Radar Reflector

[bbg]

We once called Ushant Traffic Control when approaching Chenal Du Four in thick fog to ask about visibility in the Four itself. They asked us for our position and then told us they had us on their radar at 15mls range, that was in a Westerly 33 foot ketch with a Firdell Blipper.

I have to say practical experience over many years of yacht radar use has me questioning the test results that say reflectors are not very good. I certainly agree about the Mobri tube ones, so often fitted horizontally even on French boats, but otherwise we have always found yachts with good reflectors properly mounted to show at around 4mls out, if the radar is properly tuned and set for the conditions and range in use and if it is monitored rather than just glanced at occasionally. Yachts without hoisted or fitted reflectors would show a very intermittent echo, easily missed without continuous monitoring unless the set had 'track' or 'trail' in use which retains a shadowy image on screen to show target movement. We once came across a wooden ketch with wooden masts in rough seas and fog that didn't show on radar, but passed visually by about 25yds away.. I would expect big ship radar to pick up yachts at better than we could on yottie sets, simply because they have a higher and more stable platform and much more powerful sets, but whether the return is good enough to register on their ARPA displays at the same range is debatable, and I guess continuous monitoring might be asking too much of some bridge crews when automatic electronic alarms are available from their ARPA?

Unfortunately, anecdotal experience like this isn't very insightful. Not entirely useless, but limited. I spoke with large container a ship off Land's End - passed 0.1-0.2 miles in front of me. I asked when he first picked me up on radar. The answer was "8 miles on radar, 5 miles visually". From that I could conclude that the tube reflector mounted under the spreader was doing a good job. What I conclude in fact is that, in a millpond sea, the hole my boat makes in the water gives a pretty good reflection to a high, stable and powerful radar.

It is really impossible to know unless you do a test of signature with and without the reflector (and indeed with and without boat present), because some of the signature will come from the boat and some from the reflector.

 

[idw]

Just to confirm

It's a legal requirement (but, obviously, this is not legal advice). It's the Merchant Shipping (Safety of Navigation) Regulations 2002 that give (certain of) the SOLAS V requirements legal force. On radar reflectors:

6. If a ship, to which regulation 19 or paragraph 1 of regulation 20 applies, proceeds or attempts to proceed on any voyage or excursion without complying with a requirement in—
(a)regulation 19, or paragraph 1 of regulation 20, respectively, or
(b)paragraph 1, 2, 3, 7 or 8 of regulation 18,
the owner and the master shall each be guilty of an offence, punishable on summary conviction by a fine not exceeding the statutory maximum and on conviction on indictment by imprisonment for a term not exceeding two years or a fine, or both.

http://www.legislation.gov.uk/uksi/2002/1473/contents/made


The most useful guide to the SOLAS V law seems to come from the RYA:
http://www.rya.org.uk/infoadvice/regssafety/pleasurecraftregs/Pages/SOLASV.aspx#radar

The MCA guidance linked to on the sea me website is surprisingly actually weaker than the law.

 

[AntarcticPilot]

Most of the passive reflectors they tested gave a solid 2m^2, which was, according to their predictions, quite enough to be seen. Certainly not as good as an active system, but a hell of a lot better than a bare hull and mast. They only deprecated two reflectors: the 4" and 2" tube ones.

I've had dealings with radar systems and with radar reflectors, though not in a maritime environment!

However, there are several points I'd make. The take-home point is that passive radar reflectors are not very effective on a sailing boat, for the following reasons:

1. The effectiveness of a passive reflector is proportional to the radar cross section; that is to its size. A radar reflector practical on the sort of vessel most of us sail is simply too small.
2. A radar reflector depends CRITICALLY on the accuracy of the angles between the faces of the reflector. While this angle will be correctly set when new, I have strong doubts that it would be maintained by a practical radar reflector in normal use. Certainly the standard octahedral type won't.
3. The effectiveness of radar reflectors is STRONGLY affected by angle of heel. The Quinetic report emphasizes this. The buoys mentioned by others don't heel very much; most yachts do!

In terms of radar cross-section, the hole in the water made by yachts is probably a larger reflector than a radar reflector - though less consistent and not separated from "clutter".

For all of these reasons, I regard passive radar reflectors as being marginally better than nothing - but only marginally. And for that reason I fitted an active responder at vast expense! But it was my opinion that passive reflectors were almost useless long before I found the wherewithal to fit an active responder.

 

[Robin]

Unfortunately, anecdotal experience like this isn't very insightful. Not entirely useless, but limited. I spoke with large container a ship off Land's End - passed 0.1-0.2 miles in front of me. I asked when he first picked me up on radar. The answer was "8 miles on radar, 5 miles visually". From that I could conclude that the tube reflector mounted under the spreader was doing a good job. What I conclude in fact is that, in a millpond sea, the hole my boat makes in the water gives a pretty good reflection to a high, stable and powerful radar.

