Sec. 59.12 



PROPULSION-DEVICE PERFORMANCE 



341 



propeller design of Chap. 70. It could and should 

 be increased when making the revisions to the 

 preliminary design described in Sec. 78.18. 



In the event the mean-width ratio of a partic- 

 ular screw propeller is not known, it can be deter- 

 mined by the formula 



m 



2Z 1 - 



(59. i) 



Table 59.a lists the blade-helix angles <^(phi) for 

 ten values of 0-diml ratio x' = R/Rm„x for EMB 

 model propeller 2294, used as the stock propeller 

 for the self-propulsion tests of the transom-stern 

 ABC ship model, TMB 4505. A drawing of this 

 propeller is reproduced in Fig. 78. L. 



Table 59.b lists the blade-helix angles <j) for a 

 series of ten 0-diml radii x', and for five pitch- 

 diameter ratios covering the range normally 

 encountered in ship work. The pitch is assumed 

 constant at all radii for this tabulation. 



59. 12 Pertinent Data on Flow Into Propulsion- 

 Device Positions. The flow into the positions 

 occupied by propulsion devices around a ship 

 hull is discussed in and covered by various 

 sections in Chaps. 17, 33, 52, 60, 67, and 69. The 

 duplication and repetition involved are considered 

 justified by the great importance of this phase of 

 hydrodynamics as applied to ship design, and 

 by the necessity for devoting increased thought 

 and study to it in the future. The present section 

 calls attention to a few particular features of this 

 flow, and lists a number of sources of published 

 material available for reference. 



TABLE 59. a — Derivation op Blade-Helix Angles for TMB Model Propeller 2294 



Fig. 78. L is a drawing of this propeller, used as the stock wheel for the self-propelled test of TMB Model 4505, repre- 

 senting the transom-stern design of the ABC ship of Part 4. 



The helix angle is given for the tip section, even though the blade width there is zero. 



TABLE 59.b — Tabulated Values op Helix or Blade Angle <l> por Screw Propellers of Varied P/D Ratio 

 For these calculations it is assumed that the pitch P is constant at all radii. 



