If you wonder how to calculate the number of cells you wanna use or the size of the prop you have to use or calculate thrust or see how long you can fly with a specific combo.. Now you can find it all use the links or softwares

(1) http://adamone.rchomepage.com/calc_motor.htm
(2) http://www.brantuas.com/ezcalc/dma1.asp

Or a software is available from http://www.micronradiocontrol.co.uk/scorpion_calc.html