Scratch Built Flying Dynamics
 

I build an airplane similar to the Great Planes Fundango (http://www3.towerhobbies.com/cgi-bin...?&I=LXVU18&P=7), and my test flights have been unsuccessful.

Flight #1:

Airplane climbed with full elevator. I eased off elev a little and it dove to the ground, I pulled full elev, and it started leveling off, but not enough before impacting the ground.

Flight #2:

I increased the elevator throw. Airplane flew nose up (like 45 deg)and would not climb anymore than 10 feet. Although not holding full elevator any relax in back pressure would cause the plane to descend while still being nose high. Lost control when it went too far away.

I am using the stock motor & propeller from my Multiplex Sky Scooter. These are the stats:

Motor: Permax 400 6V
ESC: Multiplex Multicont X-08 (8 Amp)
3:1 gearbox
8.4 volt 900 mah nicd battery

Airplane:

Wingspan: 40 inches
Wing chord: 6 inches

Stab span: 10 inches
Chord span: 3 inches

Distance from prop plane to fuse end: 30 inches

CG: ~30% of chord = 1.8 inches (I assume it should be 1/4 to 1/3 of chord).

I'm not sure on the weight or type of propeller.

So, are the flight problems caused by?:

1. Balance - tail heavy?

2. Underpowered. (The reviews are pretty good on this motor: http://www.hobbyking.com/hobbyking/s...dproduct=4708#)

3. Stab is too small?

4. Elevator is too small?


Please let me know what you think. I'm guessing it's tail heavy and underpowered. Would moving the CG to 1/4 chord and buying a more powerful motor/prop combo solve the pitch problems?

Thanks for any help or advice.

Dan

RE: Scratch Built Flying Dynamics
 

sounds like a couple things.

1) your nose heavy move the battery back and try again

2) not sure how more throw gave you a tail heavy result.



i think if you were tail heavy you would be fighting to keep the nose down
KZ

RE: Scratch Built Flying Dynamics
 

Welcome to the RCU forums, Airmaster23!

Your model is not stable in pitch, regardless the motor and propeller.

Any model should be able to glide with no power.

I believe your stab has no negative incidence respect to the wing, which is called decalage.

Read these articles:

http://tpbweb.com/media/catalog/568.pdf

http://www.tpbweb.com/media/catalog/428.pdf

http://www.tpbweb.com/media/catalog/238.pdf

http://tpbweb.com/media/catalog/623.pdf