I'm currently designing a kind of motor glider (ish) and am planning on using a v-tail.
I wanted to ask your opinion on the sizing of the tail that I've come up with and I'll run through some figures that I've used.
Here's some useful numbers:
Wing area (Sw) = 6000 cm2
Wing span (b) = 200cm
Distance from tail Aerodynamic Centre to aircraft Centre of
Gravity (L(h/v)) = 62cm
Mean Aerodynamic Chord = 30cm
From Mark Drela's post on the Charles River RC website (http://www.charlesriverrc.org/articles/design/markdrela_vtailsizing.htm) we know that a v-tail area needs to be the sum of the horizontal and vertical stabiliser areas.
So, I need to work out a good area for these.
I've gone with 20% of wing area for the horizontal stabiliser and 10% for the vertical. These numbers were taken from here: http://www.airfieldmodels.com/information_source/math_and_science_of_model_aircraft/rc_aircraft_design/step_by_step_model_aircraft_design.htm
This gives me the horiztonal stabiliser area (Sh) as 1200cm2 and the vertical stabiliser area (Sv) as 600cm2.
Summing these gives 1800cm2 and as I'd like a base of 20cm of the tail on the fuselage that gives me 45cm length on each side. If you also follow the angle calculation on Mark Drela's post then you get 35 degrees from the horizontal or 110 degrees between the tails.
So, do you like math/s? Me too. Let's work out the horizontal and vertical tail volume coefficients (Vh and Vv) to see if they're any good.
These are worked out using the following formulas (http://www.eaa62.org/technotes/tail.htm):
Vh = Sh x Lh / Sw x MAC
Vv = Sv x Lv / Sw x b
Plugging in my numbers gives me a Vh of 0.41 and a Vv of 0.031.
My question is: do you think I've chosen the right sized tail? Does it need to be bigger/smaller?
Thanks for taking the time to look through this post. Please note that given the restrictions of my build I can't move the tail backwards so can't increase Vh or Vv that way. I also can't move the wings forward.
Thanks again and any advice would be much appreciated.