CASE 41

Definitions, Clear Astern and Clear Ahead; Overlap
Definitions, Obstruction
Rule 11, On the Same Tack, Overlapped
Rule 12, On the Same Tack, Not Overlapped
Rule 19.2, Room to Pass an Obstruction: Giving Room at an Obstruction

A discussion of how rule 19.2(b) and the definitions Obstruction and Clear Astern and Clear Ahead; Overlap apply when two overlapped boats on the same tack overtake and pass to leeward of a boat ahead on the same tack. There is no obligation to hail for room at an obstruction, but it is prudent to do so.

Facts

Boats BL and BW, overlapped on starboard tack, are overtaking boat A, also on starboard tack but moving more slowly. Before the boats reached position 1, BW had overtaken BL from clear astern.

Question 1

What are the applicable rules
• while BW and BL are overtaking A?
• after BW becomes overlapped to leeward of A at position 2?

Answer 1

Because BW had overtaken BL from clear astern before the boats reached position 1, rule 17 does not apply between BW and BL at any time during the incident.

While BW and BL are overtaking A, rule 12 requires both BL and BW to keep clear of A. Therefore, A is an obstruction to both BL and BW. However, A is not a continuing obstruction, as the last sentence of the definition Obstruction makes clear. BL may choose to pass A on either side (see rule 19.2(a)). BL chooses to pass A to leeward. During the interval of time that BW is between BL and A and both BW and BL are still clear astern of A, rule 19.2(b) requires BL, the outside boat, to give BW, the inside boat, room between herself and A, the obstruction.

When BW becomes overlapped with A, the applicable rules change: BL becomes overlapped with A because BW is between A and BL (see the fourth sentence of the definition Clear Astern and Clear Ahead; Overlap); rule 12 ceases to apply; BL and BW obtain right of way under rule 11 over A, so A ceases to be an obstruction to BW and BL, and BL becomes an obstruction to BW and A; initially, rule 15 requires both BL and BW to give A room to keep clear; and, as soon as she is able to do so, A is required by rule 19.2(b) to give BW room between A and BL.

Question 2

When a boat is entitled to room under rule 19.2(b), is she required to hail for room?

Answer 2

No. A boat entitled to room under rule 19.2(b) is not required to hail for room, although that is a prudent thing to do to avoid misunderstandings.

GBR 1977/6