There is a gap in the line of smaller boats that one of the overlapped boats may fit through, but not sensibly both.

The windward overlapped boat is asking the leeward overlapped boat for room to pass behind the leading "layline" boat whilst the leeward boat is asking the windward boat to give room for them to pass ahead of the following "layline" boat.

Question 1.  As the leading "layline" boat is also an obstruction to the following "layline" boat (Clear astern) does she have an obligation to give the two spinnaker boats room to pass the leading layine boat?

Question 2.  If not, who gets to go through the gap? 

Something like that? 

19 ROOM TO PASS AN OBSTRUCTION  19.1 When Rule 19 Applies Rule 19 applies between boats at an obstruction except when it is also a mark the boats are required to leave on the same side. However, at a continuing obstruction, rule 19 always applies and rule 18 does not.  19.2 Giving Room at an Obstruction  (a) A right-of-way boat may choose to pass an obstruction on either side.  (b) When boats are overlapped, the outside boat shall give the inside boat room between her and the obstruction, unless she has been unable to do so from the time the overlap began. Obstruction  An object that a boat could not pass without changing course substantially, if she were sailing directly towards it and one of her hull lengths from it. An object that can be safely passed on only one side and an area so designated by the sailing instructions are also obstructions. However, a boat racing is not an obstruction to other boats unless they are required to keep clear of her or, if rule 23 applies, avoid her. A vessel under way, including a boat racing, is never a continuing obstruction.

So: 

Yellow and Blue were overlapped, both on starboard, running towards red and green, both close hauled on starboard tack. 

There is insufficient space for both Y & B to sail between R & G. 

It's Y's choice, as leeward, RoW boat which side to leave the obstructions. If she leaves red to starboard and green to port (i.e. through the gap), then she is outside wrt R, but inside wrt G. 

Similarly, if both try and go through the gap then B is inside wrt R, but outside wrt G.

I would have to wrap a damp towel round my head to think about whether "they have been unable to do so (give room) from the time the overlap began". Gut feel is that it applies - the gap is too small for 2 boats overlapped, and a gap that size always has been. Not sure how much it helps, though, because of the both inside/both outside probleim. Which means that if they force a passage through the gap, they're both guilty (as both outside and inside) of not giving room. Which implies DSQ both. 

Simple "head out of the boat, don't get involved with protests" solution is for both to duck red and green, go behind green where (hopefully) there's a bigger gap. 

If blue goes through the gap & doesn't give room to yellow, she's in danger of DSQ from the breach of 19 + (possibly) not keeping clear as a windward boat. 

Likewise, if yellow doesn't give room and forces blue to luff & flog her kite to avoid green, she's in danger of DSQ for a breach of 19. 

All a bit of a mare. 

I'm glad I'm not the only one finding this one a bit of a brain pain.  

As you may have guessed I was one of the spinnaker boats, yellow to be precise.  The situation developed faster than I, or I think the helm of the other boat, (which are both circa 40 foot yachts) appreciated.  I was concentrating on passing ahead of green, and only really became aware that there was a problem with the size of the gap when blue came closer than I was comfortable with hailing that they would need room to pass astern of red.  At this point I don't think it would have been possible for us to get behind green (where there was room in this case) in anything approaching a seamanlike way.  So we did both go through the gap, uncomfortably close together, which didn't endear us to green....  However the protest time limit has passed, seemingly without green wanting to spend time and effort in a complicated protest with two boats from a different class.  Can't say I overly blame him for that.  I am left wondering what would have happened in a protest though.  

So this was really one of those that I was trying to dissect afterwards, as opposed to being fully aware in the build up and making an active call.  But hopefully with an idea as to what to do if the situation occurs again, which is possible given the nature of solent racing.  So far though everyone seems as stumped as I am!  

There does seem, in general, to be a small problem with the rules when different "room" situations conflict.  See my previous effort here.  http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=11141&title=which-takes-precedence-18-or-19

1) Neither of the running boats were keeping a proper watch out for the stb close hauled boats

or

2) The boats on stb were on port and tacked in such a manner that the now keep clear boats could not keep clear.

There are far too many times I see situations developing and then a mark or obstruction is reached and people use the 'I didn't have time' to respond when in reality they should have seen the situation developing and made a plan of started to fulfil their room obligations way before it became apparent that they could not..

My take on this is that if Yellow chooses to pass astern of red she is required to allow blue enough room to also pass astern of red. If she cannot do this then she must also pass astern of Green. Remember that Blue does not have to anticipate that Yellow is not going to give her room (and is not required to hail as she is not needing to tack to avoid). 

