Munk and Prohaska 



successive changes of the revolutions of the auxiliary propeller, adjusting in each 

 case the revolutions of the main propeller until the model was self-propelled. 



ANALYSIS OF THE RESULTS 



The resistance tests were extrapolated to ship scale by using the Hughes 

 method and a form factor of 1.36 for fully loaded condition and 1.28 for ballasted 

 condition, and a c^ value of 0.15 • 10"^ . The self -propulsion tests were analyzed 

 by the method described in Ref . 2, which method normally is used at HyA. The 

 analysis work was done on the HyA-GIER computer. 



The wake coefficient corrections used in the different cases are given in 

 Table 4. i •; 



Table 4 



Wake Coefficient Corrections Used for Analysis 



of the Self- Propulsion Tests 



(Ship wake coefficient = model wake coefficient - 

 wake coefficient correction) 



Wake 

 Coefficient 

 Propulsion Arrangement Correction* 



Ordinary single- screw 0.140 



Ordinary twin-screw 0.010 



Interlocking propellers, distance between axes = 0.7 'D 0.097 



Interlocking propellers, distance between axes = 0.8 "D 0.086 



Interlocking propellers, distance between axes = 0.9 -D 0.074 



Auxiliary propeller system, main prop 0.140 



Auxiliary propeller system, small prop 0.180 



'''The wake correction is calculated as the difference between the ve- 

 locity in the boundary layer integrated over the propeller disk for 

 model and for ship. 



The results of the stress measurements were given by the recorder in the 

 form of curves showing the stress caused by the bending moment on the blade as a 

 function of time or of blade position, a mark being placed on the paper every time 

 the blade was in the upper position. 



The blade stress is proportional to the bending moment, and after calibration 

 the curves therefore represent the bending moment at the blade root as a function 

 of the blade position. The bending moment is a function of the resultant force on 

 the blade normal to the section where the stress is measured, hereafter called 

 the normal force, and of the distance of the center of pressure from the root. 



1528 



