AIS, Receiver or Transmitter

[Adelie]

Originally Posted by Brewgyver

First, why pick a model with a display to make your example? Do you think the average cruiser is going to run an AIS with dedicated display, but not have a chart plotter/MFD/ or computing device of some kind with at least OpenCPN? Of course not. Certainly not if you're trying to minimize your power infrastructure.

Second, "transmit mode" lasts a small fraction of a second (~25 ms, or 1/40th of a second), twice a minute. That's about 75 seconds per 24 hours. But why bother running all that through the mill, then adding the standby (RX) current draw, etc. The manufacturers publish the average power consumption.

I just installed an ACR brand transceiver, it has a published average power consumption of < 2 watts! So two measly watts, that's a hair under 4 amp hours/day. I don't think that's going to break many banks (house banks, that is).

Yes, a transceiver costs on average twice what an RX only unit does, and a $200-$300 powered splitter IS required for a transceiver - unless you run a separate antenna for the AIS, which can be done for a lot less $.

Lastly, I'd like echo that an RX only AIS is better than no AIS at all, and for RX only a much cheaper passive antenna splitter can be used, similar to the kind many boats have for FM radio reception.

I picked the model with the display because that's the most conservative choice. Integrating electronics means that if the display or the data backbone go down you lose all functionality on all integrated instruments. With its own display it will continue providing info regardless of status of other instruments. I also picked that model because it's Icom which is reputable, is sure to be FCC compliant and provides a good benchmark for comparison. Finally I picked that model because it was the one that I could find that indicated current draw in TX mode.

In the absence of clarifying info from the manufacturer (which I dug for but couldn't find) I assumed and continue to assume that 1.7amps is the average draw rather than peak current draw because that that is the conservative assumption to plan with.

Ignoring power supply issues and display issues a TX unit and ancillaries will cost in the vicinity $700 minimum.

The cost to add RX-AIS to a VHF you are replacing is about $250, $400 if you weren't going to replace the VHF anyway.


A house is but a boat so poorly built and so firmly run aground you would never try to refloat it.

[Dockhead]

Originally Posted by Don C L

Oh of course! I am talking about when I only see one running light, not both, or the port or stbd side of hull! He or she (and I am talking about the big ones) has their course and I am pretty sure they will stick to it. If I STAY on mine and the angle isn't changing then, well, then I think I may deserve to get hit! Now, if I see (not sure how it could sneak up on me, unless I am foolishly plodding ahead in the fog without electronic eyes, but) both running lights or both sides of the hull at a mile or so, I will, as they say, probably need to change my shorts. Then one has no choice but to maintain the same course and increase speed if possible.. but how did I get into that pickle in the first place??
BTW 3 or 4 miles is still really quite a ways and there's time to do things, but it's close enough that I will just play it conservatively and slow down.

Well, but the aspect of the ship -- the only thing you can tell by looking at his nav lights -- doesn't tell you much about how you will cross with him. Actually when you see both red and green at 3 or 4 miles off, that's probably the safest aspect of all, because unless you are on an exact reciprocal course (or exactly the same course), then you will definitely have an improving CPA and you should carry on or speed up.

What is frightening is to see his green, say, when you're approaching from his starboard -- what do you know? You know nothing. You don't know whether he's passing ahead, passing behind or on an exact collision course. That means you don't know what to do -- should you hold your course and speed (or speed up or turn to starboard)? Should you stop?

You can only tell with either AIS or with a series of bearings taken with a HBC. If the bearing in increasing, he's passing ahead. You should hold your course and speed (stopping is like turning to port and could be dangerous if he makes a turn to starboard). If the bearing is reducing, then for God's sake don't stop. Speed up if you can; start the engine; or probably better hold your course and speed. It means he's passing behind you.

If the bearing is steady, then you have a tough situation at only 3 or 4 miles. Can you turn far enough to starboard, to get past him? Speed up enough? If you slow down or turn to port, or stop, and if at the same time he decides to maneuver, you may be run down.

