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Practical Knots and Ropework
By Percy W. Blandford
Dover Publications, Inc.Copyright © 1980 Percy W Blandford
All rights reserved.
The first ropes were probably natural creepers, fronds and climbing plants found in the jungle, but ropes made of twisted fibers were believed to have been made in about the year 3000 BC by the Ancient Egyptians. They used papyrus leaves and fibers from hemp, flax, alfalfa grass and date palms. In the thousands of years since then, all kinds of fiber and other natural products have been used, even human hairs.
In more recent years the natural materials have been superseded by synthetic materials and nearly all cordage in the future, from fine string to the largest ropes, will be made of man-made filaments instead of the natural fibers which have been the mainstay of the ropemaker's art for nearly five thousand years.
Some of the natural fibers that were used up to the coming of man-made materials may still be found and used, so anyone interested in knotting should be aware of them. These include hemp, which makes a strong rather rough rope, and flax, which was sometimes mixed with it, but not used alone.
Italian Hemp. Italian hemp was considered the strongest, being smoother and easier to handle. Until the coming of synthetics, this was the first choice for heavily-loaded and frequently handled ropes.
Manila. Manila looks like Italian hemp and is of about the same strength and smoothness, but it is made from the fiber from plantain leaves.
Cotton. Cotton was used where supplies were plentiful to make a smooth easy-running rope with a white appearance when new, although it soon darkened with dirt.
Sisal. Sisal became more generally used towards the end of the use of natural fiber in ropemaking as it was cheaper. This came from the fiber of aloe leaves. It is almost as strong as hemp, with a light brown color and a rather rough surface. It may still be used for string as well as occasional ropes.
Coir. Coir rope was made from the fibers of coconuts and was sometimes described as grass rope. Coir ropes are only about one-quarter the strength of the same size hemp rope, but coir will float, where all other natural fiber ropes soon sink. It is also more elastic, so coir ropes of considerable size were used afloat for mooring lines and towing.
Synthetic fiber ropes were developed during World War II and their development continues with new materials and new ways of forming them into ropes being discovered. All these ropes have a chemical base and some have extremely ponderous chemical names, so it is more likely that rope making materials will be described by trade names. This is satisfactory, except that it may not be immediately obvious that two very different trade names indicate the same materials by different rope makers. The technical literature of the makers will usually give the chemical name.
One of the best known names is nylon, which is a polyamide polymer. Of the synthetic ropes, this is the material with the greatest stretch. It is a very elastic, so it cannot be used where something has to be pulled tight. Of the synthetics, it is the only one that will absorb water, although this is only to a small extent and much less than any of the natural fibers.
The synthetic ropes that have taken over from hemp and manila, with strength at least twice as great are polyethylene terephtalate. Some of the trade names are Dacron and Terylene.
A lighter rope that will float is made from polypropylene. This is stronger than any natural fiber rope, but its ability to float makes it the modern alternative to coir.
All of the synthetic rope materials have much better resistance to abrasion than natural fibers. Their strength and resistance to water absorption make them much better for use afloat, as they can be stored wet without risk of rot. Natural fiber ropes were treated with proofing solutions or tarred, but many ropes were weakened by rot before they wore out. Natural ropes are weaker when wet. Synthetic ropes do not have their strength affected by moisture.
Natural fibers are short. This means that a rope of any size is made up of a large number of short pieces and their ends project to give the hairy feel that became associated with rope. Synthetic ropes are made from continuous filaments, which may go the whole length of a rope, meaning that it can be made absolutely smooth. Much synthetic rope is smooth, except for the very occasional broken filament. Some users prefer rope with the hairy traditional surface and synthetic ropes can be made to have this sort of exterior.
Traditionally rope was made three stranded. In a section containing three round strands, each strand touches the other two and the section cannot go out of shape (Fig. 1-1A). With a greater number of round strands this condition does not apply again until seven strands are used (Fig. 1-1B). The seven-strand formation is used for wire ropes, but it is unlikely to be met in fiber ropes, although some French rope is made this way. There have been four-strand ropes, but to keep their shape there is a smaller straight central strand (Fig. 1-1C).
Nearly all traditional three-strand rope is laid up right-handed and may be called hawser-laid. If you look along the rope, the strands twist away from you towards the right (Fig. 1-1D). Rope may be laid up left-handed for special purposes. Slings for lifting a load may have opposite ropes twisted in opposite ways, as there is then less risk of them twisting around each other at the crane hook.
