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Old 14-07-2013, 10:49   #916
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Re: Freighters vs. Sailboats

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Originally Posted by chrisjs View Post
Since I went back to the NOAA chart to look at the TSS around Block, I did realize that I had no idea what the wavy magenta lines mean on the chart. I was unable to get the answer from the chart itself, on line from NOAA, or other sources, so thought this august body might know. I thought they might be ferry routes until I realized that some run into real shallow water. Anybody know what they represent??
Like this



Submarine cable.

Chart 1 is your friend.
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Old 14-07-2013, 10:52   #917
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Re: Freighters vs. Sailboats

Thanks. I live and learn!!
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Old 14-07-2013, 10:56   #918
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Originally Posted by Lodesman View Post

As Paul said, I would trust the freighter to maintain a reasonably steady course and speed, but a small sailboat's course and speed are lot more variable - that's a theme that's been repeated over and over in this thread. Perhaps if you're able to stabilize your own data somewhat as Paul suggests, the CPA/TCPA calculations won't bounce around so much, but it would still be predicated on the wind holding steady for the hour or so that you're closing.

I have not yet had the chance to use AIS in anger, but I'm well aware how much GPS Co/Sp can jump around (even in fairly large vessels). Maybe some with real-world experience with AIS will chime in, but I imagine that most AIS systems calculate the CPA/TCPA on a periodic basis with the data as reported at that instant rather than your average course and speed. As such I would follow IMO guidance and only use AIS as an informational tool and not rely on it for anti-collision.
I'm not sure where the damping comes from but the little NASA unit I've used most seems to damp it well enough. The collision avoidance use is interesting, you could argue that a primary use of ais on small vessels is having sufficiently accurate data to ensure that a collision risk doesn't arise in the first place . Just a small course change can have you knowing you will cross a mile behind a ship which is still 5 miles away instead of cutting across it's bows. From experience ais is accurate enough for that.
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Old 14-07-2013, 11:00   #919
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Re: Freighters vs. Sailboats

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Thanks. I live and learn!!
You really should have a copy of Chart 1 onboard and at home. You do not need to memorize every chart symbol, but there are about a dozen that should be thoroughly ingrained. Cables are one of them. Do not anchor on them. I have seen it done.

http://www.nauticalcharts.noaa.gov/mcd/chartno1.htm
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Old 14-07-2013, 16:21   #920
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Re: Freighters vs. Sailboats

Thanks Jack.
Downloading as we "speak".
I did not know this publication.
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Old 14-07-2013, 16:58   #921
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Re: Freighters vs. Sailboats

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Cappy:
The original discussion was about TSS. Your point is irrelevant. And I do not need an epitaph. You may well get there before me!!
And much in disagreement to your comment, they (TSS) DO exist in that area!

Nevermind, the entire area is gridded with light green recommended deep draft traffic lanes. I would imagine those little gems should be HIGH up on your reading list too.
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Old 14-07-2013, 17:04   #922
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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).
I disagree , my experience is that most large freighters in the open do not expect to alter course for a sailboat. Hence well in advance , one should adjust course to ensure a widening CPA.

In more confined situations , or with more traffic , then one often has to rely on the COLREGS. BUT I always say , do not stand on into danger.

But yes I agree with your last paragraph , there is a fine line between advance course changing , number of targets , risk, destination, sail plan , etc. that's what's makes it hard and decisions cannot be taken solely by rote or written rule.

In my opinion , I'm now with the Italian delegation to the IMO , consideration should be given to suspending power gives way to sail , certainly for vessels over 50m !!

Dave
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Old 14-07-2013, 17:07   #923
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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.

Cheers
Explain ?

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Old 14-07-2013, 17:12   #924
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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!
In my experience , very few large ships plot or track sailing boats , most don't even see you , especially at night. My average is less then 1in 5 boats I contacted actually confirmed they saw me reliably.

Hence blindly standing on , is a very dangerous thing. In my experience , unless you have no option , you should NEVER stand on into a situation where a close quarters situation develops.

