ROPE MAKING. 



4G7 



Rope- 



Mr. Chap- 

 man's expe- 

 riments on 

 tarred and 

 untarrcil 

 rope. 



From these results M. Duhrimel concludes, 1. That 

 untarred cordage in constant service is une-third more 

 durable than the same cordage when tarred. 



^. That uniarml cordage retains its strength for a 

 much Inn^tT time when it is kept in store. 



S. That tinlarn-J cordage resists the ordinary injuries 

 of the weather one fourth longer than when it is tarred. 



These results of direct experiments have been con- 

 firmed by the observations of seamen ; but they have 

 invariably found, that untarred cordage is weaker than 

 tarred cordage, when it is exposed to be alternately 

 via and dry ; that tarred cordage is chiefly useful for 

 cables and ground tackle, which must be constantly 

 Koakt-d in water ; and that cordage, suprr/icially tarred, 

 is always stronger than \%hat is thoroughly tarred, and 

 resists better the alternate conditions of clryness and 

 witness. 



Several important experiments on the relative strength 

 of tarred and untarred ropes were made by Mr. W. 

 Chapman, chiefly with the view of determining the ef- 

 fects of his method of preserving ropes with purified 

 or washed tar. Three pieces of rope were made on 

 the 10th August, 1SOS, of 113 threads in each strand. 

 The first was an untarred rope, the second a rope made 

 of washed tarred yarn, and the third a common tarred 

 rope. A part of each of these ropes had their strength 

 tried on the breaking machine ; and another part was 

 steeped in water for about three months, and then taken 

 to a foundry stove, which is supposed to have been 

 at about 130 of Fahrenheit. They remained in the 

 stove about three months. After that they lay at Mr. 

 Chapman's ropery till Nov. 3d, 1803, when the follow, 

 ing experiments were made with them : 



The tarred ropes were both brittle ; but the latter 

 was more so, and they both cracked on bending. 



The following experiments were made, in 1807, by 

 Mr. Chapman, for the purpose of showing the injury 

 arising from the retention of that portion of the essen- 

 tial oil which cannot be dispensed with, and also the 

 injury which arises from the progressive disengage- 

 ment' of the acid of essential oil. 



The first column shows the strength of the rope 

 when made ; and the second after having been exposed 

 to the heat of a stove from 85 to 100 of Fahr. 



The following experiments also made by Mr. Chap- 

 man, confirm those of Duhamel, respecting the dimi- 

 nution in the strength of cordage produced by tarring. 

 The ropes were registered on the improved principle, 

 and were made with the same yarn, and with 17 

 threads in each strand. 



The following experiments were made with ropes 

 made of the same yarns, and of nine in each strand. 



Whale oil and tallow have therefore an excellent ef- 

 fect, particularly the former. 



The following results, obtained by Mr. Chapman, Strength W 

 show the progressive weight borne by a rope made of ropeaof long 

 long wool, and the elongation which the different wool- 

 lengths sustained by these weights. 



When the rope broke, its length returned to 

 inches, though in a former trial it stood at 32 inches. 

 The girt of the woollen rope was 1.8 inches, and it 

 weighed 75lbs for every 120 fathoms. Mr. Chapman 

 computes, that woollen ropes may be about ^d of the 

 strength of good hempen ones, and |ds the strength of 

 common white ones. 



The following experiments were made by Mr. Chap. Elasticity 

 man on the elasticity of ropes of different kinds, when of ropes, 

 strained with ?ths of their breaking stress. 



The three kinds of rope last mentioned, stretched on 

 an average 1 inch in 24 with a fifth of their breaking 

 stress, which is from ^ to Ibs. of the whole stretching 

 of the registered strand laid ropes, but only from 4ths 

 to ^th of the stretching of the common made shroud 

 ropes. 



In May 1805, Sir Joseph Banks being anxious to 

 try teak tar for ropes, two three-inch ropes were made 

 of the same yarns, one with teak tar, and the other 

 with common tar. They were then placed in the same 

 storehouse, and were broken Sept. 28th, 1807. 



Common tarred rope broke with 3848 pounds. 



That made with teak tar broke with 5980 



The common tarred rope being or 'y about two-thirds 

 the strength of the other. 



Having already, in our article M ECH ANICS, Vol. XIII- 



