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Old 09-11-2005, 08:44 PM   #1 (permalink)
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Radar Absorbing Paint?

Not electrical, but all the other radar discussion has been in this group...

I've read here that the fiberglass is invisible to radar. It goes through the fiberglass and reflects off the aluminum frame structure. Can I coat the frame with a compound that eliminates/attenuates the radar reflecting back to the radar gun? Does such a compount exist? Does this idea have any potential? (Obligitory - How much does it weigh?)
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Old 09-11-2005, 08:48 PM   #2 (permalink)
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This time the 'How much does it weigh?' is a good question. Any paint that would actually work to absorb RADAR would be very heavy (and very expensive).
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Old 09-12-2005, 06:35 AM   #3 (permalink)
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fiberglass is fairly radar transparent, but this declines from source to point a bit. the ideal material to absorb radar behind the fiberglass skin radar point(o.k. the Elise is not 'really' fiberglass, i know) would be an RF absorobing matrix, and not a radar limiting "paint" - that would be better used on the skin. so behind the skin you would want, in simple terms, "that cool trainangle cone foam Rf absorbing stuff" and there is probably not enough room to mount it, and if there were, there is probably too many other components around it to make it effective - the elise as "car" has too many surfaces to make sanitary, but i suppose every little bit helps? a good detector would be WAY cheaper, than trying to sanatize the signature.
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Old 09-12-2005, 09:36 AM   #4 (permalink)
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To add to fitfan's comments, yes, you could coat the underside of the body a with radar absorb/attenuating coating. However, to get something that works, you would have to spend a lot of money. You'd also need a pretty high security clearances, and have a "need to know"...


There is a reason that the US's stealth aircraft cost so much, and it not just profit for the greedy corporations that make them. A good radar detector and defensive driving would probably be much more cost effective.

But we can always dream can't we...
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Old 09-12-2005, 09:45 AM   #5 (permalink)
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Just install angled sheet aluminum reflectors. Like 10 dollars worth from the hardware store.

Olders Corvettes, C3s, early 80s and older were tested for radar range by one of the magazines long ago. Radar could not pick them up very well from the front. Well they use a laid back radiator...when radar would hit the front of the car it would reflect skywards! You could do use the same concept on the Elise, front and rear, to a degree.
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Old 09-12-2005, 09:47 AM   #6 (permalink)
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Did you guys see the radar Mythbuster's just recently? Nothing helped.

You really need shape. The F-117 cross section is actually the size of a 3/8" ball bearing, and it is almost all shape, not paint.
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Old 09-12-2005, 10:23 AM   #7 (permalink)
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Quote:
Originally Posted by TimMullen
To add to fitfan's comments, yes, you could coat the underside of the body a with radar absorb/attenuating coating. However, to get something that works, you would have to spend a lot of money. You'd also need a pretty high security clearances, and have a "need to know"...


There is a reason that the US's stealth aircraft cost so much, and it not just profit for the greedy corporations that make them. A good radar detector and defensive driving would probably be much more cost effective.

But we can always dream can't we...
stealth aircraft costs are high because no production techniques existed at the time to make RAM's. there is plenty of info available to the public on just what techniques are needed to divert radar energy and what materials do a good job of absorbing them. all it takes is perserverance and the ability to do objective testing of candidate materials until one is found that works well.

it is ALOT more difficult to defeat airborne radar than a standard police radar gun.thats why stealth costs so much for airplanes. as stans post explains, all it takes is a few dollars worth of aluminum and some ingenuity to apply the principal of surface faceting to divert substancial percentage of radar energy skyward.
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Old 09-12-2005, 11:18 AM   #8 (permalink)
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Originally Posted by rob13572468
there is plenty of info available to the public on just what techniques are needed to divert radar energy and what materials do a good job of absorbing them. all it takes is perseverance and the ability to do objective testing of candidate materials until one is found that works well.
There are a couple of problems with attempting to defeat radar. Many of the radar absorbent coatings that are available work very well at specific frequencies. They may not work at all at other frequencies. I don't know if the various police radar frequencies are close enough together or not for this to help or hurt. Other methods include a "wire" mesh of specific spacing, again frequency dependent. The "paint" coatings that absorb "everything" tend to be very expensive.

Building deflector shields can be effective, but can also be difficult given the confines of the structure of the car, and one wrong angle, and you may generate a radar reflector, returning a stronger signal than nothing at all.

Additionally, for a project I worked on many years ago, you may have problems with things you wouldn't even think about, such as tires.

In particular, I once worked on a project that was attempting to combine AI with a scanning Doppler radar for remote site security. The idea was to scan the approach to the site and attempt to identify what was approaching it. I say this, because one of the test "objects" was a rider on a three wheel ATV. The radar passed right through the fenders of the ATV and reflected back off the tires. The ATV approached the radar at about 20 MPH. As the radar scanned left to right, it detected an area of Doppler shift at 40 MPH, a large area of 27 MPH, and another area of 40MPH. In each area, it was recording the highest approaching speed. What it was seeing was the top of one of the rear tires (it's approach speed was 40), the rider/ATV/front tire (although the tire was coming at 40, the rest was coming at 20, so it averaged to around 27 or so), and finally the other rear tire at 40. The results were confusing at first until we figured out what was going on.