Four-stranded rope may be described as shroud-laid and is normally laid up right-handed, but this formation is now rare.
With the need for bigger diameter ropes, there is a limit to what can conveniently be made three-stranded. Cable-laid ropes were made with three ropes laid up right-handed and twisted together left-handed (Fig. 1-1E). This kept the value of the retention of the cross-sectional shape due to the three formation—in effect a nine-strand rope.
In a rope the fibers or filaments are twisted together to form yarns (Fig. 1-1F). The yarns are twisted together to form strands (Fig. 1-1G), then the strands are twisted together to make the rope. At each stage the twist is to tighten the previous stage, and so the rope retains its construction.
For many thousands of years ropes were made by hand. There were simple contrivances to guide the rope and to apply the twist, but the work was done by a man walking backwards and adding fibers to build up the rope. Although some of the completed rope might be rolled, the method of construction really dictated a very long straight ropewalk, and the presence of these may be located by the lanes and districts that have retained the name. Later rope was made mechanically and even more modern machinery producing three-strand rope uses similar techniques to the hand ropemaker.
Mechanical methods have brought other rope formations. In particular there are braided or plaited ropes, in which the outer casing has yarns woven across each other diagonally, so there is a pattern of yarns spirally around in both directions. This makes a smooth flexible rope. The heart may be made up of many yarns laid lengthwise, although some braided rope is made around a three-stranded rope heart. Another type has one braided casing around another. There may be single yarns interlaced, but it is more usual for groups of yarns to be taken around together (Fig. 1-1H).
Traditionally rope has been described by its circumference. This has meant the need for anyone only occasionally using rope to visualize this in relation to its thickness. The diameter is slightly less than one-third of the circumference, so a 1-1½ inch circumference rope is not quite ½ inch thick.
With a move towards metrication, a tendency has also come to describe a rope size by its diameter. Fortunately there is a convenient relationship between circumference in fractions of an inch and diameter in millimeters. If a circumference is expressed in one-eighths of an inch, that is the same number as the diameter in millimeters. For instance, a 2 inch circumference is 16 x 1/8-inch, so the diameter is actually 16 millimeters. Or 1 1/8-inch circumference (9 x 1/8 is millimeters. The traditional measurement of length was the fathom (6 feet), but it is now more common to measure in feet or meters.
The strength of the rope is greatest when it is pulled straight. If it is taken around a sheave or pulley, some strength is lost. The larger the diameter of the pulley, the less will be the loss of strength. There is obviously a practical limit to the size a pulley can be, particularly if it is part of the rigging of a sailing boat, but taking the rope around a small curve should be avoided if a larger curve can be substituted.
There is similar reasoning in the formation of a knot. If the rope is tightly kinked to make a particular knot, it will be weakened more than if a knot with easier curves is used. However, knotting is a compromise. If the knot is not to slip, there have to be some tight turns, but sometimes there can be a knot with many moderate turns as a stronger alternative to one with fewer sharply bent turns. In any case, whatever is done, the knot will always be weaker than the body of the rope. If tested to destruction, the break often comes where the rope enters the knot.
Another knotting problem with modern synthetic ropes is the smoothness compared with the natural fiber ropes. The many thousands of knots developed over centuries have been intended for the hairy type of natural fiber ropes. Some knots that depended on that friction are less successful with smooth newer ropes. In some cases older knots have had to be discarded and replaced with new ones. In other cases older knots have been modified with extra turns to provide grip.
There have been some excellent knotting and ropework books produced, mainly from the days of square-rigged sail when there were miles of ropes on a ship and a great many situations needing special knots, splices and other treatments. Although these books can provide plenty of interest and are good sources of information for anyone with some knowledge of the subject, it would be unwise to take some of those knots and try to apply then today. They were all intended for natural fiber ropes, and many of these ropes on board ship were very coarse and rough, so they provided plenty of friction in a knot. If some of them were used on synthetic cordage, they would probably be unsafe. Modern knotting needs are not as extensive. The utility knotting requirements of the average person may be few, but many of the older knots and other rope treatments can be adapted to modern needs, either for practical purposes or as a form of decoration.CHAPTER 2
The End of a Rope
Because of its method of construction, a rope laid up in three strands may start to unlay into its separate strands, yarns and fibers if nothing is done to a cut end. The effect may not be as serious with braided rope, but that will also start to separate. This tendency is much greater with synthetic ropes than natural fiber ones. Some synthetic ropes will unlay for a considerable length if released after cutting, and it is almost impossible to lay them up again satisfactorily by hand, so a piece of cow's tail may have to be cut off and wasted.
