ROPE-MAKING. The fibres of hemp which compose a rope, seldom exceed in length three feet and a half, at an average. They must, therefore, be twined together BO as to unite them into one; and this union is effected by the mutual cireum torsion of the two fibres. If the com pression thereby produced be too great, the strength of the fibres at the points where they join will be diminished; so that it becomes a matter of great conse quence to give them only such a degree of twist as is essential to their union.
The first part of the process of rope making by hand, is that of spinning the yarns or threads, which is done in a man ner analogous to that of ordinary spin ning. The spinner carries a bundle of dressed hemp round his waist ; the two ends of the bundle being assembled in front. Having drawn out a proper num ber of fibres with his hand, he twists them with his fingers, and fixing this twisted part to the hook of a whirl, which is dri ven by a wheel put in motion by an as sistant, he walks backwards down the rope-walk, the twisted part always serv ing to draw out more fibres from the bun dle round his waist, as in the flax-spin ning wheel. The spinner takes care that these fibres are equably supplied, and that they always enter the twisted parts by their ends, and never by their middle. As soon as he has reached the termina tion of the walk, a second spinner takes the yarn off the whirl and gives it to another person to put upon a reel, while he himself attaches his own hemp to the whirl hook, and proceeds down the walk. When the person at the reel begins to turn, the first spinner, who has complet ed his yarn, holds it firmly at the end, and advances slowly up the walk, while_ the reel is turning, keeping it equally tight all the way, till he reaches the reel, where he waits till the second spinner takes his yarn off the whirl hook, and joins it to the end of that of the first spinner, in order that it may follow it on the reel.
The next part of the process previous to tarring, is that of warping the yarns, or stretching them all to one length, which is about 200 fathoms in full-length rope-grounds, and also in putting a slight turn or twist into them.
The third process in rope-making, is the tarring of the yarn. Sometimes the yarns are made to wind off one reel, and, having passed through a vessel of hot tar, are wound upon another, the super fluous tar being removed by causing the yarn to pass through a hole surrounded with spongy oakum ; but the ordinary method is to tar it in skeins or hanks, which are drawn by a capstan with a uni form motion through the tar-kettle. In this process, great care must be taken that the tar is boiling neither too fast nor too slow. Yarn for cables requires more tar than for hawser-laid ropes ; and for standing and running rigging, it requires to be merely well covered. Tarred cor dage has been found to be weaker than what is untarred, when it is new ; but the tarred rope is not so easily injured by immersion in water.
The last part of the process of rope making, is to lay the cordage. For this purpose two or more yarns aro attached at one end to a hook. The hook is then turned the contrary way from the twist of the individual yarn, and thus forms what is called a strand. Three strands,
sometimes four, besides a central one, are then stretched at length, and attached at one end to three contiguous but separate hooks, but at the other end to a single hook ; and the process of combining them together, which is effected by turning the single hook in a direction contrary to that of the other three, consists in so regulat ing the progress of the twists of the strands round their common axis, that the three strands receive separately at their opposite ends just as much twist as is tak en out of them by their twisting the con trary way, in the process of combination. Large ropes are distinguished into two main classes, the cable-laid and hawser ' laid. The former are composed of nine strands, namely, three great strands, each of these consisting of three smaller se condary strands, which are individually formed with an equal number of primi tive yarns. A cable-laid rope eight in ches in circumference, is made up of 333 yarns or threads, equally divided among the nine secondary strands. A hawser laid rope consists of only three stands, each composed of a number of primitive yarns, proportioned to the size of the rope; for example, if it be eight inches in circumference, it may have 414 yarns, equally divided among three strands. Thirty fathoms of yarn are reckoned equivalent in length to eighteen fathoms of rope cable-laid, and to twenty fathoms hawser-laid. Ropes of from one inch to two inches and a half in circumference are usually hawser-laid ; of from three to ten inches, are either hawser or cable laid ; but when more than ten inches, they are always cable-laid.
Dr. Ure gives the following relative strength of cordage, shroud-laid :— A test trial, of Manilla and Kyanized American rope, was had at Griffey's Foundry, Cincinnati, which resulted most favorably to the American manufacture. A small Manilla rope, of the best quality of Boston make, was first tried, and was broken, after sustaining a weight of 1520 pounds. The Kyanized rope, invented and manufactured by J. T. Crook & Co., of Maysville, was then put to the same test, and sustained a weight of 2,320 pounds beforeparting. A second trial was then had of the same size of Manilla rope, which sustained a weight of 2,200 pounds. A second trial was then also had of the Kyanized rope, and sustained a pressure of 2,410 pounds. Two trials were then had with a larger size of the Manilla rope, manufactured by Bonte, which parted first at 2,840 pounds, and on the second trial at 2,796 pounds. One trial was then made with the Kyanized rope, which sustained the weight of 3,220 pounds before parting. The average dif ference in favor of the Kyanized unrotted hemp rope being in the first trials 500 pounds, and in the last trial 400 pounds. This shows that the Manilla rope, which has always been considered the best that was ever used, is flir inferior to the Ame rican unrotted hemp rope. The Kyaniz ed rope is manufactured from the unrot ted hemp, and is not only the strongest rope made, but by the chemical process of Kyanizing, is by far the most durable. (See HEMP.)