CALL UMP 34              

Rule 18.1 Mark-Room; When Rule 18 Applies
Rule 18.2 Giving Mark-room

Question 1
Yellow on starboard tack and Blue on port tack, both close-hauled, are approaching the windward mark. Blue bears away and passes astern of Yellow. Yellow luffs slowly and nearly stops head to wind with the mark abeam. While Yellow is luffing Blue tacks to starboard and bears away towards the mark.
Yellow does not give room at the mark, and Blue luffs to avoid a collision.
There is a Y-flag from Blue. What should the call be?

Answer 1
When Yellow enters the zone the boats are on opposite tacks on a beat to windward. Therefore, rule 18 does not apply. When Blue has passed head-towind, the boats are overlapped on the same tack and are both in the zone. Therefore, rule 18 applies. There was neither an overlap nor were they clear ahead/clear astern when the first of the two boats entered the zone. Rule 18.2(a) applies and this requires Yellow to give Blue as an inside boat mark-room. 18.2(e) does not apply because the overlap was created during the tack and not from clear astern. Although Blue is keep-clear boat, she is entitled to room to sail to the mark and then room to sail her proper course while at the mark.
Yellow fails to give this room. Penalize Yellow.

Question 2
Will the answer be different if Blue completes her tack outside the zone?

Answer 2
No. However, if Blue becomes overlapped from clear astern, and if Yellow is unable to give Blue mark-room, rule 18.2(e) applies. Display the green and white flag.
If Yellow is able to give mark-room to Blue, but fails to give mark-room, she breaks rule 18.2(b). Penalize Yellow.