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Old 29-01-2012, 08:28   #16
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

I am on a brand new ship fitted with all the latest bells and whistles. Coming into Singapore we had to turn our filters right up as the number of alarms was completely distracting the two watch keepers and myself (Master) from the job in hand. In Singapore area most of the AIS stuff is not Class B anyway but is Class A. In some cases the number of alarms is just too high so filtering becomes essential. The Solent as mentioned above is another case in point, so too is the Delaware River in summer but that does not mean the big ship watch keeper can just ignore the other traffic including small stuff. We do try not to run anyone down; just don't tell me power gives way to sail when I'm in a channel not much wider than me, not going to happen.

As for Flying Cloud 1937 - I don't know your cruising area so I cannot say why ship's are going too fast but sometimes if you are going down river with the tide you have to go faster than you'd like in order to maintain steerage way. In other cases you might have entered a river heading for a berth and you must make a certain speed to reach that berth before the tide changes and you lose the water depth needed. Also sometimes, particularly in the US Gulf ports the channels / rivers are really too narrow for the ships now using them so when we go through even at a slow speed we create a standing wave which can be quite high and I've seen a few disasters because of that - folks in SUV's a bit too close to the waters edge, others trying to launch or recover bass boats etc when a 6 foot wave comes from nowhere. Our passage times are broadcast but not everybody listens.
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Old 29-01-2012, 08:34   #17
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

SteveT: Thanks for that real-world advice from someone who knows.
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Old 29-01-2012, 08:50   #18
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

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Hi Nick,

That would mean the citizens don't count....

unless they we required to go twittle their thumbs.

I see em on radar, I even go out of their way...but when they come in the PS, one after another...drafting between 4 and 10 foot swells in a one mile wide fairway (i mean wakes...in the US we are responsible for our wakes....that is unless your super big) depending on how close...our thumb twittle could be up to an hour.

Yea I know trying to time 4 freighters down a 20 mile streatch... would mean some big corp or 2.... is going to loose a couple of dollars.

But hey we all have to wave something in life right?

Lloyd
A little off topic, but nothing anyone can do about the wakes. They announce passages on the traffic freq, VHF 12 or 13.

The problem is no matter how slow they go, the channel is often the exact same size as their ships, cut through a shallow bay, the water has to go somewhere. Also they have to maintain speed to allow for steerage, (remember they don't have much room), and there may be several other ships behind them that all have to go through on the high tide.

In Galveston bay there are several danger areas, that are marked on the charts, as do not be in when a big ship makes passage. A wake will push you onto a shoal, or when the ship goes out it will push out the water leaving you high and dry,...for a few minutes until the water rushes back in destroying your boat.

The wakes are tall and tightly packed, and I've been nearly rolled by them when not watching out for them.

Unfortunately they paid to get the channel dug, so they get to use it. Just stay out of the way and be careful.
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Old 29-01-2012, 08:54   #19
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

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I am on a brand new ship fitted with all the latest bells and whistles.

As for Flying Cloud 1937 - I don't know your cruising area so I cannot say why ship's are going too fast but sometimes if you are going down river with the tide you have to go faster than you'd like in order to maintain steerage way. In other cases you might have entered a river heading for a berth and you must make a certain speed to reach that berth before the tide changes and you lose the water depth needed. Also sometimes, particularly in the US Gulf ports the channels / rivers are really too narrow for the ships now using them so when we go through even at a slow speed we create a standing wave which can be quite high and I've seen a few disasters because of that - folks in SUV's a bit too close to the waters edge, others trying to launch or recover bass boats etc when a 6 foot wave comes from nowhere. Our passage times are broadcast but not everybody listens.
Google Puget Sound on G..Earth.

You'll see where I lodge my complaint from. We are in a CG controlled water way...Sector Puget Sound.

My complaint isn't giving berth to a large sea going vessel Constricted.

My complaint in in ships management tracking the PS as soon as they enter Point Wilson, and also the Hario Straight(those be mostly big tankers).

I know it's 20 miles but when you have a 300 ft freighter moving 30 knots in a narrow fairway(1 to 2 miles at the widest mostly narrower) the Bow Wave coupled with the Stearn Wave reverberates between the shores, for at least 45 minutes, then when ya have 2, 3, 4(5 mins apart) in a row the sea is fouled for at least an hour.

That doesn't even consider the tankers going up Hario...off Sydney, which is half as wide as PS. And they're still doing 30 knots.

Just to be sure there is nothing but tidal current...worst case scenario 3 knots.

Lloyd
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Old 29-01-2012, 09:19   #20
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

Sorry but there is not a tanker in the world can do 30 knots unless maybe a USN Fleet Oiler. Most struggle to do 15 knots, and 300 foot is just a baby anyway, try 900 feet. At 15 knots we can't really slow down in less than 20 minutes, so if I'm under pilotage it would be unusual to be doing more than 10 knots. The exceptions would be coming down the Mississippi in a spring flood or similar. As I said I don't know your area so cannot speak for the geography there but they won't be doing 30 knots. Even containerships don't go much over 20 these days - fuel costs too much.
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Old 29-01-2012, 09:31   #21
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

Dude,

ya got to come to PS.

