Radar Reflectors (from the Ouzo Inquiry)

[peterb26]

The MAIB commissioned a report on radar reflectors after the Ouzo tragedy. Makes interesting reading. Only the active reflector met the present standards.

Whilst powerboats dont have the problem of being at a constant angle like a yacht - and can generally motor out of danger, the report is worth a read.

The full Radar Reflector Report can be found here.

If you just want to see the conclusions, I've shown them below.


<span style="color:blue">5 Conclusions
The following is concluded;
· The Sea-Me is a good example of an active reflector (RTE) exceeding the
requirements of the current and future ISO 8729 at heel/elevation angles of up
to 15&#730;, it is also very small and light. Drawbacks are that it requires power to
operate (which on a yacht is at a premium), it will only operate at X-Band and
will offer no performance at S-Band.

· The POLARef shows excellence is possible but at a price, technically it just fails
meet current ISO8729 [1] or its replacement [2]. The main drawbacks are it is
very costly at £2000 and its quite heavy at around 5kg. It is currently used as a
radar measurement standard although it could possibly be re-engineering for
commercial production which could reduce the price.

· The Large Tri-Lens performs well especially at larger angles of heel and
elevation, it just falls short of ISO8729 [1] having a peak RCS of 8.5m2 but
otherwise performs well. It is the heaviest reflector supplied for test at 5.5kg
and costs around £300.

· The Echomax 230 narrowly failed to meet ISO8729 during this testing, but
showed good peak and average RCS performance. The reflector is reasonably
priced at £130 and weighs 2.4kg; the main drawback was a RCS drop-off above
an elevation angle of 10&#730;.

· The Firdell Blipper 210-7 narrowly failed to meet ISO8729 during this testing,
but showed good peak and average RCS performance. The Blipper is priced at
£130 and weighs 1.8kg; the main drawback was a RCS drop-off above an
elevation angle of 10&#730;.

· The Standard Tri Lens does not meet ISO8729 as the peak RCS was too low at
4m2. However its consistent RCS response outperformed most of the other
reflectors when heeled over beyond 10&#730;; it is reasonably priced at £130 and
weighs 2.5kg.

· The Plastimo 16” octahedral is inexpensive at £16 and lightweight at 0.65kg
but failed to meet ISO8729 in either tested position. It had reasonable peak and
average performance averaging around 2m2 but had wide nulls which kept its
stated performance level down. Other drawbacks are that its mounting
arrangement is by suspension only (often in an unfavourable position) and
could be subject to damage.

· The Davis Echomaster failed to get close to ISO8729 during this testing. Its peak
RCS is too low at 7.5m2 and its average performance is only 1.75m2. This
reflector is priced at £60 and is lightweight; it can be mounted on a rod as well
as by suspension (in the correct catch-rain position).

· The 4” tube reflector performed very poorly.

· It is concluded that either the active Sea-Me, POLARef and the Standard or
Large Tri-Lens radar reflectors are the best reflectors at heel and elevation
angles of over 10&#730;.

SOURCE:MAIB</span>

 

[jfm]

Thanks, interesting stuff.

The report doesn't give any info on the radar reflection of a boat itself. It would be good to know, in the case of say a typical 30foot sailboat with alloy mast/boom, engine, stanchions and pulpit, cooker, fuel tank, anchor/chain, etc, how much extra radar visibility the reflectors add to what's already there. I suspect the answer is hardly anything at all...

 

[DAKA]

Havent they missed the point ?
In the real world any electronics on a small pleasure boat is likely to be turned off when not in use.
A blipper may be turned on when the Yacht feels another boat should give way, the rest of the time there is no point in drawing valuable amps.



At just £15 this has to be the best solution for a small yacht

http://www.gaelforcemarine.co.uk/Default.aspx?page=ProductDetailsPage&product_id=19572

 

[gibbowolfie]

Am I correct in thinking most commercial radar sets use S-Band?

 

[gibbowolfie]

And for small motorboats with limited height and space for a large reflector?

 

[peterb26]

I was surprised to find that a boat of mine (31 feet, no flybridge, single diesel) with a Firdell Blipper was invisible more than 2 miles away - according to a couple of friendly radar operators on commercial ships.

 

[gibbowolfie]

Well at least that's 2miles better than zero;-)

Guess it's different if they are trying to spot you after knowing you are there and spotting a small blip in the rest of the clutter.

 

[nonitoo]

Believe me, we should treat ourselves as virtually invisible on radar in poor visibility.

From experience (on board ship) small craft, whether fitted with a radar reflector or not, rarely paint on a screen over a couple of miles away. If there is much of a sea running and the sea clutter is not set correctly (or worse set on auto-clutter) you will not be seen as a primary return at all.

