ORIGINAL: CPTOZZY
I was given a Homemade half finished Airframe. The wing is symmetrical and the fuselage is a Profile. I will be adding my own electronics and motor. How do I determinemathmatically where the CG should be on this (or any future scratch designed) aircraft??
Thanks
Nine measurements with a yardstick. It takes a couple of minutes. Plug them into any online app that does CGs and click.
This is a good one.
http://www.geistware.com/rcmodeling/cg_super_calc.htm
Plug in the measurements then put 15 in the 'desired static margin' field and click. You can use the CG location given for 15. It'll be safe for sure. Of run once for 5% and once for 20% and you'll have a safe range for the CG. It's magic.
If you want to go simple, then go really simple and just balance on the spar. MOST models have the spar located where the CG can safely be. No need to figure anything if you think your model is an average layout. The simple methods work for 'normal looking' models. So use the simplest if that's good enough for you. If you'd prefer to have something that takes the important details (there really aren't too many) into consideration, spend a minute or two measuring and run the geistware app. The measuring is simple to do. They do the figuring for you.