Rope

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Eye Splice

ROPE

Special Purpose Knots

ROPE MATERIAL

There is a wide range of deferent materials used to make rope. Each of these fibres has its own properties making each the best material for ropes with certain needs for the job in hand. Rope fibres can be divided into two categories - natural and synthetic. Natural fibres mostly come from plants while synthetic fibres are chemically made and extruded in continuous strands which are then wound or woven together to assemble the final rope. The tables below summarize the main materials in both categories

NATURAL FIBRES

Hemp is made of a plant Cannabis Sativa. It is one of the oldest rope materials and is very strong. Has a tendency to rot if left wet. Sometimes tarred to increase life but sacrifices some strength. Rarely used now.

Manila is made from a wild banana plant. As strong as hemp but more resistant to rot. Still used but quality had deteriorated in recent years.

Sisal is derived from a cactus-type plant called Agave Sisalana. Not as good qualities as either Hemp or Manila but used mainly to make cheap cordage - small twines and string

Coir is made from the outer fibres of the coconut. Not very strong but is so light it will float. Stretches & therefore used as mooring and tow ropes

Cotton is used for mainly small rope and twine. Good for making small braided cords. Prone to rot

SYNTHETIC FIBRES

Nylon was the first synthetic fibre used for rope. Original stretchiness reduced so that it is good for absorbing shock loads - as in tow and anchor lines. Very strong, does not rot, wears well, resists chafe, mildew & rot.

Polyester is similar to nylon but it is slightly weaker but does not stretch as much. Can be pre-stretched so that it becomes very useful on boats. Sometimes called Dacron,

Polypropylene is similar to the ones above but is is cheaper to produce. Not as strong as Nylon or Polyester but will float. More prone to chafe & UV breakdown. Fibres often mixed with other types to make various copolymer ropes optimised for particular tasks.

Exotic Materials have recently been developed with properties surpassing other synthetics. These include Kevlar, Spectra, Vectran, Zylon & others. These are expensive and have some drawbacks - such as not working well on tight bends

TERMS

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KNOTS

Rope Topics

With the advent of velcro the tying of knots is becoming a lost art - particularly in the general community. There are literally hundreds of knots for different ropes and purposes - both practical and decorative. The few shown below are among the most basic but between them a wide range of uses can be made. Further special purpose knots are shown below. (Clove & Rolling Hitches, Sheet Bends)

EYE SPLICE

Rope Topics

An eye splice is formed by unlaying the end of a rope for a short distance, then turning the end back to form an eye, and tucking the separated strands into the standing part. Let the strands lie across the standing part approximately at right-angles to the lay of the standing part. Have two strands on top and one underneath. Lift a strand of the standing part with a spike, and tuck No. 2 strand under it (Fig. a). Lift the next strand and tuck No. 1 strand under it, going in where No 2 comes out (Fig b).

Turn the loop over and lift the only strand of the standing part which has no other under it, and insert No. 3. Notice its direction (c). Pull all the strands tight. This completes the first tuck. Take each strand in turn and "go over and under one;" as No. 2 in Fig d. Taper off by halving the strands before tucking the third time, and again halve them before the fourth tuck.

SPLICE

Rope Topics

CARE of ROPE

Rope Topics

   The life of ropes is reduced by any of the following:
          * Excessive stress                           * Abrasion or cutting on sharp objects
          * Stowing away when wet              * Inadequate ventilation
          * Exposure to chemicals                 * Excessive exposure to UV
          * Kinking                                       * Passing through the wrong size blocks
          * Exposure to petrochemicals

     Rope made from synthetics is sensitive to heat and can be damaged if left lying against hot objects such as engine manifolds or exhausts.
    Minimise frictional damage to ropes by avoiding slip or idle over winch drums or by running tight over stationary fittings. Severe chafing in synthetic ropes can cause internal fusing leading to ultimate failure.
    Synthetic rope having a lot of repeated heavy loading and stretching could suffer internal chafing and heat damage. Check for flattened fibres, powdered fibre or a broken central core.
    The most common and frequent damage to rope is caused by abrasion. Protect rope where it is likely to chafe. Canvas , rubber or plastic hose is ideal.
    Avoid sharp bends in rope to minimise uneven stretching.

