What are straight helical fletching? Do you use right or left wing feathers?   What are teh advantages of such???

i may be wrong but i dont think there is a thing.  there is a stright offset that does help rotate the arrow but helical puts a twist on the feather.

Steve,
Go to trueflightfeathers.com and look at their fletching guide.  It will answer all of your (fletching) questions.
-Chad