Thrustline/angle for 3D plane?

[hardlock]

With the centerline through the motor, wing, and hor stab on a 3D flat plate wing plane, I have the motor a few degrees to the right for torque.

Pitch trim isn't equal for inverted however. Landing gear has minimul drag but may be the cause, not sure. Normally is down thrust used only if thrustline is above wing or is it added for gyro effects or something?

Thanks

[raptor22]

You'd want it if the motor is BELOW the wing (thrust will sorta pull the bottom forward more). In your case, you would need upthrust. However, you seem to have the motor on wing level, so it shouldn't be an issue. My guess is that your incidence (elevator trim w/ a flying stab like that) is off. Check it.

Here's a quick way to do so: stall the plane with power off at high altitude. Let the nose drop straight down. Keep it there w/ no power. If you need to apply down stick to keep it down at any point then you need down trim to correct your problem because it is not 0-0.

--Alex

[raptor22]

Downthrust is also used to counteract apositive pitch moment in planes like trainers with excessive incidence.

--Alex

[hardlock]

Even at 35% CG I still have to run with a touch of up trim for level glide. Adding power has a neutral effect on pitch so guess the plane is the cause. Will try the dive test with and w/o LG to see if that's what's causing it.

Thanks,

Ken