Posted: 6/23/2011 14:31:07
We are a group of four crazy norwegians, we are going to compete in the redbull flugtag competition in Norway and we need some tips. its not allowed with engines. we are dropping the plane from a 6 metres high ramp. max weight on airplane is 200kg.
- what is the best center of gravity, in percents?
- should the wings be over or under the aircraft body?
- speed/wing ratio.. how much speed do we need when the wings are 7 metres long (both of them)
Posted: 6/29/2011 23:03:03
Joakim: These events are way cool! Good luck. I would love to do one some day ... so I envy you. All aircraft design is a compromise (so you will get a million different answers to your questions). 1) Best CG? 25% ... 1/4th of the wing chord (front to back) back from the leading edge. The airplane will be stable, and you won't have to worry as much about the tail. 2) High or low wing? ... High. This will give you built-in lateral (roll) stability. 3) Speed/wing ratio? This is kind of a strange question. Lift is based on wing area (L=1/2*rho*V^2*S*CL). "1/2*rho*V^2" is known as dynamic pressure (or "q") ,,, Google it. "S" is your wing area. CL is the coefficient of lift (use 0.5 ... but it depends on the airfoil you will be using ... Google it, too). Using a Clark-Y airfoil, it is very easy to build (it has a flat bottom), and you can get the coordinates (points to plot to make the shape) off the internet. Have fun! -Ron