Using Ted Fancher's Imitation numbers as base it has a Tail Volume Coefficient of 0.45. Question - what is a good range for this? What happens as you move lower and higher? What is better to change - tail moment length or tail area to adjust to be closer to the 0.45?
Best, DennisT
I don't know what a good range is, but to answer that I'd take a look at the current machines that are winning and calculate their TVCs. You run the risk of fulfilling the adage that if you take the average of the "numbers" on a bunch of stunt planes and build your own you probably won't hit an optimum -- instead, you'll have a plane no better than average!
(I'm reminded of a review in the 1990's of a 1970's book on sailplane design. If you followed the authors rules on how to make the bestest sailplane ever, you ended up with a sailplane that flies like it's 1970.)
TVC probably has the strongest effect on the acceptable range of center of gravity that you can get away with. So flying a slimer, you'd be motivated to go to higher TVC, so the change in CG doesn't affect the flying qualities as much. I don't know if anyone has yet experimented with an electric that has a smaller tail -- it would be interesting. Higher TVC also gives the tail more authority in turns, so if you went smaller you might need more elevator throw.
Making the tail moment arm longer and the tail smaller should give you roughly the same static stability, but because of circular airflow you'll need more elevator in the corners, and you may end up with a plane that's hard to get started rotating and hard to get stopped.
I suspect that evolution has given us airplanes that are close to optimal -- but people thought that in 1965, and look where we are now! If anyone wants to experiment, a test dog that lets you bolt various tails on at various lengths could be very educational indeed -- but you'd need a really good pilot willing to put a lot of effort into the exercise.