CG first flight.
 

Is it better to have my Tower 40 trainer a little nose heavy first flight? How will I know if its to nose heavy. Been flying awhile, but curious about other's thoughts.

Virtually all the conventional trainers will perform best balanced at 25% mac not 30%. Expressed another way that ideal starting point is the quarter chord or you could simply divide the distance from the leading edge to the trailing edge by four and the sum is the distance back from the leading edge that is your ideal target balance point. This applies to any straight chord untapered wing and indeed most trainers including yours is straight chord.

This 25%mac or quarter chord is also on most airplanes at or very near the position of the main wing spar.

"How will I know if it is too nose heavy" Very simple just lift it on two fingers at the target cg point under the wing and if it sits level it is balanced at that point, If the nose angles down then it is nose heavy and the cg is forward of your desired point, do not angle the nose down for "Mother And Country' when balancing your airplane.


John

I see absolutely no reason to go further forward than 25% on a trainer. I've seen the bad advice of going a little more nose heavy many times, but it never results in a plane that flies right.

Normally I would suggest that you just follow the instructions, but as the years go by it seems like so much is lost in translation, i.e., I seldom trust any ARF that comes from overseas to being correct.

Where you balance any model depends on many factors, such as pilots experience and intended use of the model. But your immediate goal is a successful first flight, and John's numbers will get you there.

What you are setting up is a model which will be very speed sensitive, it will have a speed that it will fly level, faster and it will climb, slower and it descends. It trait also gives it the ability to self recover from mild upsets in the air assuming you are flying at the trimmed speed. So if in a slight climb it slows and the nose come down, it will overshoot, so it will pick up too much speed and then the nose will rise back up. Left alone, it will eventually come back to it's trim speed flying level until the pilot does the next "upset".

The more nose heavy, the more pronounced the effect. This is how full size general aviation aircraft are set up, you set the power and then adjust the pitch trim. For it to work properly for models you have to balance the CG location, throttle, and elevator trim. Other factors are engine thrust, decalage (angle of the wing to horizontal tail). The trade off you are making is manoverbility in the air and landing speed. Too far forward requires higher speeds for landing because there is a limit to the force the tail can generate as the speed goes down. As the balance is moved back, it becomes easier to land, right up to the point where you got back too far with the balance. At that point the model gets much more difficult to hold a commanded pitch change rate and the elevator control become divergent. Further back and a model become less and less controllable.

Follow the instructions for CG. Nose heavy doesn't want to slow down on approach or flair. Now remember that is an extreme nose heavy plane. You set CG with an empty fuel tank. Then add the weight of the fuel and fly fine.

I agree w Jetmech, for a well-known plane like the Tower Trainer just follow the instructions. I'm an instructor, we have a couple of them in the club and they are fine.