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Old 08-11-2011, 09:53   #136
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Re: Radar or Not ?

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Originally Posted by Astrid View Post
I'll second what psneeld says. A properly tuned radar will pick up anything out there large enough to return an echo. One simply needs a good working knowledge of how to use it effectively and have a radar repeater at the helm. AIS is wonderful too, and can provide similar information as radar on any vessel out there that is also equipped with AIS. Unfortunately, in many areas of the world, AIS equipped vessels are not the norm and the vast majority of small boats will not have it and so will not show up on one's own screen. If one is navigating and depending on AIS for collision avoidance at times of minimal visibility, one has to realize that a large proportion of potential obstacles out there will not be registering on your AIS. AIS supplements radar, but does not replace it as the primary means of collision avoidance in poor visibility.
And AIS wont pick up Thunder storm cells, waterspouts, a floating container load lost at sea...... Frankly I think there is way too much emphasis on being run down at sea. I found Radar very useful for many of these other day to day things. Sure sitting at the nav station at night with the autopilot steering the boat it was nice to check the radar screen for ships...
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Old 08-11-2011, 15:02   #137
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Re: Radar or Not ?

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Do you have a stabilizing gyro for your ARPA function? I didn't, and in bouncy conditions the ARPA was very erratic to the point of being useless.

He has a multihull.
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Old 08-11-2011, 19:25   #138
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Re: Radar or Not ?

"As a slight aside, any opinion on the relative value of a pivoting mount for the antenna? I'm told it improves display clarity as the antenna stays more level with the horizon. "

I loved mine until we got into 20 ft. swells with a nasty corkscrew motion and the self levelling mount hit the stops hard on every roll. The thing tried to tear itself out of the transom (it was one of those backstay mounted struts that screwed into the transom next to the backstay) and I had to immobilize it for the rest of the passage. Once in the islands I took it off and reinstalled it on the mast without the self levelling gear. Never again will I sail offshore with such a thing.

I cant see close-in stuff anymore (i.e. within a couple or three boat lengths) and sometimes if the boat is heeling a lot it will have a bit of trouble seeing stuff to one side but it is worth it to have a solid mount that doesnt try to leave the boat
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Old 08-11-2011, 19:52   #139
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Re: Radar or Not ?

I never had any issues with a std mount. considered a dampened swing mount but never went with it.
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Old 08-11-2011, 20:17   #140
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Quote:
Originally Posted by Cheechako
And AIS wont pick up Thunder storm cells, waterspouts, a floating container load lost at sea...... Frankly I think there is way too much emphasis on being run down at sea. I found Radar very useful for many of these other day to day things. Sure sitting at the nav station at night with the autopilot steering the boat it was nice to check the radar screen for ships...
In my experience thunder cells won't kill me nor will small boats. Being hit by a 20000 tanker most definitely will. !

On comments about Arpa. It's almost useless on a conventional monohull in any seaway. You really need a sat compass to stablise it. If you get a chance compare Arpa vectors with the same AIS vectors , it will give you a good laugh. Without rock solid heading that's updating at least at 10 hz ( and no overshoot or excessive damping, so fluxgates dont cut it ) and a fast arpa processor most small boar arpa readings are rubbish.
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Old 08-11-2011, 21:22   #141
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Re: Radar or Not ?

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The first time was rounding a point on the Chesapeake Bay. Shoal waters to port, the Bay to starboard, heading north. The menhaden boat was on the same track, headed home to Reedville. I lost sight of him about 1,000 yards away when a very heavy rain squall moved over us. However, I could see him on my radar, steaming along at maybe 20 knots and headed right for me. I had a choice at that point. I could "assume" that the helmsman on the menhaden boat could see me on his radar and change course to avoid running me over, and hold my course. Or, I could take the safe decision and turn to port into the shoal waters, which I did. He drew more than I did, so I knew that would keep him away. Watching on the radar, he never changed course. Visibility was a couple of boat lengths, not enough to make a difference. I never saw him as he went by, thought the radar said he was 200 feet away.

The second time was in the channel between St Vincent and Bequia. Again, a heavy rain squall moved in. This is a busy ferry route between the two islands. I could see the ferries (two of them) coming up on me from ahead and astern. Visibility was maybe 50 feet. Again, I didn't trust the assumption that they would see me on radar and change course, so I moved off the route. Never did see the ferries, the rain was coming down so hard.

