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INTRODUCTION: ROPE FORMATION.
KNOTTING is an ancient device with which very early inhabitants of this earth must have been acquainted. From the beginning, mankind must always have used some kind of knot to join animal sinews, plant fibres, or hide strips which, in ancient days, were the prototypes of the varieties of cordage now employed.
A large number of knots has been invented by the skill of man, and on their strength and correct tying depend the lives of thousands and thousands of workmen—seamen, building trade operatives, etc., day by day. The importance of being able to make the knot best suited for the occasion both rapidly and correctly may come in a new light to some when it is pointed out that both lives and property have over and over again been sacrificed to ill-made knots; and this little volume is put forward in the belief that few things better repay the workman's time and trouble in learning than the manipulation of ropes and cordage.
Cordage is used almost daily by everyone in some form or other, but comparatively few can handle it methodically. Men break their nails and teeth gnawing at their own knots endeavouring to untie them, and time and material are wasted. Time spent in learning a few of the simple bends and hitches, reliable under strain and easy to unbend when the strain is released, would never be regretted. It is not necessary for a landsman to learn all the numerous uses to which rope is put, but a knowledge of common "bends" is an inestimable convenience, if not a necessity.
The security of a knot ought not to be, as many seem to think, in the number of turns or hitches in its composition, but in the efficacy of the nip. A "bend" or "hitch" must be so formed that the part of rope under strain nips some portion of the knot, either against itself or the object to which it is attached; and in learning a bend, or impressing it upon one's memory, it will be found most helpful to notice particularly the nip of each separate one as it is studied.
Rope, though usually of hemp, is made of other materials for certain purposes. Coir rope (cocoanut fibre), being light and buoyant, is useful for warps, rocket lines, life-buoy lines, and drift-nets. Manilla grass is adapted for reef points, yachts' hawsers, and wherever tar would be injurious. Hide is required for wheel-ropes, or where great strength with pliability and small circumference is needed. Cotton is serviceable for fancy work, etc. The "yarns" are formed by twisting the hemp right-handed; the "strands," by twisting or laying up the yarns left-handed; and the rope, by laying up the strands right-handed.
Three ropes laid up left-handed form what is known as a cable-laid rope; four-stranded ropes are laid round a heart. Ropes are sometimes laid left-handed, but if the strands are to be laid left-handed the yarns are laid right-handed. If the parts of hemp, etc., be twisted more than is necessary to hold them together, strength is lost. Upon following the course of a yarn in a rope it will be found that, by this alternate laying, it runs nearly straight with the direction of the rope's length.
A three-stranded rope will bear a greater strain in comparison with its size than any other of the same material; cable-laid ropes and four-stranded ropes are, roughly speaking, about one-fifth weaker. Rope is measured by its circumference, and is laid up in lengths of 113 fathoms, sizes varying up to 28 in.; but it is not usually made up in coils when the size exceeds 5 in. Very small ropes are distinguished by their yarns rather than their size; thus sailors speak of nine-, twelve-, and eighteen-yarn stuff, which is commonly called "seizing stuff."
If the fibres of which a rope is composed were laid parallel to one another and fastened at the two ends, the combined strength of these fibres would be utilised to the full; in other words, they lose strength by being twisted or "laid up." But, on the other hand, the length of the fibres being at most but a few feet, their usefulness in this state is very limited, and the inconvenience of using them so is prohibitive. For this reason the fibres are first twisted into "yarns"; these, again, are laid up into "strands," a strand being formed of several yarns; and, finally, three or more strands are formed into a rope. As twisting diminishes the strength of a rope, it is important that the yarns be carefully laid up, so as to bring an even strain on every part. It should not be laid up too hard—that is, it should only have sufficient twist in it to prevent the fibres from being drawn out without breaking.
"Hawser-laid" ropes are made of three strands laid right-handed, or "with the sun," as it is termed. "Shroud-laid" are made of four strands laid right-handed. A "cable-laid" rope is made of three hawser-laid ropes laid up left-handed, and therefore contains nine strands. Obviously the size of a rope is regulated by the quantity of yarns composing the strands, and not by the number of strands that it contains.
With regard to the weight of ropes, it may be said that ropes of all kinds are usually measured by their circumference. The weight of clean, dry, hemp rope in pounds per fathom is one-fourth of the square of the circumference in inches; for example, a 3-in. hemp rope (about 1 in. in diameter) weighs ¼ x 32 = 2¼ lb. per fathom (6 ft.). A flat hemp rope, with a width of about four times the thickness, weighs in pounds per fathom about twice the square of the circumference in inches; for example, a 3-in. by ¾4 in. flat hemp rope will weigh about 2 x 7 = 14 lb. per fathom.
