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Old 12-07-2013, 01:54   #826
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Re: Freighters vs. Sailboats

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Originally Posted by Lagoon4us View Post
Something to be aware of AIS shows an icon on a plotter's screen, the Icon is not accurate in it's relative position to you on the screen, you must go to AIS Info to get accurate position and bearing of the 'target'

The visual icon on the screen should only be used as an indication that there's a vessel equipped with AIS in the vicinity.

Conjointly using Radar overlay is helpful.

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I'm curious as to why you say this. The displayed AIS icon should be close to spot-on. Some systems even visually display the length and beam of the target, but others just show a triangle. Even so, the triangle should be accurately located on the chartplotter screen. When I overlay AIS and radar on my screen, the radar and AIS images are on top of each other.

Displaying additional information about the AIS target is certainly useful. Vessel name, dimensions, speed, course, CPA, and TCPA can be valuable data.
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Old 12-07-2013, 02:05   #827
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Re: Freighters vs. Sailboats

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Originally Posted by Seaworthy Lass View Post
Actually "Constant bearing" has two possibilities - collision or no collision.


I have never seen this written before, but a constant bearing will only result in a collision for converging tracks.

If your tracks are even slightly divergent (and this may not be obvious at a distance) and you are getting a constant bearing, no collision will occur.[...]
Interesting observation! I hadn't considered this, but it's true. One obvious example is if we take one of these "constant bearing collision" scenarios that we've been discussing, and turn both vessels 180 degrees. We will have a constant bearing as the vessels diverge. I can think of several ways that we could be in such a situation.

By the way, I haven't been suggesting that anyone start calculating arcsins on the water. That type of analysis is strictly for armchair use only. If you want to work this stuff out on the boat, eyeballs, compass, plotting sheets or computerized AIS or MARPA are the way to go.
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Old 12-07-2013, 04:42   #828
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Re: Freighters vs. Sailboats

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Originally Posted by Seaworthy Lass View Post
This is precisely why we give freighter operators nightmares!

If you are scanning the horizon every 10 minutes (and there is a lot to be said for stepping this up to 5 min and improving technique) you may first be spotting a freighter at only 5nm. Otherwise it is 5-10 nm with good visibility.

The freighter is possibly commencing a turn (not apparent to us yet as he is slow to make changes) at exactly this stage. If we react instantly thinking we are in open water and should just stay clear, it is violating ColRegs and our action may put us back on collision course.

Anyway, at 5-10 nm when we first spot the freighter, we are only determining that there may be a risk of collision, there is no certainty as there is a few degree error in the estimate, even with the radar on. We don't want to be making huge course corrections unnecessarily and the one one thing we mustn't do is make small changes to our course at this stage - it is VERY confusing for the freighter.

This is a fine art in determining when to turn away so that you are not making a big change in course totally unnecessarily (here in the Med there are often one or two freighters visible and I don't want to be constantly doing this) AND so you are not just avoiding hitting but giving yourself a safe margin, AND you are not changing course at a time the freighter is expecting you to hold it (and that regulations say you should).
Not really.....if you really think little sailboats making slight course changes are giving freighters and ships nightmare...you haven't sent much time on their bridges or you have found the only paranoid ones on the planet.

And changing early and significant isn't all that hard...especially with big commercial traffic and it's heading is usually easy to determine buy where it is and where it's headed (next POC).
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Old 12-07-2013, 04:49   #829
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Re: Freighters vs. Sailboats

Can someone give me an example of a constant bearing decreasing range situation where a collision wouldn't be in the future?

Don't bother with constant bearing and "no range change" examples as that is not a "seamanship tool" I would ever even worry about.
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Old 12-07-2013, 05:07   #830
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Re: Freighters vs. Sailboats

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Not really.....if you really think little sailboats making slight course changes are giving freighters and ships nightmare...you haven't sent much time on their bridges or you have found the only paranoid ones on the planet.

And changing early and significant isn't all that hard...especially with big commercial traffic and it's heading is usually easy to determine buy where it is and where it's headed (next POC).
In the Med we generally have very little idea of the likely destination of the other boat. We just don't have that luxury without AIS .

