However, the frequency and amplitude of the cyclic stress change with cable length. 

 This may well result in a significant change in the coefficient of drag and mass since 

 the amplitude and velocities of vertical oscillation will vary. This is possibly one 

 cause of the discrepancies noted. 



Table VII. Summary of Calculations for STU Lowering Operation 

 to 2, 500 Feet 



Cable Length, L 



83. ft 



830. ft 



1,660.0 ft 



Parameter, fl 



0.005 



0.05 



0.10 



Parameter, /3 



3.00 



3.00 



3.00 



c/L 



0. 0283 



0.283 



0.566 



Period of Oscillation, T 



5.45 sec 



8. 00 sec 



9. 23 sec 



Frequency of Oscillation, a: 



1. 153 rads/sec 



0. 786 rad/sec 



0.681 rad/sec 



, coL 

 c 



0. 0326 



0.222 



0.385 



I' From Curves 

 max 



0.660 



1.165 



1.225 



S Ijj - Dynamic Load 



±3,752.0 lb 



±707.4 lb 



±371.9 lb 



Static Load 



5,500 lb 



3,400 lb 



3, 100 lb 



Static + Max Dynamic Load 



9, 252 lb 



4,107 lb 



3, 472 lb 



Static - Max Dynamic Load 



1,748 lb 



2,693 lb 



2, 728 lb 



From the record given in Figure 35 there also appears to be a somewhat 

 irregular, long-period reinforcement of the dynamic stress amplitude. During the 

 lowering operation it was not possible to record the actual motions of the load, and 

 thus any departure from purely vertical motions are unknown. At a lowering velocity 

 of 132 feet per minute it is quite possible that the load motion will become unstable 

 and that sidewise oscillations will occur, giving rise to complex lift forces on the 

 structure with resulting variations in the cable tensions. There Is no evidence in 

 Figure 35 to support the result shown in Figure 34 that dynamic stresses may increase 

 at greater depths, because of the limited depth of 2,500 feet to which the STU was 

 lowered. There Is a pressing need for a load-lowering operation to be carried out in 

 which both the cable tensions and the load motions are recorded, thus allowing a 

 more definite analysis of the results. Preferably this full-scale experiment would be 

 carried out with a formalized body shape so that coefficients of drag and mass could 

 be more accurately estimated. 



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