CHAPTER 57 



Estimate of Total Resistance for Surface and 

 Submerged Ships 



57.1 General 313 



57.2 Summary of Kinds of Ship Resistance ... 313 



57.3 Ratios of Major Resistance Components . . 313 



67 . 4 Methods of Approximating the Total Resist- 



ance of a Ship 315 



67.5 Ship Friction Resistance Calculation from 



Chapter 45 310 



57.6 Residuary Resistance Prediction from Refer- 



ence and Standard-Series Data 316 



67.7 Telfer's Method of Predicting Ship Resist- 



ance 318 



57.8 Analytical and Mathematical Methods of 



Predicting Pressure Resistance 321 



57.9 An Approximation of Separation Drag . . 321 



57.10 Slope Resistance and Thrust 321 



57.11 Ship Still-Air and Wind Resistance from 



Chapter 54 322 



57 . 12 Calculating the Overall Wetted Surface and 



Bulk Volume of a Submerged Object . . 322 

 57 . 13 Drag Coefficients and Data for Submerged 



Bodies 322 



57. 14 Pressure Resistance of Submerged Bodies as 



a Function of Depth 323 



57 . 15 Resistance Due to Flow of Water Through 



Free-Flooding Spaces 323 



57.1 General. This chapter covers methods 

 of estimating, calculating, and predicting full-scale 

 resistance data for bodies or ships, intended to run 

 on the surface or submerged, based upon available 

 information. It does not discuss the extrapolation 

 of model-test data to full scale for any specific 

 ship design. Descriptions of this procedure, at 

 least as utilized by members of the American 

 Towing Tank Conference, are published in 

 SNAME Technical and Research Bulletin 1-2, 

 entitled "Uniform Procedure for the Calculation 

 of Frictional Resistance and the Expansion of 

 Model Test Data to Full Size," of March 1952. 

 Details of the testing and extrapolating proce- 

 dures, corresponding to those in general use in 

 America, are described in Bureau of Construction 

 and Repair Bulletin 7, entitled "The Prediction 

 of Speed and Power of Ships by Methods in Use 

 at the United States Experimental Model Basin, 

 Washington," 1933. 



This chapter also gives some information con- 

 cerning the resistance of fully submerged bodies 

 resembUng submarines. These data may be found 

 of benefit to the marine architect when he is 

 called upon to approximate the drag of a non-ship 

 form to be towed submerged. 



57.2 Summary of Kinds of Ship Resistance. 

 The various categories into which, in the present 

 state of the art, the resistance of a ship to steady 

 straight-line motion is divided, are listed in 



Sees. 12.1 and 12.10 of Volume I and defined in 

 Sees. 12.2 through 12.7. This subdivision, based 

 on the Froude theorem that the resistances due 

 to tangential and to normal forces on the ship 

 are for the most part independent and therefore 

 can be segregated, is repeated here in Table 57. a 

 for the convenience of the reader. However, the 

 interactions listed in Sees. 12.1 and 12.10 are 

 placed under a separate heading. 



The following sections describe, in turn, various 

 means of estimating these different kinds of 

 resistance. 



57.3 Ratios of Major Resistance Components. 

 Useful ratios in analysis and design are the per- 

 centages of the friction and residuary resistances, 

 according to the Froude subdivision, making up 

 the total hull resistance. The solid line in Fig. 

 57. A, dividing the total Rt into friction R^ and 

 residuary Rr over a T^ range of 0.4 to 2.0, is 

 adapted from V. M. Lavrent'ev ["Marine Pro- 

 pulsion Devices," Moscow, 1949, Fig. 37, p. 85]. 

 The same original diagram is published by G. E. 

 Pavlenko ["Soprotivleniye Vody Dvizheniyu Su- 

 dov (The Resistance of Water to the Movement 

 of Ships)," Moscow, 1953, Fig. 5, p. 16, covering 

 a range of F„ from 0.1 through 0.6]. The broken 

 line is based on data from the SNAME RD 

 sheets for about twenty ships, more easily driven 

 than those of the Taylor Standard Series. It 

 includes a roughness allowance (lO')ACp of 0.4. 



313 