Dave
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Old 14-07-2013, 17:20   #925
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Re: Freighters vs. Sailboats

Cappy:

I see two TSS routes in/out of the East Passage. Do you see more than I do??
Plus what is your point?? I am not a f.cking idiot, just because I did not immediately recognize the TSS abbreviation ( I did know about traffic separation schemes) or know what the undulating magenta line was. Are you such a genius??
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Old 14-07-2013, 17:26   #926
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Re: Freighters vs. Sailboats

I gave up on this thread months ago, surprised to see that the post count now is over 900!!!

Think how futile is a sailboat challenging a freighter! Forget about books, course plots, rules..... think survival! GET OUT OF HIS REACH!

In many ways this entire topic makes me think of a framed drawing hanging on the wall in my home office. It depicts a mouse giving the finger to an attacking hawk captioned:

"THE LAST GREAT ACT OF DEFIANCE!"

Go for it, grab your rules, challenge that big sucker after all, you think you have the right of way......and even that was discredited long ago in this thread.
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Old 14-07-2013, 17:39   #927
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Re: Freighters vs. Sailboats

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I have no desire to apply this method when at sea, I was just trying to check the calculations of some of the posters.
We must be near consensus on that!

Easier by far to put a cursor on the blip, hit the "ACQUIRE TARGET" button, and let the computer figure out the CPA and the time to CPA.

Saves wear and tear on the hockey puck.
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Old 14-07-2013, 17:49   #928
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Originally Posted by foggysail View Post
I gave up on this thread months ago, surprised to see that the post count now is over 900!!!

Think how futile is a sailboat challenging a freighter! Forget about books, course plots, rules..... think survival! GET OUT OF HIS REACH!

In many ways this entire topic makes me think of a framed drawing hanging on the wall in my home office. It depicts a mouse giving the finger to an attacking hawk captioned:

"THE LAST GREAT ACT OF DEFIANCE!"

Go for it, grab your rules, challenge that big sucker after all, you think you have the right of way......and even that was discredited long ago in this thread.
Foggy, that's fine , and in one to one , open seas , most sailors simply stay well clear , only a fool in a small boat attempts to assert stand on with a big freighter.

bUT , where you have multiple targets , and they are all sorting out how to pass each other , you may simply not have an option to " GET OUT OF ALL THEIR REACHES " , now you have a dilemma, what do you do.

Dave
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Old 14-07-2013, 17:54   #929
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Re: Freighters vs. Sailboats

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Originally Posted by chrisjs View Post
Cappy:

I see two TSS routes in/out of the East Passage. Do you see more than I do??
Plus what is your point?? I am not a f.cking idiot, just because I did not immediately recognize the TSS abbreviation ( I did know about traffic separation schemes) or know what the undulating magenta line was. Are you such a genius??
There is more than just the A to Narragansett lanes. There is the A to Buzzards Bay lanes. In addition, there are 'recommended 'Deep Draft' lanes, which go all the way from the Race to Cleveland ledge (Buzzards Bay), all the way around BI, and cross (at right angles) the A to Narragansett lanes.

There are several of these 'Recommended' lanes on the east coast. Penobscot Bay ME has one. There is one off New Jersey Coast. One at the entrance to Delaware Bay, One in Chesapeake Bay, Thimble shoal channel. Give me time and I can probably remember more.

My point is, MANY people are out boating, and sadly many many many of them NEVER take out a chart to have a look at what is around, beneath and over them. Everyone has myopia. They only look at what THEY need or want to do (regarding the ocean) There is a larger responsibility to protect your, your family, your guests and most importantly MY life.

Although you have never said it, do you rely ONLY on chart plotters for your navigation information??? I have seen NO chart plotter (either in Raster or Vector) that gives ALL the 'real' chart info.
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Old 14-07-2013, 19:09   #930
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Originally Posted by goboatingnow View Post

I disagree , my experience is that most large freighters in the open do not expect to alter course for a sailboat. Hence well in advance , one should adjust course to ensure a widening CPA.
Can't speak for the Med but in my experience well offshore Atlantic they generally do, usually well before they appear over the horizon. A benefit of a steel radar reflecting hull
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