And sorry, as the stand on vessel, making small changes in heading (eg 10 degrees) is plain wrong. Stand on vessels should continue on their course or make a large, obvious change in heading when they feel they need to divert to avoid a collision. You also have no idea at that stage if the freighter hasn't just initiated a course correction himself!
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Old 12-07-2013, 05:27   #831
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Re: Freighters vs. Sailboats

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Originally Posted by Seaworthy Lass View Post
In the Med we generally have very little idea of the likely destination of the other boat. We just don't have that luxury without AIS .

And sorry, as the stand on vessel, making small changes in heading (eg 10 degrees) is plain wrong. Stand on vessels should continue on their course or make a large, obvious change in heading when they feel they need to divert to avoid a collision. You also have no idea at that stage if the freighter hasn't just initiated a course correction himself!
If you can tell me exactly when you KNOW you are the stand on vessel and the other KNOWS it's situation...then I'll assume you know something practical about the COLREGs.

As Lagoon4us pointed out...a small sailing vessel's course is often all over the place so I doubt frieghters pay close attention to small course changes anyhow....if they are concerned about maneuvering room at some point they will just adjust to ensure their CPA no matter what the sailboat does.

I boat in high density traffic areas too...I guess I know the travels of the big boys as far as courses go....not necessarily their destinations...I guess just a habit of good seamanship to know your waters.

Your arguments sound very text book compared to real world.
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Old 12-07-2013, 05:59   #832
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Re: Freighters vs. Sailboats

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If you can tell me exactly when you KNOW you are the stand on vessel and the other KNOWS it's situation...then I'll assume you know something practical about the COLREGs.

As Lagoon4us pointed out...a small sailing vessel's course is often all over the place so I doubt frieghters pay close attention to small course changes anyhow....if they are concerned about maneuvering room at some point they will just adjust to ensure their CPA no matter what the sailboat does.

I boat in high density traffic areas too...I guess I know the travels of the big boys as far as courses go....not necessarily their destinations...I guess just a habit of good seamanship to know your waters.

Your arguments sound very text book compared to real world.
I am surprised you ask!
One of the fundamental principles of ColRegs is to establish which vessel is the 'stand on' vessel.

And it is so easy to remember a simple mnemonic like this: "Generally anchoring our red tugboat diligently minimizes surge loads", that there are no excuses for forgetting the basics.

In this thread I am discussing the techniques used for open water (not in traffic lanes).

If I am sailing there is very little chance any freighters I see are anchored or that I am overtaking them or that their movement is restricted or no one is in command (although I sometimes wonder ).

Once they get closer it is apparent if any day shapes are exhibited (or at night lights) indicating that the above does not apply.

So therefore I am the 'stand on' vessel and I must hold my course until it is no longer safe to do so.

And there has been nothing 'armchair' here about cruising Med waters full time for the last 6 years .
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Old 12-07-2013, 06:52   #833
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Re: Freighters vs. Sailboats

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Originally Posted by Seaworthy Lass View Post
I am surprised you ask!
One of the fundamental principles of ColRegs is to establish which vessel is the 'stand on' vessel.

And it is so easy to remember a simple mnemonic like this: "Generally anchoring our red tugboat diligently minimizes surge loads", that there are no excuses for forgetting the basics.

In this thread I am discussing the techniques used for open water (not in traffic lanes).

If I am sailing there is very little chance any freighters I see are anchored or that I am overtaking them or that their movement is restricted or no one is in command (although I sometimes wonder ).

Once they get closer it is apparent if any day shapes are exhibited (or at night lights) indicating that the above does not apply.

So therefore I am the 'stand on' vessel and I must hold my course until it is no longer safe to do so.

And there has been nothing 'armchair' here about cruising Med waters full time for the last 6 years .
The real question is when you determine you are stand on or not. Because it's a judgment thing...because there are no numbers or absolutes are given in the COLREGS....and it's worded "risk of collision"...slight or large turns done far out are NOT in violation in the strictest sense and make GOOD sense. Most large vessels do this because they don't want to get into a close quarters situation. If they don't see you...then you are going to course change whether stand on or not.

