194 THE PROBLEM OF THE HULL AND ITS SCREW PROPELLER. 
De Pyros. 
As in Problem A, the slip before cavitation equals s=S TCE where Zs 
is taken from curve I, Fig. 6, but as soon as the cavitation curve of S is passed, 
while the equation remains the same, the value of Z; must be taken from curve 2, 
Fig. 6. 
Turning now to the second vessel, which is of the Lake type, the range of appar- 
ent slips of the second order is entered. In the estimates of revolutions both in 
and out of cavitation, the values of Z; are taken from curve 1, Fig. 6, but in the 
estimates of power in the cavitation range a corrective factor must be introduced. 
Let this factor be called K,. Its values are found as follows: 
Turning to Fig. 7, attention is called to two re es Z», one plotted on 
Sy 1M) eb he soy 
PeEmpE 575 and 7=. .78, while the other is on = i. WEE! By. 51. Now 
for either of these points to find the value of K,, take the value of © E oa P. ‘, called 
Gy Ids SObe 
EHP’ where this same value of 7 cuts the cavitating thrust curve for the basic 
slip S of the vessel. The Z, value for this value of 5 = call Z,,, then K,= 
Z,—Z, and ENT 
Log I. H. P.,=Log I. H. P. --Log K—2Z,-+-Z, 
Log S. H. P.,=Log S. H. P.--Log K—2Z,+2Z, 
and, by transposing the equation, 
Z,=Log S. H. P.,+2Z,—Log S. H. P.—Log K 
is obtained from which, when the actual power and load fraction are known, the 
cavitation loss can be closely approximated. 
Also, by transposing, the equation— 
2Z,=Log S. H. P.+Log K+Z,—Log 5. H. P.u, 
from which the load fraction © E ee poe corresponding to Z, can be ascertained. 
VESSEL D. 
Hull. Propeller. 
Seis es 2020 750 Blades Oiseau estane 3 
B=19’ SS OTHE] RVR NNT RS EOE Sa MUR SAT 2 
H=16.1' OTE A Ay AR ete ane see Standard 
Je iy DANS WEA NANOS BRA ee 6.17’ 
Toto ai Tor eee DP evean are os UAC GR aR TEN 5.542 
