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Radar reflectors

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delliottg
Former Mainsheet C250 Tech Editor

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USA
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Initially Posted - 04/08/2007 : 11:08:12

I'm contemplating a radar reflector for the boat. Since we'll be sailing on Puget Sound with lots of commercial traffic/ferrys, fog, etc., this seems like a good idea. After reading [url="http://www.ussailing.org/safety/Studies/radar_reflector_test.htm"]this article[/url], I'm pretty much settled on a Davis Echomaster Deluxe. A friend who's opinion I value, wants to get one of the Mobri type for his 43' Polaris, but after reading the article above, I can't figure out why, and he's not around this weekend to ask.

Here are some questions:<ul><li>What type of reflector do you use, and why?</li><li>Where do you install it?</li><li>Does anyone have a story on how well they've worked (or worse, didn't)?</li><li>If you don't use one, what was your reasoning? Obviously if you sail on a small inland lake there's no pressing need.</li></ul>

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 04/08/2007 : 11:26:43

I've read very uncomplimentary things about the Mobri... even from West Marine (who won't carry it). After some research, I chose the standard-size Tri-Lens, which will go on the hardtop of my new powerboat. (It apparently came out after your 1995 article, but other tests have ranked it on top. See http://www.tri-lens.com/practical_sailor.txt) For sailboats, it comes with a mast bracket for mounting on the front of the mast, perhaps near the spreaders. The shape should allow a headsail to cross with no problem.

I also have a little Furuno radar unit, but in my mind being seen is at least as important as seeing, and the Tri-Lens seems to stand out rather dramatically, in terms of lack of dead-spots and tolerance of heeling (or in my case, having the bow up). A reasonable alternative would be one or even two Echomasters that you could run up on flag halyards to the spreaders. But since mine will be only about 8' above the water and I'll be out among 30+ knot fast ferries, I decided to spring for the best.

Edited by - Dave Bristle on 04/09/2007 12:15:13

frog0911
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Response Posted - 04/08/2007 : 23:22:17

Here is a the one I built. My neighbor says it makes PennyII look like a large barge. It is made from standard aluminum repair paneling used as repair patches for aluminum containers and comes in 12x12 pieces. If you look in the yellow pages under container repair you probably can find a repair facility that will sell you three patches. If not try the googling the same.

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Nautiduck
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Response Posted - 04/09/2007 : 11:10:51

I have done quite a bit of research on this and am going to buy a tri-lens (medium size). The testers agree that this is the bet unit and can handle the broadest range of conditions including various heeling angles which is a critical factor for a sailboat deflector. At over $200 it is not cheap but the ability to be seen in the fog in the Puget Sound shipping channels is no time to take chances. If you spend a lot of time there you should also consider a radar unit.

Edited by - Nautiduck on 04/09/2007 11:13:38

Dave Bristle
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Djibouti
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Response Posted - 04/09/2007 : 12:12:45

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Nautiduck
 ...am going to buy a tri-lens (medium size)... At over $200 it is not cheap...<hr height="1" noshade id="quote"></blockquote id="quote">
$196 at Defender. (I paid $176 at their big warehouse sale.)

I should ammend my earlier statement... In a shipping lane, it's more important to see than to be seen, based on the Neptune's Law of Tonnage. That's why I got radar in addition to a reflector.

Edited by - Dave Bristle on 04/09/2007 12:19:02

Stu Jackson C34
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Response Posted - 04/09/2007 : 12:46:04

On another board a respondent suggested balling up a whole bunch of aluminum foil and sticking it in a bag and running it up the flag halyards. Advantages: costs are way less, and the reflection was reported to be superior.

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Nautiduck
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Response Posted - 04/09/2007 : 14:23:14

Uh, Stu others also posted that the guy was basically crazy to use that approach. People can claim that a pie plate gave off a great image but, in the end, safety items like radar reflectors ought to be judged by science and testing, not anecdotes. The most recent testing, noted by Dave, indicate that the tri-lens is the current best choice.

Go read the West Marine Advisor for thier view. Here is their comment on the tri-lens: "TheTri-Lens RTE uses three Luneberg lenses providing strong returns. The combination of three very narrow nulls when the boat is level, and only slightly wider nulls when the boat is heeled up to 30 degrees, makes it one of the best RTEs on the market. We strongly recommend the two larger sizes." They don't like the smaller size.

