Earning rights by tacking
The situation
Red tacks onto starboard a couple of boat lengths in front of Green, who is sailing on port. Red completes the tack and becomes the right-of-way boat.
The question
Can Red expect Green to keep clear the instant she has rights?
The ruling
No. When a boat acquires right of way — here by tacking — rule 15 requires her to give the other boat room to keep clear at first, unless she gained the right of way through the other boat's own actions. So Red must give Green time and space to respond. And while Red was still tacking, rule 13 made her the keep-clear boat in the first place.
Newly acquired rights come with a grace period — give the other boat room to keep clear (rule 15).
Opens the situation on the boat-length grid — scrub it and see exactly how the boats meet. Free, no account needed.
Rules cited
See the underlying rule: Rule 15 — Acquiring Right of Way.