these last three values are vectorially by trigonometry determined from fig2 across a rotating blade row such as the row of fig2 static pressure rise u03b7 sub r x reduction of relative dynamic pressure where u03b7 r channel efficiency of a rotating blade passage the known aerodynamic 34 blade loading 34 equation is equ6 where c d blade drag coefficient the term u03c3c d cot u03c6 r in equation 5 can be rewritten as equ7 it is known that for sheet metal fan blades an optimum value for u03b7 r in equation 6 would be 0 8 now substituting numerical values into equation 6 equ8 the iteration process starts from here to select a blade cross sectional configuration at the chosen radial station r 9 86 in which will satisfy c l u03c3 1 013 firstly a trial value of c greater than zero is selected and calculations are made to obtain u03b8 u03c3 and a c next fig7 is employed to obtain c l and then c l u03c3 is calculated these four variables are repeatedly calculated until the value of c l u03c3 obtained by equation 6 is equal to the value of c l u03c3 obtained by the use of test data such as that shown at fig7 the final iteration results are as follows c the chord length see fig2 was found to be 10 33 inches and all of the remaining geometrical parameters of a circular cambered plate blade can be calculated as follows equ9 since c l at u03b1 optimum c l u03c3 u03c3 1 013 the.