Radar Reflector Test Reports

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GeoffSchultz
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Re: Radar Reflector Test Reports

Post by GeoffSchultz »

Remember that AIS class B is not approved in the US. You can buy a class A transponder, but those are quite expensive.

I have a Milltech Marine SR-161 http://www.milltechmarine.com/SR161.htm single channel AIS receiver that I've had installed for about 3-4 years. It interfaces to a RayMarine C80 display which is at the helm. Although this is only a single channel receiver, I've never perceived that I've missed seeing any ships. Typically I can see ships at 30-50 miles out, so there's plenty of time to obtain all of the AIS data.

I think that one of the key issues of AIS is being able to call a ship by name and say "Princess of the Sea, Princess of the Sea...this is BlueJacket, the sailboat 2 miles on your port bow. I just wanted to make sure that you saw me since it's rather dark out here." That works much better than "Cruise ship and lat/long..."

Personally I want an AIS transponder as I want them to be able to see me as well as I see them. I done lots of off-shore passages and am amazed at how fast these ships can approach you. I want to give both of us every chance to see one another. I don't find AIS very useful in crowded harbors, but I see it as extremely usefull when off-shore.

Oh, I did find that the RayMarine chartplotters have a limit of 50 targets....Here's an image from NY Harbor.

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ericsmith3d
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Re: Radar Reflector Test Reports

Post by ericsmith3d »

AIS Class B transponders were approved by the FCC about a month ago--after a long and perplexing delay. I don't know if any individual transponders have been approved. See here:

http://www.panbo.com/archives/2009/01/a ... tions.html

for some interesting possible additions to the AIS repertoire.

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Castaway
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Re: Radar Reflector Test Reports

Post by Castaway »

We have a Sea Me radar target enhancer, mounted at the top of the mizzen mast. It's light, small, and shows up well on other people's radar. Tests suggest it works well when heeled, too. I have crossed the North Sea to Norway with it on several occasions and never noticed a period of more than a minute without the unit being triggered, even when 100 miles offshore, but then, there are a lot of oil rigs and support vessels around there. Since the tested apparent cross sectional area is about the same as small ship, I presume I can be seen by anyone using ship's radar (both X & S band required on commercial vessels). I would not wish to rely only on passive avoidance of collision whilst at sea, but I feel more confident with the Sea-Me than the Firdell Blipper I carry; this tends to swing around a lot if hoisted on a spare halliard, unless taken to the masthead, where it chafes the headboard.

I'm still struggling with AIS reception/chart plotter integration, but I hope it will prove more useful and understandable than radar. I would not wish to use class B AIS transmission in busy waters; it is effectively telling large ships that you are a vessel of no account. At least, if they have an anomalous radar signal it may stir them enough to look out of the bridge window!
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch, centreboard, 1987)
Lerwick Boating Club
Shetland Isles, Scotland

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THATBOATGUY
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Re: Radar Reflector Test Reports

Post by THATBOATGUY »

Hey Gerald,

The busiest bit of water I've ever sailed was over the top of Norway and into the North Sea. I loaded up a raymarine radar screen using every MARPA slot available and wishing I had more! That was a scary night indeed and as far as I could tell the big guys were busy trying not to hit one another and didn't much care about little ol' us. I think next in line would be down along the Mexican coast near Cozumel. Again the Marpa came in very handy. Trying to figure out the lighting on a cruise ship is crazy; is that a green running light or a Chinese lantern? heh heh

George
George and Kerri Huffman S/V Marquesa Freedom 40 CC CK Sail MarquesaImage

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Castaway
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Re: Radar Reflector Test Reports

Post by Castaway »

George,

Exciting times in Norway! The Norwegian policy in inshore waters is for all commercial vessels to have precedence over pleasure boats, apparently regardless of the IRPCS. Possession of Class B AIS would just be proof that it was your fault they ran you down!

I think the Sea-Me is being developed to work on both X and S band radar, and that will be my next buy in sailing electronics. Improvement in passive reflectors seems to involve an unacceptable weight penalty. Any substantial increase in mass at the top of the mast is undesirable, especially if said mast is flexible and the sea rough. Although the figures and polar diagram for the Tri-Lens seem the answer to a small boat owners prayer, mounting one on a Freedom masthead might be impractical, if not downright dangerous.
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch, centreboard, 1987)
Lerwick Boating Club
Shetland Isles, Scotland

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Michel
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Re: Radar Reflector Test Reports

Post by Michel »

Gerald, only if you have wraparound sails, there's no other place for a radarreflector then the masthead. If no wraparounds, you could mount a reflector say two thirds up the mizzen, some 12 meters above sea, and visibility to the horizon would be 13 kilometers. With a radar equipped ship approaching you (assume radar height also 12 meters) they would spot you at 26 kilometers. Quite enough, I'd say.

http://www.pvv.org/~bcd/shadowworld/info/horizon.html
Michel Capel, Freedom 44 #4 1981 'Alabama Queen', NED8188, cat ketch with wishbones, home port Enkhuizen, the Netherlands, 52*42.238'N 005*18.154'E.

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GeoffSchultz
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Re: Radar Reflector Test Reports

Post by GeoffSchultz »

I must say that I haven't found MAPRA to be very useful on a sailboat underway in anything less than flat seas. On a RayMarine C series chartplotter, the calculated course/speed/CPA bounce around way too much to be useful. AIS on the other hand is rock solid, not relying calculations from a moving platform.

-- Geoff
BlueJacket
1997 Freedom 40/40
http://www.GeoffSchultz.org

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Castaway
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Re: Radar Reflector Test Reports

Post by Castaway »

Michel,

I take your point, but I do have wrap-around sails, and the Sea-Me sits at the masthead, weighs less than half a kilo, and has an effective cross sectional area an order of magnitude above the minimum recommended. The power drain is so low that I keep it on all the time when at sea. Installation was a breeze, as well: for the first two seasons, I fitted it with the mast in-situ, from a bosun's chair. That put it 13m above the waterline: hence the continual triggering on a 200 mile crossing.

If I change the mizzen to a conventional sail, I'll fit a radar, too. Meanwhile, the various poles and towers I have seen strike me as cumbersome and vulnerable on a 10m boat.

By the way, there was a comparative test of reflectors in 'Yachting Monthly', June 2005, with similar results to that included in this thread.

Kind regards,
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch, centreboard, 1987)
Lerwick Boating Club
Shetland Isles, Scotland

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Michel
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Re: SeaMe install with mast standing

Post by Michel »

Gerald,

How did you get the wiring down the mast when installing the SeaMe with your mast standing? I'm always interested to learn new tricks!
Michel Capel, Freedom 44 #4 1981 'Alabama Queen', NED8188, cat ketch with wishbones, home port Enkhuizen, the Netherlands, 52*42.238'N 005*18.154'E.

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THATBOATGUY
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Re: SeaMe install with mast standing

Post by THATBOATGUY »

Michel wrote:Gerald,

How did you get the wiring down the mast when installing the SeaMe with your mast standing? I'm always interested to learn new tricks!
Gravity... it's not just a good idea, it's the law!


Ducking now! heh heh ;)

Really I'm waiting for a legit answer myself because just when I thought I knew every trick for a tough wire run someone comes along with a new idea. I have used a vacuum cleaner and feather tied to a piece of light mono-filament line to get a pilot fish though a complicated tuna tower once.

George
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