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Old 15-10-2016, 17:08   #151
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Re: Is radar like the extinct typewriter?

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^^ dont trust any small boat marpa to be remotely accurate. At least in any sort of seaway. Even on big ships the accuracy is often only good to about 0.5' depending on a lot of factors.



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Furuno has ARPA.

I've targeted a vessel that also had AIS, it was spot on in relatively calm (3-4') seas.
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Old 15-10-2016, 17:11   #152
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Re: Is radar like the extinct typewriter?

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naah...

Hear, hear is an expression used as a short, repeated form of hear him. It represents a listener's agreement with the point being made by a speaker. ... The phrase hear him, hear him! was used in Parliament from late in the 17th century, and was reduced to hear! or hear, hear! by the late 18th century.

DH likes to be akarut....
And in the UK Parliament it is pronounced...' Ear Ear" with copious pounding on the table and the occasional fart.
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Old 15-10-2016, 17:19   #153
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Re: Is radar like the extinct typewriter?

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"The time for taking all measures for a ship's safety is while still able to do so. Nothing is more dangerous than for a seaman to be grudging in taking precautions lest they turn out to have been unnecessary. Safety at sea for a thousand years has depended on exactly the opposite philosophy." U.S. Navy FleetAdmiral Chester W. Nimitz (read about Admiral Nimitz here)
If I am not mistaken, i think it was Admiral Nimitz who began and almost ended his Naval career by grounding his warship in a navigational error near Japan
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Old 15-10-2016, 17:21   #154
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Re: Is radar like the extinct typewriter?

AIS is a hell of a lot of bang for your buck. For a couple of hundred USD you get a lot of additional navigation info and related safety. Its a much bigger step up to purchasing Radar, 10x maybe. We use AIS continuously when on passage and only rarely Radar. The times we use Radar it is really handy and I wouldn't not have it for the type of sailing we do. For basic cruising with a budget issue, then AIS is the way to go first.
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Old 15-10-2016, 17:26   #155
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Re: Is radar like the extinct typewriter?

I don't think anyone would argue with that reasoning Paul....AIS is great value


But even an old cheap Radar that still works is an option to consider which was the OP's question.
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Old 15-10-2016, 17:26   #156
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Re: Is radar like the extinct typewriter?

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Furuno has ARPA.

I've targeted a vessel that also had AIS, it was spot on in relatively calm (3-4') seas.
Arpa or marpa? What sort of stabilisation? What size antenna? what sized vessels? It's course changes that throws them out, even small ones like your own boat yawing. Not such a problem flat seas, but if the target vessel (or your own) is not holding a steady course or speed your (M)arpa will start telling porkie pies. Not to say it will be completely wrong, but I wouldn't trust CPA's inside a mile or so.
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Old 15-10-2016, 17:41   #157
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Re: Is radar like the extinct typewriter?

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I don't think anyone would argue with that reasoning Paul....AIS is great value


But even an old cheap Radar that still works is an option to consider which was the OP's question.
Didn't know I was supposed to read the original post if the thread got greater than 100 posts If I had a functioning Radar onboard I sure wouldn't tear it out to end up with no Radar. Makes no sense.
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Old 15-10-2016, 17:43   #158
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Re: Is radar like the extinct typewriter?

Snowpetrel, I have used a few small MARPAs radars that were connected to the sat compasses and they stabilized well enough for decision making.

I think the newer ones also integrate GPS fed COG & SOG data to give you reliable true motion and ground stabilization.... but not sure.

Still, on old yacht radars.... offsetting a VBM set to your COG to the target position and watching the trend....is better than nothing, if target has no AIS .
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Old 15-10-2016, 17:45   #159
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Re: Is radar like the extinct typewriter?

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Arpa or marpa? What sort of stabilisation? What size antenna? what sized vessels? It's course changes that throws them out, even small ones like your own boat yawing. Not such a problem flat seas, but if the target vessel (or your own) is not holding a steady course or speed your (M)arpa will start telling porkie pies. Not to say it will be completely wrong, but I wouldn't trust CPA's inside a mile or so.
Are porkie pies similar to lirty dies?
You certainly can't bank on the CPA, but it will still probably be a lot better than the one you come up with by judging the lights bouncing around between waves.
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Old 15-10-2016, 17:56   #160
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Re: Is radar like the extinct typewriter?

