Radar Reflectors

[skip1930]

Who's running radar reflectors up in the rigging?
Mine is tubular, and sits on a spreader bar.
So about 18 foot [?] above the water.
I was told on the VHS with antenna 25 foot above the water
that I was 'on the scope' 7 miles away by wheelhouse personnel on
the Mesibi Miner a 1000 footer. Bare in mind there radar
is maybe 105 foot above the water.
It's all line of sight, sightings.




skip. I did winter lay-up pipe fitter work on this boat years ago. Yes, your job sails away every March.
The Mesibi Miner makes about 71 round trip trips each season for taconite [iron] ore.

[Caboose]

I use the "rain catcher" type myself. With Navy and other large ships in area, I consider it money well spent.

[Salty19]

Wow, Skip!   Now that is a barge to avoid!   Very cool that they cared enough to even respond to you...a speck of fiberglass which would be little more than a slight noise if they hit you.  Nice reflector, and great range on that radio too.

[curtisv]

Skip,

I have the same radar reflector but have only hoisted it in the fog.  And blow the horn in fog too.   -..

High as possible is best so attached to the main halyard with one reef in the main is one way of getting it up there, though it could be blocked by the mast.  In thick fog, reefing the sail also slows you down.

Not as high is a spreader halyard for anyone that has them and want to raise a radar reflector only when needed.

High on the backstay might also be a good place for it.  You picked a good spot though, high and not near the mast.

Curtis

[skip1930]

"though it could be blocked by the mast." Without doing the true analysis on reflected radar beams, I was under the impression that a beam hitting an aluminum mast has almost no bounce back. I'm thinking it matters not if the radar reflector is up against the mast or not. The thing reflecting the 'bounce' is the reflector, not the mast, or the hull. Just a guess. We have a guy in our USPS club that was an Air Force Radar Engineer at the A.F. Testing grounds. I'll ask him.

skip.

[curtisv]

Radar is microwave and I don't think microwave passes through aluminum.  The shape of the mast gives a weak reflection.  The right angles in the reflector gives a strong reflection back at the source.  Fiberglass is transparent to microwave.

I kinda makes sense.  Most aircraft fuselages are alunimum and they show up fine on radar.  Stealth planes use carbon fiber and don't show up on radar.  AFAIK aluminum boats show up fine on radar, but wood and fiberglass don't.

Curtis

[skip1930]

Read the book SKUNKWORKS, The story of Stealth by Leo Janus and Ben Rich. It is so cool. You want to be amazed and so proud of Lockheed. Aeroplanes and ships on water show up on radar mostly because of transponders. You can see live, every aeroplane in the air from a computer screen at your home. That's kind of fun tracking them in real time.

The air frames on the 117 are aluminum and titanium, no carbon fiber. The hardest thing not to get a radar return on was the pilots helmet and the three piet [sp] tubes sticking out for computer stabilization flight control. The book covers the Russian mathematical concept of zero radar return and how to hide a pole holding up a mock-up of an aeroplane at the Air Force radar testing grounds in the desert.

skip.

[NateD]

I picked up a cheap temporary reflector that folds flat, but can be assembled and hoisted if I'm on large water and the conditions warrant it (they haven't yet).

I did a bit of research before purchasing it, and it seems that they are all sensitive to how they are installed and angle of heal. I'm having a hard time finding the exact source, but I remember reading that the tube type reflectors were not as good as the ball type. There have been some studies on it, here is one of them:

http://offshore.ussailing.org/Assets/Offshore/SAS/2007+Radar+Reflector+Test.pdf.pdf

[curtisv]

The air frames on the 117 are aluminum, no carbon fiber. The hardest thing not to get a radar return on was the pilots helmet and the three piet [sp] tubes sticking out for computer stabilization flight control. The book covers the Russian mathematical concept of zero radar return and how to hide a pole holding up a mock-up of an aeroplane at the Air Force radar testing grounds in the desert.

skip.[/color]

OK.  btw- I remember hearing that the stealth had the radar reflection of a flying lawn chair.

Someone better tell the folks at Davis that aluminum doesn't reflect radar.
http://www.davisnet.com/marine/products/marine_product.asp?pnum=00153

The B-2 is made of carbon fiber.  http://www.infoplease.com/spot/northropb2.html

Here is a book entry where it explains that a coating is needed to absorb radar reflection.
http://books.google.com/books?id=-WSRxqMJcCoC&pg=PA982&lpg=PA982&dq=carbon+fiber+stealth+aircraft&source=bl&ots=RBoFdYCiPi&sig=Mbjb1glisdMTTHGkwGM2ZrsXM4Q&hl=en&ei=gWKzTYe7EqTf0QHj97X-CQ&sa=X&oi=book_result&ct=result&resnum=11&sqi=2&ved=0CG8Q6AEwCg#v=onepage&q=carbon%20fiber%20stealth%20aircraft&f=false
It suggests that carbon fiber can be used but this is just a material science book.

And as it turns out the F-117 uses carbon-fiber as well.
http://www.marketwatch.com/story/stealth-plane-already-being-mothballed-by-air-force?pagenumber=2
http://composite.about.com/library/weekly/aa122297.htm

Now we are both going to show up on someone's watch list for googling this topic.  :-(

Curtis

[skip1930]

~Lawn chair? More like the size of an Eagle's eye ball in California as seen from a radar unit in Washington D.C. [in the book Skunkworks.]

~Never said aluminum and titanium doesn't reflect radar. I said or implied that it is the shape of the piece that does not return an echo. An vertical oval shaped mast is not a very good shape to return a radar echo. In the picture below is the Air Force's answer to an invisible pole, holding up a wooden mock-up of a 1/4 scale 117. Interestingly all base personal were made to lay down on the cafeteria floor, windows covered, while the wood mock-up flow from Burbank to the radar desert testing area was removed from the C-130 and placed on the pole, tests made, and mock-up returned back into the C-130. Then personal was released to regular duty.

~And yes, fiberglass just lets the radar hit mostly pass clean through fiberglass.

~Yes the B-2 developed years after the 117 by a different aerospace company, does use much more carbon fiber. And the B-2 is much more curvy without angular shapes than the 117. In fact a 117 could not fly without a computer, not the pilot, controlling the flight surfaces. Which is where the piet tubes come in to play for yawl, pitch, and roll computer control. Additionally the 117 is so unstable and un-aerodynamic that she can barley fly faster then 200 knots. But when you invisible who cares?

~Side bar: In the first Gulf War a pilot who was to be first to go 'down town' tossed and turned all night long, worried as to just how stealth the 117 was. That is until walking to his plane in the hardened bunker he saw hundreds of bats dead all around the foot print of his aeroplane. The bats had no radar return and simply crashed into the airframe, killing themselves on impact. The pilot was no longer worried.

~The only reason for this curvy shape of the B-2 was the further development of super computers that allowed the mathematical development of zero return curves. Curves that were immensely more friendly and aerodynamic allowing a much greater speed. As in any aviation scenario, power gets you altitude while horizontal and vertical stabs get you speed.

~Yes, the Air Force ground crew 'buttered up' the airframes prior to ever 117 mission to downtown Bagdad after the bomb-bay doors were closed around the 2000lb smart bombs. That 1/3" crack around the opened and then closed Bomb-bay doors did return an 'acceptable risk' echo return on the way home.


skip. NOTE: Hold the Ctrl key down and tap the + key to enlarge the caption print. Hold the Ctrl key down and tap the - key down to go back to size.

[curtisv]

OK Sip.  Thanks for the book recommendation.

Curtis