georgehere

Hi Guys...I know this has been covered before,I just can't find it, but.....acquired a low wing plane, needing new tail feathers and reinforcing in some areas. It's got "Lucky Lady" on the side and made of Styrofoam and preformed plastic at the cockpit, apparently sold as a RTF plane. First owner mounted an OS .32 Heli engine on it with a tuned pipe. The engine runs great. After adding all my electronics, I need to balance it, but have no paperwork for it. On my other planes (constant chord) I went 33% back from the leading edge and that worked. Does the same theory work on the tapered wing, using the greatest part of the chord for the measurement?

Jemo

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http://www.palosrc.com/instructors/cg.htm

georgehere

Jemo...Thanks for sending me to that site on CG calculation, but that is for a swept wing, as on a jet. Mine is tapered wing. leading edge straight, 90 degrees to the body, trailing edge tapered.

Thomas Williams

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georgehere the site jemo gave you is for most wings not just for jets.They simply used the wing on that page as a sample.Just put in the figures from another plane you have or have had and you will see how it works.I put in some figures from a plane and it was correct.

Jemo

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That CG calculator works pretty good. I have tried it with several wing types. If nothing else it gives you a CG to start with.
I never used it for a Jet wing

georgehere

Hi Jemo...I tried to put my numbers on that chart....could not get it to work. My root base chord is 9 1/2", so I used three inches back from the leading edge and the nose dropped vertical on the CG device. I moved the CG to 2 3/4" and with two ounces of lead got it to an acceptable attitude, still nose down but flyable. Took it to the field today, and with the heart pumping. it jumped off the ground and screamed around the sky on the tuned pipe...Get this...NO trim required. Never had a plane do that. Your response was appreciated, tho.

georgehere

Didn't see your post, Thomas. Will try it again. Thanks.

Jemo

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Did you put all the numbers in, ???.
A, B, S, Y and %
If you did, it will work.

moodier

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Just looking at that formula forCG,think I know why my teachers told me to pay closer attention in math class never thouhght would need it again.Could I ask a simpler question?Anyone know where the balance point should be for a Top Flight 5'5" wing AT-6?Can't find the plane anywhere ,did find info on a Lanier 62"wing one is 3.5"back on that one.Would that be close enough.It drops nose on landing when throttle cut back they say that indicates nose heavy?

jetmex-RCU

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Try this:

http://www.home.earthlink.net/~pjburke1/aindex.html

Scroll down the left side of the page until you find the "Finding the CG" link. Covers straight wings, tapered wings, biplanes, etc. Fairly simple as well.

Jemo

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It can't get easier than this. Just enter your dimensions and click on the button.
http://www.palosrc.com/instructors/cg.htm

georgehere

Jemo...Today it works. I entered whole numbers(no fractions) without the (") indicator, but did not know what the %MAC shud be so I put in 30 and it came up with 2.05. here are my numbers...A-9.5..B-6..S-0..Y-10.5 These latest numbers are what I just measured on the wing. I just lack the % to put it on the chart. Thanks for staying with me on this. Looks like the CG is going to be even less than the 2.75 i am now using.

Jemo

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You can usually use between 25% and 30%, depending on the airfoil . If you have a symmetrical wing use 30%.

georgehere

Jemo..Just put in the numbers from my previous post and used 30% symmetrical foil and it came 2.36. Didn't miss it by much at 2.75. Maybe I can take off some weight now. Saving the CG site.

Jemo

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George,
Once you get in the ball park with the calculator. Then adjust by the way it files, or I should say, the way you want it to fly.
A calculator like this, is used to give you a good safe start.

georgehere

Jemo...I can't believe how sensitive this plane is. Measured accurately and put in the numbers and put it on the CG machine to rebalance. Earlier, with my guesstimate 2.75" I had added 2 oz of lead in the tail and it was still seriously nose down. I flew it that way and landed fine, but boy! was it quirky. I put in too much aileron on the turns every time and had to back off. The plane flew level and tracked true, but very sensitive.
With the new numbers and 2.4" back from leading edge the tail dropped. I took off 1/4 oz of lead and it balanced slightly nose down, just like I like it. Just a 1/4 oz of lead removed did that much. Can't wait to fly it. Many thanks.