Radar Reflector Placement

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  • 06 Aug 2019 17:40
    Reply # 7814581 on 7789361
    Anonymous member (Administrator)

    If you go for AIS where I live, it's really worthwhile to include transmit. A lot of the commercial fishermen have AIS, but they turn off the transmitting – so you won't know about them, and they won't know about you unless you have transmit on…

    Shemaya

  • 06 Aug 2019 16:24
    Reply # 7814315 on 7789361

    AIS seems like a no-brainer.  AIS type B transceiver by Raymarine E32158 (about $1K USD on Amazon) consumes only 3 watts..... screen not included.  Some folks are satisfied with a receiver only, but a transceiver means two sets of eyes working for you.... you see them, and/or they see you.   The likelihood of being seen on AIS is many times greater than on radar.   This is a far better safety value per dollar than a life raft.....  There are units at as little as 1/3 the price.... I just chose this one because the specs were easily available.

          I love the idea of foil in the top of the wooden mast.  The crinkled up foil in a bag is a brilliant idea!   The multiple facets it provides should be very effective...... Cheap and simple, hoisted on a spare halyard, probably better than a factory reflector!

    Last modified: 06 Aug 2019 16:30 | Anonymous member
  • 24 Jul 2019 14:49
    Reply # 7794733 on 7794486
    Shemaya wrote:

    Hi David,

    I've been thinking quite a bit about what you said about the height of the radar reflector. I also use a radar detector – used to have a CARD, now have a MerVeille – and I know what you mean about the height of the antenna for those, and receiving useless distant signals if the antenna is too high. But for folks using radar, whatever return signal they are receiving is shown on the screen, including its distance from the vessel with the radar. So if they are only interested in traffic in the nearest 5 miles, they can simply focus on that range on the screen.

    Because of this, it seems to me that the radar reflector should be high, to have the best chance of not being filtered out by the "squelch" adjustment for sea clutter on the radar. Considering the experience I had with the whale watch boat, I would say that my reflector, at about 4 meters height, really is not high enough to be ideal. It's certainly better than nothing, but if somebody has the option of easily carrying one higher, that would seem better. Or am I missing something?

    Great thought about studying the Lake Michigan traffic by AIS on the computer ahead of time. Isn't it extraordinary what's available these days.

    Shemaya

    Well, that raises another matter: a radar operator needs training, experience and practice to adjust the set correctly and to interpret what's on the screen correctly. Your whalewatcher hadn't set the controls for sea state correctly, I'm thinking? A mariner with a Mate's ticket should be better, but even so, there's plenty to distract him and to occupy his time on the bridge.

    For this reason, personally I prefer to take the initiative away from the radar operator, where possible, and oversee my own fate by using an AIS receiver to assess the risk and take action if necessary.

  • 24 Jul 2019 12:11
    Reply # 7794546 on 7789361
    Anonymous member (Administrator)

    I am not so sure about that, Shemaya. If your radar reflector was well above waveheight at that occasion, it most certainly produced as good echo as it would have done if moved even higher up. It is just that the echo from the wave-crests will be so dominating on the screen, so active use of the clutter control is necessary to (hopefully) spot that radar reflector above the clutter.

    Arne


  • 24 Jul 2019 12:02
    Reply # 7794545 on 7789361

    I have found that when sailing offshore during the day there may be no other vessels visible, but when darkness comes other vessels' lights appear ie vessels that are invisible by day become visible at night.  And because of the arrangement of their lights, it may be easier to work out their track relative to yours.  And presumably the converse applies, ie at night your vessel may be easier to spot and to interpret.  Win, win.  ie "Hello darkness, my old friend ... "  

    And this may reinforce a general plan:  daylight for for departure and arrival with the length of a passage overnight. 

    (Bonus.  I have a sparkling memory of sailing down a ribbon of moonlight hundreds of miles offshore, totally alone except for accompanying dolphins ... "Magic Moments".) 



  • 24 Jul 2019 11:16
    Reply # 7794486 on 7789361

    Hi David,

    I've been thinking quite a bit about what you said about the height of the radar reflector. I also use a radar detector – used to have a CARD, now have a MerVeille – and I know what you mean about the height of the antenna for those, and receiving useless distant signals if the antenna is too high. But for folks using radar, whatever return signal they are receiving is shown on the screen, including its distance from the vessel with the radar. So if they are only interested in traffic in the nearest 5 miles, they can simply focus on that range on the screen.

