The best way to attach a tubular radar reflector to a shroud.

[Alan Mighty]

Originally Posted by a64pilot

But I’ve never seeing one of those little stick reflectors, nor have I seen one fo the Tri lens ones either, and I’d have to assume if they worked better, then the USCG would have incorporated some at least to test.

So it goes ...

In 1998, the Mobri tubular radar reflector was touted as being used by the USCG on Aids to Navigation! Supposedly after an 18-month study. Who knows where the truth lies? see: https://www.ahoycaptain.com/mobri.html

[Capt. Ray]

My electronics degree thesis was microwaves and I completely endorse the below. The only thing on a fibreglass boat any radar is picking up is your engine block. Reports of improved radar reception using the typical reflector are anecdotal and defy physics. U less it is at least a metre wide, even the "corner reflector is all but invisible.

Originally Posted by Breaking Waves

Honestly don’t bother. That design reflector does essentially nothing at all - it is a really bad design which has been demonstrated in essentially every independent test ever conducted. Just for example see http://newcontent.westmarine.com/con...ors-Report.pdf

I will just quote from it’s summery “The 4” tube reflector is not considered suitable due to its poor performance. It is also recommended that the 2” tube reflector is not suitable since the performance of this target will be even lower.”

And from a prior test:” The two Tubular reflectors performed as might be expected, and were essentially invisible. Only the larger 4" diameter (2" radius) device came anywhere near detectability, with an average return at a 0° angle of heel of just over 1 m2, with no deep nulls. On S-band, the average return was almost 0.5 m2, not enough to be detected. When heeled, however, things fall apart and the return drops to a few duck units (see fig. 8). The smaller is invisible under all conditions, and, with its minimal windage, might make a nice addition for the Stealth Bomber.”

[StuM]

Originally Posted by masonc

I use stainless tie wraps for durability, but also put two small PVC tile wraps for grip.

The stainless tie wraps probably give a better radar return that the tube

[masonc]

Originally Posted by StuM

The stainless tie wraps probably give a better radar return that the tube

Yes, I get it, I wasted my money. I use an AIS transponder when sailing inter island, and the commercial traffic see that every time. I have wooden masts so the reflector is about the only thing radar might see.
When I come into a busy mooring field at night like Marigot, the city lights are so bright I can't see boats. I run the radar at eighth mile, and I can see all the boats. The radar reflector might be helpful at that range.

[Breaking Waves]

I have always like the MIAB incident reports.

Radar visibility was an issue in the loss of the Ouzo, which MAIB investigated. The whole report is worth reading - but section 2.6 and Annex 4 go into detail on radar reflectors.

OUzo had a significantly better reflector than the tubular versions, and the report's conclusion was still " it was unlikely that deployment of the radar reflector on Ouzo would have made very much difference to the RCS of the yacht."

Ouzo had one of the 6" flat pack Octahedral designs. Reflective performance is proportional to the 4th power of linear scale - this one would have been (roughly) 5x 'stronger' than the 4" tubular design. However, also note that this 6" design is 1/2 the minimum size specified in the Offshore Safety Regulations - so only 6% the performance (after the 4th power is taken into effect) of the MINIMUM standard, and the 4" tubular is 1% of the MINIMUM standard. Raw size does in fact matter quite a bit here.

[a64pilot]

Originally Posted by Capt. Ray

My electronics degree thesis was microwaves and I completely endorse the below. The only thing on a fibreglass boat any radar is picking up is your engine block. Reports of improved radar reception using the typical reflector are anecdotal and defy physics. U less it is at least a metre wide, even the "corner reflector is all but invisible.

I have a little background in Radar myself, mm wave though and for targeting, but I agree with you, but will point out that your mast, rigging, even your Radar transmitter and quite likely Solar panels, Bimini frame, lifelines, port lights etc contribute some.
We are seen, but not as well as we would like, and I doubt it’s from the engine that is buried inside of the boat and likely at least half of it is under waterline.

However an active transponder doesn’t rely any on the RCS or reflectivity of the vessel. If it’s made well, it ought to work exceptionally well.

Years ago I built a jammer for cars, it’s power output was extremely small, I mean pretty much undetectably small, reason is all it had to do was overwhelm the return signal, which is astonishingly small, it fascinated me that it’s detectable at all.

