nearly equal to the drag of the ship. Consequently the required holding pow- 

 er of an anchor in depths of water where a proper scope can be used may be 

 assumed to be equal to the estimated drag of the ship. 



When anchoring in deeper water, however, it is not practicable to 

 pay out a length of line which is five times the depth of the water. Under 

 this condition, the hydrodynamic force on the anchor cable cannot be neglect- 

 ed, and the tension in the cable may be much greater than the drag of the 

 ship. An anchor with a holding power greater than the estimated drag on the 

 ship would then be necessary to prevent dragging of the anchor. Since this 

 condition would also impose greater tension in the cable, the cable size 

 should be selected accordingly. 



To meet tne various conditions of anchoring, curves have been com- 

 puted from which the magnitude and direction of the tensions in the anchor 

 cable at the anchor and at the ship can be determined when the drag of the 

 ship, the velocity of the current, the depth of the water, and the type and 

 length of the anchor line are known. The application of these curves is il- 

 lustrated by a numerical example . 



CHARTS OP FORCES ON AN ANCHOR LINE 



Figure 1 shows diagrammatically and serves to define the geometrical 

 quantities and the forces in the anchor line which are employed in the sub- 

 sequent figures and discussion. 



The laws of force on a cable in a stream are well known (4). On 

 each element of the cable the hydrodynamic forces consist of a component 

 normal to the cable, whose magnitude diminishes as the square of the sine of 

 the inclination of the element with the horizontal, and a tangential compon- 

 ent whose magnitude is small compared with the normal component, except when 

 the inclination of the cable is very small. 



A general solution for the shape and tension of a cable in a ptream, 

 when the weight of the cable or the tangential force component or both are 

 taken into account, cannot be expressed in simple analytical terms. It is 

 usually necessary to express these solutions in terms of new functions, de- 

 fined as integrals, for which tables must be computed. However, the use of 

 these tables is as simple as the use of tables of the trigonometric functions, 

 and by their use numerical solutions of cable problems can be obtained readily, 

 The application of such tables to the solution of cable problems in which the 

 weight of the cable can be neglected has been illustrated by numerous examples 

 in a recent Taylor Model Basin report (5). 



New charts have now been constructed in which the weight of the 

 cable is not neglected; see Figures 2, 3, 4, and 5- The tangential component 



