m21sniper

This is a question i asked Mr. Dick Landgraff, formerly of NAVSEA. Mr Landgriff was the project leader when the Iowa class BBs were reactivated in the 1980s, and wrote the Stealthing SHIPALTS(basically an instruction manual) for the installation of RAM(Radar absorbant Material) on USN Oliver Hazard Perry FFG7 class frigates for the purposes of reducing their radar signiture.

Below is my original question to him, and his response. I got a kick out of it, and well........this info could be useful to someone....

"Originally Posted by M21Sniper
Hmmmmm. I could really use a stealth treatment for my Porsche 928S.

Tell me more(about using a bra to reduce the RCS) Mr. Landgraff!"

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Well, unless your car has air scoops in the sides to deflect Radar beams into the chamber never to bounce back out, a car bra will do you no good. The beams are readily reflected by the radiator grill, headlights and bumpers.

A Radar beam will Deflect away enough if the surface it strikes is more than 15 degrees off vertical. So a well sloped windshield with a plastic sheet glued ON FRONT will deflect beams up instead of through the glass and bouncing back out off the metal inside the car.

A typical car bra is made of a multi-layered rubber sheet that must be strapped tight to the metal of the car. OR it has to come with thin aluminum sheet already installed on the back side. Such RAM blankets were used by both US and British ships in the Gulf War as reported by Norman Friedman. He wrote an excellent book on the war but, in my estimation, gave out too much information --- at the time.

What happens is when a Radar beam hits a reflective surface, it oscillates for a micro-milli-teeny-tiny second before bouncing back to the receiver. Though the beam is not as narrow as a Laser beam, it is usually within a 30 degree cone thus allowing any surface angled more than 15 degrees to Deflect it out into the neighborhood.

In a RAM blanket or a RAM covering over metal, it's at that point of oscillation that disperses the Radar within the rubber material. 90 degree inside corners are the ideal Radar reflectors so both surfaces have to be covered. If the RAM is not attached to metal, then the beam goes through it, oscillates on the metal, and goes back out through the material.

The material itself? Well since we had to specify it on our drawings and they were not classified I guess I can tell you. Rubitex Type 3R. It's about a quarter of an inch thick and is a little stiff. We did use a much thinner material on handrail stanchions but it has to be glued in place and really was not as effective as the thicker stuff.

But as I said earlier, your radiator and headlights will still reflect a beam back at the Smokey. So the only use of the car bra has is it's "publicly" advertised use as a bug catcher.

Oh yeah. One more thing. A lot of Police agencies know about this and are changing over to Laser units to measure incoming or outgoing velocities. So, save your money unless your car is like Wonder Woman's Invisible Airplane."
http://www.worldaffairsboard.com/showthread.php?t=10381

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Heh, ok, someone go buy a ton of that stuff and let's get to work!

Fabio421

So I guess it would work with a 944 as it has retracted headlights.

m21sniper

It would actually work on a 928 with the headlights off too because they're so heavily sloped. Just cover the lenses with a good reflective polycarbonate, and that should take care of the headlights(when they're off at least) as a source of reflection.

If someone wanted to spend some time and money on this they could probably get pretty friggin' good results.

Normy

-I think I've read somewhere that some of the older corvettes were pretty stealthy to radar- they are fiberglass first. Second...they have mostly angled surfaces, and third, and apparently most importantly... the radiator is mounted at an approximately 15 degree angle, with the lower edge farther forward than the top.

N-

m21sniper

Yeah, that would reflect the radar return from the radiator straight down at the ground.

Hmmm, ok, i guess we need a radiator angling kit for our 928s.

Someone writing a list?

Hehehehe.

Ron_H

Very interesting........

Has anyone thought about 3M clear bras?

SharkSkin

I have yet to see one for early cars...

m21sniper

I guess if you made it of the same plastic he was referring to for the windshield it could work i guess, but the front part of the nose on the OBs(the part where the front license plate would go) is almost directly perpendicular to the LOS for a radar wave, and would be like a day glo neon sign on radar.

