Passive radar reflector - anything better than Echomax?

[Refueler]

The orientation of a metal mast has to be at 90 deg to the incoming signal in order to return it adequately. The mast is after all a smooth flat surface relative to the wavelength (usually X or S band) of marine radar. If the boat is heeling, and pitching, the return is severely attenuated as the return will head up towards the sky. I have yet to come across a mast that stays in perfect straight alignment while sailing. It is entirely possible that junctions of e.g. spreaders or the boom might fortuitously make a decent return, but such junctions do not have the engineered "perfect" right angles necessary to bounce the signal back strongly. It's not only a 90deg corner that is needed but panels big enough to send a beefy and worthwhile signal back to the transmitter's vessel.

This is why the tube reflectors are such useless items; they cannot present a big enough reflecting surface especially when tilted. A Qinetiq notes, the returns are very poor.

I agree with most of that ... but a mast is not a flat or true square on most boats ... most are an oval shape that gives any orientation of the mast a small amount of it reflecting back to the radar set.
Second if your sails are salty .. damp or wet - they can add to the RCS. Not a lot but every little bit helps.
Yes pitching rolling and movement alters the orientation of the mast and sails ... but that also can aid the situation ...

How did a 10,000 GRT container ship plot my 25ft boat from over 10nm on his ACAS when I had no reflector hoisted ... ??

 

[Tranona]

I am quite happy that my 2-- 4 inch tube reflectors mounted on the inward angled mid shrouds work very well. I know because an RNLI life boat had to find me in a big confused sea in F7 one night & the coxswain came to see me after. He commented what an excellent radar return my 2 reflectors gave him. So that disproves the accuracy of tests, as far as I am concerned. Especially as the skipper said that his radar set was very old & soon due for renewal.

Interested in how he could say that it was the reflector that his radar picked up. Surely it is the whole boat that the radar sees of which the reflector might be a part?

 

[Refueler]

Interested in how he could say that it was the reflector that his radar picked up. Surely it is the whole boat that the radar sees of which the reflector might be a part?

Fair comment and I agree with you. Passive reflectors cannot be resolved unless they are tested completely isolated from all other around.

 

[TernVI]

Have you ever noticed that most nav marks and many harbour piles etc have good old corner reflectors on them?
Ships have been using these for navigation for half a century.

People don't read the whole of the Ouzo report, the bit about ship radars being just about blind due to looking down at a small yacht's reflector or whatever, at certain ranges.

 

[Refueler]

Have you ever noticed that most nav marks and many harbour piles etc have good old corner reflectors on them?
Ships have been using these for navigation for half a century.

People don't read the whole of the Ouzo report, the bit about ship radars being just about blind due to looking down at a small yacht's reflector or whatever, at certain ranges.

Just to clarify that last bit ... the problem there is sight line of radar antenna to sea surface ... basically if the yacht cannot see the radar antenna because of the ships hull / bow - then the radar cannot see the yacht.

I posted years ago a photo illustrating this ... a 100,000 ton tanker I was working in Hamburg. I stepped ashore to walk to a point where I could take a photo showing the bow obscuring any view of item ahead of it for quite a distance.

Trying to find it again ... but it was some years ago ... its on one of my computers somewhere !

 

[RAI]

I hoisted the Rain Catcher after that Container vessel incident - but never liked it as genny swept across it on every tack. Changed to the tube type based on the sq area of foil quoted as same as my Rain Catcher.

So this was your preference?

 

[Refueler]

So this was your preference?

Gor Blimey Guv .. yeh dinna give up do yer !!

In truth - as I mentioned later ... I regard it as an addition to the RCS of my boat ... not the answer or solution. If it adds RCS - great ... if not, it satisfies the onlooker that I have something up there ... and because it does not chafe the genny - it can stay up there.

 

[PilotWolf]

What happened to the ?SeaMe active reflectors?

Fitted one to a boat years ago and it seemed to be the best option.

W

PS. Not convinced still the POB was responsible having spent a fair bit of time on the bridge with the crews ~ I know the officer was a relief and mistakes are made but I don’t know anyone who would deliberately make a career ending decision. . .

 

[RAI]

What happened to the ?SeaMe active reflectors?

Fitted one to a boat years ago and it seemed to be the best option.

W

Echomax do one too. I prefer the dual band X and S version as ships carry both radars. I also carry a large rain catcher and an old Echomax passive reflector.

 

[PilotWolf]

Echomax do one too. I prefer the dual band X and S version as ships carry both radars.

It was a fairly new piece of technology at the time. So think single band?

W

 

[matt1]

As far as I know seame are no longer trading.

i recently went to the trouble of sourcing a second hand tri lens (again, no longer produced) because it didn’t come out with the strongest return in tests but did have a very consistent return

As a new radar user I’ve become convinced the best return is from a rail mounted outboard!

 

[TernVI]

Just to clarify that last bit ... the problem there is sight line of radar antenna to sea surface ... basically if the yacht cannot see the radar antenna because of the ships hull / bow - then the radar cannot see the yacht.

I posted years ago a photo illustrating this ... a 100,000 ton tanker I was working in Hamburg. I stepped ashore to walk to a point where I could take a photo showing the bow obscuring any view of item ahead of it for quite a distance.

Trying to find it again ... but it was some years ago ... its on one of my computers somewhere !

not as such!
As I said, it's worth taking in the whole report, rather than the chinese whispers forum interpretations of it.

 

[RAI]

It's said of fibre glass boats is the the best RCS is a hole in the water with an engine in it.

 

[Refueler]

not as such!
As I said, it's worth taking in the whole report, rather than the chinese whispers forum interpretations of it.

I agree whole report - because too many people get selective about parts of it ...

"not as such" ?? You mention not seen .. so I added example of one aspect where you will never be seen - the sheer length of vessels, the sight line of the antenna with bow of vessel etc. The distance a yacht would have to be ahead of a container vessel as example would be serious !! That tanker photo _ I tried to find is taken looking from shore to the bow .. and you cannot see the bridge windows. I was standing quite a long way ahead of her.

 

[PilotWolf]

Think you can been seen?

W

 

[TernVI]

It's said of fibre glass boats is the the best RCS is a hole in the water with an engine in it.

Lots of things are said and many of them are utter bollocks.

 

[RAI]

Lots of things are said and many of them are utter bollocks.

Not all of them though.

 

[RAI]

Lots of things are said and many of them are utter bollocks.

Not all of them though.

 

[TernVI]

Keep going, it takes 186000 repetitions to make a truth IIRC?

In the slightest of seas, the hole made by the hull is no bigger/deeper/steeper than the troughs between waves.

 

[James_Calvert]

Keep going, it takes 186000 repetitions to make a truth IIRC?

In the slightest of seas, the hole made by the hull is no bigger/deeper/steeper than the troughs between waves.

But a more consistent shape conducive to a stronger echo maybe?

Anyone actually know?