The Sea Cadet, No. 3, Vol. 3, November 1945

IT might have been an Ancient Greek, or it might have been an Ancient Egyptian, who discovered that if a bunch of fibres were twisted to­gether it gained strength. But whoever it was, he certainly “started something.” He started rope. For over a thousand years the main features of rope have not changed. The best rope in the world is made from Italian hemp, which is clean and flexible and very strong. It has, of course, been scarce lately, but it will, owing to merit alone, soon recapture its former market. In the struggle to attain Empire self- sufficiency many experiments were made, the best of them resulting in two types of rope, New Zealand hemp and sisal. New Zealand hemp has many of the points of manila, but sisal, which is made from the fibre of the agave plant, a spiky-looking bush grown mostly in Tanganyika, Kenya and Por­tuguese East Africa, is not favoured at all in the Navy. It is alight golden colour, very bristly in appearance and fairly smooth to the touch, but slips too easily when wet. The largest ropes, which are eighteen inches in circumference, and need a pull of 108. tons to break them, are made of manila fibre and are used for deep-sea towing because they are heavy and elastic. This means that the tug towing a large vessel in a heavy sea has a heavy length of rope out which acts as a spring taking up the jerks due to the pitching of both vessels. These large ropes will stretch sixteen feet in each hundred, a great advantage when dealing with in­termittent strains. A rough rule will tell a sailor the strength of a rope. English ropes are always graded by circumfer­ence, and the formula is: square the circumference in inches and divide by three. The answer is the breaking strain in buttons, a good sailor will only use a load of one-sixth of the breaking strain. This is shrewd, sound, commonsense, as a load on a rope maybe sub­jected to a jerk and this jerk will double the strain on the rope for an instant. Ropes are made in long, narrow sheds called ropewalks, the prepared fibre 70 being fed into a machine which by a system of rollers gently pushes the fibres together into a soft, narrow line without twist. It is then coiled into metal cans. These are accurately weighed in order to get uniformity of size in the finished yarn. Then the fibre is passed from the cans through three consecutive mach­ines, which stretch it and clean it up. Next it is spun, the twist binding all the separate fibres together, which naturally gives the friction between fibres upon which the strength of a rope so much depends. If these “yarns,” as they are called, are to form a tarred rope they are then run through a vat of boiling creosote mixture and reeled onto drums. These drums contain generally a ton of spun yarn, and are laid apart for fifteen months seasoning. After this the yarn is wound off onto bobbins and laid up or twisted with other similar yarns to form strands. Twenty to forty yarns form a strand, according to the size and type of rope required. Now three, or sometimes four, strands are taken and by means of a By JOHN COLLEY
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