Barging at the committee boat
The situation
Seconds before the start, two boats reach toward the committee-boat end of the line on the same tack. Green is the leeward boat; Blue is overlapped to windward, a little ahead, and runs out of room between Green and the committee boat.
The question
Can Blue demand room to squeeze between Green and the committee boat?
The ruling
No. At a starting mark surrounded by navigable water, rule 18 does not apply while boats are approaching the line to start, so Blue gets no mark-room. Under rule 11 the windward boat keeps clear of the leeward boat: Blue must keep clear of Green and cannot barge into a gap that isn't there. If there's no room, Blue has to bear away, slow down, and start somewhere else.
There is no right to barge in at the committee boat — windward keeps clear and a starting mark gives no mark-room.
Opens the situation on the boat-length grid — scrub it and see exactly how the boats meet. Free, no account needed.
Rules cited
See the underlying rule: Rule 18.1 — No Room to Barge at the Start.