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Didn't know I was supposed to read the original post if the thread got greater than 100 posts If I had a functioning Radar onboard I sure wouldn't tear it out to end up with no Radar. Makes no sense.
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Old 15-10-2016, 18:40   #161
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Re: Is radar like the extinct typewriter?

Been following this robust thread for days. I have zero experience with radar. Beer can racer and multihull coastal on vacation time.

I was looking at Furuno stuff on website last night. OMG... for top of the line stuff their 'does all' units easily 10-15K all in! Holy Schizel Batman! That is a lot of jing, man.

I retire in two years and am just now starting to get serious about the finances of boats and such. Can anyone recommend to me a good course in navigation and radar simulators? Don't think I will be buying a luxurious boat like that sweet Oyster.
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Old 15-10-2016, 18:45   #162
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Re: Is radar like the extinct typewriter?

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Lobster boats are the stand on vessels when they're working traps, since they are engaged in fishing.
Many lobstermen make that claim but,

(d) The term "vessel engaged in fishing" means any vessel fishing with nets, lines, trawls or other fishing apparatus which restrict manoeuvrability, but does not include a vessel fishing with trolling lines or other fishing apparatus which do not restrict maneuverability.

The USCG course instructor I once had in Portland, Maine was adamant that lobstering isn't one of the types of fishing that is included because lobstermen are not restricted in their ability to maneuver. They might not want to maneuver to avoid you while hauling traps any more than I do when I'm out trolling in my Boston Whaler on the lake, but there's nothing to physically prevent them from maneuvering. Whoever is right about this really doesn't matter, the point I was making is that especially in the fog, you better watch out for and avoid them because chances are, they won't be seeing or avoiding you.
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Old 15-10-2016, 19:44   #163
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Re: Is radar like the extinct typewriter?

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Arpa or marpa? What sort of stabilisation? What size antenna? what sized vessels? It's course changes that throws them out, even small ones like your own boat yawing. Not such a problem flat seas, but if the target vessel (or your own) is not holding a steady course or speed your (M)arpa will start telling porkie pies. Not to say it will be completely wrong, but I wouldn't trust CPA's inside a mile or so.
ARPA, pitch, roll, yaw, heading within 2 @10hz.
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Old 16-10-2016, 04:21   #164
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Re: Is radar like the extinct typewriter?

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naah...

Hear, hear is an expression used as a short, repeated form of hear him. It represents a listener's agreement with the point being made by a speaker. ... The phrase hear him, hear him! was used in Parliament from late in the 17th century, and was reduced to hear! or hear, hear! by the late 18th century.

DH likes to be akarut....
Correct on all points
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Old 16-10-2016, 05:09   #165
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Re: Is radar like the extinct typewriter?

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Snowpetrel, I have used a few small MARPAs radars that were connected to the sat compasses and they stabilized well enough for decision making.

I think the newer ones also integrate GPS fed COG & SOG data to give you reliable true motion and ground stabilization.... but not sure.

Still, on old yacht radars.... offsetting a VBM set to your COG to the target position and watching the trend....is better than nothing, if target has no AIS .
I agree. I have never used a yacht radar that had usable MARPA. I've heard tell that some Furuno radars can do it, but I somehow doubt it. The problem is lack of bearing discrimination, I think, and the complexity of the motion of small vessels in a seaway. In my experience, it just doesn't work other than as a party trick in perfect conditions (flat sea, strong target, etc.).

The compass data is crucial to this having any chance of working, but I have an excellent 3D stabilized compass (Airmar H2183), and it doesn't seem to make any difference.

A decent sized open array radar and satellite compass might be a different ballgame.


But why do you say using the EBL (I presume that's what you meant) is only "better than nothing"? This is an extremely powerful tool. Even with poor bearing discrimination, the trend is clearly visible as the target walks down the line. This is analogue and goes perfectly with the idea of how radar can be used as an extension of your vision -- different category from the information you get from plotter and AIS (which are, as many have said here, telling you what SHOULD be out there, in theory, rather than what is directly observed).

And as you know, there are many other wonderful tools -- trails, true motion, etc -- which allow you to vividly visualize what is around your boat.


But radar is not something you can just switch on and use -- it's not like a plotter, giving you a ready-made, pre-processed and immediately understandable representation of the information it provides. Radar really takes some study and some skill. I'm guessing that a lot of people who consider it superfluous don't really know how to use it. If they did, I bet they would feel blind without it, as I do.
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