Edited by - Nautiduck on 04/09/2007 14:28:18

PZell
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Response Posted - 04/09/2007 : 16:00:47

An article I read somewhere showed that the optimum placement on a sailboat was at about spreader height so that large vessels would see you at a reasonable distance.

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Dave Bristle
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Djibouti
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Response Posted - 04/09/2007 : 16:14:52

There's gotta be nothing like a garbage bag tied up and hanging from the spreaders...

I wish I could find the article that included a bag of aluminum foil as part of a reflector test--I think it was in Sail mag, and my recollection was it didn't do too well. The geometry of the reflective surfaces relative to each other is critical to making an adequate signal go back in the direction from which it came--like the facets on an automobile marker that return headlight rays in the direction they came from. Crumpled foil might have some random surfaces properly angled, but probably not many. The Echomax and similar reflectors work best when oriented in a particular way--the "catch rain" position--so incoming signals bounce off two or three surfaces (like rails on a pool table). Large objects like barges don't need that precision, but small ones like 12" reflectors do, and some designs--especially the Mobri--"disappear" when the boat heels.

Edited by - Dave Bristle on 04/09/2007 16:15:57

delliottg
Former Mainsheet C250 Tech Editor

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Response Posted - 04/09/2007 : 17:23:33

Well, after reading up a bit on the Luneberg lens, I've decided that I'm going to get the standard sized one for the boat.

Looking at the diagram in the owners manual (I'm 30 miles away from my boat right now), it looks like there might be enough room above the crane & below the masthead light to mount the reflector? My recollection of my masthead is that there isn't, seems like the crane is just below the light, and the reflector would block the light. Maybe at the spreaders as noted is the place to go.

I know that the reflector needs to have hard 90° angles in order to maximize the returns. I remember as a kid being told that I could defeat police radar by putting balled up aluminum foil in my hubcabs. That didn't work so well, and the Mythbusters proved it a while back.

As far as having my own radar set, this is definitely on my want list, but have to run it by the comptroller first. I think the first scary, foggy night we spend on the boat will solve that problem.

Oh, and my usually reliable friend's reasoning for the Mobri? "It looks cool". He was relieved he hadn't gotten one yet after I sent along the research. For the time being he's just going to keep his Davis in his spreaders.

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Tom Potter
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Response Posted - 04/09/2007 : 19:21:42

I read in some magazine recently (the name eludes me) someone had created a home made radar reflector by string a bunch of CD's together and hoisting them up. There's a use for all those AOL CD's!

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Dave Bristle
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Djibouti
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Response Posted - 04/09/2007 : 21:26:31

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by tompotter
 I read in some magazine recently (the name eludes me) someone had created a home made radar reflector by string a bunch of CD's together and hoisting them up. There's a use for all those AOL CD's!

<hr height="1" noshade id="quote"></blockquote id="quote">
I... ummm... have my doubts. I think what he created was just a string of CDs. It might repell birds, but I wouldn't count on it showing up on a freighter's screen.

Edited by - Dave Bristle on 04/09/2007 21:28:41

OLarryR
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Response Posted - 04/10/2007 : 05:19:52

I can vouch for the CDs strung up. It has helped keep the birds away along with the owl hung off the backstay and a beach ball with big eyes hung off the jib sheets near the bow. Come to think of it, I have never seen a large commercial vessel ever approach me near my finger slip...so it looks like it also works to ward off big boats as well !

Previous owner left a radar reflector in the quarterberth. Never used it...but then again have not anchored out all night as of yet. I have only stayed overnight at a visiting marina. Years ago, when I would anchor out with my ODay 23, it was always in protected waters and that was the best safeguard against getting creamed by a large vessel. Now being on the Potomac and where I am located, there are limited anchorage spots that are in protected waters. I think my concerns would be more from getting creamed by a small fishing boat doing an early morning run than from a commercial vessel (ie. tourist sightseeing boats) that stay in the channel.

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 04/10/2007 : 13:00:12

A radar reflector is an invaluable tool. With it, the freighter captain will be able to precisely predict the moment of impact.

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redviking
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1771 Posts

Response Posted - 04/10/2007 : 17:50:38

Has anyone tried one of these?

http://www.defender.com/product.jsp?path=-1|17|82825&id=275607

I use the Davis reflector from the spreaders on fog runs already, and I am looking to get AIS real soon, but this looked like a good inexpensive permanent solution...

