There is no right or wrong on whether to apply the International Regulations for Preventing Collisions at Sea (IRPCAS) for racing at night.

The pre-amble to Part 2 of the Racing Rules of Sailing states, in part, that “…If the sailing instructions so state, the rules of Part 2 are replaced by the right-of-way rules of the IRPCAS or by government right-of-way rules.” When this option is used it is usually by the race committee of a night race.

Clubs that do use this cite safety at night as their main concern. Applying the IRPCAS limits quick manoeuvring particularly luffing. Visibility of the other boat in some conditions at night might mean that determining which tack a vessel is on may be problematic. One club also took the view that boats may not be able to confirm whether the other vessel is a competitor in your race or a recreational vessel.

The clubs that choose not to invoke the IRPCAS made their decision on the basis these regulations did not have to apply between competing boats and they saw no persuasive reason to revert to the IRPCAS overnight. A common view was that the IRPCAS were only slightly simpler in the basic right of way rules. Additionally, two competing boats adhering to the RRS Part 2 would not be in breach of the IRPCAS. Many of the IRPCAS continue to apply to competitors, such as those regarding channels, power vessels and certain commercial vessels. Moreover, RRS Part 2 and the IRPCAS, while different, are not inconsistent with regard to general obligations to keep clear.
 
There is no right or wrong way of handling this. There is an understandable safety argument in favour of applying the IRPCAS. That said, the fleet of racing yachts are conditioned to using the RRS and are quite adept at protecting their vessels and crew in night races.

Importantly, if the IRPCAS are applied then it has to be done in the sailing instructions, and it should describe clearly when they switch on or off. An example from one club’s sailing instructions is “Between the hours of Sunset and Sunrise, RRS 10 to 24 inclusive shall cease to be applicable and shall be replaced by the International Regulations for the Prevention of Collision at Sea.” Race committees should also note that the IRPCAS only changes the RRS Part 2; rules 10 to 24.

The RRS can be found here https://www.sailingresources.org.au/class-assoc/racing-rules/.
The IRPCAS can be found at http://www.imo.org/en/OurWork/safety/navigation/pages/preventing-collisions.aspx

By Glen Stanaway https://www.sailing.org.au/about/ourstaff/