Viking Tri Lens Radar Reflector

B

Babylon

Well-Known Member
Joined
7 Jan 2008
Messages
4,401
Location
Solent
Visit site
I currently have one of those pretty ineffective little plastic reflector tubes clamped onto the top of a backstay, but want to remove this and fit a mast-mounted unit instead. (Mast is down so this is my opportunity. Boat is 27ft with a 10m mast.)

Would welcome advice/opinion re the Viking Tri Lens (or one of the Echomax units).

Thanks
 
All radar reflectors are a waste of money and space -- a point backed up by the fact that the report commissioned by MAIB after the Ouzo incident revealed that none of those that are commercially available actually achieve the minimum performance standards set for them.
(see http://www.maib.gov.uk/cms_resources/Radar%20reflectors%20report.pdf)
But a radar reflector is now a legal requirement for any boat that goes out of "categorised" waters, and the MAIB report says that tri-lens is the best of a bad bunch. What the effect of sticking several kilos of dead weight at the top of your mast might do to your stability is a question that neither the MCA nor MAIB seem to have bothered themselves with.
 
I have fitted a Tri-lens on my 29ft Legend and, so far, I haven't had any near misses with large ships.........though I don't know if this is due to the radar reflector, or my vigilant lookout!!

The reason I went for the Tri-lens is that it's performance is one of the better one's, and it is a neat fit up the mast, without too much additional weight.

Cheers, Allan
 
Personally, I think I would spend the money and fit an active reflector - a SeaMe or ActiveEcho. Both actively amplify the received radar signal, and I believe both act as radar detectors (so you know when a ship has "pinged" you).
 
I may be wrong, but I think the transponders only do 3cm wavelegth and not the 10cm used to penetrate rain. I've got a SeaMe and a Trilens.
 
Yes you're right about actives , but if you read the MAB report the passive reflectors dont do 10cm either!
 
Allan

Yes, that was my thinking - one of the better ones (especially when heeled) and not as windage-bulky as the Echomax etc.

I cannot give a good reason not to fit a SeaMe (except cost) as others have suggested, but what I'm looking for is simply a better fitted passive unit than the next to useless small tube currently carried.

For what its worth, I also have a perfectly servicable C.A.R.D. radar detector fitted - which emits a loud beep AND indicates the bearing when it picks up a radar signal. And next year I intend to fit radar - so I can do the looking.
 
In which case you a cheap plastimo octahedron type reflector (under £20) that packs flat. IF your sailing at night hoist it on a spreader.

Look at the MAB report it has the best overall performance and heeling isnt an issue.

I carry one and a seame
 
[ QUOTE ]
if you read the MAB report the passive reflectors dont do 10cm either!

[/ QUOTE ]
Seems odd....Since when were reflectors sized to frequency?
and WTF is 10cm used for if it doesn't bounce back from a piece of metal?
 
IIRC the report said that 10cm is less sensitive than 3 cm; so the RCS is only 25% of that with 3cm.

Similarly heeling reduces RCS to 25% of the vertical value. So as was said earlier, there is not much left of the original value.

I think I have heard that Sea-me will operate on both frequencies later this year.
 
Bilge - 10cm is a wavelenghth, not a frequency.

All purpose built reflectors are, by definition, sized to a particular wavelength. That's not to say they don't work at other w/l's, just that they're not optimised there, and for a tiny surface like a yacht's reflector you need all the optimization you can get.

A reflector for 10cm would in theorey need to me 10/3 times the size of the conventional 3cm one, which perhaps suggests why no-one has one, it would be the size of a tea-chest.

Tri lenses have the benefit of cleverly reflecting the energy back whence it came and not scattering it about the sky like most others, but they still need to be of big enough "aperture" to be efficient even at that.


More on Luneberg Lenses here..

http://en.wikipedia.org/wiki/Luneberg_lens
 
Think of the measurment as the width of a beam - from a torch if you like, you could easily shine all of a 3cm beam on a 9cm object so you could see all the beam reflecting from it. If you had a 10cm beam there is no way you could do it! A 10cm beam would need say a 300 mm object to shine on to be sure of you being able to see all the beam, now move the targets around a bit and it becomes harder and harder to ensure that all the beam stays focused on the target even if its 3 times larger than the beam. Hence small radar reflectors dont work very well with a 3cm wave length - if at all.

So a 10cm wave length radar reflector would be very large to work well - three and a bit times the size of a "good" 3cm one.

A veriatable dustbin up the mast!
 
Hi Hedwig
Can you tell me were the 'legal' requirement to carry a reflector is please. I have the MCA requirements for craft over 13.2mtr (I think), but they don't mention radar reflectors as a legal requirement.
 
[ QUOTE ]
All radar reflectors are a waste of money and space -- a point backed up by the fact that the report commissioned by MAIB after the Ouzo incident revealed that none of those that are commercially available actually achieve the minimum performance standards set for them.


[/ QUOTE ] I think you are being a little harsh. All the radar reflector reports show that the minimum effective area is not achieved at all angles and bearings, but all the ones I have seen also say that one of the better radar reflectors is better than nothing.

