THE PROBLEM OF THE HULL AND ITS SCREW PROPELLER. 181 
of the power augment factor ‘‘K”’ is greater than unity, then denoting the total 
power by I. H. P.., 
Ko xX ERP. 
a EE eG NO Ls 
Dy Vel Vee, eG SC IE BN es = ; 
10”, 
Log I. H. P., = Log I. H. P. + Log K + Z,. 
These equations neglect all correction for the effects of cavitation which will 
be discussed further on. 
Problems Illustrating Analysis of Propeller. 
In order to illustrate all that has been treated in the foregoing, two problems 
are here given, the first being the series of vessels used by Commander McEntee 
in his article on the ‘‘Propulsive Efficiency of Single-Screw Cargo Ships’’ which 
was read before this Society at its 1919 annual meeting. 
It must be remembered, however, that in Commander McEntee’s vessels the 
ships were not evenly balanced in their lines, the effect of shifting the middle body 
aft having its greatest effect on that vessel having the resultant shortest after 
body. As the curves on Fig. 1 for estimation of 5. B. C. are based on forward and 
after bodies of equal length, the result may be a slight under estimate of 5. B. C. 
and of K in the case of one or more of the vessels of the fuller nominal block 
coefficients. 
Problem 1: Vessels of Type 2, Single Screw. 
Sa 117.9 11.4 10/.88 10.37 9/.86 
H=26/ Nom. B. C. 7242 . 7438 . 1634 . 7830 ,8026 
= .1432 1K, By 758 SS .786 801 815 
; K 1.175 1.2 1.23 1.27 fies 
=.454 S. B. C. .7925 813 -825 84 .855 
iS) 14 155 17 -195 2175 
P=14/.75 
Blades =3 
T. S.=6230 
PXR=1764 
1—S=.86 845 .83 .805 . 7825 
V=14.97 14.71 14.45 14.01 13.8 
I. T.D=3.09 
hs Tele 1 aSilei7/ 
P. C.=.696 
E. H. P.=3575 
S. H. P.=4726 
