RULE 11

Let’s look at what Rule 11 says:

ON THE SAME TACK, OVERLAPPED

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

(* Emphasis added)

As opposed to Rule 10 where boats are on opposite tacks, Rule 11 deals only with boats that are on the same tack and overlapped. Ie, both on a port tack or both on a starboard tack and neither is clear ahead or clear astern. Rule 10 doesn’t go any further than looking at opposite tacks. It generally doesn’t really matter what boat is on the windward side or which is on the leeward side or if boats are overlapped.

However, Rule 11 focuses very much on windward and leeward but only where both are on the same tack and overlapped.

Let’s remind ourselves about the three main components of Rule 11"overlapped", "windward/leeward" and "on the same tack".

Clear Astern and Clear Ahead; Overlap

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.

Rule 11 overlap
Example 1
Clear astern, clear ahead and overlapped

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:

  1. 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.
  2. If green was not in the picture, yellow and blue would not be overlapped. Blue’s spinnaker is not in a normal position.
  3. However, blue and yellow are overlap because the green boat in between blue and yellow overlaps both.
Rule 11 overlap normal position
Example 2
Equipment in normal position

The next important aspect of Rule 11 is the meaning of windward. We find this under the definitions in the rules.

Leeward and Windward

A boat’s leeward side is the side that is or, when she is head to wind, was away from the wind. However, when sailing by the lee or directly downwind, her leeward side is the side on which her mainsail lies. The other side is her windward side. When two boats on the same tack overlap, the one on the leeward side of the other is the leeward boat. The other is the windward boat.

This is a bit confusing as it explains what leeward means and simply then refers to the opposite site as windward.

In essence, it is that side where the wind comes from or the opposite side to where the mainsail is deployed when sailing downwind.

Note that in example 3 below, we have overlapped boats on the same tack. If they were on different tacks, Rule 10 will apply.

Rule 11 windward
Example 4
Windward boat keep clear

The third component of Rule 11 is "tack which we can also find in the definitions…

Tack, Starboard or Port A boat is on the tack, starboard or port, corresponding to her windward side.

Having just described the definition of "windward", tack is easy to understand. In any case, here are some examples…

Rule 11 Tack
Example 4
Tack port/starboard
Scenario 1

Let’s have a look at the below events. Blue is sailing close-hauled and meets up with yellow which is behind and still needs to round the leeward mark.

It is clear that the boats will collide so both boats take evasive action. At positions 3 and 4 both boats protest the other.

Does Rule 11 apply?

Take a few seconds to look at the scenario.

NO, Rule 11 doesn't apply.

Because yellow is on a starboard tack and blue is on port, Rule 10 applies. Irrespective of windward/leeward or being overlapped, blue is required under Rule 10 (opposite tack) to keep clear. Blue should take two penalty turns for not keeping clear of yellow...
Scenario 2

Below, you find four boats trying to round the far marks through a gate-mark. Just applying Rule 11 (we cover the others later), which boats need to keep clear?

Rule 18.4 does not apply at a gate 4 boats

Rule 11 keep clear boat(s)?

Take a few seconds to look at the scenario. Applying Rule 11 and the three elements within it. Which boat or boats will need to keep clear?

Yellow and red need to keep clear under Rule 11!

If we just look at Rule 11 then yellow and blue are on the same tack and overlapped. Yellow is the windward boat and needs to keep clear of blue.

On the other side, and for the same reasons, red needs to keep clear of green.

Scenario 3

The below scenario is a little confusing but try to determine which boat pairs are overlapped?

Rule 11 overlapped or not overlapped

Who is overlapped with whom?

Take a few seconds to look at the scenario. Apply Rule 11 and in partigular the element of "overlap" (clear astern/clear ahead).

...they also overlap when a boat between them overlaps both...

Green is overlapped with yellow and yellow is overlapped with blue. But because yellow is in beween and is overlapped with both green and blue, green is also overlapped with blue.

On the other side, red is clearly overlapped with purple and purple is overlapped with light-blue. However, red in not overlapped with light-blue becuase as the boat in between light-blue is not overlapped with both red and purple.

So to sum up Rule 11

  • Extremely common "must-know" rule.
  • It applies to boats that are:
  • A boat is overlapped when either boat is neither clear ahead or clear astern.
  • A boat is on the tack, starboard or port, corresponding to her windward side.
  • Windward site is in general the side closes to the wind.
  • When you approach another boat always consider if you will become the windward or leeward boat. Then when the need arises, you are in a position to make an informed decision.

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