Approaching the Gate Mark, I don't think that Rule 18 applies because the first sentence of says, "Rule 18 applies between boats when they are required to leave a mark on the same side and at least one of them is in the zone." In this case, only one of them was required to leave the Gate Mark to port or starboard. Therefore, Boat B was not entitled to Mark-Room. (Q1).

Clark Chapin

I am going ot agree with Clark but go one step further and say that 18 doesn't apply becuase the marks of the gate for boat B were not marks  for boat A. See definitaion of Mark.  Thus look to the rules in Section A & B to start

It may just be me but I am struggling to picture this situation. If the boats were on port tack and A established and overlap to leeward of B (as it must have been for rule 17 to apply) then at the starboard hand gate mark B must have been outside and overlapped to windaward and not inside as described. Am I missing something.

Thanks Clark, as the LA2 course in appendix S designates the leeward marks as 2S and 2P I was working on the basis that the boats we sailing to 2S. If we assume that they were sailing to 2P it all makes much more sense.
As others before me have said the mark had a required side for boat B but not for boat A - see rule 28.1. Because of this the preconditions set out in 18.1 were not met so no part of rule 18 ever applied between the two boats. It follows that the situation is governed by the other Part 2 rules.
When A was clear astern of B on the same tack she had to keep clear of B under rule 12. As soon as she established her overlap to leeward of B then B had to keep clear of A under rule 11. A had to initially give B room to keep clear under rule 15 which from the fact that they sailed a few boat lengths before the incident it would appear she did. A was also obliged under rule 17 not to sail above her proper course which as up to the time of the incident as she was sailing a convergent course with B on the way to her finish line she seems to have obeyed. When B called for mark room it seems likely that A had to change her course to take avoiding action although this is something that would be needed to be established as a fact by a PC. If it was established that A had to change her chosen course to take avoiding action then B failed to keep clear (see definition of keep clear) and broke rule 11 for which she should be DSQ. In a protest the PC would then need to consider if B's call of mark room was due to a genuine misunderstanding of the rules or whether or not she was "trying it on". If the latter there would be a case for considering it as deliberate rule breaking to gain an advantage and give her DNE under rule 2.
When A luffed sharply and hit B she broke rules 16.1 and 17, assuming that B was unable to keep clear and A was sailing above her proper course. A also broke rule 14 but as there was no damage or injury and she was right of way boat she is exonerated under rule 14(b). A cannot claim exoneration under rule 64,1(a) because nothing compelled her to take the action she did, she could just have easily born away to fullfil her rule 14 oblighations to avoid contact with B. Whether or not A's subsequent turns exonerated her from the breaking of these rules is a moot point as rule 44.2 required her to "get well clear" of the other boats before starting her penalty and as she never did then it is my view that she never completed the penalty as technically she never started it. In any event rule 22.2 required A as a boat taking a penalty to keep clear of B which clearly she did not do breaking that rule. 
The fact that the boats were in different races and on different legs of the course would have no bearing on the situation unless rule 24.2 applied (which it didn't) - see the preamble to Part 2
So in summary DSQ A for the rule breaches above and a possible DSQ/DNE for B depending on the facts found in relation to her course to the mark and it's effect of A.

 

Along the same vein the following race Boat B is about to start and is 20 seconds from the start 4 boatlengths from the RC (mark of the course)  Boat C, in a different class is finishing and to windward of Boat B (Boat B close hauled Boat C downwind course)  both boats are on starboard tack.  in this case the starting Boat ( Boat B) is ROW to leeward and they are starting.  It appears that rule 18 does not apply here as both boats are not required to leave the mark on the same side so rule 19 applies and B as the outside boat is required to give the finishing boat room between her and the comittee boat ( Obstruction) .  Clark what do you think?

Rules 18 - 20 do not apply to Boat B.  Preamble for Section C states that 'Section C rules do not apply at a starting mark. . .'    So without any more details I think 11 (same tack overlapped) is the primary rule and B, the starting boat, needs to keep clear of C the finishing boat.

