I use a postal Digital scale that I got from Staples.

I think this is the one I have:
http://www.staples.com/DYMO-3-lb-Dig...product_897130

I also use it to measure epoxy so I get an even mix by weight.

The above has a 3 pound limit which is fine if you weighing parts of a sailplane. If you want to put the whole thing on the scale at once then this would be more suitable.
http://www.staples.com/DYMO-10-lb-Di...nalize=certona