ROPE MAKING 



liiil'K MAKING. 



Th* aiwurth of twUted cordage has been made the subject of 

 arum aperiwenta. IWeuinur, early in the last century, found 

 Mb* wen-made mall hempen cord broke in different places with 5S, 

 * 7 and 7S Iba.. ita mean breaking weight being 85 lU. ; while th.- 

 three atnunU of which it wa oompoeed bore 294. :i:)4. and 35 11-. 

 rvpectively ; to that the united absolute utrength of the strands wan 

 Wlb*. although the average real strength of the rope was only 

 5 Iba, Jwwiag a lo of strength from twisting equal to 33 Ibs. It 

 appears that the cord and by Reaumur was of very unequal quality, 

 ai' another portion of it broke with 72 Ibs., while iu strands bore 

 aenaratoly 90, 88, and 80 Iba. ; which shows the diminution of strength 

 him twisting to hare been from 84 to 72 Ibs., the loss being in thfa 

 in.Unoc only U Iba. The Utr experiments of Sir Charles Knowle* 

 (n^f^f. a diminution of strength nearly equal in amount to the first- 

 mentioned of Reaumur. He found a white or untarred rope of 

 81 inches in circumference break, pn an average of several trials, with 

 4455 Iba. ; while the aggregate strength of its yarns, which were 72 

 in number, and bore on an average 90 Iba. each, was 6480 Ibs. ; the loss 

 Iwing equal to 1928 Iba., or about 30 per cent Duhamel endeavoured 

 to ascertain what degree of .twist would produce the most useful 

 fleet. He caused some ropes to be made, so that only one-fourth 

 of the length of the yarns was absorbed in twisting, instead of 

 the usual proportion of one-third. These ropes were tried in shipping, 

 and found to be lighter, thinner, and more pliant than those of tin; 

 ordinary make. Tin 1 following ittatemcnt shows the comparative 

 strength of ropes formed of the name hemp, and the same weight per 

 fathom, but twisted respectively to two-thirdn, three-fourths, and four- 

 nftha of the length of their component yarns : 



Orgm of twto. Weight borne in two experiments. 



4098 Ita. 4190 Ibs. 



4S50 ' C75J 



610S 7897 



The result of these experiments led Duhamel to try the practicability 

 of making ropes without any twist, the yarns being wr.ippcd round to 

 keep them together. These had great strength, but very little dura- 

 bility, the outer covering soon wearing off, or opening at bendiugs, BO a* 

 to admit water, and occasion the rope to rot. But while such untwisted 

 keina of rope-yarns, or mirage*, are unfit for most of the purposes to 

 which cordage is applied, they are used with advantage for the tackle 

 of great guns and some other purposes fur which the greatest strength 

 and pliancy are required. The usual reduction of length by twisting 

 is one-third ; this applies to liiroiul or Aarorr-laid ropes ; those which 

 are raMr-laid are further shortened, so that 200 fathoms of yarn are 

 required to make 120 fathoms of cable. Uopes formed in the common 

 wanner, with three strands, do not require a heart, or central strand 

 because the angles formed by the union of the three cylindrical strands 

 are no obtuse that the pressure of the operation of laying or closing 

 the rope causes the strands to fill them up completely ; but when 

 the number of strands exceeds three, a heart is essential to keep them 

 equidistant from the axis of the rope, and to fill up the vacuity thai 

 would otherwise be left by their not meeting in the centre. The heart 

 can however add very little to the strength of the rope ; as its fibres li< 

 much straighter than those of the outer strands, and, not being abl 

 to extend with them when the rope in stretched, arc soon pullet 

 asunder. The following simple rule for calculating the strength o 

 ropes is given by Kobison: Multiply the circumference of the rope 

 in inches by itself, and the fifth part of the product will express the 

 number of tons the rope will carry. For example, if the rope be 

 6 inches in circumference, 6x6= 36, the fifth of which is 7',, the 

 number of tons which such a rope will sustain. The following rules 

 for calculating the vtiyhl of cordage may also prove useful : To tiix 

 the weight of shroud or hawser-laid rojic, multiply the circumference 

 in inches by iUelf, then multiply the product by the length of the rope 

 in fathoms, and divide by 420, the product will be the weight in 

 cwt*. Kxample : to find the weight of a 6-inch hawser-laid rope 

 120 fathoms lone, 6x6 = 36x120= 4320, which, divided by 420 gives 

 the weight of the rope, 10 cwt. 1 qr. 4 Ibs. Again : to find the 

 weight of cable-laid cordage, multiply iU circumference in inches by 

 itself, and divide by 4. The product will be the weight, in cwts., o 

 a cable 120 fathonu long ; from which the weight of any other lengtl 

 may be readily deduced. Kxample : required the weight of a 12-incl 

 cable, 120 fathoms long; 12 x 12 = 144, divide by 4, and the product 

 3H, is the weight in cwU. 



Mr. Chapman, master ropemaker at Deptford Dockyard, in 

 treatise recently published on this subject, gives the following names 

 length*, and weights of certain kinds of rope or line as usually mad 

 in England: 



Dwpmllntu 



Lrngth. 



. 120 fathomi 



Hud Irsd linn . 

 ll.inl.ro' linos II tbnads 



20 



I ; 



Weight. 

 30 Ibs. 

 14 



u 



is 



4 

 1 



Kin. I.. 

 FUbing linen 



linn 



Length. 

 . 13 



Log line* 2* 



Marline ' 2 



Hewing twine 24 



Urefing twine 



Much of the cordage used on shipboard requires the process of 

 rt-ing before it is fitted for its work. This consists in binding a 

 mailer rope very tightly round a larger one, to preserve it from rot- 

 ing after friction. It is done as shown in fy. 4, where a horizontally- 



Fig. 4. Serving a Rope. 



stretched rope is being "served" or covered with spun yarns. A 

 mallet, having a concave groove on the side furthest from the handle, 

 is laid' on the rope ; two or three turns of spun yarn are passed 

 tightly round the rope and round the body of the mallet. A boy 

 passes a ball of yarn continually round the rope ; while a man winds it 

 on by means of the mallet, the handle of which serves as a lever to 

 enable him to strain every turn as tightly as possible. The yarn thus 

 appears like a screw whose threads pass almost transversely round the 

 rope. 



All the ropes hitherto described are round or cylindrical ; but flat 

 ropes are also made, chiefly for mining purposes. They are either 

 formed of two or more small ropes placed side by side, and united by 

 sewing, lapping, or interlacing with thread or smaller ropes ; or of a 

 number of strands of shroud-laid rope similarly united. In either case 

 it is necessary that the component ropes or strands be alternately of a 

 right-hand and left-hand twist, that the rope may remain in a quies- 

 cent state. The latter method of making flat ropes was first patented 

 by Mr. Chapman, in 1807 ; and he considered it to afford the strongest 

 possible combination of rope-yarns, his belts or flat ropes appearing to 

 be even stronger than xalntgn (which are skeina of rope-yarns without 



Fig, .'.. Flat-rope Making. 



any twist) of the same number of yarns. This seeming inconsistency 

 is occasioned by the imperfection of hand-spun yarns ; because if each 



