CG..Superstar 40 Help!!
 

Just finishing assembly of a Hobbico Superstar 40 with OS 40 LA engine. This plane is the version that has the wing halves permanent glued together rather than the screw together with metal re-enforcer. Since there are some variations of this plane, the closest to my model download manual that I found at the Hobbico site specs the CG to be 4 5/32" from the leading edge. With an empty fuel tank, the plane is very nose heavy. It would require at least 2 oz. of weight to the tail to come close to balance, even after moving Tx and battery toward the rear.
All hobbico's "site posted" specs for CG of this model is 3 5/8". This would definitely put my plane in an easy to balance range. There are no modifications to the standard build of the kit. Just wondered if the less common SS 40 kit with wings permanently joined is so much different from the purely ARF's? As a beginner, I want to stay within the recommended balance range but a 1" discrepancy is a major factor for an inexperienced beginner. Any help is GREATLY appreciated.
Jim

Superstar
 

I know what you mean on the CG of this plane, my manual that came with the plane showed one thing and the one I downloaded showed another. Im not sure if its a old version, mistake or what.
What I did was balanced the plane on the main spar, balanced out perfect with the .46FX.

Dbow

CG..Superstar 40 Help!!
 

Use the 3 5/8" setting. I flew mine over 150 flights with that measurement..... the last 50 or so as a tail dragger configuration.
A guy at our field told me mine was wrong. I brought my manual to the field the next time and he brought his. His manual said 4 5/32" and mine 3 5/8". My plane flew great!!! That is a great trainer.... the LA is a little low on power but it is VERY reliable. Just don't pull too much elevator, too soon, on take off. Let the speed build up and ease on the elevator. I had a rough time with "WILD" take offs because I was always tip stalling by giving too much elevator...too soon. I blamed the .40 LA till my instructor took it off at 1/2 throttle :rolleyes: .... Good luck..

lownslo......... Bob

PS... I just went to my shop and dug out a wing half from the Superstar, that I saved for covering practice. 3 5/8" ends up right at the rear of the main spar. (basically what Dbow said) That is a good rule of thumb on a "constant cord" wing. You will have better control at that setting.

CG..Superstar 40 Help!!
 

The over four inch figure sounds a bit to far to the rear for a typical forty size trainer. When in doubt always use the more forward figure and I am sure you will find the figure lownnslo indicated is much closer to the mark.

To put your mind at ease 90% of all our aircraft fly well at 25 to 33% of the cord. So just figure where the quarter chord point is from the leading edge and that will be a safe starting point and you can refine the handeling later after flight testing by just moveing the CG aft in small increments.

John

CG..Superstar 40 Help!!
 

All your help makes a lot of sense. With a standard build, doesn't figure that you would almost have to tape a beer can onto the tail. Tx and battery movements make small adjustments but not to a great extent. Hobbico must be in error with that particular manual. Don't know if there's a lot of weight difference between the OS 40 LA and FX but it can't be much. Assume the FX may be slightly heavier but maybe much the same. Will start out with the 3 5/8" CG and see how that works.
Thanks

CG..Superstar 40 Help!!
 

Just remember that a nose heavy airplane will still fly and a tail heavy airplane won't. If you have a simulator , or access to one, try adjusting the CG one inch at a time toward the tail on a trainer until you see what I am talking about. It doesn't take much movement to make a big difference, so be careful on your real airplane. Much less expensive to experiment this way . :D

I checked tower hobbies and also Hobbico.com. If you have the Hobbico Super Start Select, with an OS LA engine, the CG reference points are 3-5/8" for a more docile flight characteristic (For a beginner ) and to 3-7/8" for a more responsive flight characteristic. ( A more experienced pilot ) - Use the 3-5/8 Cg reference point to begin with per the directions. I would use this information if I were assembling it for myself. I believe the Tower Hobbies max reference point of 4-1/2 " is possibly an error. Place your finger tips under the wings at this measurement, per the directions and the airplane should balance. Will most likely be a bit nose heavy.

By the way, this is a great trainer. Should serve you well over and over again if you take it easy and learn slowly. Get on a buddy box with an experienced pilot who will become your best friend.

Good luck.

CG..Superstar 40 Help!!
 

I'm not sure if you got the Select version with servos and engine pre-installed, but mine had a problem with the aileron servo popping off about 30 sec. into it's maiden flight and dropping into the throttle servo causing a virtually uncontrollable plane. Good thing my instructor could land it. Anyway, double check everything.

FR