Radar Reflectors

Tugw

Tugw

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Cyclops or Tri Lens?, I cant make my mind up.Already got an active type but i wanted something in reserve should the lekky decide to die.Ive read loads of reports and i am now completely at a loss

whats the panels opinion?:confused:
 
IIRC the large Trilens was the best commercial passive reflector tested. Great, if you can find room for one. They can be a snag hazard on the front of the mast, though, so may not suit smaller boats and the smaller model was not as good. The cyclops didn't perform quite so well but is neat if you still have room for any more gear and weight at the masthead!

I have been overtaken by technology, as I fitted a RTE before the dual-band models came out. I have a sausage shaped type to hoist from the crosstrees as back-up and hopefully to give some small S band response.

Rob.
 
The report on the Ouzo disaster strongly suggests that passive reflectors aren't a lot of use; better than nothing, but not by very much! And the technical detail that report presents is actually pretty damning about the effectiveness of passive reflectors; the best (which was a piece of heavy and expensive lab equipment, not a practical option for a sailing boat) was still not up to the expected standard for reliable detection by a ship's radar.

I happen to have been involved some time ago professionally with radar reflectors in another context entirely (satellite radar altimetry!), and I was not in the least surprised by the findings of the Ouzo report. Even before it was published, I had strong doubts about the effectiveness of radar reflectors on sailing boats. Reasons are practical limits on size (a passive reflector can't reflect more energy than actually falls on it!), precision of angles and maintenance of that precision (errors of much less than a degree will compromise their effectiveness), loss of effectiveness when not at the optimum angle to the horizontal and, of course, intereactions with the mast and rigging - the MAIB report on the Ouzo sinking tested the reflectors in ideal conditions with no interference from an aluminium mast and stainless steel rigging.

Passive radar reflectors aren't quite snake-oil, but are only about one step up from that unless you fit a VERY expensive piece of lab equipment, well separated from mast and rigging. They are not much of an improvement on the reflection from the mast and rigging of a modern yacht, and in calm water the "hole in the sea" that a GRP boat presents to radar will give a pretty big reflection. I removed my passive reflector when I fitted a Sea-Me, and have no qualms at all about it.
 
I have read the reports,thats the problem, As far as i can see its a waste of time putting one on the boat.(the RTE being the exception).I just thought i must be missing something or i had understood the reports wrong.I have the single band RTE and feel quite comfortable with it (although i do plan to upgrade to the dual band when the cash is available) but as with most other gear on the boat its always nice to have some sort of backup.(that my theory anyway) :)
 
Isn't there a legal requirement to carry a radar reflector?

A large octohedral is probably the most cost effective.
But as they have gross windage mine only every came out in poor vis.
 
AntarcticPilot said:
But a transponder (even single band) counts as a reflector under SOLAS. The OP says he has one, so no problem even if it is a legal requirement - which I didn't think it was for small craft.
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Well I learned something here . . . In 2002 some of the SOLAS requirements were (in theory) extended to pleasure vessels. As far as I know MCA seems to be the only national authority that is taking any effort to follow up on that. MCA guideline details are here . . . http://www.dft.gov.uk/mca/pleasure_craft_information_packdec07-2.pdf

Regarding specifically radar reflectors, the wording is pleasure vessels 'should' 'if practical' carry them. From a legal point of view that seems (to me) to make it a recommendation rather than an absolute requirement. But the wording is a slightly ambiguous and I am not sure that is the correct interpretation. If it came to a court of law you might have to prove it was impractical to have a reflector on your specific vessel.

AntarcticPilot is correct that in the OP's case, the inclusion of an active device would seem to already fulfill any requirement, thus not requiring an additional passive reflector.

This SOLAS requirement was written before widespread (class B) AIS usage, and I personally think an AIS transceiver would do a great deal more good than a passive radar reflector.
 
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Just a thought, would two or three reflectors mounted together increase the returned signal?
 
CJU said:
Just a thought, would two or three reflectors mounted together increase the returned signal?
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I am guessing not .... on the basis that three times almost nothing = still very insignificant.

Best to have a radar relector, even if it is the passive type, just in case insurers might need to enquire.
 
I've noticed in working at test ranges that the MOD use octahedral reflectors, both on target rafts and their support boats; even the Sea Harrier FRS1 ( as in Falklands War ) with the Blue Fox radar which was not highly regarded could pick up these target rafts from a few miles.

What gets me is that when radar was in its' infancy in WWII, it seems U-Boat periscopes were relatively easy to detect; we seem to have got worse not better !
 
MartynG said:
I am guessing not .... on the basis that three times almost nothing = still very insignificant.

Best to have a radar relector, even if it is the passive type, just in case insurers might need to enquire.
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It depends whether the returning signals are in phase with each other or not.

If they are in phase then they will enhance each other but if they are out of phase it is possible for them to cancel each other out.
 
VicS said:
It depends whether the returning signals are in phase with each other or not.

If they are in phase then they will enhance each other but if they are out of phase it is possible for them to cancel each other out.
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And as a yacht inevitably has many radiators in its mast and rigging, the polar diagram of the passive return from a yacht is pretty much unpredictable - and then it all changes when you tack. A passive reflector will, at best, modify this; perhaps for the better in some directions but potentially for the worse in others.

Ships, on the other hand, present massive plane surfaces of steel to the radar!
 
And as a yacht inevitably has many radiators in its mast and rigging, the polar diagram of the passive return from a yacht is pretty much unpredictable - and then it all changes when you tack. A passive reflector will, at best, modify this; perhaps for the better in some directions but potentially for the worse in others.
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This is probably what scuppered PBO's ( or TB's) first attempt to compare radar reflectors out on the water back in 1999 and is the reason why the only way to compare them is under laboratory conditions as QinetiQ did .

Interesting to dig out the old PBO article .. which was eventually quite good, and find Tim Bartletts mug shot on the front page :eek:
 
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