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Help on CG

Old 11-05-2007, 03:12 PM
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daz3nt
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Default Help on CG

If i measure my plane and wings can someone help me on the ceter of gravity i have tried the cg calculator but get stuck on the mac part of the ecuasion. Thankyou all

P.S damn no spell check lol
Old 11-05-2007, 03:20 PM
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Mr67Stang
 
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Default RE: Help on CG

MAC = Mean Air Chord

What kind of plane are you working on? Most planes will be flyable with the C/B set from 25%-30% of wing chord (this is length not span). so if you have a wing that is 10 inches from leading edge to trailing edge you can safely fly it with it ballanced at 2.5 inches from leading edge.
Old 11-05-2007, 03:23 PM
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Default RE: Help on CG

In adition the above works on rectangular wings not tappered or delta.
Old 11-05-2007, 03:27 PM
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daz3nt
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Default RE: Help on CG

Ok starting to make sense. Its a high wing trainer dont know what make could be a home built one. anyway it has a wing chord of 12 and a half inches including ailerons and 11inches excluding ailerons. Im guessing I should take the ailerons into consideration so it should be aprox 3inches from the leading edge?
Old 11-05-2007, 03:29 PM
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daz3nt
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Default RE: Help on CG

of course yes it has a flat bottom and has a dihadral. Ithink thats what its called the wing tips are higher than the middle of the wing if you know what i mean lol
Old 11-05-2007, 03:37 PM
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Default RE: Help on CG

Yes you are describing dihedral. With your Chord length of 12.5 in devide by 4 (25%) = 3.125 inch or 3 1/8 from leading edge. This should be a safe starting point.
Old 11-05-2007, 03:38 PM
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daz3nt
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Default RE: Help on CG

Thankyou Verymuch I should sleep well tonight. Thanks again everyone
Old 11-05-2007, 03:42 PM
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daz3nt
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Default RE: Help on CG

Ok one more problem just come to mind. is the downthrust of my engine important on my trainer?
Old 11-05-2007, 03:48 PM
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OzMo
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Default RE: Help on CG

Likely (but not always) the CG on a trainer will be on the spar . make sure your fuel tank is completely empty when balancing. and no breazes from furnace etc. balance laterally as well by holding it with a loop of string to the prop shaft and by the tail end of the fuse(a well centered pin helps). this will make a much better flying plane good Luck
Old 11-05-2007, 03:50 PM
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daz3nt
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Default RE: Help on CG

lmao thanks I love your quote OzMo
Old 11-05-2007, 03:57 PM
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Default RE: Help on CG


ORIGINAL: daz3nt

Ok one more problem just come to mind. is the downthrust of my engine important on my trainer?
Yes.

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