I think the best thing I ever did to learn about ARF weights was, like Barry, weigh every single part and wrote it down. It made me totally aware of what weight I'm adding to the ARF and where it was going. I bought this one digital scale after reading a good review in RCU. It works great and is very accurate (.1 ounces at low end, .2 at high end I believe). Anyway, I wish more people would post their ARF weights here. It really helps us to know what we're getting.

30lb scale
e*Bay item 3805374437

50 lb scale
e*Bay item 2995997314