That part of the nose would have to be heavily coated in RAM or angled(preferably canting inward from top to bottom by at least 15 degrees as he states above). Same for the front marker/fog lights and T/S lenses.



The more i think of it, if someone really wanted to do this and spend the money, i think they could get some purty daggone good results. There is actually a heck of a lot of open source RCS data on the net, so it's not as if there's no guidelines to go by. The one area where i think you'd run into real problems with excessive returns is the wheelwheels and the rims.

SharkSkin

The lights in the bumper are pretty reflective, and the aluminum bumper itself probably has a huge radar signature. I don't think the bumper cover itself is going to reflect any radar. Oh... unless you have metallic paint.

Maybe we can talk to the guys that make Rejex and see if they can come up with a radar-absorbing variant.

Fabio421

I remember my uncle telling me a story about this. Back when he was in the military. A guy he knew was court marshalled for theft of Govt. property. The guy was into fast cars and had stolen some sort of anti-radar paint and then painted his corvette with it. My uncle had said that this guy had painted verything he could see with that paint. Door handles, mirrors etc. It wasn't for looks it was for functionality. He wasn't sure if it worked or not. I think the guy was caught before he could ever know for sure. I always thought it was a pretty cool story.

m21sniper

It's actually highly doubtful that the front bumper cover is radar transparent, especially after paint is applied. Very few materials are truly radar transparent(used on radomes, etc- fiberglass is one of them). Even if it was transparent, if it was dirty with roadgrime it could potentially still give off a return because of the near 0 degree return path to the emmiter.

"Hiding" from radar is more about reflecting the return waves away from the emmiter than absorbing or trapping them(ie, it doesnt really even matter if you 'bounce' a strong return, just as long as it's away from the radar source.

There's an F-117 pilot that posts on my board too.

The driving light lenses would be easy to cant downward and coat with polycarbonate, and i guess you could certainly cant the bumper downward behind the cover, though it would be a lot easier just to get rid of it.

The SR-71 and U-2 used a special paint developed by the Lockheed Skunk works called "Iron ball". I wonder if we could secure some. The technology is abour 40 years old now, and supposedly it was quite effective. Hehehe.

I wish i was rich. I'm the kinda nutjob that would spend 20k on a project like this just to see if it actually worked, lol.

m21sniper

LOL, that is a pretty cool story.

Now, if we could just get a scraping of that paint, we could get some more made.....

JEC_31

To me, it all boils down to two things:

1) Mr.Landgraff's astute observation that more and more speed enforcement is done with laser.
If I were so inclined to be focusing time, energy, and money into stealthifiying cars, I would research ways to defeat the mighty laser.


2) If Smokey can see you, and his eyes don't agree with his speed detection equipement readout - you are in a world of trouble. Whether you're using a common detector or $20,000 worth of ultra-high-tech jammer-paint (LOL), you still have to slow down before the Enforcer can get a visual on you.

AO

Agreed. The point of the exercise is not to have a radar null-signature, but to not get pulled over/hassled by the police. In my experience, if the police believe you are speeding, they will pull you over, and they will issue a citation regardless of what "evidence" they think they may have - I was once pulled over for an "estimated speed in excess of xx MPH". Your best bet is to not get pulled over in the first place, then invest your time and energy into understanding the legal arguments behind the legality of speeding. Knowledge is far better than some passive magic in a bottle.

PorKen

I've been thinking of getting a car bra, just to cut down on laser reflection off of my WHITE paint. (Dark colors reflect less light.) Even though I don't like bras much. (Don't you miss hot summer days. )

Without the engine driven fan, there is plenty of room (on the 16V) for tilting the radiator. I have a spare hood, and I keep eyeing putting a rad outlet in it, along with an angled radiator. (I read that this is the best aerodynamic setup.)