Radar reflector proof of concept pic - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 


Like Tree2Likes
Reply
 
LinkBack Thread Tools
  #1  
Old 11-08-2012
Senior Member
 
Join Date: Jan 2011
Posts: 695
Thanks: 0
Thanked 18 Times in 18 Posts
Rep Power: 4
Frogwatch is on a distinguished road
Radar reflector proof of concept pic

Here is my fabric Radar reflector proof of concept version. The contrast seems poor no matter how I take the pic. It is 14" diameter meaning it is about 1.36X the area of a large Davis (I think the Davis is 12").
So far, it easily folds flat requiring only 4 pieces of velcro to be unfastened. When you start to open it, it almost springs into shape.

Not to whoever mentioned the old radar reflecting flags. Those flags were a lame idea. This is a corner reflector of the type that Practical Sailor finds to be most effective. However, the final version will be weighted to always be in the correct orientation regardless of how much the boat heels. The final version will have a vertical line thru the center instead of the three lines seen holding this one.
Attached Thumbnails
Radar reflector proof of concept pic-radar-reflector-002.jpg  
Reply With Quote Share with Facebook
  #2  
Old 11-08-2012
Member
 
Join Date: Nov 2012
Posts: 40
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
Navigator Wannabe is on a distinguished road
Re: Radar reflector proof of concept pic

Corner reflectors function on the principle that the angle between the planes is 90 deg. Only then do they reflect the signal back to the source.

Shape is probably more important than area here, think stealth bomber.

Your fabric 'planes', in any wind, will likely have a sail shape, and the angles will be close to 90, never precisely 90 deg. Have you evaluated how that will affect its efficiency?

Plus, one question: Why stow a radar reflector? I thought that was one of the items you install and forget.

Side note: Heel should have a strong effect only on elongated corner type reflectors. The round or spade shaped ones should work reasonably in any position. Right?

Quote:
Originally Posted by Frogwatch View Post
Here is my fabric Radar reflector proof of concept version. The contrast seems poor no matter how I take the pic. It is 14" diameter meaning it is about 1.36X the area of a large Davis (I think the Davis is 12").
So far, it easily folds flat requiring only 4 pieces of velcro to be unfastened. When you start to open it, it almost springs into shape.

Not to whoever mentioned the old radar reflecting flags. Those flags were a lame idea. This is a corner reflector of the type that Practical Sailor finds to be most effective. However, the final version will be weighted to always be in the correct orientation regardless of how much the boat heels. The final version will have a vertical line thru the center instead of the three lines seen holding this one.
Reply With Quote Share with Facebook
  #3  
Old 11-08-2012
Senior Member
 
Join Date: Jan 2011
Posts: 695
Thanks: 0
Thanked 18 Times in 18 Posts
Rep Power: 4
Frogwatch is on a distinguished road
Re: Radar reflector proof of concept pic

I doubt they will form a sail shape to any degree as they are fairly taut. Any distortion from 90 degrees I expect to be small enough to not matter. Consider that the planes on the Davis ones are often far from 90 degrees. Distortions from the ideal are also small in relation to the wavelength. Thus, wrinkles in the fabric will not affect the performance much.
Stowability is important on a smaller sailboat and I do not like having a radar reflector up all the time as it causes windage aloft.
Numerous tests have been done on similar corner cube reflectors (like Davis and Plastimo) with round cross sections finding that heel has a huge effect. You an prove to yourself that angle of incidence does matter for a single corner reflector as large angles mean you need to make at least one more reflection to get back to the sender and because the projected area goes down with angle. So, I have long been puzzled at why Davis and Plastimo want theirs mounted in a rigid manner where any heeling has a large effect on performance.
Yes, the stealth fighter (not the bomber, that is different) is designed to NOT reflect Radar back but to reflect it at weird angles (hence the weird angularity of them). If one was not concerned about his clientele, one might consider selling "stealth kits" made from this fabric to certain "importers" who operate fast speedboats.