    Because of this, it seems to me that the radar reflector should be high, to have the best chance of not being filtered out by the "squelch" adjustment for sea clutter on the radar. Considering the experience I had with the whale watch boat, I would say that my reflector, at about 4 meters height, really is not high enough to be ideal. It's certainly better than nothing, but if somebody has the option of easily carrying one higher, that would seem better. Or am I missing something?

    Great thought about studying the Lake Michigan traffic by AIS on the computer ahead of time. Isn't it extraordinary what's available these days.

    Shemaya

  • 24 Jul 2019 07:24
    Reply # 7794334 on 7793207
    Shemaya wrote:

    Hi Scott,

    At a bare minimum, I would add some kind of radar reflector to your minimal-version list. Could be anything, except maybe not the skinny cylinders that don't test very well. Arne's tinfoil in a bag would do the trick. It's amazing how fast those big ships come up – even when keeping a good lookout. Nice to have something that gives them a hand with seeing you.

    I'm guessing that there are higher traffic routes and lower traffic routes for crossing the lake? And areas where you know you have to particularly watch out for north-south shipping traffic. Doing those sections in daytime would help…

    Shemaya

    Scott,

    I agree with that. Your first line of defence is the largest Echomax inflatable reflector, 230I, hoisted when needed, and in our size of boat, I'd arrange a halyard to a point halfway up the mast lift so that it's something like 3 - 5 metres above the water. An AIS receiver would be next, but a higher budget would be needed.

    Have you got a ship-watching AIS app on your computer? It would be a good way of establishing the patterns of traffic where you are. Looking at the MarineTraffic app right now, when it's the middle of the night in Michigan, I see a dozen freighters on north/south passages, along with one ro-ro ferry and two large power yachts. No fishermen or other leisure craft. I suggest that this will be the scenario when you cross, as it's an 80 mile passage and you want to set off and arrive in daylight. It's similar to the English Channel crossing from the Solent to Cherbourg in that way. It's when you're near the coast that you're at greatest risk, as there are likely to be more vessels behaving unpredictably, so that's best done in daylight.  In the middle of Lake Michigan, on a clear night, freighters will be keeping a steady course and speed, and they'll be manned by skilled professionals who are used to avoiding crossing traffic. I'd rather be there than driving along a busy highway amongst a mix of big trucks and cars with drivers of all levels of skill.

    Last modified: 24 Jul 2019 07:27 | Anonymous member
  • 23 Jul 2019 23:23
    Reply # 7793222 on 7789361
    Anonymous member (Administrator)

    I am glad to hear that the foil inside the wooden mast works, David.

    On the dug-out hollow masts of Malena (1995) and Johanna (2002?) I did exactly that, just after having coated the mast halves inside with epoxy resin, and just before closing the masts. I never got around to check with the ferry crews if they could see us, but I was pretty confident that it would work. I added the foil from deck level to mast top.

    (I also recommend doing this in the Chapter 6 of ‘The Cambered Panel Junk Rig’, TCPJR)

    Arne


  • 23 Jul 2019 23:07
    Reply # 7793212 on 7789361

    For those thinking of building a hollow wood mast then installing aluminium foil, crinkled up and glued in place, in the top three meters of the mast, produces an excellent radar reflector. This also applies to aluminium masts with a wooden top mast. The Pardey's did this on Serrafyn and Taliesin and reported excellent feedback  from commercial and other sailors on the strong signal return, often being told that they looked like a 200 foot freighter on the radar screen.

  • 23 Jul 2019 23:03
    Reply # 7793207 on 7789361

    Hi Scott,

    At a bare minimum, I would add some kind of radar reflector to your minimal-version list. Could be anything, except maybe not the skinny cylinders that don't test very well. Arne's tinfoil in a bag would do the trick. It's amazing how fast those big ships come up – even when keeping a good lookout. Nice to have something that gives them a hand with seeing you.

    I'm guessing that there are higher traffic routes and lower traffic routes for crossing the lake? And areas where you know you have to particularly watch out for north-south shipping traffic. Doing those sections in daytime would help…

    Shemaya

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