At our club we had an incident which involved the meaning of “Mark Room” (b) which is “room to round the mark as necessary to sail the course.”
Boats Inside Windward and Outside Leeward were approaching a leeward mark to be left to port and they were both on port tack, overlapped at the zone and at the mark, with OL having luffing rights (Rule 17 did not apply). The next mark was a gybe mark and to head to it, the proper course for both boats was a beam reach on port tack.
Assuming OL must give IW Mark Room, when can OL luff IW? Does Mark Room (“round the mark as necessary to sail the course”) mean that IW has the right to round the mark (transom perpendicular has cleared the mark) and she is on a beam reach pointed at the gybe mark ? Or could OL luff her up to close hauled as she rounded the mark, so that she clears the mark pointed higher than her proper course?
Paul Zupan has said in another post that his reading is that Mark Room means to leave the mark on the required side by sailing on a heading necessary to sail the course, but does "necessary to sail the course" mean proper course ? The word "necessary" seems to imply that, but I can find no definitive authority for this.