134 THE PROBLEM OF THE HULL AND ITS SCREW PROPELLER. 
Log s = Log S + Log I.H.P., + Log Ay — Log 1.H.P.— Log A, 
Log s = Log S — Z, + Log Ay — Log A, when K = 
Now let Log Ay — Log A, = Zs, and plotting it on values of a 
curve I on Fig. 6, it will be found to be expressed by the equation— 
Zs = 2.861 Log (<) — .0788. 
as shown by 
This curve reaches the value Z; = 0 at a value of {= .9385 and this value 
v 
of 0 is retained at least until > = I isreached. Beyond that the question of cavi- 
tation enters and certain variations may occur, depending upon the values of = 
e. h. p. 
and the corresponding values of © EEL = 
The form of the equation for apparent slip, where K = 1, now becomes 
Log s = Log S — Z, + Z; and when Z, = Z; 
s = S, that is, when the vessel is loaded ae so that at any fraction of load 
€. hiyp. : Gy lal 50) 
EHP’ and corresponding speed v, when Z; for ve Li for 2 EHP. = -, the apparent 
slip has become equal to the basic slip and the propellers are passing into the 
cavitating zone, with or without loss, depending me the quality of the wake 
which the vessel carries. 
To illustrate the method of estimating seven when cavitation does not 
exist, the calculations for Problems 1 and 2 will be continued. 
Estimate of Revolutions. 
Problem 7. v = II 
Chilsk lecaaanmen bcidos Us oman OO Mee Ase Hoda 1716 1827 1970 2220 2569 
7 Ds He SUR BAS ee caharhe UCN Ses Lbs .7348 7479 7614 785 .8076 
Zs for 7 Fig. SAGDIG RA Ws ele a SU + .298 + .280 LO eet +.182 
Rea OLIN 8 NAIL LO AMR eco .1010 1142 126 .1510 1798 
_vX 101.33 
oe aig cy eee $4.07 85.31 86.46 89 92.14 
Actualirevolutions 4 cee eect 84.5 85.5 86 88 93.2 
Problem 2. v = 32. 
SS La bey eo a2 eee ee DSSS COM See EAR OMAGH SV . 1965 
v ae 9 OPIN SBS Ue ery SUANITUDY YES MPN al 209.6 
AURA a VPS nage MA ay ne Actual revolutions........... 208+ 
ZU NANA SM Ne AMEN EAST VE +.53 