One more thing, the reflector weighs 5 ozs unweighted so it really does need the weights.
Reply With Quote Share with Facebook
  #4  
Old 11-08-2012
fallard's Avatar
Senior Member
 
Join Date: Nov 2009
Location: Mystic
Posts: 903
Thanks: 0
Thanked 8 Times in 7 Posts
Rep Power: 5
fallard is on a distinguished road
Re: Radar reflector proof of concept pic

The Davis reflectors (either metallized foam or aluminum) are comprised of 3 mutually orthogonal, intersecting planes. This creates a "corner cube' reflector. It really shouldn't matter what the heel angle is with these reflectors, as long as the intersecting planes are very close to precisely orthogonal and the projected area remains the same. (Due to the spherical overall shape of these devices the projected area doesn't change with viewing angle.) If the reflective sheets are not in plane and precisely orthogonal you will not get a precise retroreflection--that is, exactly backwards to the interrogating radar.

You can get a sense of how directional the retroreflection is by observing a driveway reflector with a flashlight. (Your typical driveway reflector is comprised of a whole lot of corner cube reflectors.) Start with the flashlight at hip level and bring it up to your temple, where your eye and the flashlight are very close, and you should see a dramatic difference in the reflection. Try this directly in front of the reflector and off to the side and the only difference you'll see should be due to the reduction in the projected area of the reflector (the "cosine law").

Yes, I know there are folks who have tested them and said the "catch rain" position works best, but I don't recall the reason there should be any significant difference due to the angle of presentation.
Reply With Quote Share with Facebook
  #5  
Old 11-08-2012
Maine Sail's Avatar
Senior Member
 
Join Date: Jan 2003
Location: Maine Coast
Posts: 5,416
Thanks: 11
Thanked 125 Times in 93 Posts
Rep Power: 15
Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice
Re: Radar reflector proof of concept pic

Quote:
Originally Posted by fallard View Post
Yes, I know there are folks who have tested them and said the "catch rain" position works best, but I don't recall the reason there should be any significant difference due to the angle of presentation.
Actually the "double catch rain" position has tested the best. In the real world I honestly don't see much difference.

Funny thing that just yesterday I was working on one of my commercial customers boats. She is an 80' Deadliest Catch style off shore fishing boat. They lay strings of eel traps hundreds of miles off shore netting 70,000 - 110,000 pounds of eel in a two to three week trip..

All their string buoys have radar reflectors on them... Despite having them marked on GPS they still rely on the radar reflectors when it is foggy.. But remember, radar reflectors don't work...
chef2sail likes this.
__________________
______
-Maine Sail / CS-36T


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




© Images In Posts Property of Compass Marine Inc.


Reply With Quote Share with Facebook
  #6  
Old 11-08-2012
svHyLyte's Avatar
Old as Dirt!
 
Join Date: Nov 2008
Location: Tampa Bay Area
Posts: 2,791
Thanks: 15
Thanked 113 Times in 107 Posts
Rep Power: 6
svHyLyte is on a distinguished road
Re: Radar reflector proof of concept pic

Quote:
Originally Posted by fallard View Post
The Davis reflectors (either metallized foam or aluminum) are comprised of 3 mutually orthogonal, intersecting planes. This creates a "corner cube' reflector. It really shouldn't matter what the heel angle is with these reflectors, as long as the intersecting planes are very close to precisely orthogonal and the projected area remains the same. (Due to the spherical overall shape of these devices the projected area doesn't change with viewing angle.) If the reflective sheets are not in plane and precisely orthogonal you will not get a precise retroreflection--that is, exactly backwards to the interrogating radar.

...

Yes, I know there are folks who have tested them and said the "catch rain" position works best, but I don't recall the reason there should be any significant difference due to the angle of presentation.
The angle of incidence equals the angle of co-incidence. To get a signal reflected back to its source requires two planes at 90ļ to one another, whether vertical, horizontal or some combination of the two. In the "catch rain" position, one has virtually some combination of the two regardless of the angle of heel.

