celso.ferraz

I constructed this pusher RC, and i'm having problems to get into the air.
Fisrt, the main landing gear was too far from CG and elevator had not enough power to rotate.
Moved the landing gear fwd to 40% of MAC. CG is at 25% of MAC.
Now, I realized that, the more power i set on accelerator, the more hard it become to rotate.
That makes me wander if there are gyroscopic affects from motor and/or propeller.
The plane weights 0,8kg, motor is 1100Kv and propeller is 8 in diameter.
Does anyone faced something like this?

celso.ferraz

I spent the day thinking about this issue and concluded that:
1 by the time I discovered the pitch-down moment, the wheels were blocked, as if they had brakes.
2 in such case, there will be a pitch-down moment caused by the thrust vector multiplied by the distance between ground and the thrust vector.

I hang the plane by its center of gravity and applied power. The elevator responded well, for pitch up and down, at various leves of power.
Let's go for another tentative flight and see what happens.

Gtarling

It's difficult to see the angle the wing is at when the model is sat on its wheels, but I'd suggest it needs a bit more wing incidence to get airborne. Easiest way is to lengthen the nose undercarriage leg a bit and try again. If you think it's the motor thrustline preventing it from getting airborne, try a takeoff run and when it's at full speed, kill the throttle. If it leaps into the air, be prepared to open the throttle again quickly!

celso.ferraz

Gtarling, thank you for the contribution.
One thing I did, was to move the main landing gear forward, closer to the CG.
This gave more authority to the elevator at the rotation.
I could not try another flight, because of rain last week.
Next saturday i will try again, and will publish the results here.
I believe it will take off this time. I will keep in mind your advice.

celso.ferraz

This plane flew well last sunday. Takeoff was easy. No problens on rotating.