The previous rule 18 (which is the rule for rounding or passing marks and obstructions) began to apply when boats were “about to round or pass the mark or obstruction.” Though this was a useful, self-adjusting criteria given the varying speeds and levels of boat handling in the wide spectrum of boats and conditions that are raced under, it was also very vague and almost arbitrary. The new rules now create a definitive location where rule 18 begins to apply. It is when the boats reach the Zone, which is now three lengths from the mark (see definition Zone; note that sailing instructions can change the Zone to two or four lengths; and team and match racing are staying with two lengths, and radio-controlled boats are staying with four).
The game change here is that even if the boats are approaching the mark quickly and/or have a lot of sail handling to perform before rounding the mark, outside right-of-way boats do not need to start giving room until they or the inside boat reaches the Zone. However, outside boats are required to give the room the moment either of them reaches the Zone, so they must be ready for that obligation. And for boats clear ahead of others, they are “safe” from being overlapped on the inside when they reach the Zone, which is now three lengths from the mark, not two as in the previous rules.
