Is this for rules geeks only? Or will it be important when the racing starts?
Teams are only allowed four daggerboards total for their race yacht. As the article above says, they are likely to build a pair for light wind and a pair for medium to heavy conditions. Realizing that damaging even one board could mean losing the competition, in October the competitors introduced a Protocol amendment to allow “replacement daggerboards.” Any of a team’s AC45X daggerboards could be used as replacements, which should cover any situation. Only two replacement boards are allowed to be used, but that seems likely to be enough.
If you want more details you can download the latest Protocol here and read Article 35.10 (f) for more info.