Round wire ropes weigh in pounds per fathom seven-eighths of the square of the circumference in inches; for example, a 3-in. wire rope weighs about 7/8 x 32 = 7 7/8 lb. per fathom. A flat wire rope weighs in pounds per fathom ten times the sectional area in square inches; for example, a flat wire rope, 3 in. by ¾4 in. = say 2 sq. in. area, will weigh about 10 x 2 = 20 lb. per fathom.
The maximum safe load on a rope depends on many circumstances, such as quality, age and dry ness of rope, nature of load, mode of lifting, etc Approximately, the safe load on a new hemp rope in hundredweights with direct lift is three times the weight in pounds per fathom. On a sound old rope fall one-half the square of the circumference is sufficient load. A Bessemer steel wire rope will safely carry in hundredweights three times the square of its circumference in inches, and a crucible steel wire rope four times the square of its circumference. For hemp ropes the minimum diameter of sheave should be circumference of rope + 2, and for wire ropes the diameter of sheave in inches should be equal to circumference of rope in sixteenths.
The principle of rope making is very readily shown by holding the ends of a piece of twine or whipcord, about a foot long, in the hands and twisting it so as to increase the lay. If the twine be now slackened by bringing the hands nearer to one another, a loop will first form in the middle of the twine, and it will continue to twist itself up into a compact cord which will not unlay, as the tension to which the strands have been subjected causes friction between them, which holds them together. In other words, the tendency of each part singly to unlay, acting in opposite directions, is the means of keeping them together when joined.
Some very interesting experiments were made by Réaumur, the purposes of which were to ascertain the loss of strength occasioned by laying up the fibres of various substances, one or two of which are given.
1. A thread, consisting of 832 fibres of silk, each of which carried 1 dram and 18 grains, broke with a weight of 5 lbs., though the sum of the absolute strength of the fibres is 104 drams, or upwards of 8 lbs. 2 oz.
2. Three threads were twisted together, their mean strength being nearly 8 lbs. They broke with 17½ lbs., whereas they should have carried 24 lbs.
These experiments prove that though convenience and portability are gained by twisting the fibres, there is a great loss in the strength of the resultant rope.
In speaking of the size of a rope, the circumference and not the diameter is alluded to. Thus, a three-inch rope would be slightly less than an inch in diameter.
In practising knotting it is as well to use a tolerably firm material, such as whipcord, for small common knots, or, still better, line used for sea fishing. Either can be tied up and undone over and over again without injuring it, which is not the case with twine; it is also more easy to see which way the parts of a knot lie in the harder material, and then to find out whether the turns are properly made or not. For more complicated knots, particularly those where the strands of the rope have to be unlaid to form the knot, such as a wall knot (p. 66) or a Matthew Walker (p. 70), it is advisable to use three strands of fishing line, each about a foot long. If a "seizing" (a seizing is shown in Fig. 57, p. 51) be put round them in the centre, so as to hold them firmly together, a good representation of a rope with the strands unlaid ready for working is obtained. A knot can be made and unmade as often as required in this way, without detriment to the strands; but the strands of a rope, owing to their loose nature, will seldom bear knotting more than once or twice. If desired, the knots can be made as above described and kept for future reference. In string also it is better to use hard laid stuff at first, but when these matters are thoroughly understood knots can be made on any sort of cordage without difficulty.CHAPTER 2
SIMPLE AND USEFUL KNOTS.
THE simplest knot that is made is the overhand knot (Fig. 1). It is very useful, and forms a part of many other knots. To make it, the standing part of the rope—that is, the main part in opposition to the end—is held in the left hand, and the end of the rope is passed back over it (whence its name) and put through the loop thus formed. It is used at the end of a rope to prevent the strands unlaying, and sometimes in the middle of a rope as a stopper knot. If the end of the rope is passed through the "bight" or loop two, three, or more times before hauling it taut, the double, treble, or fourfold knot, A (Fig. 2), is obtained. This is a larger knot than Fig. 1, and is often used on the thongs of whips, being then termed a blood knot. B (Fig. 2) shows the knot hauled taut. Fig. 1 also goes by the name of the Staffordshire knot, as it forms the insignia of the county. A Flemish or figure-of-eight knot is shown by Fig. 3. To make it, pass the end of the rope back, over, and round the standing part, and up through the first bight. The Flemish knot is used for much the same purposes as the preceding knots, but is rather more ornamental.
The bight of a rope is the loop formed when a rope is bent back on itself, in contradistinction to the ends.
The conditions under which the ends of two pieces of cordage have to be joined together are various, and several methods are brought into requisition; but it is always of considerable importance that the most suitable knot be employed in each case. The value of some knots consists in the rapidity with which they can be made, of others in the readiness with which they can be undone; but it is an essential that the knot holds firmly and does not slip when once hauled taut.