It's much easier if you see his red while you are approaching from his port side. Then you can make a hard turn to starboard without much risk UNLESS he's passing behind you. You might also be able to turn to port onto his same course -- this is the one case where a turn to port is usually ok.

In any case, you have to know. You can't just eyeball it.

[K_V_B]

Originally Posted by rwidman

No, nobody is out there to kill you, there would be too much red tape.

I do think it's foolish though to expect the QE II to alter course for a 30' recreational boat when that boat can stop or turn on a dime. Sure there are "rules" but sometimes we need to add a bit of common sense.

Oh, but they will. At the distance they see you they only need to adjust course buy a few degrees to open the CPA. And they do that.
I spend time on a freighter, as a passenger, but we had full access to the bridge and a lot of interaction with the officers and the crew. It was really an eye opener to see it from the other side. I did learn that I can indeed expect the professionals to manoeuvre clear of sail boats in open sea. In constrained waters, it is of course different, but again the colregs apply. The big vessel is in this case the stand on vessel because it is constraint in its manoeuvrability.
So when entering Cork Harbour the sailboats (there were lots of them) better make room...



Sent from my iPad using Cruisers Sailing Forum

[Don C L]

Originally Posted by Dockhead

What is frightening is to see his green, say, when you're approaching from his starboard -- what do you know? You know nothing. You don't know whether he's passing ahead, passing behind or on an exact collision course. That means you don't know what to do -- should you hold your course and speed (or speed up or turn to starboard)? Should you stop?

You can only tell with either AIS or with a series of bearings taken with a HBC. If the bearing in increasing, he's passing ahead. You should hold your course and speed (stopping is like turning to port and could be dangerous if he makes a turn to starboard). If the bearing is reducing, then for God's sake don't stop. Speed up if you can; start the engine; or probably better hold your course and speed. It means he's passing behind you.

If the bearing is steady, then you have a tough situation at only 3 or 4 miles. Can you turn far enough to starboard, to get past him? Speed up enough? If you slow down or turn to port, or stop, and if at the same time he decides to maneuver, you may be run down.

It's much easier if you see his red while you are approaching from his port side. Then you can make a hard turn to starboard without much risk UNLESS he's passing behind you. You might also be able to turn to port onto his same course -- this is the one case where a turn to port is usually ok.

In any case, you have to know. You can't just eyeball it.

Well I am a little confused because unless it is a sailing vessel, I will know at night which way he is going because I'll see his steaming lights, no? And if I see a steady bearing at 3 or 4 miles, I have plenty of time to do a lot, unless we are both going 20 knots I guess, and that would only be in my dreams. Perhaps I am missing something, it wouldn't be the first time. When it comes to my 5 or 6 or 7 knots vs. his 15 to 20 knots (and inability to maneuver) it is much easier for me to do what is necessary to avoid an encounter than he or she.

[Dockhead]

Originally Posted by Don C L

. . . When it comes to my 5 or 6 or 7 knots vs. his 15 to 20 knots (and inability to maneuver) it is much easier for me to do what is necessary to avoid an encounter than he or she.

In open water, it's an almost linear function of speed. So your 5 knots can do very little, compared to what a ship making 20 knots can do. What "inability to maneuver"? A ship can move its rudder at many degrees per minute. Its ability to change the CPA is roughly proportional to the difference in speed, so far greater than ours.

[Don C L]

Originally Posted by Dockhead

In open water, it's an almost linear function of speed. So your 5 knots can do very little, compared to what a ship making 20 knots can do. What "inability to maneuver"? A ship can move its rudder at many degrees per minute. Its ability to change the CPA is roughly proportional to the difference in speed, so far greater than ours.

I agree, even at 3 or 4 miles, it wouldn't take much change for the ship to avoid me as long as he is sure of my course and speed, (well, depending on the ship of course, not so sure about fully loaded supertankers) and if I stop he won't have to do anything, maybe. I am still coming at it from the frame of reference of crossing a shipping lane.

[donradcliffe]

With respect to the Mark I eyeball, lets recognize the fact while it may be ONE of the best collision avoidance tools, sometimes it gets distracted or sleeps. I will never forget being called on the VHF by a supertanker in the middle of the Indian ocean, AFTER it had gone right by me. Another time, as I was going from the Tuamotus to Tahiti, I saw a local trading ship one night after it had gotten way too close--it was the first ship I had seen in months, and I had gotten sloppy.

