Paul - using several pages of print outs from PRPLRIT'
and other sources this is the table I came up with for
a 160 hp engine (like 320 Lyc) with a prop sizeds for
about 190 mph for a clean RV6 or KIS two place class
of airplane.
fixed pitch 70X78             const spd   var gear
   mph  rpm   bhp f lbs eff    f lbs eff  f lbs eff
    0   1940  108  407   0      603   0    525   0
   30   1950  109  393  28      530  26    505  25
   60   1960  110  353  51      480  50    460  47
   90   2080  118  327  66      425  63    420  62
  120   2400  130  307  76      366  73    365  73
  160   2500  149  283  81      299  80    299  80
  190   2720  160  268  83      268  83    268  83

Vance why would your fixed pitch and constant speed props have about the 
same eff. at 30, 60 and 90  MPH? I think you are off here.
I think you are way off.  I think you forgot to increase the eff. 
for the constant speed prop. Put a HP column in there for the constant
speed prop.

Let us define our terms here.

Theory thrust is = HP * 550/FPS.

Prop eff is = actual thrust/ theory thrust
 
Paul Lamar
 
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