Cable 



Candidates employing cable as the suspending medium were examined 

 in much the same manner as pipe systems. In general, the same types of 

 questions were necessarily asked and answered. The state-of-the-art, projected 

 future capabilities, the magnitude and types of loadings, and anticipated 

 problem areas were given most of the emphasis in the study of the 

 "flexible support" concepts. 



There are two contenders: wire rope and synthetic rope. Both types 

 have been widely used in ocean-related industries. The desirable and 

 undesirable features of each are well-documented and in many cases are 

 common knowledge. 



Synthetic Rope. There are three primary types of materials used for 

 manufacturing synthetic cables: nylon, dacron, and polypropylene. Nylon 

 was the first of the synthetic fiber cables. It has a slight negative buoyancy 

 in water and has a good deal of permanent elongation. Dacron is stronger 

 than nylon but is not generally available in large diameter cables. Polypropy- 

 lene is slightly less strong than nylon but has the added asset of slightly 

 positive buoyancy; it is available in diameters up to 5 inches with breaking 

 strengths on the order of 600,000 pounds. 



Primary advantages of synthetic fiber cables are that they are 

 comparatively buoyant, so no strength is lost due to cable weight, and that 

 they are available in construction which does not twist under load. Dis- 

 advantages include a high degree of elasticity, susceptibility to fish bites, 

 and a requirement for large storage areas for large diameter ropes. 



Wire Rope. Wire rope is a mainstay of the ocean industries. Its 

 development has closely paralleled the improvements in high-strength steels. 

 it is possible to purchase high-strength rope in lengths up to 5,000 feet, 

 4 inches in diameter, 6x61 classification. This rope is used in dredging 

 operations and has a breaking strength of 713 tons. It is flexible enough to 

 be used as a hoisting rope. The continuous length of a rope that can be 

 manufactured is limited by the weight-handling capacity of the wrapping 

 machines, which is 80 tons.^ As a result, the maximum lengths of 4-inch, 

 3-3/4-inch, and 3-1/2-inch ropes are 5,420 feet, 6,160 feet, and 7,070 feet, 

 respectively. The development of greater capacity rope would require 

 substantial industry wide demand. 



For reasons of safety and to account for the susceptibility of cable to 

 dynamic loading, a safety factor of at least five is recommended for most 

 usages. This high factor also takes into consideration the relatively low 



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