ROPE STRENGTH REDUCTION (APPROXIMATE)

Rope Topics

Fisherman's Bend, Round Turn, & Timber Hitch -- 30%
Bowline, Sheet Bend & Clove Hitch -------------- 40%
Reef Knot ----------------------------------------- 55%
Hard Eye Splice ----------------------------------- 10%
Soft Eye Splice ------------------------------------- 20%

MONKEY'S FIST

Rope Topics

      Originally made for a throwing line the Monkey's Fist is now often used for decoration. As a throwing or heaving line the fist needs a weight inside - traditionally a piece of lead. However for a light throwing line a golf ball is a suitable alternative.
     A 3 - 10 mm diameter line is suitable and about 20 M will be needed. Before starting the knot seal the ends with heat or mask both ends. Once a basic knot is created from the diagram insert the chosen weight into the centre and then tighten the knot evenly and bit by bit.
    There are many options for finishing off - splicing, whipping or simply cutting the line and pull it through until the cut end just disappears

ROPE MAT

Rope Topics

Items Needed
30M of 12mm Rope
or
20M of 8mm Rope

Masking Tape
Chalk
Sail Needle
Whipping Twine

1. Draw this pattern on the floor - 70 X 50 cm for 12mm rope or 50 X 30 cm for 8mm rope

2. Mask the rope ends and fasten an end to the floor (Top Left) & follow the pattern

The Finished Mat

3, 4, & 5. Take care to go over & under each strand as shown. Masking a few places to the floor for the first circuit makes then job easier.

5. When back at the starting point continue the pattern for another 3 plys

When the fourth ply is back at the start point pull the mat into the required shape. Turn it upside down and cut the rope ends; then stitch the ends to the adjacent ply. Place the whole mat under something heavy for a few days to flatten it.

ROPE STRENGTHS

Rope Topics

AVERAGE BREAKING LOADS IN Kg

	DOUBLE BRAID			3 - STRAND		3 STRAND OR 8 STRAND PLAITED
ROPE SIZE (MM)	100% POLYESTER	VECTRAN CORE	HMPE (Spectra/ Dyneema) Core	NYLON	SILVER (Polythene)	POLYPROPYLENE
2	--	--	240	--	--	--
3	--	550	350	--	110	--
4	350	700	570	320	210	250
5	610	1200	920	--	265	--
6	900	1500	1500	740	370	590
8	1300	3000	2750	1320	610	1040
9	--	--	3500	--	760	--
10	2800	5200	4150	2040	930	1530
12	3200	6700	5530	3000	1240	2170
14	4150	10400	7600	4020	1410	2990
16	4580	11900	9360	5200	2080	3700
18	5350	14200	12400	6570	2540	4720
20	5800	16400	15200	6570	2540	4720
22	6100	20200	18700	9800	3680	6820
24	6500	23200	20700	11800	4310	7970

Rope Topics

SPECIAL PURPOSE KNOTS

ROLLING HITCH
To attach a line to a chain, spar or other rope to allow a lengthwise pull to be applied. Note that the pull direction is towards the double turns and the knot should be drawn tight and the pull exerted gradually.

CLOVE HITCH
To tie a line to a ring or spar - but not ideal as it can come undone with a staedy rotating pull and can jam under strain. Best used for a short term temporary connection.

SHEET BENDS
To join 2 ropes together - even when different sizes. The double sheet bend is more secure and is usually best for large diameter ropes, large diameter differences or different materials.

OTHER REFERENCES

Rope Topics

There exists an excellent reference called "Pocket Guide to KNOTS & SPLICES" by Des Dawson. It contains very clear colour diagrams and very easy instructions to making over 80 knots and splices.
The ISBN is 85648 695 8

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