T 



Tjf = 16,000 feet for plow-steel wire rope [7a] 



and 



T 



yf = 2000 feet for forged stud-link anchor chain [7b] 



When 7 is given, the ratio T s /WYcan be computed from one of the 

 Equations [7]. A circle of radius T s /WYon any of the polar diagrams deter- 

 mines the region within which the anchor-line tensions are under the safe 

 working load but outside of which they are unsafe. 



REQUIRED HOLDING POWER 



The holding power of an anchor falls off rapidly as the angle of 

 the anchor line with the horizontal at the anchor is increased from zero. The 

 variation of the holding power with this angle has been investigated (2), and 

 the results are reproduced in Figure 13 of Reference (3). Expressed analy- 

 tically, the ratio of the holding power H^ at a finite angle O to the hold- 

 ing power H at O = is given by the formula 



-]f- = 1 - 0.017400 



H = ^*o [8] 



1 - 0.017400 



where O is in degrees. In using Equation [8] to design an anchor, if^ is 

 set equal to the maximum value of T that is anticipated. 



APPLICATION OF CHARTS 



When the drag of the ship, D, the weight per unit length of cable 

 in water, W, the depth of the water, Y, the speed of the current, V, the type 

 and size of the anchor cable have been given, and the value of n has been 

 computed, the charts can be applied directly. The length of line and the 

 tension corresponding to a zero angle of the cable with the horizontal at the 

 anchor can then be determined from Figure 2. If this indicates that the 

 length of cable for O = ° ls impracticably long, then Figures 3, 4, and 5 

 can be applied to find the tensions in the line and the angle of the cable 

 at the anchor for lengths of line corresponding to S/Y = 5. 3, and 2. The 

 points spotted as solutions on the charts should be examined to ascertain 

 whether they lie within the circle of safe working loads. 



In an anchor problem where a suitable size of anchor cable must be 

 determined it will be necessary to repeat the foregoing procedure for various 



