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Old 26-05-2015, 18:49   #76
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Re: Question - I know this will blow up!

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Originally Posted by btrayfors View Post
Yep, I believe you. But, I wouldda thought your radar would have picked up his pilot house/trunk cabin, masts, etc. Where is your antenna mounted?

Mine is on a pole on the stern, about 10' above the water. I didn't want to put it on the mast because I wanted to favor targets close in, i.e., those that I might collide with :-)

I've had some great experiences in Maine fog with the radar! And, I agree, there's no way AIS can hold a candle to radar as a versatile, synoptic navigational tool. But, paired with radar it can be helpful, e.g., in identifying a target already seen on the radar.

Cheers,

Bill
You have to experience Maine fog to appreciate the situation. Not saying there aren't other places just as foggy.
Anyone who hasn't picked their way thru miles of pot bouys spaced 10ft or less apart,rocks everywhere,& lobster boats roaring around at 20+kts,buzzing you for fun, with visibility at 100ft-really can't appreciate the situation. Ships-hell they are the easy part-at least they maintain a semblance of a course.
I am not trying to discourage anyone from cruising this area.For the most part it's clear or clear enough. Anything over 1/4 nm vis. & you can't get into much trouble at 6kts. You will be motoring anyway-not much wind with really thick fog.
With common sense,you can usually avoid the really thick stuff,but be prepared for getting caught out in it.

My dome is 12ft (16ft off water) up mast-that's the way boat came & I'm happy with it. Much lower than the same types of radar used on some of our larger fish boats.Your pole setup is fine also.

Radar has a +/- 25deg vertical beam IIRC,& I have them on the top of ferry wheelhouses at 50-60ft off water-they pick up bow/stern ramps & wake-no complaints from capts. (Google Earth L'etete Passage Deer Isl ferry)
I don't like putting them more than 12ft above deck(extension ladder height) for serviceability & for roll effect fading on boats used in rough wx.
Never experimented with swinging stands-don't think they would stand our year round fishing.
Don't see any advantage to putting them 60ft up a mast,say,on a sailboat either.Lot of shock "shaking"-hard on components-esp.mag filament-farther up you go.Also,difficult maintenance, & roll effect again. You might see another < 60ft boat @ 5nm, instead of 4nm-which is the best any radar up to 10KW & 6Ft scanner will see another similar boat in true "radar reqd" conditions.
My 30yrs experience has taught me that the "book" is a guide. actual experience is the "bible".
/ Len
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Old 26-05-2015, 19:13   #77
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Re: Question - I know this will blow up!

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Originally Posted by Stu Jackson View Post
OK, how'd I know you knew all that stuff?

Try this:

Where is your radar reflector? - SailboatOwners.com
Excellent question Travellerw re Radar vs AIS.
Scroll down to comment #11 in the above forum that Stu Jackson posted, and the answer is obvious
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Old 26-05-2015, 22:54   #78
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Re: Question - I know this will blow up!

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Originally Posted by Markhunter1097 View Post
Excellent question Travellerw re Radar vs AIS.
Scroll down to comment #11 in the above forum that Stu Jackson posted, and the answer is obvious
I never asked radar vs ais.. I simply asked if radar had other uses beyond collision avoidance. And if its crucial..


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Old 27-05-2015, 01:14   #79
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Re: Question - I know this will blow up!

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Originally Posted by Hudson Force View Post
Thanks for causing me to revisit Tomaz423's ideas. Sometimes I tend to focus on items in a thread that I strongly agree with and pay less attention to thoughts that are new to me. If I'm going to keep learning, then I need to accept new ways to use my tools. I've never considered viewing the space within a crowded anchorage field with the radar. I'll need to try this!
This is a very good trick, which I use from time to time.

You can also use a radar guard zone as an anchor alarm -- very useful if you have a critical distance to land features. Or as an alarm for swinging into other boats at anchor.

I used the latter trick in Ushant once, when I was anchored for several days in a gale (normal weather for Ushant) in deep water not far from a French coast guard cutter. I had all 100 meters of my chain out and I was nervous about swinging into the cutter in case the wind changed, or the cutter swinging into me. The radar guard zone really helped me to sleep at night.
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Old 27-05-2015, 01:23   #80
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Re: Question - I know this will blow up!

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Originally Posted by travellerw View Post
I never asked radar vs ais.. I simply asked if radar had other uses beyond collision avoidance. And if its crucial..
To use radar for collision avoidance, you have to either use MARPA or know how to do a radar plot, something few recreational sailors know how to do, in my experience. A very simple collision avoidance plot can be done by putting the EBL on the target and seeing if the target is "walking down" the EBL -- sign of a dangerous constant bearing. This is useful because although recreational radars have poor accuracy for bearings, the errors get averaged out this way.

