Not free but a very good CAD program for the money is ViaCAD 2D/3D V8 as it not only let's you design it but you can then extract 2D drawings from the model. I used it on my model and it really helped make designing and the build much much easier. Also I knew what materials where needed. Still ended up with a few tweaks here and there but that is better then major OS moment. Good luck.

Michael