CALL UMP 6              

Rule 10 On Opposite Tacks
Rule 16.1 Changing Course
Rule 19.2(b) Giving room at an Obstruction

Question
Before the start Yellow and Blue, reaching on starboard tack, approach an anchored boat. When Yellow is at the obstruction, she is clear ahead of Blue. Yellow passes to windward of it, bears away alongside it, then gybes in order to sail around its stern. Very soon after Yellow gybes, Blue is still on starboard and gains a small inside overlap. Blue changes course trying to avoid contact with Yellow but there is contact. There is a protest. What should the call be?

Answer
Blue becomes right-of-way boat the moment the boats become overlapped, or
when the foot of the mainsail of Yellow crosses the centreline when she gybes,
whichever happens first, Yellow gives up her right-of-way, so rule 15 does not
apply to her. Yellow must give room to Blue under rule 19.2(b), and keep clear
of Blue under rule 10.
Yellow fails to keep clear of Blue. Penalize Yellow.