At most find-sites that have arrows there will be a non-equal mix of S- and Z-wrap on the bindings. The dig report will assert that left-handed fletchers were responsible for those that aren’t the majority direction arrow binding, probably without mentioning whether it’s the Z- or S- that they are talking about. I can’t find where it was written down the first time, but it has been repeated until it became lore. Consider the Ötze website:
According to technical archaeologist Harm Paulsen, the two arrows could not have been fashioned by the same person. The fletching shows that one was wound by a left-hander and the other by a right-hander.
and the Mary Rose Trust:
Hopkins (1998) studied 408 shafts from chest 81A2582 (O9) and recorded that, in every case, the binding thread had been wound in a clockwise direction from the tip end of the shaftment (ie, the portion of the arrow where the fletching is placed) to the nock end (ie, ‘Z’ wound). This indicates that the arrows were bound by a right-handed person (Waller, pers. comm. 2009)…
Weapons of Warre, p680
Anatomy of an Arrow (from Weapons of Warre)
Note that having stated everything was Z-wrapped, the MRT used an S-wrap to illustrate the text…
I’ve been making some arrows using left wing feathers recently, because that’s all I could get in the colour I needed and perversely I’ve been finding S-wrap much easier than the usual Z-wrap. It hit me this morning, it isn’t the handedness of the fletcher, it’s whether you are using left or right wing feathers. You get a more even, tighter binding if you push the binding thread past the smooth upper side of the feather than if you go the other way against both the curl of the feather and the grain of the hooklets.
Anatomy of a feather – left wing. S-wrap works with the trailing edge in this case.
The left wing vs right wing fletching arguments are probably older than the history of flint arrowheads, but western archers generally have a preference for right wing feathers for right-handed archers. This may go some way to explaining the disparity at the find sites. I’m more agnostic when doing straight fletched arrows, as long as the whole set are the same, helicals are a whole different thing. I don’t find S or Z twist any easier or more difficult than the other, you just rotate the arrow the other way. I’m sure professional fletchers would get to the point where they would pick the wrap direction instinctively.
Hildred, A (ed.) Weapons of Warre – The Armaments of the Mary Rose, Mary Rose Trust, 2011