In any case, considering that the Davis Echomaster tested as one of the most effective radar reflectors in Practical Sailor's testing (2001), that they are inexpensive; and, that they can be stored flat yet assembled in a few minutes and hoisted (in the catch rain position) with an off-set lift line and held steady with a down haul, I'm wondering if the OP's "design" isn't somewhat an exercise in reinventing the wheel?
chef2sail likes this.
__________________
"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
Reply With Quote Share with Facebook
  #7  
Old 11-08-2012
Senior Member
 
Join Date: Jan 2011
Posts: 695
Thanks: 0
Thanked 18 Times in 18 Posts
Rep Power: 4
Frogwatch is on a distinguished road
Re: Radar reflector proof of concept pic

Here are some test results for other reflectors:
http://www.bethandevans.com/pdf/Rada...tor%20test.pdf

Yes, the RCS varies radically with heel. So, they should be gimballed as mine will be. The Davis is not so easy to assemble or stow.
Mine is considerably larger than the Davis.
Reply With Quote Share with Facebook
  #8  
Old 11-08-2012
fallard's Avatar
Senior Member
 
Join Date: Nov 2009
Location: Mystic
Posts: 903
Thanks: 0
Thanked 8 Times in 7 Posts
Rep Power: 5
fallard is on a distinguished road
Re: Radar reflector proof of concept pic

Sorry if this sounds argumentative, but the principle behind the Davis style reflector is the "corner cube" comprised of 3 mutually orthogonal reflective surfaces--not 2 as svHyLyte has stated. Two orthogonal reflecting surfaces comprise a "roof reflector" which only retroreflects in a plane orthogonal to the 2 planes that comprise the "roof". Tilt matters a whole lot with a roof reflector.

That said, I put my foot in my mouth in post #4 when I said the orientation didn't matter. That was wrong and I should have put my brain in gear before spouting off. The reflecting aperture does fall off as the reflector is tilted because of self-blockage, thereby reducing the radar cross section.

The link posted by Frogwatch in post #7 documents a properly run test, with Table 1 showing the results of tilting the reflector.
Reply With Quote Share with Facebook
  #9  
Old 11-08-2012
Senior Member
 
Join Date: Jan 2011
Posts: 695
Thanks: 0
Thanked 18 Times in 18 Posts
Rep Power: 4
Frogwatch is on a distinguished road
Re: Radar reflector proof of concept pic

In reality, this thing has been a helluva lot of effort for what I expect to be a minimal return. However, as I expect it to be just one of several things my new business (just incorporated today) , that is ok.
My wife thought i had gone bonkers till I pointed out how muuch effort it took to develop the optics my other business makes. OK, she still thinks I'm bonkers.
Reply With Quote Share with Facebook
  #10  
Old 11-09-2012
Barquito's Avatar
Barquito
 
Join Date: Dec 2007
Location: Madison, WI
Posts: 2,013
Thanks: 0
Thanked 16 Times in 16 Posts
Rep Power: 7
Barquito is on a distinguished road
Re: Radar reflector proof of concept pic

Frog -

Bonkers is good.

Do you have a way to test the radar echo for your device?
__________________
Bristol 27
Cirque
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Should i use a radar reflector Captain milos General Discussion (sailing related) 26 09-27-2012 01:07 AM
Radar reflector brokesailor Gear & Maintenance 9 08-14-2011 07:52 AM
Another radar reflector? T37Chef General Discussion (sailing related) 13 03-15-2010 08:01 PM
Do I need a radar reflector? Patbarbeau Gear & Maintenance 61 07-24-2009 04:49 PM
Do I need radar reflector in my situation? FrankLanger Seamanship & Navigation 43 02-25-2007 04:09 AM


All times are GMT -4. The time now is 12:41 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.