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Old 05-05-2014, 07:17   #1
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Radar Reflector

My apologies if this has been asked before and answered, but I could not find it if it has.

We have a radar reflector mounted on the mast, some kind of pill shaped PVC container, about 2 or 3 meters from the top of the mast. So far it has not been a problem, but I can see it snagging a halyard one day and causing a lot of misery.

In deciding whether to keep it, it would help to know if it actually WORKED. i.e. does it actually significantly improve the radar return of the boat to the point that it might prevent some under-crewed monster tanker turning us into so much fibreglass chaff and an inexplicable scratch on their bow.

Has anyone any experience of seeing the difference? For reference, we are a fibreglass boat with a pretty darn solid old 50 foot(ish) aluminium mast.

Matt
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Old 08-05-2014, 23:54   #2
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Re: Radar reflector

Seek and ye shal find... or something to that effect.

Anyway, found this test from USSailing, I reckon they are credible, and basically it tells me my Firdell Blipper is not much use. I particularly liked the way the article managed to use ducks as a unit of measurement.

http://offshore.ussailing.org/Assets...ctor+tests.pdf

I'll replace it with something more effective, in a safer place, I am not even sure I have the better of the two models, but both rated pretty poorly.

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Old 09-05-2014, 01:01   #3
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Re: Radar reflector

Have a radar-equipped boat give you feedback on the strength of your reflection.

Show us a photo of your reflection set-up. The "pill" models I've seen didn't appear to interfere with halyards, etcetera.

Having a steel boat, I don't worry about such things. From feedback, I show up great on radar. Regardless, reflectors are better than nothing on a wood or plastic boat.
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Old 09-05-2014, 01:10   #4
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Re: Radar reflector

Yes, well according to the test, the Firdell Blipper was pretty ordinary.

It's not too bad in terms of halyard snagging, but it is another point of potential problems... I think, as I remarked, I will find one that at least has a good return.
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Old 09-05-2014, 01:48   #5
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Re: Radar reflector

Hmm... I have seen other reports that suggest the Firedell unit was pretty good but... that was some 15 years back or so and I have no idea what they were being compared against. Certainly I believe they are much better than the ones than look a little like a fluro tube

I had one on a 30' steel Starfire back in the late 80's and my mate did some simple tests using his cheap(ish) low end radar unit. The returns were much better with the Blipper hoisted aloft than without it. We are talking about 3 or so mile range IIRC. Not a very extensive test but it gave me some confidence that it was a useful reflector.

I currently use the simple interlocking plates of Al sheet mounted in the "catch water" position.

Interestingly a couple of years back, the Aussie navy where handing out these "simple" reflectors to the legal Indon wooden fishing boats that were operating around Ashmore reef while the Navy were chasing the "other" wooden boat arrivals. They wanted to know where the legal boats were; presumably these reflectors worked
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Old 09-05-2014, 01:49   #6
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Re: Radar reflector

Yours appears to be the standard configuration for radar-reflecting pills. I wouldn't lose sleep over halyard issues.

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Old 09-05-2014, 04:09   #7
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Re: Radar reflector

I've already had the main halyard flip over the darn thing once. A moment's work to unflip it, and the halyard was very loose at the time, but when the proverbial pooh hits the air circulatory device I would rather that did not happen again.

If I am going to have something up there I would rather it rated a bit better than the device that is there currently.

Wotname, you are right, those flouro looking ones rated VERY poorly indeed in that test document. There was a funny looking three prong one that looked good, I will think of a way of mounting at the top of the mast out of the way.

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Old 09-05-2014, 06:25   #8
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Re: Radar reflector

We ended up using the tri-lense radar reflector. I think it was the mid size. Performance was good even if the mast was not perpendicular to the sea surface.

I would do some research on how high to mount it. 3 ft-lbs on the deck (one pound mass 3 ft off the water) is 45 ft-lbs on the top of a 45 foot mast
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Old 09-05-2014, 19:04   #9
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Re: Radar reflector

Quote:
Originally Posted by LakeSuperior View Post
We ended up using the tri-lense radar reflector. I think it was the mid size. Performance was good even if the mast was not perpendicular to the sea surface.

I would do some research on how high to mount it. 3 ft-lbs on the deck (one pound mass 3 ft off the water) is 45 ft-lbs on the top of a 45 foot mast
Thanks LakeSuperior, sounds like you got the same impression I did on that model. Much more return than many of the others, and much more tolerant of heel.

Good point about the momentum up on the mast too, though thankfully the S42 has a pretty conservative rig for the boat's displacement and beam, so I think the effect will be manageable.

Having seen a large ship bearing down on us at 4am on Bass Strait, and being unable to raise them on the radio, I would like to add to the visibility of the boat as much as practical. Not least of which was that the ship in question was absolutely NOT following the rules about where they are allowed to travel down there and was cutting a corner rather badly.

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Old 09-05-2014, 21:17   #10
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Re: Radar reflector

Re RADAR reflectors, visit this page:

Marine Accident Investigation: Ouzo

which has several documents related to the loss of the yacht OUZO in 2006, after a collision with a ferry.

