Sec. 59.14 



PROPULSION-DEVICE PERFORMANCE 



345 



_ .^. . , r ^T(for all propellers) 



ror this model, Lf-i - -rz _ . /•, ^ ~ \T727 



0.5p 2 Ao(.for all propellers) V/f(avera()i 



M'' 



.,--K 



--K- 



I I I I I I I I I 



I I I I I 



JfT' 



I I I I 1 I I I I I I I I III I I I I I I I I I I I I I I I I I I I I I I I I I I I I 



07 0.8 0.9 



Taylor Quotient, Tc^ • V/C 



1 

 I I ITl 



3CP3 



Ship 5peed. kt 



For 3inqle-5crew Ships, . 



such as -those for c 



which data are shown y 



in Diagrams 2. and 3, '^ 



the Thrust- Load c3 



Coefficient Ctl — , 



_ FVopeller Thrust T o 



0.5pAoVX^ i 



-086 

 -084 

 -082 

 -0.80 

 -0.76 

 -0.76 

 -0.74 

 -072 

 -070 

 -0.68 

 -066 

 ■ 064 



Ship Speed, kt 



Fig. 59.1 Variation of Thrust-Load Coefficient With Ship Speed and Speed-Length Quotient 

 FOR Three Merchant-Ship Models 



sure curve is drawn for a Ctl value of 2.5, with a 

 ratio -Ap/+ Ap of 0.737. 



It is emphasized that the data presented in this 

 section apply to perfect conditions in an ideal 

 liquid, and that they conform only rarely to 

 conditions encountered in practice. 



Knowledge concerning the local values of the 

 induced velocity, symbolized by fcf// , in the 

 vicinity of the individual blades of an actual 

 screw propeller behind a ship, would be extremely 



useful information. However, present develop- 

 ments (1955) permit only a direct determination 

 of the hydrodynamic pitch angle /^/(beta), as in 

 Sees. 59.17, 70.27, and 70.28, and this determina- 

 tion must often be made by trial-and-error 

 methods. 



59.14 The Thrust-Load Factor and Derived 

 Data. As an indication of the manner in which 

 the thrust loading on actual ships varies with 

 speed throughout the normal running range, 



