ORIGINAL: BMatthews
I haven't used the Plane Geometry spreadsheet. And while I only fly sport models and never built a big pattern ship I know that to achieve a nice neutal handling model I've always ended up with the CG back around 30 to 35%. And on the flat foamie I've got the balance is back around 40%. If it were any farther ahead on any of those the models would be nose heavy and need lots of up trim. But it would seem that Dick, our resident pattern model designing guru, agrees with your numbers. So all I can do is shake my head in confusion and realise that I still have much to learn.
I believe Dag is expecting purer response from the model upon application of yaw force, with the model in any attitude. His numbers are similar to those I use in my designs, except my TVC is lower.
With CG back to 35% MAC, the model's response will be less pure in yaw. Snap roll exits become a little less predictable and spins could overshoot easier.
Don't want to put words in his mouth but I think Dag is seeking the best compromise for a truly neutrally responding precision aerobatic model. Based on the numbers I see, he will