Who keeps clear when two boats are on the same tack?

• Overlapped (rule 11): when boats are on the same tack and overlapped, the windward boat keeps clear of the leeward boat.
• Not overlapped (rule 12): when boats are on the same tack and not overlapped, the boat clear astern keeps clear of the boat clear ahead.
• Proper course (rule 17): if a boat clear astern becomes overlapped within two hull lengths to leeward of a boat on the same tack, she must not sail above her proper course while they remain on the same tack and overlapped within that distance, unless in doing so she promptly sails astern of the other boat.

Source: Racing Rules of Sailing 2025-2028 with Australian Sailing prescriptions, rules 11, 12 and 17.