How does a-, b- and c-grain balsa differ?
What kind should i use for what parts? Pleeaase...!

Cafeenman has a great site with a ton of information including what you are asking about. I recommend checking out his site at www.airfieldmodels.com

For your specific questions:
http://www.airfieldmodels.com/inform...ding/balsa.htm

Scott

also check with SIG Mfg THEY HAVE A VERY GOOD PAGE ON bALSA IN THEIR CATALOG