Are the boats on the same tack?
See the definitions of “tack” and of “windward”.
At the beginning of the sequence which boat, if any, is obliged to keep clear?
See Rule 12
Once an overlap exists, is yellow obliged to keep clear?
See Rule 11
Once an overlap exists, is blue obliged to keep clear?
See Rule 16 and Rule 11
If blue were obliged to keep clear, how long would its obligation last?
See Rule 16
Did blue keep clear?
See the definition of “keep clear”.
Did yellow keep clear prior to turning?
Did yellow pass head to wind?
Did yellow keep clear after passing head to wind and before reaching a close-hauled course?
See Rule 13
If yellow did not keep clear while tacking did it breach Rule 13?
Was yellow compelled to break a rule? Did any compulsion arise from the breach of a rule by another boat?
See Rule 43
Reminder: To determine what issues arise in any sequence, consider the rights and obligations of each boat afresh at each step in the sequence.