20 or 30 knots it doesn't matter...the wake is still more then most 50 footers can handle. That's if just one of ya is coming down.

Besides I do 11 knots, and they pass me like I'm on anchor. Wow 900 ft...all I know is they are big and bad.

All ya have to do is ask... The local boating community is near the tipping point...when change will be demanded.

The question is do we do it know when the economy is bad or do we wait for labor to improve.?

Lloyd
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Old 29-01-2012, 10:12   #22
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

My goodness, 30 knot Tankers?? I know the area your speaking of and it can be bad ! but it's been that way for years and you know when they are gonna be there, if you use your equipment, the ships your speaking of have to maintain a safe speed for there own safety and other ships in the areas safety, Im sure as a past Capt of Large vessels that used these waters, that these Capts are maintaining a safe speed for the handleing of there vessels, as you must do for yours ! They can't reduce speed to an unsafe level, so it's your responsibilty to do what you have to do to be safe ! ITs a no win situation for you I guess. but the shipping is not going to get to be less it's gonna get worse !! Just my 2 cents Bob and Connie
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Old 29-01-2012, 10:53   #23
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

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Or... you can just install a class-A transponder

ciao!
Nick.
I was just about to say that Nick. The price difference is not that much. There is no sense in cheaping out on your safety.
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Old 29-01-2012, 11:48   #24
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

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Sorry but there is not a tanker in the world can do 30 knots unless maybe a USN Fleet Oiler. Most struggle to do 15 knots, and 300 foot is just a baby anyway, try 900 feet. At 15 knots we can't really slow down in less than 20 minutes, so if I'm under pilotage it would be unusual to be doing more than 10 knots. The exceptions would be coming down the Mississippi in a spring flood or similar. As I said I don't know your area so cannot speak for the geography there but they won't be doing 30 knots. Even containerships don't go much over 20 these days - fuel costs too much.

I calculated hull speed at 40kts for the average freighter, plus most of them add bow bulbs to further extend speed.
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Old 29-01-2012, 12:02   #25
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

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I calculated hull speed at 40kts for the average freighter, plus most of them add bow bulbs to further extend speed.
I seriously check your reality sensor. I think its wires are crossed. most freighters are under 20 , even the fast cats are under 40

dave
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Old 29-01-2012, 13:01   #26
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

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I seriously check your reality sensor. I think its wires are crossed. most freighters are under 20 , even the fast cats are under 40

dave
Agree, 30 - 40 knot traditionally styled tanker/bulky/container ships is fantasy, although i have been passed by a few Maersk container ships doing 25 knots, that was a while ago though....

As far as fast cats go, they averaged 40 knots doing the Darwin - Dili run on the HMAS Jervis Bay. I clocked them doing 46 one night, we passed each other just under a mile apart and the rooster tail was nearly as long as the cat itself, pretty impressive to say the least........

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Old 29-01-2012, 13:42   #27
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

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I calculated hull speed at 40kts for the average freighter, plus most of them add bow bulbs to further extend speed.
I've been at sea my entire working life (since 1977) on ships up to 500,000 tonnes DWT and 1300 feet LOA and the fastest I've ever been and that with 45,000 SHP was 21 knots. That was in ballast and with a 4 knot tidal stream up the back. It is not just a function of water-line length, try factoring a Block Coefficient of close to 1 into the equation. The bulb is more for fuel efficiency than speed. If you follow the link below you will see why large commercial vessels are so slow - a displacement hulled yacht hull speed is 1.34 x √ LWL. An oil tanker or other freighter will be using 0.6 x √LWL which is quite a bit slower!



Royce's Sailing Illustrated: The Best of All Sailing Worlds, Modern and ... - Patrick M. Royce - Google Books
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Old 29-01-2012, 17:00   #28
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Re: AIS Class B Can Be Filtered Out by Big Ship Radars

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I've been at sea my entire working life (since 1977) on ships up to 500,000 tonnes DWT and 1300 feet LOA and the fastest I've ever been and that with 45,000 SHP was 21 knots. That was in ballast and with a 4 knot tidal stream up the back. It is not just a function of water-line length, try factoring a Block Coefficient of close to 1 into the equation. The bulb is more for fuel efficiency than speed. If you follow the link below you will see why large commercial vessels are so slow - a displacement hulled yacht hull speed is 1.34 x √ LWL. An oil tanker or other freighter will be using 0.6 x √LWL which is quite a bit slower!



Royce's Sailing Illustrated: The Best of All Sailing Worlds, Modern and ... - Patrick M. Royce - Google Books
I stand corrected, that was theoretical top speed with unlimited fuel, and engines.

18-22kts is from wiki, with note of vessels tending to go slower due to fuel costs.
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Old 30-01-2012, 03:10   #29
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Quote:
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I stand corrected, that was theoretical top speed with unlimited fuel, and engines.

18-22kts is from wiki, with note of vessels tending to go slower due to fuel costs.
That's more like it. We see 14-16kts mostly with the Panamax ships around here.

ciao!
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