Rule 10; On Opposite Tacks
Rule 11; On the Same Tack, Overlapped
Rule 17; On the Same Tack; Proper Course
Definitions; Tack, Starboard or Port
A boat sailing downwind changes tack when she gybes and her sail fills on the new side and lies there if unrestrained.
Situation 1
Yellow is a leeward boat subject to rule 17. She is sailing her proper course, which is nearly 140° from the true wind angle. Blue is keeping clear. From position 1 to position 3, Yellow pulls the boom across the centreline to the starboard side of the boat, and almost immediately pulls the boom back across the centreline to the port side of the boat. The force of the pulling action back to the port side causes the mainsail to completely fill in position 2.
Question 1a
Does Yellow change tack in position 2?
Answer 1a
No. Yellow’s windward side does not change. She never sails by the lee and at no time would her mainsail lie on her starboard side if unrestrained.
Question 1b
Does Yellow gybe between positions 2 and 3?
Answer 1b
Yes. Yellow gybes twice as the foot of her mainsail crosses her centreline twice.
Question 1c
Answer 1c
Question 1d
Answer 1d
Situation 2
Question 1c
Does rule 17 still apply in position 4?
Answer 1c
Yes. Yellow does not change tack.
Question 1d
Would the answer be different if the mainsail had never filled in position 2?
Answer 1d
No.
Situation 2
Yellow is a leeward boat subject to rule %= rule('17') %>. She is sailing her proper course, which is nearly 180° from the true wind angle. Blue is keeping clear. Yellow bears away and begins to sail by the lee. At position 3, Yellow's crew pulls in the mainsail and it fills on the opposite side without crossing the centreline of the boat. At position 4, Yellow returns to sailing directly downwind and the mainsail continues to lie on her port side.
Question 2a
Does Yellow change tack in position 3?
Answer 2b
Answer 2a
Yes. In position 3, Yellow is no longer sailing by the lee and she is not sailing directly downwind. She is therefore on a tack corresponding to her windward side, i.e. port. See the definitions Tack, Starboard or Port; and Leeward and Windward.
Question 2b
Does she gybe between position 2 and 3?
Answer 2b
No. The foot of Yellow’s mainsail never crosses the centreline so she never gybes.
Question 2c
Does rule 17 still apply in position 4?
Answer 2c
No. Although Yellow never gybes, she changes tack twice. Rule 17 ceases to apply if the boats do not remain on the same tack.
Situation 3
Yellow is a leeward boat subject to rule 17. She is sailing directly downwind on starboard tack. Blue is keeping clear. Yellow then pulls her boom across the centreline to the starboard side of the boat and almost immediately pulls the boom back across the centreline to the port side of the boat. The mainsail does not fill until it is back on the port side of the boat.
Question 3b
Question 3a
Does Yellow change tack?
Answer 3a
If the umpires are satisfied the entire sail has crossed the centreline and would lie on the starboard side without the force of the crew keeping it there, then the boat has changed tacks.
The umpires will use the principle of ‘Last Point of Certainty’ when applying the rules about ‘on a tack’. See General Principles for Umpire Decisions.
Question 3b
Does the sail need to fill in order for the boat to change tack?
Answer 3b
No. To decide if the boat has changed tack is not dependent on whether the sail has filled. However, when the sail fills it is more likely that the umpires will be certain that the boat is on the other tack.
Question 3c
Does Yellow gybe?
Answer 3c
Yes. Yellow gybes twice.