Ed Anderson wrote:

Ken,
     I can't be much help on the RV-4, but on my 13B powered RV-6A the Ross
PSRU prop flange is exactly (within 1/8") of the lycoming installation (that
way the cowl fits my 13B).  With the rear part of the engine 8" from the
firewall.  This configuration gives me a empty C.G. 0.3 " forward of the
design recommendation (Van said no problem).
   A forward C.G makes for a very stable aircraft but can trim a few MPH off
due to down force requred on horz stab.  On the otherhand with me and a full
load of fuel the C.G moves to approx 25% Cord or just about over the center
of lift.  Aircraft flys great, when I can get it flying.

   You did mention that you had clustered all the radiators, etc at one C.G,
that makes it hard to assess as if you put your radiators and oil cooler up
front next to the spinner you certainly get more of a foward C.G. than if
you hung them under the engine.  However, I have heard that the -4 could use
a little more weight up front.
  Ed Anderson

Ed Anderson

 
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