The boat on the left is reaching with her port side toward the wind; therefore her port side is her windward side and she is on port tack. When she luffs up to head to wind she remains on port tack. The boat on the right is sailing by the lee with her mainsail lying naturally on her starboard side. Therefore her port side is her windward side by definition and she is also on port tack.
and that whether we are on port or starboard tack is determined by our wind- ward side; i.e., if our windward side is our port side, we are on port tack. This definition tells us that our windward side is the side closest to the
wind, and that our leeward side is the opposite side. If the boat is heading di- rectly into the wind, then whichever side was the windward side before the boat was head to wind is still considered the windward side. The only exception is when the boat is heading directly downwind or “by
the lee” (which means the boat has continued to turn past directly downwind without the boom changing sides). In that case, the windward side is the side opposite the side the boom is on.
“If I’m sailing close-hauled on port-tack in light air and heel the boat sharply to windward such that the boom falls to the port side of the boat, am I now on starboard tack; or if I’m sailing by the lee and forcibly holding the mainsail over the port side with my arm, am I still on starboard tack?”