The AIS alarm never sleeps, unless it has been turned off, which I never do at sea. I also have a switchable external alarm which will wake the dead.

Another good thing about AIS transceivers, the authorities are much happier when they know where you are and where you have been. Twice I have come up the Old Bahama Channel (5 miles from Cuba) direct from Puerto Rico to Ft Lauderdale with an AIS transceiver. Each time I saw Coast Guard cutters loitering around off Miami with nothing to do and they ignored me. I'll bet their computers could show them were I had been for the last 6 months, so they saw no need to board me.

[rwidman]

Dockhead, You seem to spout this same "rules" BS every time you get a chance, much like a broken record. I think we all know the rules but we should be using some common sense to apply the rules. We are humans, not robots.

I get a kick from imagining you calling the QE II on the VFH and saying "Captain, this is the small sailboat approaching and I am the stand on vessel so I am going to need you to change course for me." Reminds me of the joke about the Navy captain and the lighthouse.

Common sense and common courtesy tells us to give way to a ship that's dozens of times the size of our recreational boats. It's one of those situations where you might be right, but you might be dead right.

You don't have to violate any rules to avoid a big ship, just pretend to yourself that you were planning on going that way anyhow.

[chuckr]

Have not read all but one little item not to be taken lightly is the military ships - just cause you got AIS and Radar and all are running you still have to maintain a watch - we were sailing the Black Sea and we saw a big ship coming at us at some difference from starboard and crossed directly in front of us - no AIS no radar - no nothing - and we had to slow down to avoid him and give him distance

don't see them often but we have seen them -

[anacapaisland42]

Rules are nice, but I love our boat, I don't really care who has right of way, Big or small, I'll get out of the way.
Obviously I don't race.
I think that I would prefer "receive" to tell me where to move to to avoid a collision. Having sailed out of the Panama Canal exit without AIS worrying what speed/course those awfully big boats were on, and having been completely confused by a large cruise ship doing slow speed circles at night off Cozumel, I really would have liked it at those times.
Bill

[rwidman]

You can never count on the other guy to move out of your way but you do have control of your own boat. You can stay out of their way.

I can picture it now, me cutting in front of a 1,000 ft tanker and my wife saying "Watch out for that big ship!" and me saying "Oh don't worry, we have the right of way, he has to stop or turn."

[DotDun]

Originally Posted by rwidman

Dockhead, You seem to spout this same "rules" BS every time you get a chance, much like a broken record. I think we all know the rules but we should be using some common sense to apply the rules. We are humans, not robots.

I get a kick from imagining you calling the QE II on the VFH and saying "Captain, this is the small sailboat approaching and I am the stand on vessel so I am going to need you to change course for me." Reminds me of the joke about the Navy captain and the lighthouse.

Common sense and common courtesy tells us to give way to a ship that's dozens of times the size of our recreational boats. It's one of those situations where you might be right, but you might be dead right.

You don't have to violate any rules to avoid a big ship, just pretend to yourself that you were planning on going that way anyhow.

As Dockhead has explained, rules apply 'when collision is imminent'. Without rules, neither vessel knows what to do or what to expect of the other vessel. Without rules and each vessel performs a course change that they think is 'common sense and common courtesy', there is no guarantee the un-coordinated course changes prevents a collision. Each could play such 'common sense and common courtesy' game until a collision happens. When a collision is imminent, following the rules is the only common sense!

If you are the stand-on vessel and make course changes, how is the other vessel suppose to trust you won't make additional course changes as you've already demonstrated that you don't follow the rules? At that point the other vessel can't rely on your navigation skills/judgement.

The 'collision is imminent' circle is variable, Dockhead suggests inside 10nm. So make your 'common sense and common courtesy' course changes prior to that circle and all is good. But once 'collision is imminent', you should follow the rules.

[rwidman]

Originally Posted by DotDun

As Dockhead has explained, .............

