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Old Oct 18, 2001, 12:40 PM
Lifes 2 short, go sloping
colorado @ 5500feet
Joined Sep 2001
1,054 Posts
center of gravity calculator

I design and create my own planes, the only step I have a problem with is finding the CG. can someone send me a URL or the name of a site to search for so I can get a free CG calculator.

I want to say I am a zagi owner, and have fun with electric flight but my heart belongs to slope soaring . There is nothing like getting a 3 hour flight on a good day and only coming down because your neck and arms are tired, and u get thirsty in the sun. Some guys I fly around wear "camel Bags" so they don't have to stop to get a drink while flying. Over an hour of straight combat is common and there is no bigger motor or battery pack needed....you go as fast as the wind will let you which can reach 250mph with the right (expensive) plane and pilot. Anyway if you haven't sloped yet give it at try if you can, I was hooked after the first day!

thanks for any help you can give.
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Old Oct 18, 2001, 12:57 PM
Electriaddict
dorysch1's Avatar
Melville Saskatchewan Canada
Joined Mar 2001
1,579 Posts
Try this and measure 20% back from Leading edge
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Old Oct 18, 2001, 03:03 PM
Lifes 2 short, go sloping
colorado @ 5500feet
Joined Sep 2001
1,054 Posts
thanks, I will put it work.
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Old Oct 18, 2001, 09:10 PM
Master of disaster
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Northern Virginia
Joined May 2000
707 Posts
dorysch1, will this work for delta wings also?
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Old Oct 19, 2001, 10:32 AM
Lifes 2 short, go sloping
colorado @ 5500feet
Joined Sep 2001
1,054 Posts
Thanks I tried it out on one of my existing scratch builts and the CG is right on, a great starting point, it was only 1/4 off from my CG I am using.

Thanks and for anyone else it does work!
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Old Oct 19, 2001, 08:33 PM
Dude, where's My Plane?
JasonJ's Avatar
Green Lane PA USA
Joined Mar 2001
2,167 Posts
Oh yeah thats right man, as far as delta goes, if you check out the above post where the 20% mark was mentioned, you see at the bottom it says between 16 and 20 percent for deltas is mentioned. check out the CG on the CAD pick on this fourm for a quick delta refferance.
http://www.rcgroups.com/forums/showt...threadid=14189
The whole CG calc is on the EDF fourm.
Compound wings are harder and Deltas have some considerations so thats why the mark is 18% or so. the MAC is the average chord or width of the wing, so if the tip of the wing is 3 inches and the root is 9 inches the average is 3+9=12 and devide by 2 to get 6. So 6 inches from the trailing edge of the root or 3 from the leading edge of the root is the aveage.
now take the 6 X .20 (20%) and you get 1.2. Measure 1.2 inches from the Leading Edge of the Root rib and thats the CG.
I like to use MM in the calcs cause its easier to use than trying to figure out what fraction 1.2 inches is .
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Old Oct 22, 2001, 10:32 AM
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Melville Saskatchewan Canada
Joined Mar 2001
1,579 Posts
exactly what Jason said
I learned the hard way that there is no easy way to "Pin Down" CG exactly the first time but this should get it close to fly and then adjust as necessary
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