I know I should have a RaRefl (according to the MCA) but I really think I can spend my money more wisely.

Even taking into account the visual scan of the Bridge personnel that usually takes the form of a horison scan and once you sink below the horizon, if there is any sea running, it is not easy to spot a small craft. Most seem to be white anyway and easily get lost among the whitecaps.

 

[gibbowolfie]

I'm just waiting for AIS B Transponders to become more wallet friendly then I'm getting one.

 

[Andrew_Fanner]

[ QUOTE ]
I'm just waiting for AIS B Transponders to become more wallet friendly then I'm getting one.

[/ QUOTE ]

Isn't AIS the thing Ouzo didn't have switched on? About the only things I can put up would be an octohedron, its light and can be hung in the cockpit, or a SeeMe ontop of the mast, the oct may be a bit too much wind resistance as I've never been happy about topweight. No radar arch or hardtop.

As a result I hand an octohedron in catchrain position from the canopy frame.

 

[Poignard]

You haven't mentioned what effect the the height of the reflector has on the range. Surely this must be significant? Do you know if anyone has researched this?

 

[gibbowolfie]

Unsure but mine would be on! I have a hard top but still not going to put a big drum up there especially when the visibility is questionable.

 

[DAKA]

Does anyone else feel this Radar/reflector subject should be continued on a new Post with 'Ouzo' missing from the title ?

I have some strong feelings on the subject but feel this thread is prejudiced due to the tragedy connected to the name 'Ouzo'.

 

[gibbowolfie]

Go for it but personally I'm away in 30 mins and spending the evening over charts and the Shell Channel Pilot;-)

 

[Marsupial]

Not quite, all commercial ships have x band the big ones have x and s. - its in the MAIB report.

X band SHOULD/MIGHT/COULD see targets 3cm across S band 10cm but this is an over simplification.

 

[[2068]]

I don't claim to understand the ins and outs of S Band, X Band etc. However, I have a 29ft mobo, and wish to fit some sort of radar reflector for improved rcs if it gets foggy or unexpectedly dark (the planet does seem to spin a bit faster sometimes). The budget could stretch to a Sea-Me, but would wipe out the budget for the EPIRB.

EPIRB plus an octahedral, or a Sea-Me ?

dv.

 

[Marsupial]

I carry a plastimo octahedral and a sea-me, the 406 is due this year; the sea-me draws .35 amp at full power - not a lot, it will run for a week on a 44 amphr battery, but in case the batteries take an early bath I have the flat pack to hoist.

I know the sea-me works, I know the passives dont.

My own radar expert who is ex raf explained the MAIB report results to me in easy language and he reckons the octahedral is the best practical option for a passive unit unless you go for the RTE. Look at the results; the cheap octahedral often outperforms the wizzy stuff. sorry about this pun but its the law of diminishing returns.

He did add however that he would not expect to get more than 1 sq mtr out of any of the passive types in the field. Couple a low CSA with the probability that the radar will get a return less than 50% of the time form these devices and this is a cause for concern. This is based on his years of experience with radar his interpretation of the published results. (The data are a static test, the field is dynamic)

My own opinions scattered on many threads in here are based on years of practical experience using radar in little boats, his is based on years making, testing and installing it in airports and aircraft.

 

[Hurricane]

This somewhat surprises me.
I spent quite a long time looking into passive reflectors before I bought an Echomax 230.
SOLAS V (a reg that we are all bound to operate under) requires that all vessels over 15m have a radar reflector that meets these ISO standards.
It goes on to say that all other craft (less than 15m) should "do their best to display an effective reflector".

When I looked into it, the Echomax was the only one that actually met the regs.
I dont think that the Seame one counts cos it only covers one of the bands.

Here is Echomax's claim
http://www.echomax.co.uk/Echomax_Products.htm

I may have to think again.
One wonders - does it comply or doesnt it?

 

[aknight]

I've had a similar decision to make. I went for a tri-lens and a Sea-me. I'd rather optimise my chances of being seen than have to rely on the PLB or EPIRB. That said, I am watching as beacon prices fall and will almost certainly go for GPS-equipped PLB - maybe start looking for a bargain at SIBS or Earls Court.

 

[Marsupial]

Clearly on the latest information the ecomax does not comply and the report says so! Funny how all the passive refectors performance claims are overstated by the manufacturers the actives are understated . .

Also the 4" and below plastimo tube types and anything less than 100mm in size is invisible to S band, and that includes all metal parts, masts, booms, rails etc. They need to be less than 3cm to be invisible to X band. and this is in a perfect world ie the lab. Indeed, there is a lot of thinking to be done by boaters and manufacturers.