Welcome Long John!
I scrolled through this thread back a bit and cannot figure out to what you are responding.
But I’ll throw my two scents in anyway 😀 One of the cool things about feathers is that one side is smoother than the other. Natures way of getting every little advantage, lift wise. The difference in surface texture causes one side to have more turbulent flow, and thus induces lift. On an arrow, this affect will spin the arrow.
Thus, even straight feathers induce rotation.
While I don’t think it makes a hill of beans difference one way or the other (as far as killing a deer or hitting a bulls eye) I have to respectfully disagree with your analysis of what happens when an arrow flies with helical feathers. In my experience, they do slow down at a faster rate than straight fletched arrows.
In fact, many years ago I shot straight fletch and helical fletch through a crono and measured their speeds every yard out to 30 yards (compound bow with sights, archer with beer). The helical fletch curve dropped below the straight fletch curve and kept on dropping (made a pretty excel graph). I lost the data in a hardrive failure a few years back. But I seem to remember that at 30 yards, the velocity was at least 15 fps slower for the helical fletched arrows.
I have found other advantages to using straight fletching too: Since the feather is not being stressed by bending around the shaft, it tends to last longer and it flies more quietly since the feathers are not causing so much turbulence. Not to mention being easier to put on the shaft in the first place…