All of the common synthetic materials used for ropes will melt if heated. They will burn eventually if heating with a flame is continued for too long, but the first effect of heat is to melt the filaments. This can be a disadvantage in some circumstances as friction may generate heat across a rope to soften and melt it to a dangerous state. The ability to melt and fuse the filaments together by applying heat can be used to seal the ends of synthetic ropes. It may also serve as a test if you are uncertain about whether a piece of rope is synthetic or made from natural fibers. A flame applied to the end will char natural fibers, but synthetic fibers will melt.
Few tools are needed for knotting and general ropework, but a sharp knife is important. For fine line, such as thread and cord, a pair of scissors can be used, but for the majority of ropes, a knife is the usual cutter. Almost any knife will do, but riggers, sailors and others who work with rope prefer a thin-bladed type of knife with a handle made from a piece of wood on each side of the blade extension. These types are very similar to the knives used by a butcher. A thin blade about 5 inches long with a good edge will deal with most ropework (Fig. 2-1A). It is also useful to have a spike for picking knots open, getting fancywork into shape and tucking splices. This may be a plain tapered marline spike (Fig. 2-1B), and a rigger often has his knife and spike in the same sheath, which hangs low in his belt (Fig. 2-2). The spike and the knife may have holes so lanyards can be attached as precautions when working aloft. With a light cord lanyard around the neck there is no risk of dropping the tools which could be lethal to anyone below.
Some other spikes are described later, but there is no need to buy a special spike for most knotting because any pointed tool can be used. It is convenient to have a handle on the spike and one sold as an awl or ice-pick may be used.
A ropeworker or sailmaker may call a finer pointed tool a pricker or a stabber. Any of these may be useful in knotting. Some clasp knives have a spike folded on the back. This is safe stowage and convenient for carrying in a pocket. At one time wood and bone were used for spikes as these were considered less hard on rope fibers, but it is common now to only find wood used for very large splicing spikes called fids.
Those concerned with ropework frequently may have an electrically heated knife for cutting and sealing synthetic ropes in one action. It may be a tool something like a soldering iron, but with a knife instead of a bit, or a static bench unit through which the rope is passed and the cut made by pulling a handle. If rope is being taken off a reel, this seals what is left as well as the piece being cut off, but most of these tools leave a rough end as the melted material hardens. There will have to be some other treatment before putting the rope into use, particularly if the rope has to pass through a hole or a pulley block.
It is possible to heat any knife and use it for cutting and sealing, but there is always the danger of overheating, which will draw the temper of the steel. If an old knife can be kept for the purpose, the risk of the steel being softened may not matter, but once the temper of a blade has been drawn, it will not keep its edge when used for ordinary purposes.
Most users of rope will find it more convenient to cut and seal in two stages. Most ropes can be cut by slicing with a knife. Very hard, tightly-laid ropes can be cut with a fine metalworking hacksaw if a knife will not work. Very thick ropes were cut with a hatchet, but for most ropes in normal use it is unlikely that the user will have to resort to this method.
If synthetic rope is to be cut, it is advisable to put on a stopping. This temporary whipping may be adhesive tape or a turn or two of thread or any light line on each side of the intended cut (Fig. 2-3A) to prevent unlaying. Sealing is often done with a match flame. This is convenient, but it is a dirty flame that will blacken the rope end. The flame from a cigarette lighter is cleaner and burns longer. For normal use, hold the end of the rope over the flame and turn it to evenly heat the extreme end (Fig. 2-3B). Quite a brief heating will usually be enough, but make sure there are no stray filaments that have curled away from the flame.
Remove the flame and moisten the first finger and thumb of the other hand, then quickly roll the end of the rope between finger and thumb (Fig. 2-3C). With a little practice, a rounded end with a slight taper can be produced. This method is used for laid or braided rope. Moistening your finger and thumb prevents burning yourself and stops the softened filaments from sticking to your skin. Be ready to lick your fingers a second time. If the end is not to your satisfaction, it can be heated and rolled again. Be careful not to heat the rope further along, or you may get fibers set rigidly fused together where you wanted the rope to remain flexible. You cannot undo the effect of heating and fusing.
Excerpted from Practical Knots and Ropework by Percy W. Blandford. Copyright © 1980 Percy W Blandford. Excerpted by permission of Dover Publications, Inc..
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