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Racing Rules: "Overlap" #277224
01/23/15 07:00 PM
01/23/15 07:00 PM
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Hillsborough, NC USA
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Isotope235 Offline OP
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Have you ever heard (or participated in) an on the water exchange like:
"I'm going to need room at the mark."
"No room - we aren't overlapped."
"Oh yes we are - I need room!"?

If you don't know exactly what "overlap" means, you can't follow and enforce the rules on the racecourse.

In fact, "overlap" applies to several of the fundamental Racing Rules. It is referenced in rules
  • 11 - Same Tack, Overlapped,
  • 12 - Same Tack, Not Overlapped,
  • 17 - Proper Course,
  • 18 - Mark Room, and
  • 19 - Room to Pass an Obstruction.

What is "Overlap"?

Like other critical terms, "overlap" has a specific definition in the rules. I strongly encourage you to read the "Definitions" section closely. Unlike the other terms listed there, however, "Overlap" is defined in a backwards way. The terms "Clear Ahead" and "Clear Astern" are defined. If one boat is neither clear ahead nor clear astern of another, then the two boats are overlapped. Here is the full text of the definition:

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 do not apply to boats on opposite tacks unless rule 18 applies or both boats are sailing more than ninety degrees from the true wind.

When the terms apply

The terms "Clear Ahead", "Clear Astern", and "Overlap" always apply to boats on the same tack. The figure below shows four pairs of boats, in four different colors, on the same tack. Between each pair, the terms apply. Either one boat is ahead and the other astern, or the two are overlapped.
[Linked Image]

The terms also apply to boats on opposite tacks if both boats are sailing more than ninety degrees from the true wind, or rule 18 applies. The next figure shows four pairs of boats, in four different colors, on opposite tacks. The terms "Clear Ahead", "Clear Astern", and "Overlap" apply to the green and blue boats, but not to the yellow and orange boats. The green and blue boats are all sailing more than 90 degrees from the true wind, but the yellow and orange boats are not.
[Linked Image]

The only time that these terms apply to boats sailing 90 degrees or less from the true wind is if Rule 18 is in effect. Imagine that two boats were broad-reaching on opposite tacks towards a leeward mark and as they neared the zone, the wind shifted 45 degrees. Now one is sailing dead downwind and the other is on a beam reach. Ordinarily, with one boat sailing 90 degrees (or less) to the true wind, the terms would not apply. Because rule 18 is in effect, however, they do. See the following diagram:
[Linked Image]

to be continued...

Attached Files
OverlapSameTack.png (166 downloads)
Boats aheahd, astern, and overlapped on the same tack.
OverlapOppositeTack.png (164 downloads)
The terms sometimes (but not always) apply to boats on opposite tacks.
OverlapRule18.png (162 downloads)
When rule 18 applies, the terms ahead, astern, and overlap do too.
Last edited by Isotope235; 01/23/15 07:10 PM.
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Re: Racing Rules: "Overlap" [Re: Isotope235] #277225
01/23/15 07:19 PM
01/23/15 07:19 PM
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Isotope235 Offline OP
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How to Determine Overlap

In order to determine whether or not boats are overlapped, you must look at their hulls, and their equipment in normal position. A few examples of "equipment in normal position" are
  • rudders in their down and locked position,
  • a retractable bowsprit when extended sailing downwind, or
  • a spinnaker flying.

Some examples of equipment not in normal position are:
  • a retractable bowsprit extended while sailing upwind,
  • a spinnaker with sheets or halyards loosed, or streaming out while hoisting or dousing (or shrimping),
  • a line trailing in the water behind a boat.
Equipment in normal position counts; equipment out of normal position does not.

Draw an imaginary line through the centerline of each boat. Draw another imaginary line perpendicular to the first at the aftmost point of the hull or equipment in normal position. If one boat (her hull and equipment in normal position) is entirely behind that second line, then she is "clear astern" and the other is "clear ahead". If neither boat is clear astern of the other, then the two are "overlapped".

