Help with CG on 4 star 40
 

I have recently finished a 4 star 40 and am completing a few final things before flying it. My question has to do with balancing the airplane. A little background info: I have built and successfully flown a Lazy bee and Speedy bee. I had no trouble balancing these planes. The method (maybe this is were I am going wrong?) I use to balance them is to hold the airplane up on my finger tips on the specified CG point. Then adjust accordingly until the plane balances on that point. I tried this with the four * and it seems I am chasing it all around. I hold up the airplane on the main spar and the nose goes down. So, I add a little weight to the back (1/4 oz lead). Then it seems like it will balance for a moment then the slightest movement of the tail going down and it just keeps on going like it is tail heavy. Then I can hold it up a second time and the slightest movement of the nose going down it just keeps on going like it is nose heavy. So then I thought well maybe I have the balance point on the spar since it will tip both ways. With the bees, I could hold them on the cg and run around the room. They would not tip front or back. Is it because they are so short coupled? If I am way off here, maybe some can suggest a more proper method of getting the cg in the correct place. Thanks for any help!

Help with CG on 4 star 40
 

The longer tail moment is the culprit. My 4* 60 doesn't seem to be so touchy on CG, as some other planes. Balance it a tad nose heavy, if it flys well...you're done. If it lands 'hot', add a bit of weight to the tail, or adjust your battery and/or RX. The 4* is a floater, and it doesn't seem to mind balancing a tad behind the spar.

That 4* 40 should land at a quick walk...say 5-7 MPH.

Help with CG on 4 star 40
 

Silly question, but you are balancing the plane upside down right?

Help with CG on 4 star 40
 

Waldo:

When you put your fingers under the wing the true cg of the plane will be above your fingers, therefore, unstable.

nbcguy has it right. Turn the plane over and it will be easy.

Bill.

Help with CG on 4 star 40
 

Well, no. I never really thought about it. This is my first low wing plane. Now it makes since.


Thanks for the replies!