I think others have answered your question pretty well. Navigation, detecting and tracking squalls, etc.

Radar is a powerful navigational tool. If you don't have a chart plotter, or if it fails, you can do really accurate positions by taking radar fixes. It's much better than a regular hand bearing compass three point fix, because you have very accurate RANGE, besides (rather less accurate) bearings, which means you already get a position from a single point. A hand bearing compass doesn't tell you range. See: Radar navigation - Wikipedia, the free encyclopedia

It's awfully nice to have radar when you're picking your way into a tight harbor entrance on a dark night or in a thick fog.
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Old 27-05-2015, 03:42   #81
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Re: Question - I know this will blow up!

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Originally Posted by Dockhead View Post
To use radar for collision avoidance, you have to either use MARPA or know how to do a radar plot, something few recreational sailors know how to do, in my experience. A very simple collision avoidance plot can be done by putting the EBL on the target and seeing if the target is "walking down" the EBL -- sign of a dangerous constant bearing. This is useful because although recreational radars have poor accuracy for bearings, the errors get averaged out this way.

I have to disagree on the necessity of MARPA. You have answered that question yourself. Use the EBL(s) as you have described.

I have to somewhat disagree with the "inaccurate bearing" statement you make & I have seen others state. Yes-a 16" dome has a horizontal beamwidth of 5.5 deg to 1/2pwr points,but the center of an echo is close enough to ctr of oncoming target to avoid collision. In thick conditions,you will be motoring (no wind),& at reduced speed (if you're wise),especially in tight quarters or busy areas. Better to have any radar than none in bad conditions,dark nights,& for other handy uses as described by you & other posters IMHO.

As with any tool,radar must be learned (by operating in clear wx) & used with caution as an AID to prudent navigation.

The rest of this post I heartily agree with. /Cheers Len

I think others have answered your question pretty well. Navigation, detecting and tracking squalls, etc.

Radar is a powerful navigational tool. If you don't have a chart plotter, or if it fails, you can do really accurate positions by taking radar fixes. It's much better than a regular hand bearing compass three point fix, because you have very accurate RANGE, besides (rather less accurate) bearings, which means you already get a position from a single point. A hand bearing compass doesn't tell you range. See: Radar navigation - Wikipedia, the free encyclopedia

It's awfully nice to have radar when you're picking your way into a tight harbor entrance on a dark night or in a thick fog.
Yes-I agree / L
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Old 27-05-2015, 04:06   #82
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Re: Question - I know this will blow up!

Its been said before, you cannot replace radar with AIS. In a fog bank, you need radar, or someone on the bow. Its not fun not being able to see your own furler. A radar can save you in on a bad day. in 20 years ais may be ok, but for now, its a toy most of the time, and helpful a few hours a year.
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Old 27-05-2015, 04:17   #83
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Re: Question - I know this will blow up!

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Originally Posted by deblen View Post
Yes-I agree / L
Thanks. A clarification: I didn't mean that radar bearings are uselessly inaccurate. Just that they are far less accurate than range. It's really important to understand that. Also, the bearings depend on accurate heading data, something few small boats have, so can be even much worse than their theoretical limits. I don't know the figures, but the difference in accuracy between range and bearing must be at least a couple of orders of magnitude on the average installed average recreational set.

This does not matter when you're using the EBL, because you don't need an absolute bearing, and the errors in the relative bearing are averaged out. The EBL is such a useful tool -- I am always surprised how many recreational sailors don't even know what it is.
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Old 27-05-2015, 04:49   #84
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Re: Question - I know this will blow up!

In my commercial days on the water everything I ran had RADAR.

My current boat (CAL28) does not. When I was working on the water, I had to go in spite of weather or darkness, now-a-days not so much. If I'm out and weather goes to hell, I anchor and wait; if tied to the pier... I stay tied!

The above notwithstanding, were I to order my "electronics pecking order" it would be:
  1. GPS
  2. Depth Sounder
  3. Autopilot
  4. VHF
  5. RADAR
  6. AIS

Of course all of the above are trumped by compass, charts, binocs, ears, and eyeballs (in no particular order)
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Old 27-05-2015, 06:21   #85
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Re: Question - I know this will blow up!

Myself and another forum member here were doing a delivery a few years ago in real Maine Pea-Soup. Over 100 nm with 100' +/- visibility. Not unusual here in Maine...