Sten

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redviking
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Response Posted - 04/10/2007 : 17:52:11

you will have to copy the whole address, it just won't link over

sten

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 04/10/2007 : 21:09:13

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by redviking
 Has anyone tried one of these?

http://www.defender.com/product.jsp?path=-1|17|82825&id=275607

I use the Davis reflector from the spreaders on fog runs already, and I am looking to get AIS real soon, but this looked like a good inexpensive permanent solution...
<hr height="1" noshade id="quote"></blockquote id="quote">
(You can copy and paste the URL...)

Sten: That appears to be the Mobri design. It's amusing that they show it mounted on an angle to a shroud (as it would be above the spreader), since that's exactly what causes problems with them--as they are tilted vertically, they become "invisible" faster than most other designs, especially from the sides that they're tilted toward or away from. (From foward and aft, they'll usually be OK.) Your Davis is shown to be better. I'm disappointed in my friends at Defender for carrying the Mobri when even West won't do it.

(I have another Big Bust Ecstasy ad to my left here... Who's been buying porn vids??

)

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 04/10/2007 : 21:11:04

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dlucier
 A radar reflector is an invaluable tool. With it, the freighter captain will be able to precisely predict the moment of impact.
<hr height="1" noshade id="quote"></blockquote id="quote">
...and, according to the rules, raise you on VHF to tell you when that will be.

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Oscar
Master Marine Consultant

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USA
2030 Posts

Response Posted - 04/11/2007 : 20:37:49

Radar reflectors are not as effective as we hope they are. It's better than nothing, but your outboard gives a bigger return. BUT, when the waves around you are as long as your boat the radar operators have to turn down sensitivity, to de-clutter the screen, and you disappear with it. I have heard yachts that called the big boats and said "do you see me?" and more often than not the answer is "no." Even when they said "I'm a mile off your port bow...." and the big boat looked out the window they STILL didn't pick the white boat out of the whitecaps. In the channel on the Chesapeake they are looking out the window, and there's a pilot on board that knows where he is..... the waves are small, and he's tweaking the radar, he will probably see you. On open water there's one able bodied seaman on the bridge and he is bored, sleepy or sleeping. He will NOT see you, or be looking at the radar. I've had them come straight for me, 100 miles off shore......1000 foot container ship.... The burden is on us.....squarely.

There are two approaches, they all cost money.

1: Increase your visibility to them:

* Active AIS (Automated Identification System).....a transponder that participates in a timed protocol and in turn transmits a data block which is received and displayed by all participating vessels. Data include, but are not limited to: call sign, position, course, speed, destination.......Mandatory over 300 tons. You WILL show up on their screen. About $3000.-

* An active radar reflector.....takes THEIR radar signal, amplifies it and slings it back at them. Greatly enhances the possibility of being seen. Bruce Schwab is a believer...about $1000.

http://www.sea-me.co.uk/

2: See THEM with enough time to get out of the way.......

* Radar. It helps, a lot. But it has it's limitations. As the water gets rougher, you too have to crank up the sea clutter, and yes the 1000 foot steel bathtub will show up, but you may not have a lot of time...... And, is everyone alert, at night, is the motor running, will you hear the alarm.

* Passive AIS. This is a VERY cool device, and I have just incorporated one in my personal avoidance strategy....( I also have radar, and a radar reflector.) AIS broadcasts on VHF 85/87. Intercepting and decoding the signal is simple. If you're a real geek you can feed a sound output into a laptop and run very cheap software to decode it and plot it. The next step, around $200, lets you buy a little black box, and feed it's output to a laptop with GPS feed and charting software running, or feed it to the increasing array of chartplotters that will display the information.....(Raymarine C and E are in the game....) In fact Raymarine has it's own brand box and will sell it to you for $1000, but that's another story alltogether. So, with your laptop, GPS feed and this:

http://www.milltechmarine.com/products.htm

You can display EVERY boat over 300 tons on your screen, see their name, speed, course and a bunch of other stuff...call them on the radio and kindly ask if they'll please not run you over.....it's VERY cool. Finally you can set an alarm and plug your laptop into the stereo and let it wake you up when the steel shadow comes near.......

