THE PROPULSIVE EFFI.CIENCY OF SINGLE-SCREW CARGO SHIPS. 



By Commander William McEntee, Construction Corps, U. S. Navy, Member. 



[Read at the twenty-seventh general meeting of the Society of Naval Architects and Marine Engineers, held 



in New York, November 13 and 14, 1919.] 



In a paper* read before the last meeting of the Society giving the results of a 

 series of experiments made at the U. S. Experimental Model Basin with models of 

 single-screw cargo ships it was shown among other things that for good propul- 

 sive efficiency it was necessary to have the run finer than the entrance, and for ves- 

 sels of this class having a parallel middle body equal to about one-third the length 

 of the ship the minimum power is required when the fore-and-aft position of the 

 parallel middle body is such that about two-thirds of it is forward of the midship 

 section and one-third abaft it. Those results, which it is believed were the first of 

 any extensive series of experiments with self-propelled models of single-screw ships 

 to be made public, were confirmed by a somewhat similar series of tests made at 

 Clydebank on models of vessels of the same general class. The results of the latter 

 tests were presented in a paperf by Mr. James Semple before the Institution of Na- 

 val Architects in April, 19 19. 



In view of the importance of this class of vessel it was considered desirable to 

 extend the investigation, and the present paper contains the results of the tests of 

 five additional models, the characteristics of which are given in the following 

 table : — 



Table I. 



The lines of the parent form, Model No. 2023, are shown in Plate 48. In Plate 

 49 are shown the sectional area curves for the five models and the parent form. 



The investigation had for its object determination of the effect of varying the 

 amount of parallel middle body and the longitudinal coefficient simultaneously while 



*"Variation of Shaft Horse-Power, Propeller Revolutions and Propulsive Coefficient with Longitudinal 

 Position of the Parallel Middle Body in a Single-Screw Cargo Ship." 

 f'Experiments on Full Cargo Ship Models." 



