I do CAD work professionally. I do rendering for fun.
Many CAD packages have a very steep learning curve. Then to add insult to injury, they are very expensive.
Most people just need to lay out some curves in 2D to get an idea of what they want to build. QCAD is perfect for that. And it's cheap, or free depending on which version you pick.
http://www.qcad.org/qcad.html
A lot of people like Sketch-UP. I've never learn it, so I can't say much about it. But it seems to to modeling okay. On their website they say sketch up is NOT a CAD package. So what is it, I wonder!!!
If I had to recommend a solid modeling package to someone who was just starting out, and didn't want to spend a lot of money, I would suggest ViaCAD. It has a lot of horsepower, it's easy to learn, and it's affordable.
http://www.punchcad.com/products/viacad2d3d.htm
Let us know what you decide to do!
Mike...
The quality is remembered long after the price is forgotten, so build your teardrop with the best materials...