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Old 23-11-2019, 09:57   #1
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To reflect or not to reflect

Hi
Having been a monohull sailor and now moved across to catamarans, I would like to ask what the consensus view is on the need for a radar reflector. Some people I have spoken to recently said there is no need as the cat is more stable and the mast provides a good radar target. I am nervous about this assertion even if in addition you have radar fitted Because radars have been known to fail. So belt and braces for me is to fit a good passive or active reflector.
What do you think?
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Old 23-11-2019, 10:17   #2
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Re: To reflect or not to reflect

Yes do it.

When you are crossing the channel at night into a filthy gale you need all the help you can get and reflector helping other traffic see you is one. The passive type don't need power or maintenance and whilst not brilliant, Qinetiq did some tests about 10 years ago on them, I wouldn't not have one.

https://www.ussailing.org/wp-content...ector-Test.pdf

We have been called up a couple of times doing this by commercial ships asking our intentions, quite re-assuring they have seen us.

https://www.gumtree.com/p/sailing-eq...tch/1358818116
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Old 23-11-2019, 10:35   #3
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Re: To reflect or not to reflect

Does it matter what some people assert? Is your country/sailing locale signatory to SOLAS V?

Quote:
SOLAS V 19.2.1.7 requires vessels if less than 150 gross tonnage and if practicable, [shall have] a radar reflector or other means, to enable detection by ships navigating by radar at both 9 and 3 GHz.
Unless the catamaran has the "other means" it must have a radar reflector unless one cannot be fitted. It is possible that you can't fit one that meets the SOLAS requirements, but then a best-effort approach is recommended.

https://www.rya.org.uk/knowledge-adv...eflectors.aspx
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Old 23-11-2019, 20:09   #4
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Re: To reflect or not to reflect

Hi SJFK,

I agree with you on making damn sure you are visible in foul/foggy/high seas conditions. Yes, AIS is very good and a case can be made for relying on it, BUT depending on where you are cruising, not all ships have operational AIS.

I also believe safety items are not an area to cheap out when there is that low probability- high consequence decision. I was highly impressed by our Echomax unit in a way I was not expecting. That is, the signal the other ship sees is about 10 times what your radar reflectance would be normally with a passive reflector, so the other ship Basically thinks you are a sizeable ship, therefore worthy of avoiding.


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Old 24-11-2019, 10:30   #5
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Re: To reflect or not to reflect

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Originally Posted by SJFK View Post
Hi
Having been a monohull sailor and now moved across to catamarans, I would like to ask what the consensus view is on the need for a radar reflector. Some people I have spoken to recently said there is no need as the cat is more stable and the mast provides a good radar target. I am nervous about this assertion even if in addition you have radar fitted Because radars have been known to fail. So belt and braces for me is to fit a good passive or active reflector.
What do you think?
I'd call BS on the mast being a good reflector. It has no reflective surfaces. Look at the way stealth aircraft are designed, just like your mast with curved surfaces.
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Old 24-11-2019, 10:37   #6
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Re: To reflect or not to reflect

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I'd call BS on the mast being a good reflector. It has no reflective surfaces...
+1
I totally agree and there is no negative from flying a reflector.
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Old 24-11-2019, 10:39   #7
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Re: To reflect or not to reflect

I hesitate to weigh in on this as I do not know what reflective technology has come out in the last ten years. I can say with nearly forty years in the wheelhouse of offshore tugs those aluminum ones do little or nothing at all. No matter what the regulations are and what sudo science goes along with it. Radar requires mass to bounce off and paint on the screen.. A fiber glass boat just doesn't give much to bounce off, like say a steel boat. Then there is the sight of eye thing where the sailboat is low in the water leaving it easy to be lost in the sea clutter that is automatically tuned out on modern digital radars. Always stay in compliance with your regulations. But do not rely on something that has way less reflectivity than say your mast. Keep a diligent watch. Stand by on VHF channel 16 so you can hear a ship calling you or you can call them. Use all your tools radar, AIS etc. You eyes and ears being the most important. Keeping a proper watch is also a regulation stated clearly in the International Rules of the Road
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Old 24-11-2019, 11:11   #8
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Re: To reflect or not to reflect

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+1
I totally agree and there is no negative from flying a reflector.
Except in certain areas where stealth is a good strategy for avoiding unfriendlies.
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Old 24-11-2019, 11:48   #9
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Re: To reflect or not to reflect

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I hesitate to weigh in on this as I do not know what reflective technology has come out in the last ten years. I can say with nearly forty years in the wheelhouse of offshore tugs those aluminum ones do little or nothing at all. No matter what the regulations are and what sudo science goes along with it. Radar requires mass to bounce off and paint on the screen.. A fiber glass boat just doesn't give much to bounce off, like say a steel boat. Then there is the sight of eye thing where the sailboat is low in the water leaving it easy to be lost in the sea clutter that is automatically tuned out on modern digital radars. Always stay in compliance with your regulations. But do not rely on something that has way less reflectivity than say your mast. Keep a diligent watch. Stand by on VHF channel 16 so you can hear a ship calling you or you can call them. Use all your tools radar, AIS etc. You eyes and ears being the most important. Keeping a proper watch is also a regulation stated clearly in the International Rules of the Road
Sea clutter is the biggest problem in detecting small boats. Fiberglass and wood do return a radar signal. In calm conditions even my 20 year old radar can see the 20 foot wooden or fiberglass fishing pangas at distance up to 3 miles. In seas over 4 feet they disappear in the clutter. A radar reflector mounted at 15 feet height above the deck would probably make it possible to see a small boat in these conditions.
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Old 24-11-2019, 12:17   #10
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Re: To reflect or not to reflect