Beau - when A "luffs sharply" she is certainly sailing above her proper course but as leeward boat on the same tack she is right of way under rule 11 and therefore entilted to exoneration under 14(b). She is of course breaking rule 17 but that is not a right of way rule (Part 2 Sect A) but a General Limitation ( Part 2 Sect B). At no time does her breach of rule 17 mean that she is not right of way and entitled to exoneration under rule 14(b). A leeward boat breaking rule 17 remains right of way boat which is why the decision in an incident where a rule 17 leeward boat luffs and the windward boat fails to keep clear is always a double disqualification, W under rule 11 and L under rule 17.

Doc - your assessment is quite right. According to the preamble of Part 2 Sect C the Section C rules do not apply between boats (note the plural) at a starting mark surrounded by navigable water when they are approaching it to start. In your case B is approaching it to start but C isn't so Section C rules apply between them. Rule 18 does not apply for the reasons you say. As long as the CB meets the definition of an obstruction (which seems more than likely) then then B must give C room to pass between her and the obstruction under rule 19.2(b).

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.

This I understand so for the starting boats Rule 18 or 19 does not apply.  But in this case where the starting line is on the port side of the committee boat and the downwind finish is on the starboard side of the committee boat then Rule 18 or 19 may apply for the finishing boats  as it is not their start.  If not then the finishing boats are windward boats and the starting boats are lined up from the finish mark to the committee boat and the finishing boats have nowhere to go and are subject to Rule 11  Do they Luff up head to wind and wait for the boats to start before they finish?  Seems like a Catch 22

Bill, thanks. Got it. I guess it comes down to weather Boat A gave Boat B "room" to keep clear.

Doc -. No Section C rules apply betwen the boats that are starting (see preamble to Sect C) and rule 18 applies between the boats that are finishing, most probably 18.2(a) or (b), However for the reasons I have already said rule 19 applies between boats that are starting and boats that are finishing because the boats (plural meaning both the starting and finishing boats) are not approaching the starting mark to start. The outside overlapped boats lining up to start must give room to the inside overlapped boats finishing to pass between them and the CB under rule 19.2(b). The inside finishing boats will break rule 11 but will be exonerated under rule 21(a) as long as they are only taking room to which they are entitled.

Beau - even if A didn't give B room to keep clear she is still right of way and entitled to exoneration  for her breach of rule 14 under rule 14(b). Of course in those circumstances A would also have broken rules 16.1 and 17 and not be entitled to exoneration for those breaches

I think that Bill Handley has covered this in parts but let me try to summarize.  Rule 18 does not apply because A and B were not sailing to the same mark.  As the leeward boat, A has right of way and may luff provided she complies with 16.1.  If A fails to avoid contact while luffing she may be exonerated under 14(b) provided she does not pass head to wind.

Don't forget that B breaks rule 11, but is exonerated under 64.1(a).

John - I am not sure I agrree but it depends on the facts, I did say in my original post that a PC would have to establish facts found.. The way I understood the situation was that the boats were on convergent courses with B to windward sailing lower to get to the mark and A to leeward sailing higher to get to the finish. B was obliged under rule 11 to keep clear. At some point A had to take avoiding action to avoid contact with B and it was at that point that B broke rule 11. The avoiding action A chose was a bad decison which resulted in contact but B's breach of rule 11 had happened long before contact. Nothing compelled B to break rule 11 at that earlier stage so she is not entitled to exoneration.

If the facts were that some time before A needed to take avoiding action she decided to make a change of course to pass atern of B and misjudged her luff then I agree that the breach of rule 11 took place at or just before contact and B is entitled to exoneration.

Yes, this is complicated.  Somehow we wandered away from the original question which was whether B was entitled to mark room.  As Rule 18 did not apply, the answer is no.  As described, A has right of way and is entitled to sail a proper course, i.e., one that will get her to the finish line as soon as possible.  Luffing to go astern of B may be a proper course but A is bound by Rule 16.1.  In any case, A makes contact with B, violating Rule 14, but she may be exonerated under 14(b).  A major question to be determined by the PC is whether B is entitled to exoneration for violating Rule 11 because A failed to give her room to keep clear.

A decided to take penalty turns but in doing so may have violated Rule 44.2 by interferring with B.