Unusual Two-Propeller Arrangements 



20000 



to 000 



INTERL. PROPS OUTW DBT 068 ■ D, P No. 5915 



— • — •— ■ • • WST 477.0, P Na 5815 



DIST. (i86'D, P Na5915_ 



FULLY LOADED 



./y 



~it 



J^' 



/y 



/ 



y 



// 



// 



^ 



7^ 



7^ 



!'/ 



/// 



i 



SERVICE 

 SPEED 



12 13 U 15 t« n 18 



Fig. Al - Propeller horsepowers from tests 

 with outward -turning interlocking propellers 



two propeller loadings were therefore different. K this arrangement should 



be preferred to interlocking propellers, the two propellers should have different 



diameters and pitch. 



Stress measurements were carried out on both propellers running at the 

 same number of revolutions as well as at different numbers of revolutions. The 

 stresses were nearly the same as for interlocking propellers (Fig. 18). The in- 

 fluence of the aft propeller on the stresses of the forward propeller was ex- 

 tremely small, but the influence of the latter on the stresses of the former was, 

 as could be expected, more pronounced. 



1543 