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Sea clutter is the biggest problem in detecting small boats. Fiberglass and wood do return a radar signal. In calm conditions even my 20 year old radar can see the 20 foot wooden or fiberglass fishing pangas at distance up to 3 miles. In seas over 4 feet they disappear in the clutter. A radar reflector mounted at 15 feet height above the deck would probably make it possible to see a small boat in these conditions.
Had a friend who used to work as First Mate aboard large commercial vessel on the USA West Coast (plenty of fog). That was one of his concerns...that they could not distinguish small vessels from sea scatter...and would never know it if they ran them over.


OP: Not sure where you got your bad info, but modern cats, and most all small fiberglass boats make poor RADAR targets, and what is the advantage of not running a refelctor? Nada.
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Old 24-11-2019, 14:19   #11
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Re: To reflect or not to reflect

I clearly remember doing a radar training drill where I was piloting up a river by radar with all the windows cloased off. I was using the metal rings on the mooring bouys as a guide to stay in the channel. We had done a few miles and were approaching the end when the helmsman called down to check if I was seeing anything ahead."no, completly clear ahead" I replyed. A short while later the helm called again and when I said still nothing they called me up on deck. 100m ahead was a large lightweight cat, probably about 45ft, that was cmpletely invisable. I think it may have had a carbon mast but since then I have done a positive radar image check before sailing. Forget any of the tube types they don't work you need a traditional box type rigged about 15ft up.
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Old 24-11-2019, 14:57   #12
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Re: To reflect or not to reflect

Several comments.
First everything has a Radar return, just some things reflect more than others, and a metal mast can be a decent reflector, depending on its angle to the beam.
RCS or Radar cross section is all about three things, size and material, and angle, a sail isnít a good reflector due to material of course, but itís huge, and could be with some metal screening in it.
Anyway the tube reflectors donít have the area to be good reflectors, and the Old fashioned Davis reflectors are very good, but again just arenít big enough.
There is really noting new, the physics of RCS has been understood for a long time.

Think of a Radar as a searchlight. Itís really similar. A reflector is like reflective tape, it works, the more you have the better, problem is only small pieces are sold, and nearly everyone only has one small piece.

However if you really want to be seen, you need a strong light of your own, thatís a transponder or active reflector if you will, the strength of the light determines how far and how well your seen, your dinghy is just as big as a 60í Cat.

Listen to the guys who have run Commercial shipping and how well we are seen, two reasons we arenít run down more often, we are keeping watch, and while that tanker canít see me, my Radar sure can see him.
Second is the big sky, little bullet theory.

So if you want to hoist a Radar reflector, Iíd say hoist more than one, as has been said it canít hurt, just donít expect it to do much, cause itís not.
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Old 26-11-2019, 05:29   #13
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Re: To reflect or not to reflect

Back in the day , I was a US Navy pilot in anti submarine work.

As a tri owner then I was as concerned as anyone about being run down.

When borrowing reflectors and flying to them the best by far was the WWII life raft folding units that were fairly large with a metal woven screen.

Don't last forever , but there cheap enough.
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Old 26-11-2019, 07:09   #14
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Re: To reflect or not to reflect

I wonder if the idea that the need for reflectors is less on a catamaran springs from the idea that the mast is a good reflector if held vertical and that cruising catamarans don't heel much.


The error, I'm guessing, is that masts are extremely directional reflectors, and even a little heel will send the reflection into the sky or the sea.


The optimum reflector for a cat would be somewhat more focused in the horizontal. But not a mast.
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Old 26-11-2019, 07:53   #15
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Re: To reflect or not to reflect

A mast really isnít a directional reflector.
A factory made radar reflector (aka corner reflector) is though, thatís how they work.

I doubt that a Cat has much if any larger an RCS than a similar sized mono. itís most likely the metal bits that contribute most to RCS, the lifelines and rigging, mast, Solar panels etc.

But what really hurts us is that we are relatively low to the water and we would easily get lost in ground clutter, we give a return, but itís lost in the clutter.

Years ago late 70ís I believe a motorcycle magazine conducted a test to determine the range at which a Police Radar could determine a motorcycles speed.
What they found out was very confusing at first, some of the little sport bikes could be tracked further than the full dress Harelyís they eventually figured out it was the headlights, the headlights were concentrating the Radar beam and reflecting it back to the Radar and many of the Sportbikes had dual headlights if you took the headlight bucket and re-aimed it way up or down, a motorcycle especially a sport bike was very tough to detect. Back then most Standard Japanese motorcycles headlights had one mount on either side and it was simple to move it so it would point way high or right at the ground.

Now almost if not all sport bikes headlight reflectors are plastic and donít reflect Radar.
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