It is really impossible to know unless you do a test of signature with and without the reflector (and indeed with and without boat present), because some of the signature will come from the boat and some from the reflector.

In a millpond sea we could pick up seagulls and pot markers quite clearly on yacht radar, so no hole in the water return in this case! I quite agree with your last paragraph which is why practical magazine type testing doesn't work.

Those cigar reflectors really are useless however IMO and we have enough anecdotal evidence of that from years of sailing in French waters and comparisons between passing French boats (mostly using tiny and/or wrongly mounted octahedrals or Mobris) and passing UK or Dutch (mostly using mast mounted Firdell or similar reflectors ones) as seen on our radar. I think the important factor is consistency of return, a good echo that is infrequent is easily missed, yet a weak one that is always there is not. To me that is the most important function of a good passive reflector, that it can give a consistent return even when the boat is swinging around and heeling to wind and seas. The original octahedrals if big enough (not the Xmas cracker French ones mounted point up on the backstay) are good at giving a reasonable echo but less good at it being consistent when rolling around which IMO is where the multiple array ones like Firdell and others score. The Mobri ones might well have multiple arrays but reflecting areas are little more than matchbox size, their only advantage would seem to be in complying with local or race rules and presenting minimum weight and windage.

 

[bbg]

... their only advantage would seem to be in complying with local or race rules and presenting minimum weight and windage.

For some of us that is the most important factor!

 

[Brent Swain]

I once saw some tests by a British cruising magazine , comparing high tec radar reflectors with the old fashioned passive ones. They concluded there was little or no difference in effectiveness between them, but a huge difference in price. Seems the high tec ones are a scam.

 

[Coaster]

I once saw some tests by a British cruising magazine...

I view magazine tests with considerable caution. For example I have the current (February) Yachting Monthly here and am reading Dick Durham's article on a Beneteau First 38. He tells me the boat is 15 tons (page 90, column 3, 11 lines down from the subtitle "Performance").

I rather doubt that figure.

So far as I know the QinetiQ report referred to earlier in this thread is the only substantial independent test available.

 

[dulcibella]

The Sea-me not only improves acquisition by other radars - the panel switch also gives a red flash whenever the transponder operates. We found on long passages in fairly empty bits of sea that this feature gave us warning that we were not alone long before visual or radar ecquisition of the ship. This was very useful in ensuring that the watch was on the ball whenever it mattered.

 

[Twister_Ken]

The Sea-me not only improves acquisition by other radars - the panel switch also gives a red flash whenever the transponder operates. We found on long passages in fairly empty bits of sea that this feature gave us warning that we were not alone long before visual or radar ecquisition of the ship. This was very useful in ensuring that the watch was on the ball whenever it mattered.

And that red flash can also be wired into a buzzer, so you get an audio warning.

 

[alan_d]

Unfortunately, anecdotal experience like this isn't very insightful. Not entirely useless, but limited.

Indeed. Another point worth considering is that shore-based radars (port control, VTS etc.) are likely to be much better at spotting small craft than ship-based radars, so do not take too much comfort from being identified by them.

 

[rotrax]

Indeed. Another point worth considering is that shore-based radars (port control, VTS etc.) are likely to be much better at spotting small craft than ship-based radars, so do not take too much comfort from being identified by them.

Hi,My wife and I are fortunate to have a mentor who is a Yachtmaster examiner and one of the best qualified skippers in the south.He regulrly sails the ex 67 clippers,the Nic 55s and others out of the combined services sail training centre at HMS Hornet in Gosport.On a trip last year to the Canaries the new Queen Elisibeth passed a couple of miles away.He spoke to the bridge of the liner and asked about their radar signal.The reply was not encourageing.With a visual the watchkeeper could identify the yacht as being in the same place as an indestinct variation on their screen.The yacht was a Nic 55 cutter with a normal reflector-Echomax I believe.

 

[Robin]

Hi,My wife and I are fortunate to have a mentor who is a Yachtmaster examiner and one of the best qualified skippers in the south.He regulrly sails the ex 67 clippers,the Nic 55s and others out of the combined services sail training centre at HMS Hornet in Gosport.On a trip last year to the Canaries the new Queen Elisibeth passed a couple of miles away.He spoke to the bridge of the liner and asked about their radar signal.The reply was not encourageing.With a visual the watchkeeper could identify the yacht as being in the same place as an indestinct variation on their screen.The yacht was a Nic 55 cutter with a normal reflector-Echomax I believe.

