Let’s look at what Rule 12 says:
(* Emphasis added)
As opposed to Rule 11 where boats are overlapped, Rule 12 applies to boats that are on the same tack and NOT overlapped. Unlike Rule 11, under Rule 12, the concept of windward and leeward boats is irrelevant.
We looked at most of the individual elements of this rule when we looked at Rule 11 but we will reiterate them here. Skip this if you are confident you have these elements under control…
One boat is clear astern of another when her hull and equipment in normal position are behind a line abeam from the aftermost point of the other boat’s hull and equipment in normal position. The other boat is clear ahead. They overlap when neither is clear astern. However, they also overlap when a boat between them overlaps both. These terms always apply to boats on the same tack. They apply to boats on opposite tacks only when rule 18 applies between them or when both boats are sailing more than ninety degrees from the true wind.
Note that when the rules talk about "in normal position" it simply means that you are not allowed to manipulate your equipment to gain a tactical advantage. For example, letting out your spinnaker in order to establish an overlap.
The below example 2 reinforces 2 issues:
- Green is overlapped with yellow because green is no longer clear astern when her spinnaker (in normal position) is behind a line abeam of yellow’s aftermost point.
- If green was not in the picture, yellow and blue would not be overlapped. Blue’s spinnaker is not in a normal position.
- However, blue and yellow are overlap because the green boat in between blue and yellow overlaps both.
A boat keeps clear of a right-of-way boat
(a) if the right-of-way boat can sail her course with no need to take avoiding action and,
(b) when the boats are overlapped, if the right-of-way boat can also change course in both directions without immediately making contact.
Contrast this with the next scenario where we have a very similar situation.