As Brass said it all hinges on 19.2 (b) but I would suspect that unless Green has just tacked on to stb (at which point she is required to give the keep clear boats time to keep clear as per rule 15) then this may have been a relatively stable situation at which point things become clearer.

I know that neither I, nor the helm of the other boat, had assessed the gap as too small for both of us until we were really too close to do anything but go through regardless.  Why that is I'm not sure, though I have a suspicion that the way my mind interpreted the scale might have had an impact, as the boats going upwind were significantly smaller.  Meaning a 2 boatlength gap between the upwind boats might have looked ok if your brain is assuming that they are bigger than they actually are.  

My question on your take on it would be,  Why would it be that way round?  Why is it not that if Blue cannot give yellow room to pass ahead of green and still pass behind red she must pass in front of red? After all if that was the only hole in the traffic the ROW boat just lost out in a big way.  

I'm not trying to prove myself right btw, just understand the rules more fully.

As Yellow has the choice which side they pass of the obstruction then the correct tactical choice would be to pass ahead as long as they can do so without impinging red. The rules say if they choose to pass astern an inside overlapped boat is then entitled to room. We come back to 19.2b..... 

I certainly wouldn't fancy sitting on a PC trying to sort that out! Case 11 in the casebook may provide some guidance though. I guess it may hinge on whether a line of Stv tackers would be considered a continuing obstruction in this case. As the OP pointed out there was sufficient space behind the second Stb boat for both boats to pass. 

I would say that Blue going through the gap between red and green is a risk that Yellow has to take. If blue didnt pull it off then they failed to keep clear.

On congested 'round the cans' dinghy courses this happens quite a lot. I usually make a call as to whatever will lose me the least time (or gain me the most time). Usually this is the option where there is less messing around with other boats.

From definition of "Obstruction" in the RRS: "A vessel under way, including a boat racing, is never a continuing obstruction."

D'oh schoolboy error there from me, should have checked that particular definition.  

Either way, subject to 19.2b and the timing of the tack of Green I still think Yellow is required to give blue room. I do think 19.2b is unlikely to feature as well given that we are talking about 40foot boats under spinnaker so unless they had just rounded a mark this is unlikely to come in to play.

However, what I can't see is, by the rules, why Blue's right to room as inside boat on red is trumping Yellow's right to room as inside boat on green?

It is because Yellow has the choice which side of the obstruction to pass. As she chose to pass astern of Red she must also allow room for Blue to pass astern (Case 11). 

As she cannot now go through the gap because it was not big enough for both boats she effectively has no choice other than to pass astern of Green as well. 

She cannot choose to pass ahead of Green as Blue in taking the room she is entitled to in order to pass astern of Red. So she either needs to pass astern of Green as well or take herself and Blue across the bow of Red (a risky proposition).

In theory both boats would pass astern of Green but Blue could elect to go through the gap as long as she keeps clear Green.

I think that sounds about right.

The thinking man would have seen this developing and Yellow might have gone a bit lower a bit sooner to pass astern of Green and thus minimise the loss or perhaps make a gain as thy come back up to their correct course after the duck.

An obstruction is "_AN_ object" i.e. a single object. 2 boats, 2 obstructions. 

Obstruction An object that a boat could not pass without changing course substantially, if she were sailing directly towards it and one of her hull lengths from it. An object that can be safely passed on only one side and an area so designated by the sailing instructions are also obstructions. However, a boat racing is not an obstruction to other boats unless they are required to keep clear of her or, if rule 23 applies, avoid her. A vessel under way, including a boat racing, is never a continuing obstruction.

That's the problem. 

Personally, whatever I decided, I'd send it upstairs to the RRC under 70.2 for confirmation. 

Correct. but say the boat on starboard were overlapped or much closer tigether still 2 boats but then I am sure they would only count as 1 obstruction as there is no way to safely pass between them.

Agreed

Disagree. Still 2, but just treat them in the order the boats get to them. No problem. 

Or say to yourself "£$%$"%$£% Cowes week. What a complete *^%^$%^$%^ of a regatta. I don't know why I @:LL@L:LK:%$%$ bother."

There's certainly a logic too that.

What I take away though is that if I were ever faced with a situation like this I would need to act early:

It's classic anticipation stuff.  

Take blue ahead of red.  Or if blue became overlapped from clear astern take blue up and then bear away to break the overlap.  Yellow could also try and create a situation where blue can't get ahead of green because of the angle of approach, and has to follwo yellow into a gybe.

So in the event of a valid protest Yellow relies on 18.2 (e)?