Based on my experience with ferries in the Virgin Islands, I never assume they'll change course! Glad to have the radar to help me make good decisions. And even with the very heavy rain, the radar did a great job, properly adjusted.

Was the first boat commercial? I would never assume a non-commercial boat had functioning radar,
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Old 08-11-2011, 21:26   #142
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Re: Radar or Not ?

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If you navigate in high traffic areas AIS is a godsend and I'd have it before radar. Small boat radar with horizontal resolutions of 7 to 9 degrees is a poor enough device.

My experience is that in any seaway small boat radar will not detect small metallic things like buoys or other yachts. Hell the big Boys will tell you they can't se you on Radar.

Get an AIS transponder then a RADar if you can afford it buy both.

Dave

How well do those big aluminum ball radar reflectors work, does anyone know?
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Old 08-11-2011, 21:50   #143
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Re: Radar or Not ?

The main trick in learning to use a radar well is to use it all the time!
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Old 09-11-2011, 03:51   #144
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Re: Radar or Not ?

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Being a Master Class 1 with 30+ years Radar use, i might know a thing or two.....
Sorry i apologies most profusely. If you note i am called Dulls, Our thread isn't exactly help full to others....
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Old 09-11-2011, 06:58   #145
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Re: Radar or Not ?

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In my experience thunder cells won't kill me nor will small boats. Being hit by a 20000 tanker most definitely will. !
Ever think that you hitting a small boat may cause the injury or death of someone else? Or maybe just extreme financial hardship?
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Old 09-11-2011, 08:02   #146
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Quote:
Originally Posted by Rakuflames

How well do those big aluminum ball radar reflectors work, does anyone know?
Useless absolutly useless , see practical sailor
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Old 09-11-2011, 08:50   #147
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Re: Radar or Not ?

I use my 3G broadband radar in the best of weather and one of its functions for me is a "rear view mirror" so I'm not surprised by folks trailing up the rear.

Radar is more important than AIS, but it is so incrementally inexpensive as an added feature on a VHF radio that it is still worth getting. The GX-2150 does a great job of reporting anyone using its transponder.

I didn't originally even know much about it til I saw a "Dnagerous Vessel" highlihted behind me at the slip....a big recreational fishing boat has AIS class B and it appeared behind me at the dock one day!

Now, I get use from it when I go offshore. I see the big guys on radar but if there is AIS, too, you get their MMSI and can place a DSC call if need be.
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Old 09-11-2011, 09:48   #148
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About ARPA or MARPA... don't assume it's working when you get a lock or values for CCA etc. Only when you have at least a "gyro stabilized" compass with 10 updates per second, you get good data. When you have a less able compass, the ARPA readings will reduce your safety instead of improve it. I don't think you need at least a satellite compass. Examples of good compasses: the N2K sensors or Simrad/Robertson autopilot compass. It should be mounted low.

p.s. there's talk that new (commercial) radar sets take both AIS and ARPA data and combine it into one single symbol on screen. So that's where we're heading :-)

ciao!
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Old 09-11-2011, 11:47   #149
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Re: Radar or Not ?

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Do you have a stabilizing gyro for your ARPA function? I didn't, and in bouncy conditions the ARPA was very erratic to the point of being useless.
Correction: I do have a gyro....see below.

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Originally Posted by s/v Jedi View Post
About ARPA or MARPA... don't assume it's working when you get a lock or values for CCA etc. Only when you have at least a "gyro stabilized" compass with 10 updates per second, you get good data. When you have a less able compass, the ARPA readings will reduce your safety instead of improve it. I don't think you need at least a satellite compass. Examples of good compasses: the N2K sensors or Simrad/Robertson autopilot compass. It should be mounted low.

p.s. there's talk that new (commercial) radar sets take both AIS and ARPA data and combine it into one single symbol on screen. So that's where we're heading :-)

ciao!
Nick.
The Raymarine SPX course computers have internal gyro and produce: "Gyro stabilized heading output for MARPA and radar/chart overlay" @ "Standard
10 Hz, 0.1 resolution".
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Old 09-11-2011, 12:02   #150
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Re: Radar or Not ?

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Correction: I do have a gyro....see below.



The Raymarine SPX course computers have internal gyro and produce: "Gyro stabilized heading output for MARPA and radar/chart overlay" @ "Standard
10 Hz, 0.1 resolution".
A gyro AND two hulls! No wonder yours works and mine was iffy.
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