Here’s a few things to consider with RRS Rule 11:

Rule 11

When boats are on the same tack and overlapped, a windward boat shall keep clear of a leeward boat.

So what does that mean? A windward boat must keep clear of a leeward boat…

When a leeward boat has luffing rights, the leeward boat may luff up head to wind. If a leeward boat luffs head to wind, the windward boat may actually have to tack in order to stay clear. If a windward boat tacks to keep clear, she has kept clear of the leeward boat and that satisfies rule 11.

Here’s an example (pre-start) from the 2012 Olympic Laser Medal Race

The leeward boat is in a pretty strong position, So it’s a good idea to anticipate and leave room for leeward boats. Always consider that you might have to tack to keep clear as the windward boat.