I was out last week practacing landings with my superstar 40. Though I will admit that calling what i do "landing" may be a bit deceiveing but things were just getting better when disaster struck. On take off the wheels had just bearly left the ground when the plane took a hard right and into the fence. Heavy damage to the wing and when i removed it i found the aileron servo was hanging loose. I suspect that is what caused the crash. After reparing the damage and rechecking the cog It also acured to me that the wing maybe should also be balaced but I had not seen any discusion about it. How important is it? Insidently the balance of the wing is o'k even with all that glue, but the fuse is way off. If the plane is assembled it takes about 21 grams at the left wing tip to balance the plane Should i add the weight or is there a better way?

The balance you require is "Lateral balance".

Yes, you shoud do it.

Your wings generate lift in proportion to wing-speed, and angle of attack. If one wing is heavier then the other, you will have to geenrate more lift on the heavy side to support the wing in "straight-and-level" flight (normally by "trimming" the ailerons).

If you were to do a loop with a trimmed, but unbalanced plane, then the lift forces of each wing will remain equal, but because the heavy wing is heavier, Newton;s laws stipulate that the heavy wing will take longer to do the loop... F = Ma (Force = Lift, M = wing mass, A = "how quickly wing lifts in loop")... The heavier wing has less accelleration ...

What happens in practice is that the plane will not "track" evenly through the loop.

This is evident in more places than just loops, but is easier to explain that way.

Basically, a laterally balanced plane will behave more consistently than an unbalanced one.

gus

I balance laterally the old fashioned way with pins in the tail and the prop hub up front. Is there a good system to make a lateral balancer ?

Any plane definately needs to be balanced laterally. But, 21 grams sounds like a LOT to me. Since you didn't say how much "heavy damage" was done to the wing, or which side. You say that the wing balances fine, but when attached to the fuse, it is heavy to the right. My first guess was that the wing wasn't centered, but if you ballanced it, then you obviously have a center marked. It just doesn't make good sense that it would be out of balance that much. Did you forget to put the servo in the wing? <just kidding>

My second suspicision would be that you don't have the "true center" of the fuse for reference. Tieing a string around the prop hub and the tail is a good way--IF the engine doesn't have "right thrust" built in. If it DOES, then it is going to throw you WAY off on the CG laterally.

RJV,

Sorry if I mislead you, 21 GRAMS really isn't a lot after a repair--I was thinking OUNCES for some reason. By all means, the plane should be balanced weight-wise--as discribed by gus. However, if you find it doesn't track well, there is a thing called "dynamic balancing" that will really help the plan to fly better. My Great Plans kit came with a matrix of how to dynamically balance an airplane for optimum flight performance. You can see a copy of it at http://www.stillwaterhobby.com/air/flighttrim.html. It may not be there much longer as the website has come under new managment, and will be completely redone.

RJV,
It's never a bad idea to laterally balance a plane, but if it's only out by 21 grams (which is less than an ounce), then I wouldn't lose sleep over it. It's a trainer after all. If it was a pattern, IMAC or 3D plane, I'd say definitely.

(Ballgunner, lateral is side to side. I got the impression you're thinking front to back.)

Dennis-

I laterally balance my planes by picking up the front by the propeller tip, and then gently (without too much pressure) pick up the tail. I can get it pretty close by this method. I know there are other mechanical ways, but this works for me. Maybe I was just lucky, but my trainer (Avistar) did not need any lateral balance.