coated wire. Use an approved spliced or compression-fitted eye for lifting/mooring service.

        CORRECT BULLDOG GRIP ORIENTATION
     "Never Saddle a Dead Horse"

     Live (Loaded) Wire Part --------+======+--------
                                     |SADDLE|
                                     +======+
                                     |U-BOLT|
     Dead (Cut) Wire End ------------+------+

• The Seamanship Golden Rule: "Never saddle a dead horse!"
  • The saddle (bridge) of the grip must always be seated on the live (working/load-bearing) part of the wire rope.
  • The U-bolt must always bear against the dead (cut/short tail) end of the wire rope.
  • Reason: The curved U-bolt causes severe localized crimping and point-loading. If clamped onto the live wire, it crushes and damages the primary load-bearing strands, reducing termination strength by up to 50%.
• Spacing Guide: COSWP illustrates approximately 6 rope diameters ($6d$) between grips; the actual installation must follow the clip maker's instructions: $\text{Grip Spacing} = 6 \times d$ (For the approximate $6d$ guide, a 20 mm rope gives $6 \times 20\text{ mm} = 120\text{ mm}$; this calculation does not replace the maker's layout.)
• Quantity of Grips: Select the clip size, minimum number, turnback length and tightening torque from the manufacturer's table for the actual rope. A diameter-only 3/4/5-grip shortcut is not an installation specification.
• Initial Loading and Retightening: Tighten evenly to the maker's specified torque. Apply the prescribed initial test load, then check and retorque as instructed. Recheck periodically in service because bedding-in can loosen clips. Keep personnel clear of the loaded assembly.