all planes balance at one third back from the leading edge.
Well ... it is true ... kinda. Any plane can be made to ballance at 1/3 back ... but not all of them are meant to...
how do you calculate for tapered wings
I have a spreadsheet called [link=http://home.alltel.net/semidomestic/design.xls]design.xls[/link] I didn't create it, but it does work. If you use excell, it'll have to be reformatted. I got it to run fine with Corel Quattro
another option is [link=http://sky.prohosting.com/air2/cg_calc.htm]here[/link].