The twenty-four possible bottom photographs can be taken at intervals of not 

 less than 15 seconds by raising the camera unit clear of the bottom between each 

 activation of the tripping switch. Under normal weather and sea conditions this slack-wire 

 lowering technique has been used successfully to 12,000 feet. 



The over-all design was made consistent with the limitations of the 3/16-inch- 

 diameter, 3-by-19 wire rope used for lowering purposes. This size and type of stranded 

 rope has become standard in many phases of oceanographic field work. A 20,000-foot 

 length of this wire rope weighs slightly over 1100 pounds in sea water and has a 

 breaking strength of 3340 pounds. A minimum 2V2-to-l safety load factor, required to 

 allow for overloads caused by excessive ship rolling and pitching, limits the weight of 

 the lowered camera unit to 125 pounds. Loss of this static load from the total wire-weight 

 out, when the sea floor is reached, enables a specially constructed mechanical-electrical 

 dynamometer placed in the fair-lead system of the wire lowering rope to detect small 

 tensional changes in the latter and convert them into electrical signals. Table 1 gives 

 the weight-strength relationships needed to safely lower the camera to a depth of 20,000 

 feet. Figure 8 illustrates a typical deck arrangement for making a lowering from a 

 vessel. 



Steady drag forces due to wind and to sea currents, and the dynamic tensional 

 changes in the wire rope caused by roll and pitch of the vessel during inclement weather, 

 are compensated for in the circuitry of the bottom indicator. 



TABLE 1. Weight-strength relationships for lowering NEL 

 Type III Deep-Sea Camera. 





Wire Wt. 



Wire Wt. 



Wt. Ratio 





Depth 



in Air 



in Water 



in Water 



Safety Factor 



(ft) 



(lb) 



(lb) 



Wire/Camera 



(Wire Rope) 



1000 



62 



56 



0.4 



18.5 



2000 



124 



111 



0.9 





3000 



186 



167 



1.3 





4000 



248 



223 



1.8 





5000 



310 



279 



2.2 



8.3 



6000 



372 



335 



2.7 





7000 



434 



391 



3.1 





8000 



496 



446 



3.6 





9000 



558 



502 



4.0 





10,000 



620 



558 



4.5 



4.9 



11,000 



682 



614 



4.9 





12,000 



744 



670 



5.4 





13,000 



806 



725 



5.8 





14,000 



868 



781 



6.3 





15,000 



930 



837 



6.7 



3.3 



16,000 



992 



893 



7.2 





17,000 



1054 



949 



7.6 





1 8,000 



1116 



1004 



8.0 





19,000 



1178 



1060 



8.5 





20,000 



1240 



1116 



8.9 



2.7 



Wire rope r= 3/16" diom. 3 X 19 preformed galvanized plow steel 



Nominal breaking strength = 3340 lb 



Wt. of wire rope in air = 62 lb per 1000 linear ft 



Wt. of wire rope in water = wt. in air less 10% 



Wt. of NEL Type III Deep Sea Camera in air = 215 lb 



Wt. of NEL Type III Deep Sea Camera in water = 125 lb 



10 