You can of course over come poor reflectivity of a target by turning up the transmitter power, but that’s not done out of the Military world and was really back in the 50’s 60’s time frame.
A friend was an electronics technician on the F-106 and he swore that when they cranked up the targeting Radar power they could light up every fluorescent tube in an office building across the runway, maybe a mile away.

But Marine Radar is likely less than a millionth of that kind of power.

It’s interesting that there doesn’t seem to be many Marine Radar transponders sold, my assumption is that the need isn’t really there, or maybe people believe that the passive ones work well?

Radar reflective sails since we know the frequency wouldn’t be hard to make, I wonder what that hasn’t been done?

[tankersteve]

https://keyassets.timeincuk.net/insp...ce_ym_june.pdf

As A64 noted, an active 'transponder' has the best results. Not cheap, but blows everything else out of the water. This is a pretty comprehensive look at performance.

Tankersteve

[model 10]

[QUOTE=a64pilot; showing up on Radar, I don’t have a reflector.




I started asking big ships if they see me since I stopped using a reflector and started using AIS. It sounds like we are a good enough target without one. Watching them carefully on the AIS receiver, it's sometimes hard to tell if they do see you.

How accurate are the collision courses plotted in an AIS display?

[Lodesman]

Originally Posted by Breaking Waves

No, not the tubular designs. If they are angled even 1 degree, which they always will be, they are really not better than nothing.

The larger tubulars (4”) produce only 1.5% of the ISO absolute functional minimum standard at 1degree angle, and .4% of the minimum standard at 5degrees. The iso says this standard must be met (eg +100% of the standard) at all angles up to 20 degree angle for sailboats.

Those numbers are so small they will typically not even add a speck to the sea clutter.

Maybe you learned the new math, but even 0.4 is more than zero, so better than nothing.

You shouldn't get so wrapped up in angle-fixation. In a lab-setting the 1º is fixed and is therefore an issue; at sea the angle of incidence is constantly changing. As I suggested, adding it with another reflector - a little bit of reflected radar here, and little bit over there, gives a greater effective RCS and a much greater chance of keeping ARPA tracking.

[Breaking Waves]

Originally Posted by Lodesman

Maybe you learned the new math, but even 0.4 is more than zero, so better than nothing.

You shouldn't get so wrapped up in angle-fixation. In a lab-setting the 1º is fixed and is therefore an issue; at sea the angle of incidence is constantly changing. As I suggested, adding it with another reflector - a little bit of reflected radar here, and little bit over there, gives a greater effective RCS and anmuch greater chance of keeping ARPA tracking.

I don’t think of you as a troll (but this response of yours comes pretty close) - so with the greatest of respect - no.

#1 beyond essentially zero reflective power, there is also a wave length issue. These sorts of reflectors need to be “many multiples” (at least 4) of wave length to work. S band is 4” wave length and so will be totally none reflected. X band is roughly 1.5 inches, so a few waves will be reflected but many will not, which drops the .4% down even further.

#2 yes the angle will be bobbing around, which just makes it worse because all angles higher than 1 degree are even worse with this design. 5 and 10 degrees for instance are 75% worse/less than 1 degree

If you combine all the negative factors together you get a practical real world zero with this design. This design will have an unmeasurable effect on your rcs. If you want to argue that something so small it is unmeasurable is greater than zero, then you can dance on the head of that pin all you want.

And If you want to somehow defend this design, I leave you to it, because objectively and factually it does not come remotely close to meeting the minimum standards (iso nor osr) and it is “not fit for purpose” and a total scan.

And if you just want to win an Internet argument - fine YOU WIN .... just pls don’t mislead anyone here that these tubular reflectors are worth anything.

[GordMay]

Tri-Lens Radar Reflector
The standard Tri-Lens reflector from Rozenûdal Associates outperforms our previously recommended reflector, Davis' Echomaster, at about double the price.
“... Installing a radar unit may be a skipper's best defense against collision at sea—the idea being that the best safeguard is for you to see the other guy rather than hoping he sees you—but not everyone wants or can afford a radar set. And even then, hanging a relatively inexpensive passive reflector certainly doesn’t hurt...”
“... If you're in the market for a passive radar reflector, we recommend the Tri-Lens [ Â* ]...”
➥ https://www.practical-sailor.com/iss...es/4567-1.html
➥ https://www.practical-sailor.com/new...27-16-Rank.pdf

[Lodesman]

Originally Posted by Breaking Waves

I don’t think of you as a troll

I'm not trolling, but I don't think you understand what I'm saying. The '95 WM paper says it:

The marginal performance of radar reflectors in general does not mean that they should not be carried. On the contrary, anything that improves a vessels radar visibility is worthwhile, particularly short-handed vessels and those without radar themselves.
Beyond that, it needs to be again pointed out that the best defense where shipping is concerned is a good offense.

