When I set up my Bitzenburger jig to fletch arrows, how do I know how many degrees offset I'm putting on the arrows. I usually have the back dial set to -C- and the front one set half way between -C- and the right edge.Many times I've read on this forum that certain people fletch their arrows with (for example) helical with 4* offset. I haven't quite figured out how they determine the degree of offset. Do I need a protractor? Thanks for your help.

-Rob