In the poll 32 'Umpires' voted, with an overwhelming majority choosing for the Green flag. One opted for penalizing Blue and two thought Yellow had infringed a rule.
Yellow flag: 2 (6%); Blue flag: 1 (3%); Green flag: 29 (90%);
Red flag: 0 (0%); Black flag: 0 (0%) Votes so far: 32; Poll closed
Well, on the water we also went for Green!
Most of the comments were correct in finding no fault in either boat. The first rule governing this incident is 18.2(c) because Yellow entered the two-length zone clear ahead. Blue was following close behind anticipating to catch Yellow at the moment she passed head to wind.
The last sentence in rule 18.2(c) states:
"If the boat that was clear ahead passes head to wind, rule 18.2(c) no longer applies and remains inapplicable"Yellow was perfectly aware of this and only luffed next to the mark, up to head-to-wind, slowing down. Thereby forcing Blue to bear away to the outside. Yellow was the r-o-w boat from the moment she entered the two-length zone and Blue had to keep clear. Which she did.
Yellow then passes head to wind which 'switches' off rule 18.2(c) and became keep clear boat under rule 13.
After her tack she became shortly the keep clear boat under rule 10 because Yellow is on port and Blue still on SB. But after Blue also luffed and passed head-to-wind, Yellow again becomes r-o-w boat under rule 13 and then, on completion of the tack by Blue, r-o-w boat under RRS 11.
This scenario is very common in match racing, although many sailors at first find it difficult to deal with. It feels like the rules give you a better "protection" if you are entering the zone as inside boat, then as a clear ahead boat. But if you know how to deal with a close following boat, you can use the rules to your advantage and increase your lead.
Yellow also could have slowed down before reaching the mark.