Art Engel wrote:

o Rule 18 now applies in some circumstances when both boats tack
around a mark. (the current rule states that if the proper course
for either boat is to tack, rule 18 is out. The new rule says one
but not both.) I think this needs to be read carefully, because
at first read it appears to say more than it does. My initial
take is that this change only makes a practical difference in a
situation where two boats are on opposite tacks and the proper
course for both of them is to tack. This would seem to be an odd
occurrence (i.e. boats in different races that share a common mark).
I welcome more discussion on this - I'm not sure I've read it
correctly...

Would this be a relevant situation? Windward mark to be rounded to port.
Starboard tacker is short of the layline so both boats must tack. Port
tacker approaches on collision course. Under RRS2001 rule 18 does not
apply. Under RRS2005 it does. Personally I think the situation under
RRS2001 is better because it is unclear which is the "inside" boat when
close-hauled on opposite tacks.

In your example, since the boats are on opposite tacks on a beat to
windward rule 18 does not apply under either RRS 2001-04 or RRS
2005-08. No change.

Where there would be a change is where both boats are on starboard
tack (at a leave-to-port windward mark) and neither boat can fetch the
mark. Under RRS 2001-04 rule 18 cannot apply since both need to tack.
Under RRS 2005-08 rule 18 can apply since both must tack. This is an
inconsequential change in my view.

The reason for the change was a rare situation at leeward marks. Two
boats enter the zone on port but the only proper courses for the next
mark require both to tack immediately after passing the mark. Under
RRS 2001-04 wording rule 18 wouldn't apply even though except for the
tack after the mark it would be a typical rounding. Under RRS 2005-08
rule 18 will apply since both boats must tack to sail a proper course.

In the two paragraphs above I refer to both boats on the same tack.
That is WRONG - I should have said the boats were on opposite tacks.
See my separate posting in answer to Walt.

Art Engel
e-mail: artengel123 (at) earthlink.net
Web: http://www.racingrules.org