Guide to R-O-W Rules - Section A

Preamble	A boat has right of way when another boat is required to keep clear* of her. However, some rules in Sections B and C limit the actions of a right-of-way boat.*
– Overview	Section A contains the four basic rules that govern which boat has r-o-w. Defined terms: Keep Clear.
– Basic	The preamble to Section A says two things. First, it tells us what "right of way" means: a boat has "right of way" over another boat if the other boat must "keep clear" of her. Second, it tells us that even though a boat has "right of way" she may be limited in her actions by a rule of Section B (Rules 14, 15, 16 & 17) or Section C (Rules 18 & 19). "Right of way" and "keep clear" are important concepts in the racing rules and their meaning is discussed under "Right of Way and Keep Clear" in Important Concepts.
– Advanced	The r-o-w rules contained in Section A are the basic r-o-w rules and will always apply unless replaced by an alternative r-o-w rule in Section C [Rule 18] or Section D [Rule 20]. However, whether a boat has r-o-w because of a rule in Section A, C or D, the limitations of Sections B and C can always apply to restrict the actions of a r-o-w boat.
	As between any two boats, under the racing rules one always has right of way (and is the "right-of-way boat") and the other must keep clear of her (and is the giveway, burdened or keep clear boat). The only time this is not true is when Rule 21 (Capsized, Anchored or Aground; Rescuing) applies because one of the boats is or was capsized, is anchored or aground or is rendering aid to another (in which case the obligation is to "avoid" the other boat, not "keep clear" of her).
10	On Opposite Tacks When boats are on opposite tacks, a port-tack boat shall keep clear of a starboard-tack boat.
– Overview	Rule 10 gives one of the four basic r-o-w rules, P must keep clear of S. Defined terms: Keep Clear and Tack, Starboard or Port.
– Basic	If two boats are on opposite tacks, then P must keep clear of S. If they are heading on courses that would result in a collision then it is P's obligation to take action to avoid S.
	Although this rule sounds simple it generates a lot of protests because it is often not clear whether P did in fact keep clear of S. Many sailors erroneously believe that in a protest under Rule 10 the issue is whether S would have hit P assuming S had not changed course. That is not the correct standard to apply. Under ISAF Case 113, the question is: Did S change her course based on a "reasonable apprehension of collision"? In other words, if S changed course because of a reasonable apprehension that she would collide with P then P breaks Rule 10, even if S would not have actually hit P if S had maintained her original course. If S did not change course to avoid P and no contact occurred then P has kept clear and has not broken Rule 10, regardless of how close S passes to P.
– Advanced	"Hold Your Course." P, intending to cross ahead of S and thinking that she can do so, will often hail "Hold your course" to S. Rule 10 does not require S to hold her course and P's hail is not binding on S. However, S is subject to Rule 16 (Changing Course) and if S does change her course she must do so far enough from P so that P has "room to keep clear" (the space needed for P to keep clear if she acts promptly in a seamanlike way). This hail does have two significant benefits for P however. First, it alerts S to P's presence so presumably S will realize that she is subject to Rule 16 (and may not change course unless she gives P "room to keep clear"). Second, it notifies S that P thinks she can pass safely ahead of S, thus making it less likely that a change of course by S (to avoid P) will be seen by a PC to be the result of a "reasonable apprehension of collision."
	S is lifted. It is S's compass course that determines whether she has changed course, not her relative angle to the wind. Thus, if there is a windshift that would allow S to sail a course more directly toward the next mark (but might prevent P from passing safely ahead of her) S may change course to take advantage of the windshift provided that she complies with Rule 16 and changes her course far enough from P so that P has "room to keep clear" (the space needed for P to keep clear if she acts promptly in a seamanlike way).
– Example	• In Example 1, S is close-hauled beating to a windward mark. P has rounded the mark and is sailing downwind on the next leg. P must keep clear of S and so must adjust her course to avoid S. However, S is subject to Rule 16 (Changing Course) and may not change her course so close to P that as a result P cannot keep clear of S by acting promptly in a seamanlike way. See Rule 16.
– Related	In determining whether P has kept clear of S, it is important to consider whether S changed her course and if so whether she did so far enough from P so that S complied with Rule 16 (Changing Course) and gave P sufficient "room to keep clear" of S's new course.
11	On the Same Tack, Overlapped When boats are on the same tack and overlapped, a windward boat shall keep clear of a leeward boat.
– Overview	Rule 11 gives one of the four basic r-o-w rules, W must keep clear of L. Defined terms: Clear Astern and Clear Ahead; Overlap, Keep Clear and Leeward and Windward.
– Basic	If two boats are on the same tack and overlapped, then W must keep clear of L. However, this does not mean that L may sail any course she desires (or luff W without limitation). Two important restrictions apply. First, Rule 16 (Changing Course) requires that any time L changes course she must allow W "room to keep clear" (i.e., enough space for W to keep clear of L by acting promptly in a seamanlike way). Second, Rule 17.1 (On the Same Tack; Proper Course) requires that L not sail above a proper course under certain conditions if she established her overlap from clear astern of W.
– Advanced	Under the definition of "keep clear," W keeps clear of L if L may change course without immediately contacting W. This means there is a physical area around L that W may not be in. If W sails into that area (or fails to get out of that area when L sails closer to W and puts W into that area) then W fails to "keep clear" of L and violates Rule 11. Diagram 2 indicates the "area" W must avoid, on L's weather side and extending from her bow to her stern. See "Keep Clear".
