tuffy trainer

[sammiejames]

built a modified one of these ended up w/ 50 inch wing span 7 inchcord
wing is dt foam armin wing carbon arrow 10 in polyheidrel

ok n
w here the ??? how to size the tail elevator rudder and stabilizers and how long should the boom be to wk w/ new wing span


thanks for the help and the great site
sammies the dog im james

[sammiejames]

i should have said im doing ret setup to start mabey change to aileron trainer later


thanks again

[fhhuber]

boom length and tailplane size depend on how stable vs how aerobatic you want it.

Longer distance between the wing and tailplanes means you can use smaller rudder/vertical stab and the elevator will be more responsive.

Look at a 3-view of a Piper J-3 Cub or Cessna 152 for good proportions for a trainer.

Going with rudder-elevator-throttle means you need more dihedral (polyhedral... sounds like you should have that right) and having a little "washout" (bend the trailing edge of the wingtips up a little) is a good idea. Dihedral converts part of rudder's Yaw effect into roll. Washout makes the airplane more stable in a stall.

For good stability and near automatic stall recovery have the model balance appx 30% of the "chord" (distance from leading edge to trailing edge) back from the leading edge of the wing.
A little further forward or back should still be flyable. More forward means it will need more speed to prevent the nose from dropping. More back means the plane will be more responsive to the elevator.

[sammiejames]

some where i found a thread with a formula for wing tail proportion someone link me to that please
this planeis a pusher so i am concerned being tail heavy

thanks

sammies the dog im james

[fhhuber]

Weight and balance is the same pusher or tractor and positioning/size of the tailplanes is the same.

stretch the nose forward of the wing and make a pod for the battery to achieve correct CG. Common pod and boom arrangement for pusher aircraft such as the (discontinued) Wingo (best picture I could find still on the net)
Wingo was a pretty good plane but ahead of its time. It used NiCd battery. With LiPo it would have been a real winner. (they would have stretched the fuselage forward a bit more because of the lighter battery)

[road king 97]

Originally Posted by fhhuber

Weight and balance is the same pusher or tractor and positioning/size of the tailplanes is the same.

stretch the nose forward of the wing and make a pod for the battery to achieve correct CG. Common pod and boom arrangement for pusher aircraft such as the (discontinued) Wingo (best picture I could find still on the net)
Wingo was a pretty good plane but ahead of its time. It used NiCd battery. With LiPo it would have been a real winner. (they would have stretched the fuselage forward a bit more because of the lighter battery)

I still have my Wingo great flyer on a calm day. joe