Tacking in the zone
The situation
Short of the layline, Ella tacks from port to starboard inside the zone, right in front of a boat that has been on starboard since before the zone and is fetching the mark.
The question
Can Ella tack in the zone and demand mark-room?
The ruling
No. Under rule 18.3, because Ella passed head to wind in the zone, she must not make a boat that was fetching the mark sail above close-hauled to avoid her, and she must give that boat mark-room if it becomes overlapped inside her. On top of that, rule 13 applied while she was tacking — she had no rights until close-hauled. Tacking in the zone and demanding room is one of the most common ways Opti sailors foul out at the top mark.
Tack in the zone and you owe room, not the other way round (rule 18.3) — and rule 13 still applies while you tack.
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 18.3 — Tacking in the Zone.