	If Rule 17.1 does not apply, then so long as she satisfies Rule 16 L may luff W up to head to wind. However, if either boat passes head to wind then Rule 13 (While Tacking) would begin to apply to that boat.
	The rules on luffing before and after the starting signal are the same, with one notable exception. Since under the definition of "proper course" there is no proper course for a boat before her starting signal, Rule 17.1 only applies after a boat's starting signal has been made, though the overlap may have been established before.
– Examples	• In Example 2, W is passing to windward of L. In other words W overlapped L from clear astern of her. W must keep clear of L. Under the definition of "keep clear," W must stay far enough from L so that L can change course without immediately contacting W. If L changes course she must comply with Rule 16 (Changing Course) and allow W room to keep clear of her (i.e., the space needed by W to keep clear of L by acting in a seamanlike way promptly after L changes course). Since 17.1 (On the Same Tack; Proper Course) does not apply to L she is not limited to a proper course and may luff as far as head to wind. • In Example 3, W and L are situated exactly the same as in Example 2 except that L is passing to leeward of W. In other words L overlapped W from clear astern of her. W must still keep clear of L and stay far enough from L so that L can change course without immediately contacting W. Rule 16 (Changing Course) still applies to any course change by L. Since L overlapped W from clear astern and within two of her hull lengths of W, under Rule 17.1 (On the Same Tack; Proper Course) L may not sail above a proper course during the overlap while within two of her hull lengths of W. Thus, L may only luff as far as a proper course.
– Related	Rule 16 specifies the manner in which L may luff W (i.e., L may only luff in a way that allows W the space to keep clear by acting promptly in a seamanlike way). It does not specify how far L may luff W. Rule 17.1 determines how far L may luff, whether L may luff up to head to wind or only as far as what would be a proper course for her.
	When L first gains r-o-w over W, Rule 15 (Acquiring Right of Way) requires that L allow W "room to keep clear" of her (i.e., enough space for W to keep clear of L by acting promptly in a seamanlike way). This will mean that when L establishes her overlap on W from clear astern she must do so far enough from W so that W is able to keep clear without hitting L (for example, L must leave W enough space so that W will not hit L if she swings her stern when she promptly heads up to keep clear of L).
12	On the Same Tack, Not Overlapped When boats are on the same tack and not overlapped, a boat clear astern shall keep clear of a boat clear ahead.
– Overview	Rule 12 gives one of the four basic r-o-w rules, AS must keep clear of AH. Defined terms: Clear Astern and Clear Ahead; Overlap and Keep Clear.
– Basic	If two boats are on the same tack but not overlapped, then AS must keep clear of AH. This rule is pretty simple, if you (as a boat clear astern of another) run into the back of another boat then you have not kept clear of a boat that is AH.
– Advanced	AH need not anticipate that AS is about to gain r-o-w by establishing a leeward overlap on her from clear astern. Moreover, AS will be subject to Rule 15 (Acquiring Right of Way) and must allow AH "room to keep clear" of her after she acquires r-o-w by establishing the overlap (and, AS would also be subject to Rule 17.1 if she was within two of her (AS's) hull lengths of AH when she established the overlap). Thus, if AS establishes her overlap so close to AH that AH does not have enough space to keep clear by acting promptly in a seamanlike way then AS breaks Rule 15.
– Example	• In Example 4, P and S are sailing downwind with S directly behind P. Because P and S are on opposite tacks Rule 12 does not apply. Therefore, P must keep clear of S under Rule 10.
– Related	If AH is moving backwards through the water because she is backing a sail then Rule 20 (Starting Errors; Penalty Turns; Moving Astern) applies and AH must keep clear of AS.
13	While Tacking After a boat passes head to wind, she shall keep clear of other boats until she is on a close-hauled course. During that time rules 10, 11 and 12 do not apply. If two boats are subject to this rule at the same time, the one on the other's port side shall keep clear.
– Overview	Rule 13 gives one of the four basic r-o-w rules, a boat that is tacking must keep clear of other boats. Defined terms: Keep Clear.
– Basic	A boat that has gone past head to wind (whether because she is tacking or otherwise) must keep clear of other boats until she is again "on a close-hauled course." The phrase "on a close-hauled course" means the compass course you would be heading if you were sailing close-hauled at full speed with sails full and drawing. Whether your sails are actually trimmed and drawing is not relevant, only the compass heading of the boat. Nor is it relevant that you stay on a close-hauled course. If your boat heading goes from directly into the wind to a broad reach it must necessarily have been on that of a close-hauled course, even if only for an instant in time. Rule 13 stops applying at the instant in time that you were headed on a close-hauled course.
– Advanced	If Rule 13 applies then Rules 10, 11 and 12 do not (i.e., Rule 13 "overrides" the normal r-o-w rules found in Rules 10, 11 and 12). So, even though a tacking boat may be on starboard tack (because she has gone past head to wind and the wind is now coming over her starboard side) she must still keep clear of any boats on port tack that have not also gone past head to wind. If two boats are side by side and both have gone past head to wind then the leftmost boat of the two must keep clear (and the other has r-o-w).
	Rule 13 begins to apply the moment you go past a course of head to wind and continues to apply until you assume a close-hauled course. Thus, if you start to tack and go past head to wind but decide to return to your original course you must still keep clear of other boats until you are again on a close-hauled course, whichever tack that may be.
– Related	Under the RRS definition of "tack," a boat is always on either starboard or port tack. This is a change from the IYRR definitions which provided that a boat was on neither tack from the time she passed head to wind until she again assumed a close-hauled course.