I have been told on good authority that
"an extremely detailed explanations about arrows have been in the public domain at least since 1992 (my copy of R Hardy, Longbow, appendix 'some technical considerations'.) Within the volume (1992, pg 212)"
I just bought a copy of Longbow but no info in mine, so maybe it has to be a specific year ?
I have been trying to find out detailed info on the arrow lengths for some time, but so far no luck :-(