He didn't "explain" anything, he is just arguing his point of view.

Who is to say I didn't intend to alter my heading at that point anyway?

I hope you realize that nobody ever wins an Internet argument. It just goes on and on until someone gets tired of it or the thread gets closed. We all go away with the same point of view that we started with.

[Dockhead]

Originally Posted by rwidman

Dockhead, You seem to spout this same "rules" BS every time you get a chance, much like a broken record. I think we all know the rules but we should be using some common sense to apply the rules. We are humans, not robots.

I get a kick from imagining you calling the QE II on the VFH and saying "Captain, this is the small sailboat approaching and I am the stand on vessel so I am going to need you to change course for me." Reminds me of the joke about the Navy captain and the lighthouse.

Common sense and common courtesy tells us to give way to a ship that's dozens of times the size of our recreational boats. It's one of those situations where you might be right, but you might be dead right.

You don't have to violate any rules to avoid a big ship, just pretend to yourself that you were planning on going that way anyhow.

Here we go again.

For the sake of civil conversation, I will ignore the phrase "BS".

Perhaps you could point out where, in anything I have ever posted, I ever indicated that I would call up the bridge of the QEII, or any other vessel, and tell them "I am the stand on vessel so I am going to need you to change course for me." You have understood nothing.

There is no "right of way" at sea, and standing on is not a privilege. Standing on and giving way is part of an orderly procedure of maneuvering, which is essential for the prevention of collisions, once a risk of collision has arisen. You may choose to remain ignorant of how this works, but you can be sure, that no professional mariner will ever admire you for it. Amateurs who do not understand collision avoidance procedure are a menace to ships, and they call us "WAFI's" exactly because of these attitudes.

You seem to think that you don't need to know anything about collision avoidance, as long as you are willing to give up your "rights" and just dodge out of the way whenever you see a ship. This is a really big mistake. First of all, you don't have any rights, which you can give up. COLREGS don't create any privileges of any kind. It's very different from how it works on land. Secondly, dodging around is as likely to cause a collision, as it is to prevent one. Effective collision avoidance requires SYSTEMATIC maneuvering, not dodging around.

It is certainly basic good seamanship to prevent a risk of collision situation from ever arising, by taking action early enough. This may work 99% of the time for those who don't go out into open sea -- who sail in coastal waters where shipping lanes and channels are well defined. Just stay out of them, as I have always said, and stay out of the way of shipping. But in the open sea, and especially in areas with dense traffic, it is not always possible to avoid risk of collision situations with ships. Once one of these arises, you either follow the Rules, as you are obligated to, or you are flotsam, relying entirely on the ship to deal with the situation. If you don't believe me, ask any commercial ship deck officer.

A person who has even the slightest understanding of how collision avoidance works, would never, ever call up a ship's bridge and say anything like "I am the stand on vessel so I am going to need you to change course for me." If you are in a risk of collision situation with a ship, and you are the stand-on vessel, and the ship is not taking action when you would have expected it, you don't make any VHF call at all, so long as you have a safe maneuver you can take yourself (i.e. a turn to starboard). You obviously didn't read that when I wrote it further up in this thread, so I don't know why I would expect you to read it now, so I think I'm done with this.

[Dockhead]

Originally Posted by DotDun

As Dockhead has explained, rules apply 'when collision is imminent'. Without rules, neither vessel knows what to do or what to expect of the other vessel. Without rules and each vessel performs a course change that they think is 'common sense and common courtesy', there is no guarantee the un-coordinated course changes prevents a collision. Each could play such 'common sense and common courtesy' game until a collision happens. When a collision is imminent, following the rules is the only common sense!

If you are the stand-on vessel and make course changes, how is the other vessel suppose to trust you won't make additional course changes as you've already demonstrated that you don't follow the rules? At that point the other vessel can't rely on your navigation skills/judgement.

The 'collision is imminent' circle is variable, Dockhead suggests inside 10nm. So make your 'common sense and common courtesy' course changes prior to that circle and all is good. But once 'collision is imminent', you should follow the rules.

Explained much more clearly than I was able to.