The testers all seem to focus on the weak return of those types of reflectors - the WM test says a few ducks units when heeled. The point I'm trying to make is that while a couple ducks may not trigger an automatic acquisition, it is capable of being seen by radar, so can augment total reflected signature (mast, stanchions, shrouds, other radar reflectors). This makes the over RCS of the vessel larger, and provides some consistency of return when in the nulls of the other reflector(s).

If used as I have, it does make the MOB pole more radar visible, but it does require a decent understanding of how to optimize the radar, and manually hook the paint.

[a64pilot]

Originally Posted by Ecos

How accurate are the collision courses plotted in an AIS display?

As accurate as the courses from the GPS’s, which are horribly accurate as is the speed.
GPS spot accuracy isn’t that great but a moving course and speed average out the inaccuracies and become extremely accurate.
We had to prove that in order for the FAA to accept GPS speeds in determining calibration error and installation error of airspeed instruments in aircraft. As you can imagine it’s not easy to prove something like that, but it turned out to be orders of magnitude more accurate that the old fixed course timed routes.

I’m sure a poorly spec’s cheap, maybe home made AIS could make a mess of it, but would expect that anything on a ship, and my Vesper to be exceedingly accurate, especially when you won’t accept a CPA of anything closer than 1 mile, even if it was off by a couple hundred feet, could you tell?
We aren’t trying to graze his bow, but to make sure we stand well off, and a mile is well off.

This is the 21st Century and we really can do amazing things like control alternator output to .1V etc. easily. Something that outside of a Lab would have been considered impossible not too long ago.

[deblen]

My personal 40+ yrs experience with radar & radar reflectors on 35-65 ft GRP & Wood fishing boats in foggy Fundy Bay.


This EM18 style works very well on the boat & on high flyers . It is not pretty though https://www.echomax.co.uk/reflectors-rigid.html


The round Davis echomaster works almost as well if hung correctly.


Get a SS halyard cleat & mount it 20 or so ft up the backstay. Make up a SS bridle from a short length of 1/8 SS wire rope,a couple of crimps & a couple of 3/16" SS shackles & connect it to the Davis using 2 of the 1/4" holes in the reflector panels. Disassemble the reflector,slip it around the backstay & reassemble. Slide it up the backstay & fasten it to the cleat.
Mine has been up there for abt 10 yrs. I inspected it 2 days ago-mast down. No wear on anything,including backstay.
It's always there.
Even our dory fishermen use a Highflyer style reflector on a pole. Too many deaths & close calls years ago without them. Other fishermen won't tolerate a boat without a reflector in this area.
Maybe 5% of the Fundy/SW NS fishing fleet have AIS so far.


Len

[deblen]

Originally Posted by deblen

My personal 40+ yrs experience with radar & radar reflectors on 35-65 ft GRP & Wood fishing boats in foggy Fundy Bay.


This EM18 style works very well on the boat & on high flyers . It is not pretty though https://www.echomax.co.uk/reflectors-rigid.html


The round Davis echomaster works almost as well if hung correctly.


Get a SS halyard cleat & mount it 20 or so ft up the backstay. Make up a SS bridle from a short length of 1/8 SS wire rope,a couple of crimps & a couple of 3/16" SS shackles & connect it to the Davis using 2 of the 1/4" holes in the reflector panels. Disassemble the reflector,slip it around the backstay & reassemble. Slide it up the backstay & fasten it to the cleat.
Mine has been up there for abt 10 yrs. I inspected it 2 days ago-mast down. No wear on anything,including backstay.
It's always there.
Even our dory fishermen use a Highflyer style reflector on a pole. Too many deaths & close calls years ago without them. Other fishermen won't tolerate a boat without a reflector in this area.
Maybe 5% of the Fundy/SW NS fishing fleet have AIS so far.


Len

PS: Make sure the reflector is mounted well above or below(+/= 4+ft) of the radar line of sight. ie: +/= 25deg beam depth. This will avoid annoying false echo.