Radar Reflectors. Homemade DIY or purchase

[WASP18]

I removed the mast and we'll be in a MacTrawler mode for the rest of the season. For this reason, I built a radar reflector using aluminum flashing as material. We'll be cruising an area not far from a shipping lane (or channel). After reading up on the subject, a fiberglass boat is stealth-like unless there are metal surfaces like a tall aluminum mast. Yet a mast may not show up on a ship's (or yacht's) radar return. For a white "steaming" light, I mounted a three foot vinyl fence post where the mast would go. The radar reflector will slip over this stubby mast. I fabricated and mounted a bunch of aluminum triangles (flashing material) perpendicular to each other to a plastic wastebasket purchased from the Dollar Store. Cut a hole in the bottom of the basket where it will slip over the vinyl mast. Cost of materials was $14.95 for flashing and $1.00 for the waste basket. I also used aluminum tape to connect the triangles.
Here's a study at U Maine on the reflector subject related to kayaks.
http://www.seagrant.umaine.edu/files/pd ... refppt.pdf

[kadet]

I read an article awhile ago in one of the cruising magazines that did a comparative test on a bunch of passive radar reflectors. Conclusion was they are a waste of money as they do little to improve a yachts radar return, a dinghy outboard mounted on the rail often was a better reflector than most of the commercial units tested. The only systems recommended were active reflectors that transmitted a return electronically.

Not having a mast your plan maybe better than nothing then again it may be just as bad as having nothing. If it is that much of a concern to warrant the effort building a reflector why not get an active reflector, or an AIS transponder for half the cost, what is your life and boat worth?

[WASP18]

I read an article awhile ago in one of the cruising magazines that did a comparative test on a bunch of passive radar reflectors. Conclusion was they are a waste of money as they do little to improve a yachts radar return, a dinghy outboard mounted on the rail often was a better reflector than most of the commercial units tested. The only systems recommended were active reflectors that transmitted a return electronically.

Not having a mast your plan maybe better than nothing then again it may be just as bad as having nothing. If it is that much of a concern to warrant the effort building a reflector why not get an active reflector, or an AIS transponder for half the cost, what is your life and boat worth?

It has been said that radar reflectors are like a religion, the more you believe in them the better they work.

Did you read the U.Maine test results?

[Divecoz]

If you can copy cut and paste that test Wasp.. I too have read test reports saying passive reflectors add little " visability " ... It " seems" to me like another industry manufactured from nothing , so to speak.. Radar , Lightening Protection, Radon etc etc

[Whipsyjac]

I just clicked on the link and its more of a pdf of a power point slide show than a text report so I doubt it can be copied and pasted into a forum post.

It was very interesting but I didn't find it completely helpful. Apparently a homemade tinfoil hat thingy(no description of build process just one picture) gives the most consistently strong results over distance. The second place for distance seemed to be a flag on a pole(no mention of any metallics in it).

I agree with the post that if you want to be visible go AIS. We learned about it in our radio class, there are dozens of free apps for iPhone and Android to let you see vessels. You could be transmitting AIS which is a legal requirement for commercial vessels for a few hundred dollars, and you don't have to wear a foil hat!

Willy

[JohnCFI]

Which is all very well, except in my opinion, the greatest danger comes from those unlikely to understand or use either AIS or Radar..

[WASP18]

If you can copy cut and paste that test Wasp.. I too have read test reports saying passive reflectors add little " visability " ... It " seems" to me like another industry manufactured from nothing , so to speak.. Radar , Lightening Protection, Radon etc etc

Link http://www.seagrant.umaine.edu/newsroom ... s/20050524

Here's an excerpt from this link which is a press release:

"The most important discovery was that kayaks one mile from the radar platform are rarely visible on radar, whether or not they have radar reflectors. However, results changed under a mile where the presence or absence of a radar reflector mounted on the kayak or kayaker made a difference. Considering that a motorboat traveling at 15 knots covers one-quarter nautical mile in 60 seconds, this may make the difference between boater safety and an accident."

The foil hat had the best results according to the testers. The height and shape of the hat made the difference. My contraption actually (and coincidentally) fits on my head. It also has sharp angles, is larger and bulkier, and could be a hazard which is a problem for a kayak according to the study, but not a problem sitting on the stubby mast of my X. kayaks are as low (and below) as a wavy ocean surface. They are part of the clutter shown on the screen and yet are detected under a mile from the radar. Once I get on the water, I'll see if I can get pinged by my boating friends at the club. I'll then report back with the results.

[WASP18]

Here's a link to the complete report.
http://www.seagrant.umaine.edu/files/pd ... 5raref.pdf

[kadet]

A kayak is very different from a boat such as a Mac or other GRP yacht it is close to the sea and has very little other reflective properties so in this case a reflector would be an improvement.

From the yachting monthly report.

Interference is a fundamental problem with radar reflectors. Most objects will reflect radar waves in some way. The sea itself has good reflective properties. A boat is made up of a multitude of reflectors – from engine, to stanchions to the cooker (neither GRP nor aluminium masts tend to give consistent echoes) – all of which can disturb the path of a radar pulse. Putting a reflector near other sources of reflection (ie. the boat) therefore induces interference – which can unfortunately be either positive or negative

As I said if you believe that your home-made reflector helps and is all that is needed by all means install it, you are the captain it is your choice. Personally I would want an AIS transmitter so the big boys see me, know my course & speed and name so they can call me on VHF if necessary and I can see them etc.. My point is if you are concerned enough in the first place to go to this effort then there is obviously some risk you are trying to mitigate so it is a risk management decision you must make. I looked long and hard into this awhile ago and decided on neither as we don't have fog, the shipping channel here although busy is easily navigated to keep out of the way of the commercial shipping, and I don't go out in bad weather and the risk did not justify the expense for AIS which I concluded was the best option after looking into the alternatives. You may decide something else, I was just trying to point out that your home-made reflector may not operate as intended.

