The proper course rule probably confuses more sailors than any other rule. However, the basics are actually pretty straightforward. This article will start by explaining the basics and progress into an FAQ to help clarify the finer points.
The Basics
The proper course rule (Rule 17) is effectively an addendum to Rule 11 (windward/ leeward).
Rule 11 states:
When boats are on the same tack and overlapped, a windward boat shall keep clear of a leeward boat.
Rule 17 is there to put limits on when and how the leeward boat can exercise this right.
So let’s take a look at Rule 17 in the RRS:
ON THE SAME TACK; PROPER COURSE
If a boat clear astern becomes overlapped within two of her hull lengths to leeward of a boat on the same tack, she shall not sail above her proper course while they remain on the same tack and overlapped within that distance, unless in doing so she promptly sails astern of the other boat. This rule does not apply if the overlap begins while the windward boat is required by rule 13 to keep clear.
Now about half of that is added on for clarity but I find it makes the rule look so long and convoluted that my mind feels frazzled after ready it. So let’s cut it down to the crux of the rule:
If a boat clear astern becomes overlapped within two of her hull lengths to leeward of a boat on the same tack, she shall not sail above her proper course.
The definitions are key to understanding the rules so let’s break that down with each definition defined. So the rule states that:
IF A BOAT THAT WAS CLEAR ASTERN…
Clear astern: Boat X is clear astern of Boat Y when Boat X is behind a line abeam from the aftermost point of Boat Y.
BECOMES OVERLAPPED…
Overlapped: They overlap when neither is clear astern.
WITHIN TWO OF HER HULL LENGTHS TO LEEWARD…
THEN THE LEEWARD BOAT CANNOT SAIL ABOVE HER PROPER COURSE…
Proper Course: A course a boat would sail to finish as soon as possible in the absence of the other boats. On a beat your proper course is close-hauled. Off-wind it is whichever direction will get you to the next mark most quickly (in time) e.g. an asymmetric class would not sail directly downwind on a run.
That’s the crux of Rule 17. Hopefully, it doesn’t feel quite so complicated now.
However, there are some caveats to the rule that you should know.
FAQ
Rule 17 addresses what happens if the overlap is created by the leeward boat. But what if it’s the windward boat that creates the overlap?
Short Answer: Rule 17 doesn’t apply. Leeward is allowed to luff above her proper course.
Explanation: For Rule 17 to apply the overlap must be created by the leeward boat. The rule begins: “If a boat clear astern becomes overlapped within two of her hull lengths to leeward…”
So as Rule 17 doesn’t apply you have to go back to the original rule (rule 11). This states When boats are on the same tack and overlapped, a windward boat shall keep clear of a leeward boat.
In this scenario the leeward boat is allowed to luff the windward boat above proper course. Providing of course it gives the windward boat room to keep clear.
Beware overtaking to windward!
What about before the starting signal?
Short Answer: Leeward’s luffing rights aren’t restricted by Rule 17.
Explanation: Before the start there is no ‘proper course’. Again, this means Rule 17 doesn’t apply and you’re back to Rule 11. Rule 11 allows a leeward boat to luff a windward boat wherever they wish provided they give them room to keep clear.
Does proper course remain the same no matter the conditions?
Short Answer: No
Explanation: The World Sailing case book states that a boat’s proper course depends on the existing conditions- wind, tide etc.
Furthermore, the proper course depends on which sail plan the boat is using at the time (e.g. your proper course may change depending on whether you are flying your spinnaker or not).
Reference: World Sailing Case 134
What if the overlap is created beyond the ‘2 hull lengths’ stipulated in Rule 17?
Short Answer: Leeward’s luffing rights aren’t restricted by Rule 17.
Explanation: Again, Rule 17 wouldn’t apply and the leeward boat can luff above their proper course if they give room for the windward boat to keep clear.
In a scenario where Rule 17 doesn’t apply can you luff past head to wind?
Short Answer: No. When you pass head to wind you are no longer leeward boat.
Explanation: Luffing is defined as heading progressively closer to the wind. So by definition you can only ‘luff’ until the eye of the wind. Turning beyond that would mean you are ‘bearing away’ from the wind rather than ‘luffing’. After the eye of the wind is passed the leeward boat becomes the windward boat and who has rights shifts correspondingly.
