Just when we have made progress in convincing competitors that there is no "overtaking" in the rules...
Is this a late April Fools joke?

Well this is an interesting appendix, which I hope is either altered or not used much.  My take on it would be that while appendix RV is in play and rule 17 is replaced by RV17, then the intent would be for "B" to sail behind and above "Y", however with the rule written the way it is "B" would not be breaking rule RV17 by standing on because she has not sailed above her proper course.  At this time "Y" will have broken rule 11 because she has not kept clear of the leeward boat by 40m, as per rule 11 and RV1.1.  This rule breakage occurs at position 3.

If instead the IRPCAS were used then "Y" is to keep clear of "B" under rule 12, however because at the closest point the boats were 20m apart, no rule was broken (assuming of course that a risk of collision did not exist).  That said, if "B" was coming up and overtaking from more that 22.5deg abaft the beam (rule 13) of "Y" then "B", who would only be able to see the stern lights of "Y", would be considered as the overtaking vessel and would need to keep clear of "Y".  Which in this case she has and then again no rule broken.

Very interesting case, for sure.  These are my quick thoughts on the matter.  I look forward to seeing the debate on this one.  Thanks

Interesting, but agree with Carrick's comment, I hope it is altered or not used much. I see it has actually been in effect since Jan 2020.  Accepting that there has been little night racing locally since then, I was not aware of its existence or of any club using it. 

I always understood that the reason for replacing RRS with IRPCAS in the dark is that you can't know whether another vessel is racing or not, so the only safe course of action is to assume it is not and use IRPCAS.  (Whilst offshore overnight races would generally be at least Category 3 and require boats to carry AIS, so you might recognise the other vessel electronically, Special Regs don't require that the AIS is active [local SIs always do], the other boat could have retired, and in, for example, the Fastnet race with >300 boats, you would not be expected to recognise all other competitors simply on the basis of the name shown on the AIS signal.) 

What is an issue at night is mark rounding in close quarters.  I've experienced this once with a leeward mark rounding in strong wind and tide conditions, early in a race with boats bunched and crews struggling to drop kites and come up with limited control.  It was frightening.  Under IRPCAS, the stand on vessel is precisely that, it must stand on and cannot alter course to round a mark.  This experimental appendix seems to address this by allowing mark rounding with an increase in the zone (though judging 200 m from an intermittent flashing light on the mark at night [assuming the light is working, they aren't always] and being able to defend that in a protest room would be a challenge, to say the least) and requiring greater mark room.  Personally I think it safer to avoid the issue by setting the course to avoid mark roundings in the dark at early stages in the race when boats are still bunched.

Followup question: Can anyone think of a situation where following Appendix RV rules would lead a boat to violate IRPCAS?

My example scenario might, I suppose, by requiring Y (the stand-on vessel in an overtaking situation) to alter her course if overlapped within 40 meters but since it requires her to alter course away from the overtaking give-way vessel I don't know if that's a problem.

The thing with COLREGS in general is that when ever there is a close quarter situation, it's is not often that one or the other vessel couldn't, at some point before it happening, have manoeuvred to avoid it (considering Rule 5 - Look-out, Rule 6 - Safe speed, Rule 8 - Action to avoid collision, Rule 16 - Action by give-way vessel and Rule 17 - Action by stand-on vessel). 
And as it is the responsibility for both vessels to act to avoid these situations in advance, if there is a protest for an incident that happens during the night, when COLREGS are in force, the end result in most cases is that both are DSQ. Especially, if the finish is during night time and the boats are still in their mind racing to the finishing line according to RSS.
(We had one of these cases last summer, but in the end the protest was deemed invalid because of the other formalities, so we didn't need to go into it...)

Phil, I thought the exact same thing about “overtaking.” It’s like Lazarus...

The late Pat Lally, former Lord Provost of Glasgow called his autobiography 'Lazarus only done it once".

It’s reminiscent of this 2017 thread (one of my first ones).  :-)

https://www.racingrulesofsailing.org/posts/40-rrs-86-1-changes-to-the-racing-rules

PS: If you read through, you’ll see we eventually land at the Super Yacht rules, which address all the areas needed.  Maybe they adapted the RV from SY. 

Maybe “40 meters” in RV is a lesson learned to get around the “whose boat length” question. It would still be difficult or impossible to enforce exactly unless someone has a laser rangefinder, but I think most would be able to judge if another boat was definitely too close.

If you just specify that a keep clear boat will come no closer than 40 meters to a ROW boat and ROW boats must allow at least 40 meters of room to keep clear I wonder if that wouldn’t solve the problem without invoking IRPCAS or introducing an “overtaking” rule.

In particular I can see issues with this if, in my scenario, the overtaking boat closed inside 40 meters before establishing an overlap. The boat being overtaken is required to maintain her proper course until the overlap is established. At that point presumably windward/overtaken must come up to allow leeward/overtaking to sail her proper course but what to do about them being closer than 40 meters? Did windward fail to keep clear? Or did leeward fail to give room to keep clear?

At risk of repeating myself, all of the above discussion assumes that every vessel involved is racing, and knows that every other vessel involved is racing.  Certainly locally, that is not realistic.  Excepting current international travel restrictions due to Covid, on a holiday weekend, the stretch of the English Channel betwen the Solent and the Cherbourg peninsula will have literally hundreds of sailing vessels, some racing in your race, some in another race with a different course (still under RRS, who knows whether Appendix RV applies to them?), earlier finishers who are returning (IRPCAS but with a racing mentality) and those cruising either independently or on another club rally (IRPCAS again).  At >40m in the dark, can you see the class flag?  It is not unusual to need to make a decision about action to take with another vessel without knowing if they are racing or not.  If you were protested, what would the view of the protest committee be when you claimed in good faith that you believed the other vessel was not racing and followed IRPCAS?  IRPCAS is the internationally accepted standard.  Neither the comments above nor Appendix RV itself identify any issues with IRPCAS at night in open water; is there a problem with it that needed fixing with Appendix RV?  At best if, as comments above indicate, Appendix RV does not conflict with IRPCAS in open water, then it adds confusion and, therefore, risk; if it does conflict with IRPCAS, then the risk is greater still.  I can just about see a case for amending IRPCAS at mark roundings, though even then it is possible that a cruising boat vessel is using the same mark as a navigational way point and, when you want to turn, that vessel may stand on &/or pass close the other side.  In the open water, I think we should be sticking with the tried and tested IRPCAS.