Overlap on the Same Tack

Here is a diagram showing two pairs of boats on the same tack on a beat to windward. For each pair, I've drawn imaginary centerlines and perpendicular lines on the lead boat. Note that I've drawn the aftmost point slightly behind the hull because that's where the rudders are. The yellow boat is completely behind that line, so Blue is "clear ahead" and Yellow is "clear astern". For the other pair, the trailing boat is not completely behind that line, so the boats are "overlapped", and I've colored them both green.
[Linked Image]

I've drawn an equivalent diagram showing boats sailing a beam reach on the same tack. As above, Yellow is completely behind the aftmost point of Blue so Yellow is clear astern and Blue is clear ahead. The two green boats are overlapped.
[Linked Image]

And, finally, here's a picture showing same-tack boats on a run. I've drawn the boats as monohulls this time, because the program I used made it easier to show spinnakers that way. The interpretation is the same though. Blue is clear ahead and Yellow clear astern. Even though their hulls are not overlapped, their equipment in normal position is, so the two green boats are overlapped.
[Linked Image]

to be continued...

Attached Files
OverlapSameTackBeat.png (158 downloads)
Overlap between boats on the same tack on a beat to windward.
OverlapSameTackReach.png (157 downloads)
Overlap between boats on the same tack on a beam reach.
OverlapOppositeTackRun.png (157 downloads)
Overlap between boats on the same tack on a run.
Last edited by Isotope235; 01/23/15 07:22 PM.
Re: Racing Rules: "Overlap" [Re: Isotope235] #277226
01/23/15 07:29 PM
01/23/15 07:29 PM
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Isotope235 Offline OP
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Overlap on Opposite Tacks

Boats on opposite tacks may also be overlapped. Here are a few such circumstances. In the first, I've shown two boats on opposite tacks sailing a broad reach. The terms apply because both boats are sailing more than 90 degrees from the true wind (even if their apparent wind is directly abeam). I've drawn centerlines and perpendicular lines on both boats. Because neither boat is clear astern of the other, the two are overlapped.
[Linked Image]

Here is an example of boats sailing directly downwind on opposite tacks. As previously, I've drawn monohulls to show the spinnakers. Also, the fact that the port-tack boats are slightly angled is an artifact of the drawing program. Please ignore that imperfection. Once more, the Blue boat is clear ahead and Yellow clear astern. The green boats are overlapped.
[Linked Image]


Once more, here are two boats approaching a leeward mark. One is sailing (nearly) dead downwind on port tack, the other is on a starboard tack broad reach. Neither is clear astern of the other, so they are overlapped. This important relationship is often overlooked and misunderstood by boats sailing the rhumb-line.
[Linked Image]

to be continued...

Attached Files
OverlapOppositeTackReach.png (154 downloads)
Overlap between boats on opposite tacks on a broad reach.
OverlapOppositeTackRun.png (154 downloads)
Overlap between boats on opposite tacks on a run
OverlapOppositeTackAtMark.png (152 downloads)
Overlap between boats on opposite tacks at a mark.
Last edited by Isotope235; 01/23/15 07:32 PM.
Re: Racing Rules: "Overlap" [Re: Isotope235] #277227
01/23/15 07:36 PM
01/23/15 07:36 PM
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Isotope235 Offline OP
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Overlap Between Multiple Boats

There is one more part to the definition of overlap. That is, two boats also overlap when a boat between them overlaps both. Even if their hulls and equipment do not overlap, two boats are overlapped when they are both overlapped by an intervening boat. Here is an example. In this diagram, the two green boats are not directly overlapped, but the orange middle boat does overlap both. Therefore, the green boats are overlapped.
[Linked Image]

Important Note! The boat that overlaps both must be in between them. Some people like to call that boat the "meat in the sandwich". In order for overlap to exist, the meat must be between the pieces of bread. If there's no meat in the sandwich, then there's no overlap. I've illustrated that below. Although the Orange boat is overlapped with both Blue and Yellow, she is not between them. Therefore Blue and Yellow are not overlapped with each other.
[Linked Image]

I hope that helps,
Eric Rasmussen
US SAILING Certified Judge
Chair, SAYRA Appeals Committee

Attached Files
OverlapBetween.png (150 downloads)
Overlap with a boat in between.
OverlapNotBetween.png (150 downloads)
No overlap because boat is not between the other two.
Last edited by Isotope235; 01/23/15 07:38 PM.
Re: Racing Rules: "Overlap" [Re: Isotope235] #277233
01/24/15 10:19 AM
01/24/15 10:19 AM

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Thanks!
you rock

Re: Racing Rules: "Overlap" [Re: Isotope235] #277235
01/24/15 10:41 AM
01/24/15 10:41 AM
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Fort Myers/Cape Coral, FL
coralreefer Offline
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Very helpful, thanks!!

