This is a quote from the Rules -:

Finish A boat finishes when, after starting, any part of her hull crosses the
finishing line from the course side. However, she has not finished if after
crossing the finishing line she
(a) takes a penalty under rule 44.2,
(b) corrects an error in sailing the course made at the line, or
(c) continues to sail the course.

Does this mean that if a boat, having crossed a line joining the course side of the finishing buoys and so finished,then the re-crosses the line in order to sail away from the fleet, for example, has NOT finished?

See (c) above.

HI Terry,

I think the answer is 'No'.

(c) is to cover a boat that has not yet rounded all the marks or is a leg behind, but crosses the line while sailing to the next mark.

John

Probably worth mentioning that if you sail back through the line for a "2nd" finish that this will be recorded and you may have to explain the reason for this to the race team. Also that if you have finished and interfere with a boat still racing you will find yourself in trouble...