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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #1  
Old 02-16-2014
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Radar signature

Reviews of commercially available passive radar reflectors reveal that they are of limited utility.

Sometime in the past on a website or blog I can't recall...someone mentioned packing their mast with aluminum foil to improve their radar signature. The site or blog reported that subsequently they asked commercial ships of opportunity to evaluate their radar return and the reports were very positive...a return greatly in excess of what the commercial shipping normally saw from small sailboats.

Does anyone have any experience with this method of improving radar signature of your boat or do you have another method that you have found to be highly effective?

Also if you have an active system that is effective with low power consumption and small size that you think would be suitable for a 25-35 foot sailboat would you please comment on your experience with it?

Thanks.
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Old 02-16-2014
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Re: Radar signature

If your mast is aluminum or carbon fiber, packing it with foil will accomplish nothing except possibly corrosion.
Every test I have seen of the corner reflector type reflector puts it in the correct orientation and then assumes it will NOT stay in that orientation as the boat heels. As she heels the reflected intensity drops a lot. WHY not weight it so it always stays in the correct "catch rain" position then heeling does not matter?
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Old 02-16-2014
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Re: Radar signature

The purpose of the radar deflectors is to break up the signal to create a larger signature upon it's return. Stuffing a mast full of foil will accomplish nothing.
Now......If you wish to tie mylar or aluminum to your mast and shrouds in long streams; this will increase your radar signature dramatically.
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Old 02-16-2014
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Re: Radar signature

Quote:
The purpose of the radar deflectors is to break up the signal to create a larger signature upon it's return
I might be off on that comment. After some thought it may be that the reflectors are oreinted to reflect from all points of sail. That sounds better.
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Old 02-16-2014
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Re: Radar signature

Tin foil in your hub caps!!!!...Dale
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Old 02-16-2014
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Re: Radar signature

Weight aloft is a concern on my now smaller vessel, but on the old Tripp 45 I had a Davis ball type mounted permanently on the mast head with a piece of stainless all-thread. Wet sails absorb radar frequencies wonderfully, so if your reflector is behind a wet jib it is essentially useless. 1 pound aloft never had any noticeable effect on the boat, and if we checked with a big ship on the horizon, they always reported a good return. Looks weird, but effective. That assumes anyone is watching the radar on the heavy's bridge.
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Old 02-18-2014
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Re: Radar signature

I have a vague recollection of somebody (the Pardeys?) stuffing a hollow wooden mast with foil and having good reports on its signal return. If it wasn't them I apologize.
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Old 02-19-2014
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Re: Radar signature

Quote:
Originally Posted by fryewe View Post
Also if you have an active system that is effective with low power consumption and small size that you think would be suitable for a 25-35 foot sailboat would you please comment on your experience with it?
Passive reflectors are completely dependent of sector angles, polarization, unobstructed path, etc. They offer a slight chance your boat will be briefly more visible on a ship's radar screen, if anyone is watching closely at that moment & able to distinguish your (still) small blip from background noise. I'm also annoyed the Davis-style reflectors look exactly like a day shape for anchored vessels.

I like the idea of an active detector/transmitter device. They use very little power in passive mode. When triggered by a ship's radar, they send back an amplified signal at the same frequency that makes your little boat look like the QE2 on their screen. Might even set off audible alarms on their bridge. And maybe more importantly, it can be set to sound an alarm on your boat -- so you know you've been painted by someone's radar. Expecting a container ship to 1) see you and 2) miss you is perhaps a bit much to expect.

Downsides to the active systems (Sea-Me, EchoMax) include complexity, cost (around $800 USD for a dual band unit), and some dark sectors -- similar to passive devices. Radar & radar reflectors are a difficult issue for sailboats, and I suspect which solution works for you will have a lot to do with your personal comfort level and where you sail. Foggy areas with lots of ship traffic, probably want every radar-based tool (plus AIS) you can think of. Sea of Cortez, not so much.
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Old 02-19-2014
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Re: Radar signature

I thought I had read an article recently that compared several radar reflector types, including one or a couple active reflectors. Now it's approaching "buy stuff for the boat" season and this year I have the mast down so I was going to revisit that article to see which system, if any, I want to get.

I thought I had read this in Practical Sailor but I can't seem to find the issue. A search on their web site produced nothing. So I'm assuming it was in another magazine that I read. Could be Cruising World, Sail, Good Old Boat, or less likely, Cruisers Outpost.

Does anyone have any idea which magazine published this article? It would have likely been in the past year, but for the life of me I can't find it.
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Old 02-19-2014
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Re: Radar signature

Everything I've ever read says the old school intersecting disks set in the catch rain position is the best passive reflector. Set up a pulley system to a spreader, so it's easily raised and lowered.

Hard to say what experience we've had with it, as we've never seen ourselves on another's radar. I suppose what I rely on more is to see them with our onboard radar, but that's a much more significant investment.
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