If the overlap is established beyond 2 hull lengths away can the windward boat take any action to avoid being luffed above leeward’s proper course?
Short Answer: Yes
Explanation: If the windward boat heads enough up he can temporarily break the overlap then bear down again to create the overlap within the 2 hull lengths. As a result, rule 17 now applies.
Does luffing to re-fill your spinnaker count as proper course?
Short Answer: It depends
Explanation: You may think they would be allowed to luff up to re-fill your spinnaker as this would be their fastest course to the finish. However, proper course is defined as the ‘course a boat would sail to finish as soon as possible in the absence of other boats.’ Note, ‘in the absence of other boats’. So the question becomes, is she having to re-fill her spinnaker because she is being covered by other boats. If she is then that doesn’t meet the definition of proper course. But she would be able to luff if her spinnaker collapsed because of a lull but this may be hard to prove to a protest committee.
Rule 17 mentions the importance of the overlap being created within 2 hull lengths. But what if one boat is larger than the other?
Short Answer: It’s the hull length of the leeward boat that is used.
Explanation: Note the beginning of Rule 17: “If a boat clear astern becomes overlapped within two of her hull lengths to leeward…“
What if a leeward boat luffs so quickly that I can’t keep clear?
Short Answer: The leeward boat must give you sufficient room to keep clear.
Explanation: Rule 16 states: When a right-of-way boat changes course, she shall give the other boat room to keep clear.
Room is defined as: The space a boat needs in the existing conditions, including space to comply with her obligations under the rules, while manoeuvring promptly in a seamanlike way.
So, the leeward boat couldn’t legally luff quickly and without warning. Though, as the windward boat, you are expected to act as quickly as you reasonably can.
If two boats round a windward mark overlapped and both subsequently gybe does the new leeward boat have luffing rights?
Short Answer: Yes
Explanation: In this case the overlap wasn’t established by the leeward boat approaching from clear astern and therefore the proper course rule does not apply.
What if you had become overlapped within two hull lengths and wanted to sail above proper course to duck behind the windward boat?
Short Answer: Rule 17 allows this
Explanation: You may think this would break rule 17 as although there would be no contact leeward has become overlapped within 2 hull lengths and has sailed above their proper course. However, Rule 17 specifically allows for this scenario. It reads: “…unless in doing so she promptly sails astern of the other boat.”
Does the leeward boat have to give the windward boat room at an obstruction?
Short Answer: Yes
Explanation: Rule 19.2(b) states: When boats are overlapped, the outside boat shall give the inside boat room between her and the obstruction, unless she has been unable to do so from the time the overlap began.
If there are two port boats overlapped and on a collision course with a starboard boat can windward ask leeward for room to duck the starboard boat?
Short Answer: It’s complicated
Explanation: A right of way boat counts as an obstruction. The port leeward boat (PL) decides whether to tack or duck. If she elects to duck she must give room for the port windward boat (PW) to duck too. Basically, PW is always allowed to make the same choice as PL.
I plan to update this resource as Rules change and on the back of any feedback I receive. In the meantime I hope you find this useful as a guide to Rule 17 and luffing rights.
Excellent description of rule 17 – thank you – more detail about the start would be appreciated.
I am hovering on the start line, on starboard, point-of-sail is higher than close-haul.
Another boat approaches from astern on leeward and hovers next to me, but only inches away.
I sheet in my mainsail to turn into the eye of the wind as perfectly as I can.
I anxiously watch the gap between the two hulls. I know that if contact is made the other boat will protest and is hoping for this outcome.
On the start signal I cannot bear away and must wait for the other boat to bear away, which he does, so I eventually get a clean start, after a few seconds delay.
I believe that rule 17 applies because the leeward boat acquired right-of-way from clear astern. The leeward boat must give me room to keep clear – has she done so if I can turn a few dergrees HTW? Or does she need to give me room to tack away to port? (my stern would then swing into the leeward boat)
Are there any other rules or tactics that allow a hovering boat to preserve the space needed to bear away to close haul?
Hi Kenneth, I assume you read this part- Before the start there is no ‘proper course’. Again, this means Rule 17 doesn’t apply and you’re back to Rule 11. Rule 11 allows a leeward boat to luff a windward boat wherever they wish provided they give them room to keep clear.
With Rule 11 you can luff up to head to wind providing you give warning. Any further and you become the windward boat and have to keep clear