Highly recommend that you check out Aircraft Documentation Service at
http://airdoc.biz/ .
This was formerly Bob's Aircraft Documentation. There are two different sets of drawings available, each rated as having good detail with cross sections. These would normally be more than adequate to support your scale documentation for your scale project.
He also has listed a number of "Photo Paaks" (18) for the Curtis Robin with different color schemes, cockpit details, engine details, landing gear, maybe 300 photos in all. These are normally good quality photos, though not cheap.
If you are doing a serious scale project, then you cannot go wrong in checking this stuff out.
Keith