Radar Reflectors - Ouzo Sinking - MIAB Report

[TradewindSailor]

I've read YM's article on this report and YW's.

In YW .... QinetiQ (read Kinetic) dismissed the octahedral radar reflector as 'of little benefit on a yacht'.

I remember that either YM or PBO had an article on radar refectors some years ago where the octahedral radar reflector was reported as performing quite well ...... or am I dreaming?

I've got a Blipper unit that was reported to be amongst the best.

What's the true situation? Does anyone know?

 

[VicS]

You should read the full report for youself and draw your own conclusions. HERE

While you are at it you should also locate the MAIB report into the loss of the OUZo and read that too. You may be surprised how much is lost when it is reduced to a magazine article.

You are right PBO did a very through trial of radar reflectors several years ago. It ran for several months. IIRC it did not cover "active" devices and found that the Blipper type were the most effective of those tested. I still have the articles somewhere.

 

[Sinbad2222]

I am not sure how much the The Kinetic report is of relevant to the practical use of radar reflectors on a yacht. They tested reflectors in a static situation which never occurs on a moving vessel. A very strong return every few seconds might be much more desirable than a weaker continuous return. No tests were done to compare the performance of reflectors with a yacht in the water. It is quite possible that a yacht's engine or the hole in the water made by the hull has a larger RCS than the reflectors. Of course it is easy to criticise as comprehensive tests would be very difficult to set up. US reports contradict Kinetic and found that the Davis Octahedral was the best passive reflector.
The debate continues....!

 

[Robin2]

I think the comment on page 7 of the July PBO, that ships have radar cross-sections of 10,000m2, says it all.

I was out on a friend's boat the other day in flat-calm conditions. We were experimenting with his new (to him) radar. We could certainly see dots for the small boats around us but I would not think it would be easy to spot them in a rough sea, or to identify which represent collision hazards.

I'm sure it would be fine for detecting a large ship (which should be on AIS anyway), or perhaps a fishing boat which would not be transmitting AIS.

I was surprised (based on the Qinetic report) that the SEA-ME does not appear as a much larger target. Is this because it is choosing to be electrically frugal, rather than effective.

Its up to us to keep out of their way ...

 

[Dipper]

[ QUOTE ]
US reports contradict Kinetic and found that the Davis Octahedral was the best passive reflector.

[/ QUOTE ]

That's reassuring. Mine's a Davis.

 

[robbieg]

As I understand it the Sea me does show a "larger" return but shows a consistent return for longer. If you were out with a passive detector with another vessel with radar & you sailed away from the accompanying vessel he would see you as a target (hopefully!) but in rough conditions the target may be intermittent and as you sailed further away the strenght of the return would fade.
The advantage of the sea me is that even when heeled the return should be consistent and you should pick it up at greater distances. Since consistency of return is important to being tracked by a ship with MARPA thats quite a help. Some more info on www.sea-me.co.uk

 

[ShipsWoofy]

[ QUOTE ]
Its up to us to keep out of their way ...

[/ QUOTE ]

Is it? hows that then? Which way should I turn to get out of their way?

Does this mean small boats are no longer allowed to cross the channel? You are always going to be in someones way..

 

[Allan]

From what I remember of the PBO article they found that fitting, some radar reflectors to some some boats could reduce the radar reflection. I felt at the time that it was played down. Maybe because the makers advertise with them? It may just have been due to the expense of a full test.
It would be good to find somewhere this report is published.
Allan

 

[Marsupial]

I am lucky, I work with a guy who used the equipment in the MAIB test and spent most of life playing with radar in the RAF, he has explained the technology and how to interpret the results published in the OUZO reflector test. Let's say "its complicated" but in practise at sea there is not much to choose between any of the passive reflectors, excluding the tublar types which are invisible to everything.

The suggestion is that in use consistency of return is paramount because this alone sets you apart from clutter, but you are still hard to see. Passive reflectors are not good this.

An interesting conclusion of the report is that NO passive reflectors are visible to S band radar, it seems that in practise anything smaller than a house will be invisible to S band so "we" dont need to worry about it.

I think in the light of the obvious confusion this report has spawned and the importance of the subject the MAIB should arrange visits to Yachtclubs/RNLI centres around the land to fully explain the research findings and state clearly the implications for pleasure boaters.

 

[VicS]

[ QUOTE ]
From what I remember of the PBO article they found that fitting, some radar reflectors to some some boats could reduce the radar reflection

[/ QUOTE ] What they concluded was that interference could occur between the echo from a reflector and from other reflecting surfaces in the boat, such as the cooker, the engine and various other metal objects. The result was that at certain angles the various reflections were in phase and reinforced each other while at other angles they could cancel each other out causing various effects including almost complete disappearance of the echo on the radar screen. Several reflectors did indeed seem to reduce the echo from the basic boat. Some experiments in an anechoic chamber similar to the one used in the report for the MAIB verified the interference theory.

PBO first published an introductory article in Jan. 1999 with a promise of a second article in February giving the "amazing" reults of their tests. However as a result of the unexpected results of the tests that article did not appear. The series resumed in April, contiued in July and concluded in August.

The reflectors tested wre Cyclops 1, Cyclops 2, Cyclops 3, Firdell blipper 210-7, Firdell Blipper 300, Mobri S2, Mobri S3, Visiball, A standard octahedral reflector and a bin bag containing aluminium foil.

Two reflectors were found to give a worthwhile improvement namely the Firdell Blipper 300 and the Cyclops 3. However the former was considered to large for a small boat and the latter too heavy!

The articles may be available from the copy shop if required.

 

[Robin2]

If you are brave enough to insist on your right of way, be my guest. I prefer the practical cowardly method. /forums/images/graemlins/laugh.gif

 

[fireball]

[ QUOTE ]
If you are brave enough to insist on your right of way, be my guest.

[/ QUOTE ]
You don't have to be brave. You have to be sensible - some ships will turn to let you through if they have seen you, are small boat friendly and have the time and opportunity to do so. Those that do not appear to be taking avoiding action need to be avoided. Simple! (well - until you try and establish which ones are taking action and which ones aren't! and that assumes you can see them!)

 

[TradewindSailor]

What is important is how SHIP's RADARS display our image. Small yacht radars have little in common with the commercial units surely?

If we are so invisible to radar perhaps the MoD could learn some lessons from us for their stealth vessels? /forums/images/graemlins/smile.gif