Off Monhegan approaching Penobscot Bay I noted a target on radar and what appeared to be two smaller targets that could easily be mistaken echo's/noise by someone with little radar experience. I knew the radar was well tuned so I zoomed in and sure enough there were two very clear and well defined targets quite a ways after the main target.

I altered course to pass behind the last target. About 4 minutes later the vessel turned on AIS and I was able to hail them by name. They did not answer on 13 or 16 previously. AIS showed this as ONE TARGET. It was actually a tug towing two dredge barges on 900' cables (1800' of cable). Had we only been using AIS we could have been dismasted by cutting between the barges as each barge was separated by 8X our actual visibility....

AIS did help in giving us the name of the target but failed MISERABLY at truly defining the targets. The tug was not using fog signals, apparently not monitoring VHF prior to turning on AIS (multiple hails on both 13 & 16 with very clear location and heading info) and AIS gave ZERO INDICATION there were two barges being towed.

You'd need to pry radar from my cold dead fingers on the Maine coast. AIS is absolutely not a substitute for radar no matter how much you want it to be. For other areas radar may not be as critical but we still use it for weather, night etc.. I would easily give up my plotter, before radar, here in Maine.
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Old 27-05-2015, 06:34   #86
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Re: Question - I know this will blow up!

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My understanding is YES ALL OF THEM. Plus the watch ships that are required for each of them. If someone has some concrete information that is different please let us know.
In the Gulf of Mexico there are lots of abandoned platforms without AIS. Active platforms usually have AIS but you can't count on them always working.
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Old 27-05-2015, 09:17   #87
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Re: Question - I know this will blow up!

We are low-tech people, and we love our old Furuno radar. I like using it in the daytime while coastal piloting on paper charts, plotting occasional GPS fixes on selfsame chart. A glance at the radar gives distance to reflector [often (in Sea of Cortez) but not always = to coastline] and facilitates training the eye (of my crew and I) of distances at sea. We are preparing to be able to competently pilot and enter anchorages under only radar, sort of like in "the old days". Useful at night too, of course. In other words, using hte old radar is a useful, fun and rewarding exercise.
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Old 27-05-2015, 10:02   #88
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Re: Question - I know this will blow up!

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Originally Posted by travellerw View Post
I know this question is almost going to be as bad "What Anchor" but I need to ask.

On a cruising boat, is radar essential.

I'm in the process of replacing my aging electronics and am considering ditching my radar. I have an old C80 with radar that I will be replacing. It just seems like radar has passed its prime with AIS.
AIS and Radar are complimentary, the do different things and have different strengths and weaknesses.

However with AIS you are dependent on others to do as the should (turn the machine on if they are a commercial vessel see the following links for how badly it can turn out assuming that others are doing as they should). With small vessels they are not likely to have transmitting AIS, just receivers so you won't see very many of them.

With radar you can see most other vessels in your immediate neighborhood, and as long as you maintain a good radar watch as well as visual watch you can compensate for others' shortcomings in equipment and/or practice. Yes there are vessels that won't show up on radar, but a much smaller percentage than won't show up on AIS.

https://assets.digital.cabinet-offic...phireStone.pdf
https://www.gov.uk/maib-reports/coll...-loss-of-karen

Also there are plenty of places in the world where map coordinates do not match real world features, so GPS can not replace eyeball and radar navigation. If you stay in the US, Canada and Europe this probably won't be a significant issue.

Overall I would say that neither is essential, you can safely pilot a vessel around the world by eyeball alone. AIS and RADAR provide additional levels of safety but doing without is not inherently unsafe.

All that said, you can get an SDR (software defined radio) for $20-50 and kluge your own AIS (receiver only).
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Old 27-05-2015, 18:40   #89
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Re: Question - I know this will blow up!

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Originally Posted by capngeo View Post
In my commercial days on the water everything I ran had RADAR.

My current boat (CAL28) does not. When I was working on the water, I had to go in spite of weather or darkness, now-a-days not so much. If I'm out and weather goes to hell, I anchor and wait; if tied to the pier... I stay tied!

The above notwithstanding, were I to order my "electronics pecking order" it would be:
  1. GPS
  2. Depth Sounder
  3. Autopilot
  4. VHF
  5. RADAR
  6. AIS

Of course all of the above are trumped by compass, charts, binocs, ears, and eyeballs (in no particular order)
VHF I get, but other than that I would never put any electronic aid above autopilot. Auto is the rocks. Especially when singlehanding.

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