How things work out.... Based on the work I did with the 3D printed marine propellers I have been asked to design a 3D printed fletching jig that can apply feathers with a helical twist to arrows. First job is modelling the arrows and feathers and see from there. The other problem for me was finding common language for the terms used in archery, as opposed to straight and offset fletching etc etc. For me 1 turn per XX inches I can work with, the 1 in 18.5" is just under the 3 degree limit for spin and drag that seems to be the "do not exceed" Ahhh another journey begins, 3-4 feather fletching and staggering to try, not even sure I have the feathers orientated correctly yet.