The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

50 Table I and plotted to the base W in Diagram 1, which also includes scales for converting Y into W. The efficiency being plotted to the base W the curves derived from Taylor's ex- periments (see Table II) are plotted to the same base (see diagram), and it is found that the two curves, as has been pointed out by Mr. McEntree, bear a constant ratio to one another throughout the range of the experiment. This ratio 80 is for the 2 width ratio, --, 1. ¢., the 95 efficiency on Taylor's experiments is .84 of the ideal efficiency of this width ratio. THE Marine REVIEW B. H. P. P dlduecticnecs PaaS ve ER! is very nearly a constant for each width ratio at all maximum efficiencies. The constant is for the 3-bladed .2 width ratio propellers B. HYP: = 000595. TR As the Bs. H. P. required to drive the propellers for any given thrust is directly proportioned to the efficiency, the ideal B. H. P. will be inversely proportioned to the relative maximum efficiency of a sim- ilar propeller in Taylor's curve, 4. @., if ee TABLE I, FUNDAMENTAL EQUATIONS. it a 3 and 4. ; l=-* 2=* Bois 1 I). Ce. y SWi4 (Oy SW .o Wis .05 95 975 18574 .974 .000162 05 .000118 .009083 A 9 95 729 .948 .000371 000271 =--.125 .00019 15 85 925 6141 919 .000643 .000469 .000329 2 og 12 .889 .00100 it .000729 .000 .000512 ss 19 (8/905 :AZ19 .857 001475. 001075 .000765 3 ve 280 343 .823 .00212 2 .001545 125 .001085 aS £05 .825 .2746 788 .00300 . 00219 001535 4 6 8 .216 19 00422). <. 33>.:. ;,00808 125 .00216 Diagram 1 represents these relations. TABLE II, TAYLOR'S EXPERIMENTS. 3 BLADED PROPELLERS. oo OR 279 WR Jo WR 5 s S < SX é oS Cis) (1-s) *p° Ch) 2 .14 1.318 .290 .168 PAO; 3) 313 16 1.47 .3/6 25 .16 1215 .307 19 1.418 .378 19 1.44 397 o W/o 124 318 Zt 1.395 402 | 1.416 422 A .2065 £175 325 .24 1.344 434 2425 1.362 450 Ss 23 bigs) 325 261 1.295 439 .266 1.32 455 6 aot 1.084 .320 .2/8 1.248 440 .284 1.28 462 he) .28 1.035 .310 .30 1172 415 .307 £23 466 1.0 Ol7. .98 .300 .326 1.08 .386 334 115 445 125 347 95 .300 .347 1.005 .356 1357 1.08 423 1.5 361 .93 .300 .363 05 a0 347 1.016 39) 1.75 .3895 90 .290 07/5 90 B10 2.0 .4065 88 .283 39 .866 .30 An examination of Taylor's experi- mental data (see Table Il) of maximum efficiency with thé relative slip and pitch FIG, 5--CROSS SECTION, plotted to the base ¥, as in the ideal curve, brings out the interesting fact that for the 3 and 4-bladed propellers the value the propeller in Taylor's curve takes B. H, Pp. = d° R* X .000595. Ideals, u. p, = d° R* 00595 x 34 -- .0005. B. H. P. (It may here be noted that is aR? of the dimensions of density, Feet. Lbs. Mins, EoML I Toy M. Ge, -- = -- a density 1 Ly Lo Me Ft. Rev. per Min, Referring back to the fundamental equa- tion (2) for ideal B. H. Pp. it will be noted that it includes the factor "W" = 64 representing the density of the water.) On Diagram 1, it is assumed that as the result of Taylor's experiments (see Diagram 2 and Table II) an ideal pitch © line may be plotted to correspond with -- the ideal slip, and that a probable pitch line may be plotted for any other slip on -- G the assumption that the constant a R? is inversely proportional to the maximum efficiency. The ideal pitch line has been put on Diagram 1 from the formula vp 2 CL -- 8)" 150005, This curve suggests the notion that un- der no circumstances can a low pitch ratio give an efficient propeller. also on Diagram 2, the values of slip in Taylor's experiments with three width ratios, we find that the slip follows gen- erally the line of the ideal slip. The curve "probable maximum effi- ciency,' Diagram 2, is 90 per cent of the efficiency for .2 width ratio propellers in Plotting © Taylor's experiments, and the value of © 2 is therefore assumed to be for ak maximum efficiency. 000595 _____ =, 00066. == fs > EL 9 In plotting a curve, Diagram 2, of the probable slip for this group, the author simply enclosed Taylor's experiments in an enveloping curve, because they have been adopted as giving the nearest values attainable of the proper slip for maximum efficiency, and from these values is de- G = .00066. rived the pitch curve for dR° The curve of actual apparent slip could be deduced from that of ideal apparent slip by the following simple experiment. The ship is moored, the propeller driv- en at R revolutions per second, and the velocity of the sternward column v, meas- ured by means of a patent log. Then the imaginary pitch ratio p; is given by the equation U2 ), =, Rd but Uz U4 1s = a 6S ; Rdp ; Rdp (1 -- s) v, Sa Sef Rdp and if the torque horsepower be also measured, the value ¥ may be obtained. COMPARISON OF PROPELLERS. For comparison of propellers on_ this method the following data are required: Ge df. Rk. G ) ee oR a &, and approximations to the following G from which can be deduced