Keep them coming.


2014 Hobie 16
1995 Hobie 16
Re: Racing Rules: "Overlap" [Re: Isotope235] #277241
01/24/15 09:22 PM
01/24/15 09:22 PM
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brucat Offline
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Rudder down and locked is arguable. In some classes, it is completely normal to sail downwind with a rudder up and locked. Upwind too, in light conditions (although I've heard of some young guns doing this internationally in all conditions).

Raising a rudder simply to create an overlap would be tough to defend.

Mike

Re: Racing Rules: "Overlap" [Re: brucat] #277242
01/24/15 09:43 PM
01/24/15 09:43 PM
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Isotope235 Offline OP
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Rudder down and locked would certainly be "in normal position". Rudder up may or may not be. Sometimes, raising the rudder would be normal. For example, a Hobie 16 going downwind in light air with one rudder up would be normal position. A rudder kicked up after hitting bottom would not.

I find it difficult to envision a circumstance where the boat ahead would raise a rudder in order to establish overlap.

Re: Racing Rules: "Overlap" [Re: Isotope235] #277246
01/25/15 08:11 AM
01/25/15 08:11 AM
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Jake Offline
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Originally Posted by Isotope235
Rudder down and locked would certainly be "in normal position". Rudder up may or may not be. Sometimes, raising the rudder would be normal. For example, a Hobie 16 going downwind in light air with one rudder up would be normal position. A rudder kicked up after hitting bottom would not.

I find it difficult to envision a circumstance where the boat ahead would raise a rudder in order to establish overlap.


Or be able to be THAT precise with when overlap is or isn't present.


Jake Kohl
Re: Racing Rules: "Overlap" [Re: Isotope235] #277247
01/25/15 08:14 AM
01/25/15 08:14 AM
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Panama City, Florida
Redtwin Offline
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Didn't Russell Coutts do that a couple of ACs ago on the last run to force Team New Zealand to allow him to gybe at the layline instead of push them off into oblivion?

Last edited by Redtwin; 01/25/15 10:07 AM.

Rob V. Nacra 5.2 Panama City
Re: Racing Rules: "Overlap" [Re: Jake] #277267
01/26/15 11:01 AM
01/26/15 11:01 AM
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Originally Posted by Jake
Originally Posted by Isotope235
Rudder down and locked would certainly be "in normal position". Rudder up may or may not be. Sometimes, raising the rudder would be normal. For example, a Hobie 16 going downwind in light air with one rudder up would be normal position. A rudder kicked up after hitting bottom would not.

I find it difficult to envision a circumstance where the boat ahead would raise a rudder in order to establish overlap.


Or be able to be THAT precise with when overlap is or isn't present.


Thanks Eric, I agree with that post, just wanted to clarify from your prior one.

Jake, raising a rudder can add a foot or so of length, people will notice that.

Mike

Re: Racing Rules: "Overlap" [Re: brucat] #277274
01/26/15 12:12 PM
01/26/15 12:12 PM
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Great stuff. Keep it up.

What was the thread topic name (so I can search for it) which you went over establishing overlap on a boat pre-start (or during the sequence).. Like a "J hook" to peel someone off at the boat end.?


Jay

Re: Racing Rules: "Overlap" [Re: waterbug_wpb] #277286
01/26/15 04:37 PM
01/26/15 04:37 PM
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Hillsborough, NC USA
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Isotope235 Offline OP
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Originally Posted by waterbug_wpb
What was the thread topic name (so I can search for it) which you went over establishing overlap on a boat pre-start (or during the sequence).. ?

Do you mean the barging thread?

Re: Racing Rules: "Overlap" [Re: Isotope235] #277372
01/29/15 09:32 PM
01/29/15 09:32 PM
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Isotope235 Offline OP
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I just noticed that I included the wrong diagram for boats on the same tack on a run. I'm surprised that nobody called me on that.

Anyway, here it is:

[Linked Image]

Attached Files
OverlapSameTackRun.png (43 downloads)
On the same tack on a run.
Last edited by Isotope235; 01/29/15 09:33 PM.

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