Just my $0.03

Edited by - Oscar on 04/11/2007 20:38:34

Dave Bristle
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Djibouti
10005 Posts

Response Posted - 04/11/2007 : 22:09:28

Oscar--you've reappeared out of the mist! 100 miles offshore, as I understand it, the big tubs probably just have their S-band radar on, which basically doesn't see X-band reflectors. In the Chesapeake and near shore, they'll have their X-band on.

From what I've seen, I don't quite agree with your reflector-outboard comparison--a "good" reflector properly oriented is designed to geometrically concentrate the signal back in the direction from which it came, like a red reflector on a parked car at night. The outboard, while probably larger, generally deflects most of the signal somewhere else (like the rest of the darkened car). I expect you've noticed that many good-sized outboard-powered boats are "invisible" even at close range. But your point is well taken--you can't count on being seen! You can just try to increase the odds.

Welcome back!

Edited by - Dave Bristle on 04/11/2007 22:11:01

Admin
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Response Posted - 04/11/2007 : 22:21:51

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stu Jackson C34
 On another board a respondent suggested balling up a whole bunch of aluminum foil and sticking it in a bag and running it up the flag halyards. Advantages: costs are way less, and the reflection was reported to be superior.
<hr height="1" noshade id="quote"></blockquote id="quote">

I'd contend that other than Stu's Method above, stepping the mast creates a rather nice radar reflector that all the commercial trafic on the Sound will pick up. When I was in College rowing crew on the Ohio River the barges would pick up the aluminum riggers on a 4 seat boat sitting 7 inches above the waterline.

If you were going offshore I'd consider it, in the middle of nowhere you want the guys to pick you up on radar from 5 or ten miles out. Within the sound they'll have you.

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Nautiduck
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Response Posted - 04/11/2007 : 23:50:20

I don't mean to be disagreeable but the idea that a bag of aluminum foil or just the mast will provide adequate radar reflection is simply wishful thinking. Ditto for the outboard. I mean are you kidding? The outboard is below the deck for crying out loud.

The safety of your passengers requires a thoughtful and scientific approach to safety gear. Anecdotal stories do not cut it. Testing by Practical Sailor and others shows that there are very real differences in radar reflectors. The tri-lens is the current leader. If you venture out in the fog in the Puget Sound with a bag full of tin foil hoisted on the mast, your sorry butt is going to get run over by a container ship.

Do the smart thing. Buy the tri-lens.

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Dave Bristle
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Djibouti
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Response Posted - 04/12/2007 : 00:24:54

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Nautiduck
 ...If you venture out in the fog in the Puget Sound with a bag full of tin foil hoisted on the mast, your sorry butt is going to get run over by a container ship...<hr height="1" noshade id="quote"></blockquote id="quote">
I agree, but even with a good reflector, you'll have to hope they call you up--they aren't going to go around or wait for you to pass.

Admin: A tug on a river is a bit different from some of what we're talking about. Commercial ships (including tugs) have huge radar arrays that send much higher powered and more highly focused beams than most pleasure boats do. The tug can see lots of things a Sea Ray can't. And in a 3" chop, something 7" off the water might show up on the tug's screen, but probably not on my little Furuno. You want a container ship to see you at 10 miles or more. Many real people with lots of experience will tell you that a sailboat mast just doesn't do it, and a real test of crumpled tin foil has proven the same thing. (Sorry I can't find that test.) Radar reflectors are evolving, but they're certainly not scams.

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Oscar
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Response Posted - 04/12/2007 : 10:32:41

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Testing by Practical Sailor<hr height="1" noshade id="quote"></blockquote id="quote">

I missed their work on reflectors. I do have faith in their methods. I hate to sound cynical on the subject, but having a 1000 foot container ship trying to run you down in the middle of nowhere does decrease your confidence in the radar reflector you have hanging from a spreader 20 feet above the water......

I will investigate the tri-lens.

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 04/12/2007 : 12:22:45

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Oscar
 I will investigate the tri-lens.<hr height="1" noshade id="quote"></blockquote id="quote">
When you do, take note of the "gaps" for the Tri Lens and the Echomaster. That 1000-footer might have looking at your gap. If I used the Davis (or similar), I'd probably get two and orient them 30-45 degrees from each other,

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Nautiduck
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Response Posted - 04/12/2007 : 13:17:37

Practical sailor article:

http://www.tri-lens.com/practical_sailor.txt

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