Read the British Government report on RADAR reflectors that came out of this incident:

Marine Accidents Investigation: Download PDF document
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Old 09-05-2014, 21:54   #11
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Re: Radar reflector

I like them and trusted them over many yeang from rs in the English Channel which can be very foggy. we had occasion once to radio Ushant traffic control and ask for a visibility report as we we were approaching and wanting to transit the Chenal Du Four between ushant and the French mainland. they asked our approx position and when I told them they said we were clear on their land based radar at 15 miles range.

Anyone USA based andwanting to dispose of their Firdell Blipper, please mail it to me in Florida and I will happily refund the shipping costs.
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Old 09-05-2014, 22:00   #12
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Re: Radar reflector

Quote:
Originally Posted by GILow View Post
Thanks LakeSuperior, sounds like you got the same impression I did on that model. Much more return than many of the others, and much more tolerant of heel.

Good point about the momentum up on the mast too, though thankfully the S42 has a pretty conservative rig for the boat's displacement and beam, so I think the effect will be manageable.

Having seen a large ship bearing down on us at 4am on Bass Strait, and being unable to raise them on the radio, I would like to add to the visibility of the boat as much as practical. Not least of which was that the ship in question was absolutely NOT following the rules about where they are allowed to travel down there and was cutting a corner rather badly.

Matt
Hi, Matt,

No offense, but get over it.* Whatever makes you think they were maintaining radar watch? (They're more likely to in really bad weather.) Don't stake your safety on the imagined efficacy of others.


*Most of the ships with Australian personnel do follow the rules. Other flag vessels perhaps approximate it a bit. You just have to stay out of their way. I know this is not PC, and not Colregs until the very last moment, but at some point you have to quit being the Stand On vessel and get the heck out of the way. It makes a nice story for the off watch!

Ships no longer monitor VHF channel 16, as I understand it, although we pleasure craft are still supposed to. If the ship is near a port it wants to enter, they may use it to contact the Port Control, who usually take them off to Ch. 12, so that channel is a good one to try, also. Just understand they may or may not answer you. Even when you hail them by name.

Truly, you can't ever count on contacting any commercial vessel, includiing fishermen. The summer before last, a retired Admiral friend and his wife were sailing downwind on the east Australian coast, and were in line to be run down by a commercial vessel. The admiral took the ship's MMSI # off the AIS, and called it. This is supposed to set off an alarm on the ship, and ships' personnel are supposed to answer this call, but there was no answer. The admiral tried every way he could think of to contact the vessel, and nothing worked. He was not amused. And he got out of the way. But then he reported the incident to MRCC in Canberra, along with the GPS position and the time it had occurred. Eventually, he got a call back from Canberra, and the admiral had made a mistake with the local time of the incident. They had recently crossed from Qld to NSW, and had not yet reset their clocks. But Canberra still had figured out which the vessel had been, and the appropriate parties informed.

So if someone tries to run you down again, make sure you record your and their data, and record the time right [UTC is best], and someone will (at the very least) be upbraided, and maybe they'll ring you, too.

FYI, there's lots of information on the net about the Luneberg reflectors.

Ann
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Old 10-05-2014, 02:21   #13
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Re: Radar reflector

PBO ( UK ) did a comparison test years ago, the winner was a trash bag full of crumpled aluminium foil hauled up the mast !!

As for VHF 16 , ann, we have the same requirements as ships. All vessels must maintain a listening watch on ch 16 DSC equipped or not. Mandatory listening watch on MF was ceased some years ago.

Coast guard stations where equipped must maintain a listening watch on 16. But are not required to maintain a headphone watch , a speaker watch is now sufficient
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Old 10-05-2014, 02:59   #14
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Re: Radar reflector

I sail in the San Francisco estuary where ships have limited maneuverability/options. So, I stay out of their way. Here a ship (at the end of a 5300-mile cruse) is about to enter SF Bay from its viewpoint:

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Old 10-05-2014, 07:34   #15
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Re: Radar reflector

not wishing to denigrate laboratory tests of reflectors, but testing them in practical conditions is obviously very difficult. For what it is worth, my opinion is that consistency of return is required since i believe the ARPA systems will only recognise a target that is consistent so as to avoid being sidetracked by a single spurious echo from a wavetop or seagull. Firdell blippers may not present the highest reflective area but do present what are they have at varying angles of heel, as in the practical case of a sailboat under sail at sea. Inside a Blipper case is a multicorner array ( I saw one opened up) like a series of joined up octahedral reflectors, not huge, but multiples of them at different angles to a potential incoming signal. I think even a weaker return but one that consistantly appears in the same position to a searching radar beam will trigger the radar to see it as a potential problem and flag it on the screen as an ARPA target.
Note that my comments apply to Firdell Blipper types ( Echosafe is another similar) and not to the silly "Mobri' tube ones often seen wrongly mounted laying flat along a spreader on a sailboat, these have miniscule reflective area and as said are frequently mounted wrong anyway ( as indeed are the octahedral types that should be in the 'catch rain' position and certainly not point up as is the easiest option adopted by many)

Like I said, a personal opinion from someone who has used them for many years in foggy locations with heavy shipping traffic. We also had, indeed still have and, importantly, know how to use our own radar for collision avoidance, even before our current set which has a MARPA system and displays AIS targets also overlaid on the radar screen.

Standing by for incoming....
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