1152 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1957 



h 



10 



20 



30 



40 50 60 



a IN DEGREES 



70 



80 



90 



Fig. 15 — Variation of the distance along the cable to the touchdown point 

 during recoverj' with the critical angle a. 



Example: A cable weighing 0.7 lb/ft in sea water and having a hj'dro- 

 dynamic constant H of 70 degree-knots, is to be picked up from a depth 

 of two thousand fathoms. If the ship speed is one knot what is the cable 

 tension at the ship for surface angles as of 40°, 60°, and 90°? How far in 

 front of the ship and how far along the cable will the touchdo\ra point 

 be for these values of a^ ? 



As indicated by (9), an H value of 70 degree-knots together with a ship 

 velocity of one knot yields ao = 70 degrees. Fig. 4 yields in turn a = 

 60 degrees. Entering Fig. 12 with this value of a, we can obtain Ts/wh. 

 In this example the wh tension for a depth of two thousand fathoms is 

 8,400 lb, and hence the values of TJwh and 7',. are as follows: 



40,700 lbs 

 21,700 lbs 

 12,900 lbs 



From Fig. 14 we get in turn for the horizontal distance from the ship to 

 the touchdown point 



as X/h X 



40° 2.65 5300 fathoms 



60° 1.56 3120 fathoms 



90° 0.66 1320 fathoms 



