THE PROBLEM OF THE HULL AND ITS SCREW PROPELLER. 199 
aan i x S. H. P.a Revs. 
EH P| h. p v v Zp SSS *Zs S Ss 
| Est. Act. Este Pact. 
ROIS WEIS 7A LONGIe || east 2NesGo8e jet |) 356) 10) 400) Nf. 215) leote O74 ites 160 
05 | 474 | 12 4092 | —1.355 | 1] 732] 720] +1.025 | .21 | .09823 | 197.3 | 200 
ROS) ode aes) eset t715) |) tl 1007) | 44500 |) 1 680501) 21)||) 09093) 1)233,.3, 280 
10 | 946 | 15.52 | .5292 | —1.0414] 1] 1507| 1500] + .70 | .21 | .09568 | 254.5 | 252 
20 | 1892 | 19.25 | .6564| — .7279 | 1] 3102] 3100 | + .435 | .21| .1070 | 319.7 | 317 
BONN 2SS80l 21S al wa78S20 ee 54451|) 104732) (4750. |0-F 80) | eat) too leso2e 1459 
40 | 3785 | 22.8 | .7775 | — .4144| 1] 6385 | 6300] + .248 | .21| .1432 | 394.6 | 394 
.50 | 4730 | 24 8184 | — .3135 | 1] 8055] 8100 | + .165 | .21| .1492 | 418.3 | 425 
60 | 5676 | 25.1 | .8559} — .231 |1]| 9741] 9700] + .122 | .21 | .1634 | 444.9 | 453 
70 | 6623 | 26.15 | .8917 | — .1613 | 1 | 11436 | 11500 | + .105 | .21 | .1845 | 475.5 | 476 
80 | 7570 | 27.15! .9258 | — .1009 | 1 | 13143 | 13100 | + .095 | .21 | .2072 | 507.8 | 508 
90 | 8514 | 28.15 | .9599 | — .0477 | 1 | 14855 | 14900 | + .08 | .21 | .2277 | 540.5 | 538 
1.00 | 9461 | 29.2 | .9957] 0.0 1 | 16580 | 16550 | + .061 | .21 | .2417 | 571 | 571 
1.05 | 9935 | 29.94 | 1.021 | +0.0221 | 1 | 17445 | 17400 | + .05 | .21 | .2479 | 590.3 | 591 
*Z, taken on straight line passing over from = on curve I, Fig. 6, to 2 on 
curve 2; where curve of a = ae = crosses ordinate of unity load at lower than 
= (Fig. 7), curve 2 becomes a horizontal line coinciding with Z,=o0, Fig.6. The 
V 
change of the Z, condition does not change so abruptly as is done in making the 
estimate, for inspection of the actual revolutions indicates that it begins at about 
23 knots and changes gradually until at 26 knots it has taken its position on the 
pass-over line used in the estimate. 
Cavitation when at Is Greater than Unity. 
When the load fraction exceeds unity, the laws governing the action of the 
propeller, both as to power and apparent slip increments, appear to change, but 
the changes occurring appear to be dependent upon the value of the speed fraction 
at which the performance plots on Fig. 7. 
Should the performance plot on or above the curve E, Fig. 7, and at a load 
fraction exceeding unity, the values of Z, follow the curve marked 5 on Fig. 6, 
while should it plot below the curve E, the value Z, follows the curve 4, the equation 
for curve 4 being— 
@®, 1, 1D: 
2p5 Wd, LOE (Gye 