The commonest knot for joining the ends of two ropes, and probably the knot that is most often made, is the sailor's, true, or reef knot (Figs. 4 and 5). When correctly made it is as perfect as a knot can be. It can be made and undone with equal rapidity, and is very secure when taut. Its one disadvantage is that it will not answer when made with ropes of different sizes. as it then slips and comes adrift, but where the two pieces of cordage are of the same size it is most secure and reliable, the strain being equally distributed on every part. It requires a little practice to make it properly. To do this, take an end in each hand and lay one over the other, the right end being undermost; bring the left-hand end under the standing part of the right end, as shown at A (Fig. 5), and over the end at B, round it, and up through the bight at c. The key to the knot is the putting of the right end under the left when the two ends are crossed at the beginning of the knot, as the left-hand end then comes naturally first over and then round the other rope, and the ends lie parallel with the standing parts, as at [??]A (Fig. 4).
If the ends are not passed correctly, a granny, lubber's, or calf knot results. This is shown in Fig. 6. Though at first sight this seems to be a good knot, yet it is not so in reality, and when any strain comes upon it it slips and becomes useless. Fig. 7 is a granny knot, as it appears when hauled upon. It is considered a very lubberly thing to make a granny knot, and readers should practise until they can make a true knot rapidly and with certainty in any position.
The sailor's knot is invariably used for reefing sails, the ease with which it can be undone making it very valuable for this purpose. It is only necessary to take hold of the two parts on each side just outside the knot and bring the hands together, and the loops slip over one another, as in Fig. 4, and the knot can be opened at once.
This knot has a curious peculiarity which is not generally known. If the end of one of the ropes is taken in one hand and the standing part of the same rope in the other, and both are hauled until the rope is straight, the knot becomes dislocated, so to speak, and the rope not hauled upon forms a hitch, B (Fig. 4), round the other part. This property was the secret of Hermann's celebrated trick, "the knotted handkerchiefs." After the handkerchiefs, knotted together at the corners, were returned to him by the audience, under pretence of tightening the knots still more, he treated each knot as has been described. The knots seemed firm, but really were loosened so that a touch with his wand separated them easily.
The common bow or rosette knot is a modification of the sailor's knot. The first part of the process of making it is the same, but instead of passing one end singly over and under the other, as in the sailor's knot, both ends are bent back on themselves, and the double parts worked as before. Care must be taken to pass these doubled ends exactly as those described in the sailor's knot, or a granny bow will result. Some persons' shoes always come untied, the reason being that they are tied with granny instead of true bows.
Another way of joining the ends of two pieces of cordage is shown in Fig. 8. This is merely an overhand knot, made with two ropes instead of one. Sometimes it is called an openhand knot. It can be made very quickly, and there is no fear of its slipping, but if there is much strain put upon it the rope is very apt to part at the knot, in consequence of the short "nip," or turn, that it makes just as it enters the knot.
Fig. 9 shows the weaver's knot partly made, and Fig. 10 the same knot completed, but not hauled taut. Weavers call this the "thumb knot," as it is made over the thumb of the left hand, and is used by them in joining their "ends" as they break. The rapidity with which they make the knot, snip off the ends, and set the loom going again is wonderful. Netters use this knot to join their twine, and it also forms the mesh of the netting itself, though, of course, it is then made in a very different way. In making the weaver's knot, the two ends to be joined are crossed in the same way as in the sailor's knot, placing the right end under, and holding them with the thumb and finger of the left hand at the place where they cross. The standing part of the right-hand rope is then brought back over the thumb and between the two ends, as shown in Fig. 9. The end A is then bent down over it, and held with the left thumb, while the knot is completed by hauling on B.
An excellent way of joining two ropes is illustrated by Fig. 11. The ends are laid alongside one another, overlapping each sufficiently to give room for the knot to be made. The double parts are then grasped in each hand and an overhand knot is formed, which is made taut by hauling on both parts at once, as if the knot were single.
Though the above is the easiest way to make the knot, it is not available where the ropes are fast. In this case a simple knot is made on the end of one rope, but not drawn taut. The end of the other rope is passed through the bight of the first, and a second loop formed with it alongside the first. The knot is closed by drawing the two ropes as before. This is in every way an excellent knot, and very secure.
Fig. 12 shows the ends of two ropes joined by means of a Flemish knot. It does not require much description, and is made after the manner of the knot last described.
Excerpted from Handbook of Knotting and Splicing by Paul N. Hasluck. Copyright © 2005 Dover Publications, Inc.. Excerpted by permission of Dover Publications, Inc..
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