This was all in contrast to the jeep that was recorded at a constant 20 MPH over it's profile, since the wheels were covered by sheet metal.

Bottom line? You can probably make the Elise invisible to radar. It will cost you a lot. It will take a lot of work. You will need the right equipment, and knowledge to design, implement, and most importantly test whatever you design. Then Ladar would probably still work on your car anyway, as will timing from the sky, and Vascar units.

But if anyone ever gets a cheap source of radar absorbing paint for the inside of the clam, I'm in for a group buy.
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Old 09-12-2005, 01:17 PM   #9 (permalink)
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I got some foam.... i am not saying how or why, just that i got some....

I only know enough on this subject to know that Tim knows what hes talking about!
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Old 09-12-2005, 01:39 PM   #10 (permalink)
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Quote:
Originally Posted by fitfan
I only know enough on this subject to know that Tim knows what hes talking about!
And I only know enough to know that it's much more complicated than it would appear (pun intended). And much more expensive than I'd like...
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Old 09-13-2005, 06:04 PM   #11 (permalink)
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I saw something on TV the other day about the Stealh bomber and radar evasion and it said that some color paints work better against radar, but metallic paints work worst since the radar can pick up the metal in the paint.
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Old 09-14-2005, 09:50 AM   #12 (permalink)
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Quote:
Originally Posted by TimMullen
There are a couple of problems with attempting to defeat radar. Many of the radar absorbent coatings that are available work very well at specific frequencies. They may not work at all at other frequencies. I don't know if the various police radar frequencies are close enough together or not for this to help or hurt. Other methods include a "wire" mesh of specific spacing, again frequency dependent. The "paint" coatings that absorb "everything" tend to be very expensive.

Building deflector shields can be effective, but can also be difficult given the confines of the structure of the car, and one wrong angle, and you may generate a radar reflector, returning a stronger signal than nothing at all.

Additionally, for a project I worked on many years ago, you may have problems with things you wouldn't even think about, such as tires.

In particular, I once worked on a project that was attempting to combine AI with a scanning Doppler radar for remote site security. The idea was to scan the approach to the site and attempt to identify what was approaching it. I say this, because one of the test "objects" was a rider on a three wheel ATV. The radar passed right through the fenders of the ATV and reflected back off the tires. The ATV approached the radar at about 20 MPH. As the radar scanned left to right, it detected an area of Doppler shift at 40 MPH, a large area of 27 MPH, and another area of 40MPH. In each area, it was recording the highest approaching speed. What it was seeing was the top of one of the rear tires (it's approach speed was 40), the rider/ATV/front tire (although the tire was coming at 40, the rest was coming at 20, so it averaged to around 27 or so), and finally the other rear tire at 40. The results were confusing at first until we figured out what was going on.

This was all in contrast to the jeep that was recorded at a constant 20 MPH over it's profile, since the wheels were covered by sheet metal.

Bottom line? You can probably make the Elise invisible to radar. It will cost you a lot. It will take a lot of work. You will need the right equipment, and knowledge to design, implement, and most importantly test whatever you design. Then Ladar would probably still work on your car anyway, as will timing from the sky, and Vascar units.

But if anyone ever gets a cheap source of radar absorbing paint for the inside of the clam, I'm in for a group buy.

by all means i agree that this would not be an easy task. it is doable and and it can be done without necessarily spending alot of money. you are correct that the ram's have specific ranges of frequency absorption; there is no one magic material that will attenuate all frequencies but the are a few candidate materials that have decent absorption characteristics in the gigahertz range and would cover all of the bands currently in use.

the biggest issue with the current radar absorbing coatings that are sold (besides the fact that they are insanely overpriced for what they are) is that the sales pitch is always a one-method-fits-all approach. the problem with this is that every vehicle is different and must be individually assessed as to what techniques and materials will be used, and if they will even work. as you pointed out, some vehicles will simply be very reflective and may never be very "stealthy"...

for those that are interested, 99% of radar absorbing paints and/or materials use iron ferrite, a very common and inexpensive material. the process typically involves impregnating the coating or surface material itself with tiny (10-100 micrometer) beads of iron ferrite. the size can be tailored to provide better attenuation over a particular range of frequencies. The coatings function based on the principal that an electromagnetic field is a component of the propogating (radar) microwave and will collapse into a properly tuned ferrite core and be converted to heat. ideally a coating applied to the inside of the clams could *theoretically* work very well and the material itself can be purchased or even homemade with some basic knowledge of chemistry.