At two miles if the ship could not see a yacht, let alone a 55 footer on their radar whether it had a reflector or not then they need to check their set or the watchkeeper or both PDQ.

 

[rotrax]

Hi,I was just reporting what happened in a particular situation at sea.According to your view the brand new Supercruiser has a defective radar or watchkeeper.My view is that passive radar reflectors are not that good,even at close range.

 

[SHUG]

After fitting a SeaMe I found that major ships were giving us right of way.
I believe the reason is that they record the radar screen and anything as major as the SeaMe return must be given the benefit if the (anti) Collision Regulations.

 

[boatmike]

Now That i have mast down, I am looking to fit Radar reflector on our Vancouver 27,
any suggestions what make shall we go for....

I have only just read this thread again after posting earlier..... Gawd you lot don't arf go on!
I just thought I would remind you of the original question.....

The Vancouver isn't a big boat and I think a firdell blipper or echomax would do nicely at reasonable price. If you intend to do much open sea work it might be worth getting a SeaMe or something like it but unless you are rich (and probably like most of us you ain't) they are bloody expensive. You will then comply with SOLAS which I note most now seem to agree IS a legal requirement and it's going to be better than now't regardless of all the unbelievers who say they are useless. The best advice however has to be, proceed with a deliberate sense of paranoia and assume that tanker can't see you anyway. There are old sailors (like me) and bold sailors, but very few old bold sailors....... Enjoy!!

 

[andygc]

You will then comply with SOLAS which I note most now seem to agree IS a legal requirement and it's going to be better than now't regardless of all the unbelievers who say they are useless.

How many of "most" have actually read SOLAS Chapter V and The Merchant Shipping (Safety of Navigation) Regulations 2002?

The relevant bit is "if less than 150 gross tons and if practicable, a radar reflector or other means, to enable detection by ships navigating by radar at both 9 and 3 GHz". Since the QinetiQ experiments showed pretty effectively that most passive reflectors don't do much or anything at all for most of the time, the only means of meeting the requirement would appear to be an exceedingly heavy and expensive passive device or a dual band radar transponder. Neither would seem to be practicable on a small cruising boat of about 28 feet with limited battery capacity like I sail. As it is not practicable, I'm not breaking any law by not having one. It's then up to me, should I get caught out in fog, to be very, very careful - but that's no different from what I do anyway.

 

[LittleSister]

Reflections on reflectors

May I stir the pot on this issue by asking a couple of questions?

1) If a cylinder type radar reflector (Echomax or whatever) is mounted, as is common, on the front of the mast, will it not be obscured by the mast from the radar view of a vessel aft?

2) The question of 'out of phase' reflections from other parts of the boat cancelling out the return from a radar reflector is sometimes mentioned (as it was in an earlier post), but does the wavelength of radar bands used make that likely?

 

[Robin]

Hi,I was just reporting what happened in a particular situation at sea.According to your view the brand new Supercruiser has a defective radar or watchkeeper.My view is that passive radar reflectors are not that good,even at close range.

Our yacht radars (have had radars for 20 years) could pick up seagulls, pot markers in calm seas. If a brand new cruise ship with the latest gear could not pick up a 55ft Nicholson at 2mls whether it had a reflector or not then something is seriously wrong in my opinion.

The scenario you describe suggests that Nicholson 55 has developed stealth technology! I wonder if the navy would be worried if say a high speed inflatable with a bunch of terrorists could sneak in under their radar like that?

Not trying to be argumentative and I accept that passive reflectors are not perfect or even close but something about that scenario smells regardless of what if any reflector was in use.

 

[alahol2]

Now that everybody has agreed ...
Can anyone explain to me the first diagram in the Qinetiq report that shows, no matter how big your reflector, that you will not be seen at 2 miles and 4 miles?
I'm sure it has something to do with wavelength but I thought radar was closer to microwave than longwave.
Oh, also what does 'Stated Performance Level' mean in the tables?

 

[VexedIllologist]

Legal Requirements

What the MCA doesn't tell you is that if your yacht is an 'existing ship' for the purposes of the SOLAS V Regulations enacted into British law then there is no obligation to fit the radar reflector that the guidance implies is 'required'.

That said, I like my X and S band Radar Target Enhancer (RTE) (no advertising in this post) and I know it works well.

The poster who talks about 'relaxing the watchbill' and relying on the alarm function of an RTE mid-Atlantic epitomises the hypocrisy whereby yachties would regard a commercial vessel as 'not keeping a proper watch' for doing the same thing.

Single-handed and sleeping is a crime; not keeping a proper lookout is a crime. Now, that is the law (failure to comply with Rule 5). Plenty of honours for those who have done it, though, eh? But that's another subject...