To me closure rate is far more important than anything else...it's what determines how much time the captain has to make a "prudent seamanlike" decision.
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Old 12-07-2013, 08:26   #834
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Re: Freighters vs. Sailboats

I think it was Jackdale who mentioned the 3 ways to deal with a potential collision course. As well as changing course, changing speed or a combination of both are sensible, controllable alternatives. I've found that driving a power boat, either commercial or pleasure craft, a slight change in speed will produce the desired safety margin without appreciable effect on other vessels in your area. As long as you have a heightened awareness of ALL vessels around you, you should be OK. Under sail, making your intentions known to other vessels by radio or early course change where you may be limited in slowing or increasing speed of your vessel makes sense as well. Great thread with many knowledgeable contributors... Phil
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Old 12-07-2013, 09:22   #835
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Re: Freighters vs. Sailboats

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Originally Posted by psneeld View Post
Can someone give me an example of a constant bearing decreasing range situation where a collision wouldn't be in the future?

Don't bother with constant bearing and "no range change" examples as that is not a "seamanship tool" I would ever even worry about.

Any time I am at the helm. If I'm at risk of collision, no matter what course I was on before, I am no longer the stand-on vessel. I am the more maneuverable boat. I put the iron genny in gear (I turn it on any time I'm anywhere near a freighter) and I go wherever I need to go to avoid a collision. I make sure it's not some move that will force the freighter to maneuver. If that means doing a 180 the world will really keep on spinning if I'm delayed even an appalling 2 minutes. I'm not really the center of the universe, so it will not fly apart if I shift my course.

I'll do it in plenty of time, too. Two things I never play chicken with are oncoming trains and freighters/cruise ships.

I do this in time to sail away and will do that if I can just because I prefer sailing, but I have my engine in neutral as a backup because stuff happens.

My actions will be very clear and the freighter helm will know exactly what I'm doing unless he/she is a total twit, but I can't control for that. I can only accept my responsibility and do whatever is necessary to avoid a collision.
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Old 12-07-2013, 09:28   #836
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Re: Freighters vs. Sailboats

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If you can tell me exactly when you KNOW you are the stand on vessel and the other KNOWS it's situation...then I'll assume you know something practical about the COLREGs.

As Lagoon4us pointed out...a small sailing vessel's course is often all over the place so I doubt frieghters pay close attention to small course changes anyhow....if they are concerned about maneuvering room at some point they will just adjust to ensure their CPA no matter what the sailboat does.

I boat in high density traffic areas too...I guess I know the travels of the big boys as far as courses go....not necessarily their destinations...I guess just a habit of good seamanship to know your waters.

Your arguments sound very text book compared to real world.

If I were suddenly transported to some place with heavy, complicated freighter traffic, I would go out on someone else's boat, someone who was willing to show me what goes on there. I'd seek out a sailor more experienced in that geographical area.

As I said before, I don't think these people are going to be taking multiple compass readings on multiple freighters and calculating degrees and angles. Your own two eyes will tell you whether or not you're on a collision course.

I would say that all you should be doing is paying attention to where the other traffic is. This isn't the time to set up a cockpit cooler or untangle the lines you tangled while going through your line locker, or anything else. If there were lots of boats around me i would put casual conversation to an end and have each person on the boat assigned to a segment of the visual circle around the boat. Even if they were complete beginners, because beginners are very good at spotting things like crab traps while you're busy watching freighters. I've found that beginners love that task, because they know it's important and they were afraid there would be nothing useful they could do on the boat.
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Old 12-07-2013, 10:35   #837
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Re: Freighters vs. Sailboats

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Originally Posted by Seaworthy Lass View Post
Actually "Constant bearing" has two possibilities - collision or no collision.


I have never seen this written before, but a constant bearing will only result in a collision for converging tracks.

If your tracks are even slightly divergent (and this may not be obvious at a distance) and you are getting a constant bearing, no collision will occur.

This is of particular significance if you have made a significant change in course and still find the other vessel is still on a constant bearing. It need not be because they made a course correction at the same time. It may just be that your tracks are diverging now. You will not collide then, despite the constant bearing.

Now, there is something for all of you to think about .
Parallel tracks and same speed with constant bearing also is not a collision.