of course none of this solves the main problems that cause most of the radar reflectivity; the biggest culprits are the front radiator grille openings, the wheel wells, and the vehicle windows. on the f117 and b2 the cockpit glass is coated with gold to make the surface continuously reflective; what would happen is the radar waves would pass through the glass and then reflect off of the interior panels and the coating solved it. ideally the same technique would be needed for the elise, possibly using some of the newer metallic spray tints. the radiator and wheel wells are more difficult, possibly requiring some sort of fine metal mesh grilles to be placed over the intake openings to keep the surface contour continuous. the elise really does have a very "stealthy " shape to begin with and i would bet that stock it is already much more difficult to detect as there are so few surfaces that are negatively reflective. the big question is whether the painted clams are reflective or transparent to radar. a highly reflective surface may actually be very desirable as the shape of the clam will act to scatter the radiation rather than reflect it back as a return signature.

once again, its really just a matter of doing alot of very careful and controlled testing. the only equipment needed is newer radar gun with a signal strength meter so that quantitative readings can be taken . then its just checking different color paints, coatings and materials to determine what will work best in a practical sense. i wouldnt be surprised if a $100 worth of materials can achieve a huge reduction in radar cross section. its just knowing what to use and where to use it...
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Old 10-05-2005, 07:14 AM   #13 (permalink)
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I think that an Elise starts out pretty stealthy due to it's low proflie, almost no vertical surfaces in front (especially without front liscence plate) and fiberglass constuction. Problem is you will invariably pick up an SUV that wants to use you as his front door. Cop picks him up on his radar first, who do you think is going to get the ticket? That's why I try to avoid leading the parade of speeders.
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Old 10-05-2005, 07:23 AM   #14 (permalink)
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Well on top gear the apache hellicopter had a hell of a time getting radar lock on the exige at close range, I guess that is somthing...

It would be neat to make a stealth car, but It will always give some kind of signature if the gun is pointed in the right way, on the right day, from the right cop.
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Old 10-05-2005, 07:29 AM   #15 (permalink)
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The apache helicopter had trouble locking when restricted to the track, once at distance it had no trouble at all.

Speed measuring signs have to trouble picking up my car either. The only thing on our advantage is that it will be harder to aim at our car if the beam is narrow, but I wouldn't know about that.
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Old 10-05-2005, 11:48 AM   #16 (permalink)
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The apache helicopter had trouble locking when restricted to the track, once at distance it had no trouble at all.

Speed measuring signs have to trouble picking up my car either.
I had an interesting experience with this last week. I was accelerating away from a stop sign and noticed one of those roadside speed monitor signs . I was about half way between the stop sign behind me and the speed sign when I first saw it. I was going about 45 mph at the time, but the sign was slowly advancing 23, 24, 25. As I got almost on top of the sign, it jumped from 26 to 46 (50 indicated). As I was wondering what's up with that, I noticed a Lexus GS 470 about 10-12 car lengths behind me also accelerating away from the stop sign. The roadside radar was locked onto the Lexus until I was right on top of it!
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Old 10-05-2005, 01:33 PM   #17 (permalink)
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As a retired member of 'the skunk works' I feel that
Randy should get off his duff and design some stealthy
(anti-radar) panels that can be easily affixed to our
cars. With all due respect, after the Saffron Yellow
fiasco he hasn't been the same with regard to janitorial
control of this site.
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Old 10-05-2005, 01:52 PM   #18 (permalink)
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The roadside radar was locked onto the Lexus until I was right on top of it!
I played with one of the roadside radars once. The radar had no trouble locking onto me as soon as it had a straight line image of me. But I was the only car on the road. I guess when you are the only car, you are the strongest signal. But from this information, we must not reflect a strong signal, and it will lock onto other cars. It could be a good thing, or a bad thing depending on your speed and theirs...
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Old 10-05-2005, 01:57 PM   #19 (permalink)
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I had an interesting experience with this last week. I was accelerating away from a stop sign and noticed one of those roadside speed monitor signs . I was about half way between the stop sign behind me and the speed sign when I first saw it. I was going about 45 mph at the time, but the sign was slowly advancing 23, 24, 25. As I got almost on top of the sign, it jumped from 26 to 46 (50 indicated). As I was wondering what's up with that, I noticed a Lexus GS 470 about 10-12 car lengths behind me also accelerating away from the stop sign. The roadside radar was locked onto the Lexus until I was right on top of it!
* Around here....speed signs are on K while officers run around using Ka...so if K band goes off....no sweat.

* On the relative size/mass thing..this is one of the things the officer's training is supposed to go over. For example that Lexus would not be "seen" if an 18 wheeler was nearby....radar likes big stuff. So in a sense we do have a bit off stealthiness if we travel amongst SUVs.
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Old 10-06-2005, 02:37 AM   #20 (permalink)
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Quote:
Originally Posted by TimMullen
I played with one of the roadside radars once. The radar had no trouble locking onto me as soon as it had a straight line image of me. But I was the only car on the road. I guess when you are the only car, you are the strongest signal. But from this information, we must not reflect a strong signal, and it will lock onto other cars. It could be a good thing, or a bad thing depending on your speed and theirs...
Last fall I was doing some testing of the sensitivity of my V1 installation. I have a friend that is a deputy sheriff and he was kind enough to blast me with microwaves.

When we finished testing he told me that he did not get radar lock on my car until I was on top of him. He attributed this to the physical profile, steeply angled radiator/condenser and lack of metal body parts.
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