CAD Tool For Design Tiny Aircraft

Hi All,

I have never really used a CAD program to design anything. I toyed
with AutoCAD back in 1987 but nothing more.

I'd like to design a small model aircraft, about one meter in length.
Even though it's small, it's still complex. There are many mechanical
pieces.

The most important feature I need, by far, is interdependencies of
paramters. [There is probably a fancy name for this]. In other words,
if I change an artifact of the aircraft from one material to the
other, I would like the change to manifest in every aspect of the
aircraft that depends on the material. I guess this is standard
feature. I would like to be able to program interelationships also,
preferrably in C++, but a scripting language will do.

The other important feature is that I need the tool to be "3D-aware"
from the outset. I'm hearing others in rec.aviation.piloting that
AutoCAD is not entirely 3D-aware. I don't know what that means, and I
am definitely not interested in finding out by trial and error.

I post to CCS because the presentation of SolidWorks on its website
gives me the feeling that they understand these issues and attacked
them head on, but any CAD package would do.

Finally, I prefer cheap over expensive.

-Le Chaud Lapin-