You do not
need CAD to design or build a robot. We use it pretty religiously. We find that generating a CADD model in inventor before building the robot saves us a lot of time and money, and we end up with a better looking robot. We can also eliminate kids who miss a lot of meetings walking in and not knowing what is going on, or why things are the way they are. If a kid misses meetings, they can just consult the CADD files, and look at the robot. Comparing the two they know what needs to be done.
There is also something really nice about knowing what to buy, and how much of it you need. We have saved a ton of money this way. Before CADDing our robots we would literally guess about what might work, spend money, and then find out we were wrong after modifying the part in some stupid way so that we couldn't return it. Our first year cadding the robot I could have told you how much money we would spend total and have been right within about $100 during the second week of build season.
Here is a video:
http://www.youtube.com/watch?v=HU3_N_emoks
Hope this helps.
Edoga