Proof of concept. Three stages of the ladder, open water only, to test whether conning a boat in real time teaches this better than a quiz does. The boat is a 12 m sloop under sail; everything is magnetic, no variation applied.
A yacht cannot sail closer than about 35–40° to the true wind. Inside that she stalls, in irons. To get upwind you beat: close-hauled on one tack, then through the eye of the wind onto the other. Tacking costs you speed and thirty seconds, which is why it is never a reflex answer to a collision risk.
Take her bearing with the hand bearing compass, wait, take it again, at least three times. A bearing that does not change while the range closes means you will hit her. Drawing forward, toward your bow: she passes ahead. Drawing aft: she passes astern. Two bearings can lie; three rarely do.
Different tacks: the port-tack boat keeps clear. Same tack: the windward boat keeps clear. If you are on port tack and cannot tell which tack she is on, assume she is on starboard and keep clear. You are on the tack opposite to the side your mainsail is on — wind on your port side is port tack.
Any alteration must be positive, made in good time, and large enough to be obvious to the other vessel, by eye or on her radar. A succession of small alterations is the classic mistake: the bearing barely changes and she cannot read what you are doing. Pass at a safe distance and check that it is working until she is finally past and clear.
The standard answer is to bear away and pass astern of her. You turn away from the wind, which speeds you up, opens the range fast, and shows her your stern — an unmistakable signal. Tacking away is legal but slow, and tacking across her bow is how people get hit.
←/→ helm one degree, with Shift ten. T tack, C take a bearing, B binoculars, Space change time rate, ,/. look round the horizon, 0 look forward, R new run, Enter continue, F fullscreen. Alt+←/→ change stage. Progress is saved in this browser.