After starting and completing the first leg of the course is the starting mark any longer a mark of the course?  At that point is it just an obstruction so the preamble is no longer a problem?  Of course, to use the Gold Cup course analogy, at some point it becomes a finishing mark. But on anything but the first or last legs ...

It does put limits on it :

 Section C rules do not apply at a starting mark surrounded by navigable water or at its anchor line from the time boats are approaching them to start until they have passed them. 

Sue, John is referring to the Test Rule, not the current rule.
Warren, if subsequent divisions are still starting when boats in a division that started earlier have completed the first leg, is the committee vessel still a starting mark? I think it is.

Murray

I would think that a starting mark is only a starting mark relative to a boats own start.  Dave brought this issue up in his Zoom presentations and was quite definitive.  He did not talk about the situation where another class is starting at the time of an incident but I would think that if this is a significant issue then it would be incorporated in the rule or a case. 

For Murray, at risk of telling China Sea stories, I recall a US Sailing Case from years ago that indicates that separate divisions were separate races.  For one division the starting mark might have a required side whereas for another that started earlier it was no longer a mark of the course, let alone a starting mark.  

I don't think the definition of "mark" allows that status to expire once it's been passed. Note that rule 31 specifically refers to marks that begin or end the leg on which a boat is sailing, implying that other marks for other legs still rank as marks.

Perhaps the TR preamble should turn off section C rules from a boat's preparatory signal until she starts. That would remove the existing ambiguity of "approaching them to start".

Tim, even if the (former) start mark is still a mark per se, it doesn't have a required side on subsequent legs of the course so 18 wouldn't apply.  At best it could be an obstruction. If the SI's had a 'closed' start-finish line, except to start or finish, the old start mark would be meaningful, but only as a delimiter of one end of a linear obstruction.  (I dislike mid-course start-finish lines, both as a competitor and even more so when I used to be a judge.)

Proposed Preamble to Section C
Section C rules do not apply at a starting mark surrounded by navigable water or at its anchor line.

I'm having difficulty accepting the above proposed change to the Preamble - on the grounds of reduced safety. At least prior to approaching the line to start under the existing rules, boats have to give room at the committee boat because it's simply an obstruction [often a club member volunteer's precious possession.]. Approaching the line to start is a relatively short period of maybe up to a minute before a start in normal circumstances and frankly, I cant see a net benefit  resulting from making this change.
If understanding the concept of "approaching the line to start" is a deemed a difficulty for new chums, adopt the 1 minute signal in the starting sequence as the restriction. 

Tim
I like your suggested change

This is definitive in 2 areas.

1). This in effect defines what Starting Mark is in question, so other starting marks are excluded.
2)  It defines when the rules of section C are turned off and when they start to apply again.
  
Phil
It also limits the time that the Start Vessel is in “danger” I’d like to know your thoughts

Hi Paddy,

I just think that it would be easier and better to replace "approaching the line to start" with at the 1 minute starting signal.

"Approaching the line to start" is a value judgement which is able to be deleted, and Section C therby simplified. I think "at  the 1 minute signal" is far better than what's proposed.

Phil, the only quibble I'd make with the one minute mark is that adds a complication - there's a status change at one minute, when competitors are typically very busy and a keep clear boat may have already set herself up in a bad position that may be hard to bail out of. Simpler I think to turn them off from the time the boats start racing (at Prep) until they've started.

I'm also not sure it's a particular safety issue, as under the TR a keep clear boat should know that she's pretty much never entitled to room at the committee boat and should plan accordingly.

To J.A.'s original question:
Would "Section C does not apply at a boat's Starting Mark" be better wording?
Then on the next rounding of that mark, it is just a mark.

Phillip
Good idea “boat’s starting mark”.
Perhaps if this was incorporated into Tim’s suggestion it would dot all the I s and cross the ts 
It could read 
  
Preamble to Section C

Section C rules do not apply at a boat’s starting mark surrounded  by navigable water or at it’s anchor line from the boat’s preparatory signal until (she starts.) she passes them.

My edit “she passes them” is needed I think. 

This adds back 10 words but may be worth it !