Radar Reflector

[SJM]

I am looking for recommendations for low windage radar reflectors that are compliant with US Sailing SER-Coastal rules for racing. Below is the rule text.

"A boat shall carry an 11.5" (292mm) diameter or greater octahedral radar reflector or one of equivalent performance."

I'm not sure how to assess "equivalent performance" and if I assume its the projected area of a 11.5" octahedral style, I cannot find a tublualr style on the market.

Any thoughts?

Thanks,
-Scott

 

[Zonker]

It's the radar reflective return ("performance"), not the physical projected area.

Those little tubular ones have been shown to suck balls except when exactly lined up with the transmitter. See graph below

Does the rule require it be hoisted at all times or just when low visibility/night time?

More than you want to know about radar reflectors:

https://www.ussailing.org/wp-content/uploads/2018/03/2007-Radar-Reflector-Test.pdf

 

[BayRacer]

Here's another write-up, though a bit older. Has a bit more background information on radar tech and performance.

https://keyassets.timeincuk.net/inspirewp/live/wp-content/uploads/sites/20/filebank/reflector_performance_ym_june.pdf

Also, Practical Sailor updated a 20 year old study a few years back.

To See and Be Seen - Practical Sailor

Since 1974, Practical Sailor’s independent testing has taken the guesswork out of boat and gear buying.

www.practical-sailor.com

I think "low windage" and effective are borderline mutually exclusive. At pne point I had one of those tube reflectors above the first set of spreaders (came with the boat). One breezy and bumpy day the headsail took it out on a tack. I have one of those assemble-as-needed reflectors, but we rarely get fog in our corner of the Great Lakes and most commercial traffic runs a track far enough out to not worry too much.

 

[mckenzie.keith]

It's the radar reflective return ("performance"), not the physical projected area.

Those little tubular ones have been shown to suck balls except when exactly lined up with the transmitter. See graph below

Does the rule require it be hoisted at all times or just when low visibility/night time?

More than you want to know about radar reflectors:

https://www.ussailing.org/wp-content/uploads/2018/03/2007-Radar-Reflector-Test.pdf

View attachment 581258

NEVERMIND. Everything below is nonsense. The 279 mm sphere is not just a metal sphere. I had not come across a Luneburg lens before. Didn't know what it was.

It is interesting and unexpected to me that a 279mm sphere outperformed an octohedral. This suggests that the benefits of an octohedral are not being fully realized by existing products. Normally a corner reflector provides truly excellent returns (I have experience working with RCS measuring radar looking at a variety of reflectors including flat plate, sphereical, and corner reflectors... corner reflectors are great in that they are unmistakable returns and not terribly sensitive to angle).

I wonder if a 12 inch metal sphere would be just as good as anything else on the market? Aluminum or stainless should work fine. It doesn't really matter what metal your cal target is made from.

 

[longy]

The Davis aluminum units are the best. But must be hoisted in the proper orientation.. with a little modifications they can be made to assemble around a backstay to keep them out of the way

 

[silent bob]

The Davis aluminum units are the best. But must be hoisted in the proper orientation.. with a little modifications they can be made to assemble around a backstay to keep them out of the way

Yeah, just don't assemble them around the SSB Antenna Isolator!!!

 

[El Borracho]

The rules say “carry”? Does that mean stored below is compliant? The alloy Davis collapsible are the best. It all about projected area of the reflector, obviously, the small ones making big claims are BS.

I store my Davis below decks, assembled, in a high locker. Bcuz I am dragging it along it might as well be doing something. It comes out only when necessary.

 

[longy]

Yes, stored below complies. A few races require it to be set in the air, but do not specify how or how high up

 

[Bristol-Cruiser]

A few boats ago I had two of the tubular ones, one on each shroud above the spreader. I figured with normal boat movement something must be reflecting.

 

['Bacco]

A few boats ago I had two of the tubular ones, one on each shroud above the spreader. I figured with normal boat movement something must be reflecting.

That's what I do.

 

[SJM]

Hi All,

Thanks for all the input to my questions. The two reports on various reflector performances was most informative. I decided to go with the Echomax EM230pi Inflatable Radar Reflector as it seems to have one of the highest performance (although there are higher ones).

-Scott

 

[PaulK]

A few boats ago I had two of the tubular ones, one on each shroud above the spreader. I figured with normal boat movement something must be reflecting.

Please read Zonker's post #2. It would appear you were mistaken.

 

[Bristol-Cruiser]

Please read Zonker's post #2. It would appear you were mistaken.

That report does not address the effectiveness of two tubes which are aligned at any angles used in the tube (45°/90°).

 

[TJSoCal]

Yes, stored below complies. A few races require it to be set in the air, but do not specify how or how high up

Right. SER are specific about some items like jacklines (must be “in place while racing”), crew overboard equipment (“on deck & ready for immediate use”), etc. So we can infer that “carry” just means the item has to be onboard.

 

[Zonker]

Honestly if you care about being seen by radar, the little tubular ones are really bad.

Please read the Yachting Monthly report from above. They don't even produce a reflecting chart for it.

https://keyassets.timeincuk.net/ins...20/filebank/reflector_performance_ym_june.pdf

If you motor in the fog (zero heel), a reflector that only gives a few returns in one minute will NOT be noticed by a radar user and very mostly likely won't trigger any auto alarms either. Too spurious.

Compare the heeled reflectivity RCS to all the others tested. It is objectively shit.

 

[JRA68]

The World offshore sailing special regs also has this as an option:
a non-octahedral reflector with a documented Root Mean Square minimum Radar Cross Section (RCS) area of 2 m² (22 ft²) from 0-360° of azimuth and ±20° of heel

How would i go about calculating the RCS? is it just the relative area of the reflector?

 

[Go Left]

The World offshore sailing special regs also has this as an option:
a non-octahedral reflector with a documented Root Mean Square minimum Radar Cross Section (RCS) area of 2 m² (22 ft²) from 0-360° of azimuth and ±20° of heel

How would i go about calculating the RCS? is it just the relative area of the reflector?

All the commercial ones i've seen publish it on the package.

 

[climenuts]

I was concerned about my shitty 2" tube job (pictured below) until my buddy on the Queen of Oak Bay (a ferry) could see us on radar no problem.

This is from the Oak Bay's radar screen on a rainy February day in 20kts. We're 986. 96 & 119 are tugboats with log booms and 892 is the Queen of Coquitlam (another 7,000 Ton ferry). Our boat was mostly level and hauling the mail downwind. In my opinion they see us just fine.

Edit to cover my buddy's reflection so he doesn't get canned.

 

[mckenzie.keith]

How would i go about calculating the RCS? is it just the relative area of the reflector?

It is not really something that can be calculated for most targets. Spheres being the exception. Spheres are used to calibrate the radars that measure RCS.