How to CAD? Where to learn?

I want to make myself a custom chassis, with a lattice style structure, much like the Lightening Supermaxx chassis. The top plate will be lattice and the braces will be latice much like the Savage. Really I am wondering how to make a latice pattern, keeping the highest strength possible. So is there any "equation" to making an effective lattice design? Any help would be appreciated, as for I know some of you guys know about this stuff. Thanks