[WASP18]

A kayak is very different from a boat such as a Mac or other GRP yacht it is close to the sea and has very little other reflective properties so in this case a reflector would be an improvement.

From the yachting monthly report.

Interference is a fundamental problem with radar reflectors. Most objects will reflect radar waves in some way. The sea itself has good reflective properties. A boat is made up of a multitude of reflectors – from engine, to stanchions to the cooker (neither GRP nor aluminium masts tend to give consistent echoes) – all of which can disturb the path of a radar pulse. Putting a reflector near other sources of reflection (ie. the boat) therefore induces interference – which can unfortunately be either positive or negative

As I said if you believe that your home-made reflector helps and is all that is needed by all means install it, you are the captain it is your choice. Personally I would want an AIS transmitter so the big boys see me, know my course & speed and name so they can call me on VHF if necessary and I can see them etc.. My point is if you are concerned enough in the first place to go to this effort then there is obviously some risk you are trying to mitigate so it is a risk management decision you must make. I looked long and hard into this awhile ago and decided on neither as we don't have fog, the shipping channel here although busy is easily navigated to keep out of the way of the commercial shipping, and I don't go out in bad weather and the risk did not justify the expense for AIS which I concluded was the best option after looking into the alternatives. You may decide something else, I was just trying to point out that your home-made reflector may not operate as intended.

Your lecturing tone would be applicable to one who is foolishly operating within a busy traffic area at a major seaport. Sort of like a Piper Cub mixed in with jumbo airliners and exposing oneself to severe wake turbulence in addition to a potential mid-air collision. This is not the case and I'm not foolish. My operating area is similar to yours, and in most cases, we'll be out of the main shipping channel and would cross it only if the WX conditions are VFR so to speak.

I'm well aware of the AIS benefits and the engineering concept upon which it is based. The concept is quite similar but not the same as an interrogator/transponder system, IFF (identification friend or foe WW II design) or CAS (Collision Avoidance System) on board most commercial aircraft operating IFR, yet it produces the desired results of identification with precision. Ironically, pilots call the CAS a "Fishfinder".

Fabricating my ugly $15.00 contraption and testing it under ideal conditions with boating friends is certainly not a risk. If it proves successful in a limited way, and I expect it might, I would not place my life in jeopardy by cruising around and mixing it up with the big guys. If we eventually find ourselves cruising more often under conditions that would cry out for more safety with a AIS, then we'll buy one. Meanwhile, we expect to have fun in discovering whether this miniature aluminum train wreck mounted on my stubby mast actually works.

[kmclemore]

!	kmclemore:
	Guys, can we just cool it a bit here? Remember, this is supposed to be about helping each other as fellow sailors. Please don't make me start deleting crap and sending emails... I'm tired and not really in the mood..

[mastreb]

At the risk of wading into a topic that's got people's ire up for various reasons, I was an electronic warfare technician in the Navy whose job was to create both real and artificial radar reflections for the purposes of obscuring or revealing ship's position.

The problem with all purpose-built radar reflectors is that they're optimized for specific radar frequencies, for exactly the same reason that antenna lengths are optimized for different frequencies: Full, half, and quarter wave sized reflectors are much "brighter" than non-harmonic sizes. Reflectors that are smaller than an actual boat rely upon that principle to appear much "brighter" than an object of that size normally would. I've been involved in testing reflectors the size of a MacGregor that show up as large as a 500-foot warship to specific radar seekers (homers, actually).

Commercial radars typically operate in the I and C bands (9GHz and 3GHz) but new bands have been released for commercial use by the military (E band) and new radars are being built in that frequency range. Very larger ships may use radars operating as far down as 900MHz.

No single reflector is going to reflect all of these frequencies equally well. A reflector sized for I band is going to be invisible to C and E band radars, for example, and the problem is that you really don't know what radars all the ships around you are using. While it's generally true that larger ships operate multiple radars, and that most commercial ships operate an I-band navigation radar, you simply never know how a reflector is actually going to appear to every different ship in the harbor. Navy vessels, for example, rarely use an I-band when entering or leaving port--they're far more likely to be operating an E-band radar for navigation.

I believe the problem is intractable enough not to bother with. AIS will be seen by any ship large enough to accidentally not see you, and yahoos in stink-pots doing 40 knots aren't looking at their radar (or anything else) as they go.

Just my two cents as someone whose job it used to be.

[Ormonddude]

With results like this - I have made up my mind its FOIL HAT TIME! but seriously my PO installed a Davis 152 I am leaving there simply because it strikes up a lot of conversations from people wondering what the hull it is and i now have new found respect for the foil hat guy that hangs around town looking like a loony We need a foil hat smiley

[kadet]

I We'll be cruising an area not far from a shipping lane (or channel). After reading up on the subject, a fiberglass boat is stealth-like unless there are metal surfaces like a tall aluminum mast. Yet a mast may not show up on a ship's (or yacht's) radar return.

Sorry if I misread this but it sounded like you were wanting to alleviate a risk, and you were making some wrong assumptions about GRP yachts from my own research. I did not ever say you were foolish nor intend for that to be insinuated, you seem to have a handle on what you want to do, you are going to test, so good luck to you. I thought you were asking a genuine question and wanted advice on what we as members of this group thought of homemade reflectors. As I had done some research in this area I thought I was providing information to you to be helpful which is why I am on this forum, to give and receive advice from fellow sailors. I also work in the electronics and technology field so maybe biased towards AIS.

Nough Said

[Hamin' X]

!

Moderator Note:

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Discussion Board Policies and Expectations
Postby Heath » Thu Feb 09, 2006 8:17 pm

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