200 THE PROBLEM OF THE HULL AND ITS SCREW PROPELLER. 
while that for curve 5 is— 
I [04 
Z,=1.51 Log ~ FP) 
Should the performance plot above E, the values of Z, follow the curve 3, 
which differs slightly in equation from the cavitation curve 2, Fig. 6, the new 
equation being— 
Z,=3 Log (e) 
Should it plot below £, the values of Z,, for values of = greater than .9385, 
become zero, the increase in apparent slips being apparently independent of speed 
but entirely dependent upon power. 
In order to illustrate these phenomena, the performances of four vessels will 
be analyzed, the first, vessel H, having been used in the preparation of all the 
design curves; vessel I, a reciprocating engine destroyer plotting above E; vessel J, 
a destroyer plotting below £; vessel K, a dreadnaught plotting below E. 
The trial data of vessels I and J are not of the best as the propellers of I were 
cavitating heavily, producing excessive vibration of the engines and affecting the 
clearness of the indicator cards, while with vessel J the starboard propeller and 
torsion meter readings suffered badly through “induced cavitation” of that pro- 
peller, the port propeller running smoothly. 
VESSEL H. Type I. 
Hull. Propeller. 
Wi, 13 Wiis Ig" Number of propellers....... 2 
B= Number of blades.......... 3 
elas Kormyotiproj arcana ee oe Standard 
Ba eWer lee l G7, DD ELAS LONE On SU aie SEER MEER 18.25/ 
Nom yaaiea— Pe VN OMe 1 vee EE ar 19.75' 
B. C. on C—D=.572 IPAS Se) AS ee ESOL 328 
7 = 317 A ST Urns Be cK lt A RY 7,250 
A 
B. C. on C—D corrected for Ba 492 BPS eH EM 2,498 
Slip B. C. on X =.525 1 Wich RAIS SA SIG AS A 865 
eat a LUN A ADEA REL Nese 4 AL 21.32 
2 ANID FT IONS By i leialear theta eaters 4.35 
S=.135 VAR FE earn RAIL Gs a ahaa aN 24,800 
K=I 1 a OF EAMES chiA SUA CANNES .665 
1 Sp se eae reales Tes Ali Sha 16,492 
*The data omitted are confidential and therefore cannot be made public. 
