What's with all I hear about electric stunters balancing aft of normal?  How does the plane know what's pulling it around?  Scientific minds want scientific answers.  Please, no "first-hand" accounts.

I do what most do;  bench trim the CG "about right", then fly it to see how it handles, and adjust CG to suit.

The question is compared to what? If I compare my models converted from IC to electric (actually I had only one  ) I did not see any CG shift (except for mentioned fuel effect). HOwever when I used light prop with smaller moment of inertia, I really needed move CG forward, because it has much smaller stabilizing effect. So that could be reason - if you compare Impact with large heavy prop for piped engine and smaller hollowed light prop for electric, it can make that difference.

Another thing is tail size. I went up with tail %. I remember Ted's rule for CG which had to be % of tail to wing area. I found that it well worked for tails up to 25%. However my Max Bee had tail volume from 30% to 33% (actually one had 33% and others had 30%). I found that the rule goes just opposite, that large tail autorithy allows CG more front and still cornerring well. So it looks like small tail up to 20% needs CG front, larger tail up to 25% allows CG little back to 25% and large tail up to 33% again allows CG shift back front. Combined with logaritmic flaps with limited feedback forces I can say that it can well fly also at 10% - that was CG position on my first model with such flaps as I used it on my first WCh in Sebnitz 2002 where it finished 10th. I had identical model with classic flaps and that model had CG at 19% giving similar feeling in maneuvers. But later I went with CG back to make it sharper in corners and Max Bee as I fly it now has CG somewhere at 17%. My older IC models with classic flaps were somewhere at 22% without fuel.


http://www.netax.sk/hexoft/stunt/the_max_ii.htm