I overtook to leeward and got right of way — why did I still foul?
The moment your bow crosses into an overlap to leeward, Rule 12 switches off and Rule 11 switches on — you become the leeward boat with right of way. But Rule 15 says a boat that has just acquired right of way must initially give the other boat room to keep clear. You can't push her up the instant the overlap forms; she has to be given time and space to respond.
<iframe width="560" height="315" src="https://www.youtube.com/embed/4P4VNmjJhBE" title="Sailing Kiwi" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
<p><a href="https://sailing.kiwi.nz/run/rule-15-leeward-overlap-from-astern/">Source: Sailing Kiwi</a></p>