I was assuming converging tracks.
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Old 12-07-2013, 10:39   #838
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Re: Freighters vs. Sailboats

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I think it was Jackdale who mentioned the 3 ways to deal with a potential collision course. As well as changing course, changing speed or a combination of both are sensible, controllable alternatives. I've found that driving a power boat, either commercial or pleasure craft, a slight change in speed will produce the desired safety margin without appreciable effect on other vessels in your area. As long as you have a heightened awareness of ALL vessels around you, you should be OK. Under sail, making your intentions known to other vessels by radio or early course change where you may be limited in slowing or increasing speed of your vessel makes sense as well. Great thread with many knowledgeable contributors... Phil
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Old 12-07-2013, 11:52   #839
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Re: Freighters vs. Sailboats

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The real question is when you determine you are stand on or not. Because it's a judgment thing...because there are no numbers or absolutes are given in the COLREGS....and it's worded "risk of collision"...slight or large turns done far out are NOT in violation in the strictest sense and make GOOD sense. Most large vessels do this because they don't want to get into a close quarters situation.
You're right that colregs don't give specific ranges for when the rules kick in; for that you have to read a guide to the rules, such as the excellent one by Cockcroft and Lameijer - Guide to the Collision Avoidance Rules - A. N. Cockcroft, J. N. F. Lameijer - Google Books
This is the standard text that professional mariners around the world study.
They describe 4 stages of a collision scenario from the perspective of the stand on vessel. In the first stage, the vessels are far apart in time and/or distance - the steering and sailing rules do not yet apply, and both vessels are free to manoeuvre as they see fit.
In the second stage, the rules kick in - the stand on vessel shall hold its course and speed, and provide an adequate opportunity for the give way vessel to take the required action.
In the third stage, the rule 17.a(ii) allowance for the stand on vessel to manoeuvre if he feels the give way vessel is not acting, kicks in.
The fourth stage is where rule 17.b requires the stand on vessel to manoeuvre to avoid collision.

They discuss the various factors that determine the ranges that these stages could be considered to be in effect - this includes the speed of the vessels, traffic, other conditions. IIRC, for two large vessels they mark stage 2 as beginning at 6-8 nm, and stage 3 at 2-3 miles. If you consider in the interaction between a freighter and sailboat, that the sailboat is usually quite a bit slower, I would propose that you might move those ranges into about 5-7 nm and 1-2 nm respectively.
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Old 12-07-2013, 12:06   #840
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Re: Freighters vs. Sailboats

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You're right that colregs don't give specific ranges for when the rules kick in; for that you have to read a guide to the rules, such as the excellent one by Cockcroft and Lameijer - Guide to the Collision Avoidance Rules - A. N. Cockcroft, J. N. F. Lameijer - Google Books
This is the standard text that professional mariners around the world study.
They describe 4 stages of a collision scenario from the perspective of the stand on vessel. In the first stage, the vessels are far apart in time and/or distance - the steering and sailing rules do not yet apply, and both vessels are free to manoeuvre as they see fit.
In the second stage, the rules kick in - the stand on vessel shall hold its course and speed, and provide an adequate opportunity for the give way vessel to take the required action.
In the third stage, the rule 17.a(ii) allowance for the stand on vessel to manoeuvre if he feels the give way vessel is not acting, kicks in.
The fourth stage is where rule 17.b requires the stand on vessel to manoeuvre to avoid collision.

They discuss the various factors that determine the ranges that these stages could be considered to be in effect - this includes the speed of the vessels, traffic, other conditions. IIRC, for two large vessels they mark stage 2 at 6-8 nm, and stage 3 at 2-3 miles. If you consider in the interaction between a freighter and sailboat, that the sailboat is usually quite a bit slower, I would propose that you might move those ranges into about 5-7 nm and 1-2 nm respectively.
This is the part that the unknowing, the rookies (no matter how much water time they claim), the argument lovers, the knuckleheads...etc...etc are all missing.

Whether of not you even have to worry about the COLREGS is not an ON/OFF situation 99.9% of the time...it's something that somewhat creeps up...like I posted earlier....it's not the "collision course" that's so important...it's closure rate that should get your attention (or NOT).

That's why fighter pilots have keen reactions....all pilots dread a collision...but only some have seconds or less to react.
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