An Octahedral Radar Reflector weighs a kg or so and perhaps compares to rain water or spray on the sail, so comments about stability issues are perhaps excessive as well. I agree that you should not start putting large weighty objects up your mast without thought, but most radar reflectors are not large and heavy.

I believe that the real answer is that a Radar Reflector is an essential item on any small boat, but we should not delude ourselves as to their effectiveness. Or to put it another way, just because they are not as good as they ought to be at all angles and bearings is no excuse not to fit one. Make sure its an octahedral one or one of the modern proven designs. I make a distinction between 'proven' and 'claimed'
 
[ QUOTE ]
I think you are being a little harsh. All the radar reflector reports show that the minimum effective area is not achieved at all angles and bearings, but all the ones I have seen also say that one of the better radar reflectors is better than nothing.

[/ QUOTE ]

Hear Hear!

We have had Firdell Blippers on our current and last two boats and have had radar ourselves for around 20 years during which time we have taken a keen interest in how other boats are 'seen' and what if any reflector was fitted. This is not a scientific evaluation by any means but unlike most of the official testing it is at least under real life conditions. On our small boat radars we expect to see a typical Firdell or Gillie Firth equipped boat at around 4mls if we are looking but it can be an erratic return until say 3mls. By contrast boats with no reflectors or those silly Mobri things or tiddly point up octahedrals on the backstay that the French are also fond of we do not see consistently until much closer, say 2mls. I don't know about the Tri Lens type or SeaMees but let's say I've not yet had an apparent supertanker on radar turn out to be a 26ft yacht yet!

We once had cause some years ago to speak via VHF with Ushant Traffic Control and they asked us for our position and speed. We were 14mls from them and they told us we were quite clear on their radar! Now I know their radar is a tad better than most but hey that was quite impressive but whether our reflector contributed or not I have no idea. That was on our last boat a W33 Ketch so two metal sticks with a Firdell on the top third of the front one and a 50hp lump of iron at water level.
 
If it's really so hard to reflect radar effectively, why did it take so long and cost so much to develop stealth technology? /forums/images/graemlins/confused.gif
 
[ QUOTE ]

I believe that the real answer is that a Radar Reflector is an essential item on any small boat, but we should not delude ourselves as to their effectiveness. ...... Make sure its an octahedral one or one of the modern proven designs. I make a distinction between 'proven' and 'claimed'

[/ QUOTE ]
(My italics!) PROOF?
I fitted a Trilens (middle-size one of the three available) at about the spreaders.
Meeting a ferry crossing the Minch (in F4) I called him up and asked if he would mind monitoring the return and call me when it faded.
By the time he was a speck on the horizon astern, the Trilens was 'behind the mast' from his point of view, the worst possible aspect, and I thought he must have lost us and had his own priorities to attend to.
Then he called up to tell me that at 11.5 miles the return was ''fading and becoming intermittent'' and added; ''That's a remarkable return from a small yacht!''.
For me, that is adequate proof.
 
[ QUOTE ]
[ QUOTE ]

I believe that the real answer is that a Radar Reflector is an essential item on any small boat, but we should not delude ourselves as to their effectiveness. ...... Make sure its an octahedral one or one of the modern proven designs. I make a distinction between 'proven' and 'claimed'

[/ QUOTE ]
(My italics!) PROOF?
I fitted a Trilens (middle-size one of the three available) at about the spreaders.
Meeting a ferry crossing the Minch (in F4) I called him up and asked if he would mind monitoring the return and call me when it faded.
By the time he was a speck on the horizon astern, the Trilens was 'behind the mast' from his point of view, the worst possible aspect, and I thought he must have lost us and had his own priorities to attend to.
Then he called up to tell me that at 11.5 miles the return was ''fading and becoming intermittent'' and added; ''That's a remarkable return from a small yacht!''.
For me, that is adequate proof.

[/ QUOTE ]That's an interesting account and I hope you agree indicates the efficiency under those circumstances - but falls short of scientific 'proof'.

I think the point that I was trying to make was that some radar reflector manufacturers have made some outrageous claims regarding the efficiency of their products, which neither tests nor physics can substantiate.

In all the tests that I have read, the only certainty has been that the results have been variable and that for passive devices, the octahedral type reflectors have usually outperformed the others. For example, the Firdell Blipper that we have is in reality two octahedral reflectors mounted at slightly different angles in a plastic container to try and minimise the 'holes' in the reflection pattern.

The real point behind my post was to poor cold water on the suggestion that all reflectors are a waste of time and are useless. Some are useless, but I'd rather have our reflector up than nothing at all.
 
Its because radar has improved over the years. My father reckoned he could see shells fired from the main guns in WW2. My radar might see a dinghy mast on a good day, modern military radar (I am led to believe) can see bullets! the wave length is minute, digital radar should impriove on that! so stealth is hard under those conditions.
 
You must log in or register to reply here.

Share this page

Top