Sec. 50.2 



CALCULATION OF WAVEMAKING RESISTANCE 



207 



not in the mathematical part of the field, is an 

 endeavor to present a somewhat different version 

 of the story for the benefit of the practising marine 

 architect. It places emphasis on certain features 

 important in ship design. For the architect and 

 engineer who have progressed this far in a con- 

 secutive reading of the preceding chapters of 

 Volumes I and II, it is possible to discuss the 

 calculation of the pressure resistance of a ship in 

 rather specific terms, eliminating the terms 

 involving viscosity effects as found in the Wein- 

 blum presentation listed in (c) preceding. 



For the period from about 1950 to 1956 the 

 matters discussed here have been under intensive 

 study by the Panel on Analytical Ship-Wave 

 Relations, under Project H-5 of the SNAME 

 Hydrodynamics Committee. 



The present author takes the liberty of quoting 

 directly from the first paragraph of Sir Thomas 

 Havelock's 1950 paper, found on page 13 of the 

 SNAME 1951 reference previously cited: 



"It is impossible to give any adequate survey of this 

 work here, and fortunately it is not necessary to make the 

 attempt; there are e.xcellent summaries which have been 

 published from time to time, and in particular I would 

 refer, for a comprehensive account with references, to 

 Wigley's recent paper, "L'Etat Actuel des Calculs de Re- 

 sistance de Vagues (The Present Position of the Calcula- 

 tion of Wave Resistance)," ATMA, Paris, 1949, Vol. 48, 

 pages 553-587." 



So far as known, the Wigley paper referenced 

 here has not been translated into English. 



For the benefit of the naval architect who is 

 giving this matter serious attention for the first 

 time, two features should be pointed out in 

 advance: 



(1) Regardless of what he may have thought of 

 their work in the past, he should realize that 

 practically all the analysts who have been 

 engaged on this problem, for the period 1925-1955, 

 have followed up their theoretical work with 

 model experiments, in an effort to prove — or to 

 disprove — their theories 



(2) They have strived to make it clear that they 

 are engaged in a calculation of wavemaking 

 resistance only. Other phases of pressure resistance 

 have been considered, but not included in their 

 predictions. 



50.2 Early Efforts to Analyze and Calculate 

 Ship Resistance. Until the period 1840-1860 the 

 aim of ship designers and builders was to crowd 

 the maximum of carrying capacity into merchant 



vessels and to fire the heaviest weight of broadside 

 from war vessels. With some few exceptions, they 

 left to nature the composition of the propelling 

 power of the sails and the resistance of the ship 

 into a speed through the water that would meet 

 the service requirements of those days. 



The designers who first put their minds to a 

 technical analysis of the ship-propulsion problem 

 appeared to have an instinctive feeling, as did 

 those who labored at the task until about the 

 period 1850-1870, that there was a ship form of 

 minimum resistance waiting to be discovered. 

 The fact that speed was a dominating factor in 

 this quest for the most easily propelled ship form 

 seems to have been overlooked, because the range 

 of speeds at that time was still small. However, 

 those seeking this form of least resistance appeared 

 to have a definite thought that, somehow or 

 other, they could calculate or derive its shape by 

 analytic methods. Calculating its resistance was 

 a thought and a task for the future. 



Nevertheless, surface waves were recognized as 

 having an appreciable, if not a major effect on 

 ship resistance, so much so that J. Scott Russell, 

 W. J. M. Rankine, J. R. Napier, and others of 

 their times made use of certain properties (prin- 

 cipally the profiles) of trochoidal surface waves in 

 laying out the waterlines of their ships. They 

 evidently hoped that a useful degree of wave- 

 resistance compensation could be achieved by 

 plotting the profile of a trochoidal wave accom- 

 panying the afterbody, turning this profile over 

 on its side, and then making the waterline of the 

 ship's run a sort of complement to the wave 

 profile. This was done, in the words of J. Scott 

 Russell, to use "the lateral displacements of 

 wavy water to correct the effects of its undulating 

 surface, . . ." [INA, 1863, p. 226]. 



It is to be remembered that the developments 

 outlined in this section all took place before the 

 first model basin was commissioned by William 

 Froude in 1872. It is apparent, further, from the 

 fact that proposals such as those in the preceding 

 paragraph were made by eminent men of the 

 period, that their reasoning was not equaled by 

 their observation of ship phenomena. It is a sign 

 of real progress that the testing of ship models, 

 subsequent to this time, has been accompanied 

 by a greatly increased attention to and observa- 

 tion of hydrodynamic phenomena on ships, in 

 the full scale. 



Rankine, in the early 1860's, tackled the prob- 

 lem of the flow of water around a ship from a 



