There has been lots of English-speaking, boat-owning and boat-building wrangling over the vertical plane wording. Nobody's ever come up with a better phrasing than we have. Take a whack at it?
Without giving it much thought -
"Vertical plane shall be defined as the z axis of the boat parallel to the direction of the mast (insert diagram here)."
Not that hard I would have thought - or am I missing something?
Michael
