The Gybe-back

 We had an interesting incident at a recent event which has me thinking about the way rule 18 switches on and off during a gybeback.  The gybe -back typically occurs at mark 4, on a standard team racing S course, just before the final beat to the finish, so ignore mark numbering in the diagrams, the wind comes from the top of the diagrams which is where the finish is. Remember that the normal rules apply inside the zone but . . .

The problem is that 43.1(b) says that "When a boat is sailing within .. mark room to which she is entitled and ... she breaks a rule of Section A of Part 2, rule 15, 16, or 31 she is exonerated for her breach"

This means that the Umpires need to note when the boat is in the corridor leading to the mark.

In this diagram at position 5 the yellow boat is still within the corridor, as her boom has to clear the mark (ignore the diagram) so blue gets the penalty. However, in the scenario below we have to penalise yellow, as at position 5 she is outside the corridor to the mark and her alteration of course did not give blue room to keep clear. (OK the diagrams are not that clear but hopefully you get the point.)

Interesting, is the idea that the provisions of 18 switch on when the boat begins to turn and use the corridor. Consider this:-

The blue boat is keeping clear and had yellow held her course between positions 7 &8 would have passed clear of yellow. Yellow clearly altered in a manner which gave blue no chance to keep clear. However, since she has not yet passed the mark and her alteration was towards the mark she was using the room to which she was entitled. There was no breach of 15 as she remained right of way, is she exonerated for the breach of 16, even if the turn towards the mark was not completed?

There is, however, a get out for the blue boat in 43.1(a) since her infringement was as a consequence of yellow breaking 16 she is entitled to exonerated for her breach of rule 10.   

These complications don't occur when the inexperienced try the gybe-back outside the zone. They fail to understand the full power of the gybe-back done inside the zone and the exonerations available when this happens.