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Old 01 May 2007, 16:53   #1
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Radar Reflector

Ive just bought one of these from Rib-shop.....

http://www.rib-shop.com/product.asp?...hFor=&PT_ID=21

Can anyone recommend the best place for it on my Aframe the instrcutions on their website say to use cable ties so would I mount it against one of the verticals on the A frame or across the Top in a horizontal position?

Chris
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Old 01 May 2007, 18:09   #2
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Hi Chris,
The higher you can get it, the better. We normally try to fit them across the top bar of the A frame. Hope this is of use, if you need more info, just PM me, e-mail us or give us a call.

Thanks
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Old 01 May 2007, 18:32   #3
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Unless something has changed in the past few years, you may not want to use this too often at head level due to the radiation. However in fog I am sure it would be useful.
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Old 01 May 2007, 19:32   #4
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I am not sure what you mean, it doesn't emit radiation. If there is that much radiation from emitters in the area then any reflections from one of these would be the least of my worries.........
I have the powerboat version of this fitted high up on my frame with a home made stiffener to brace the mounting lug.
This is the old smaller version before I fitted the larger diameter version, only because the wife ran us under the prow of a yacht in a marina and snapped it off! The large diameter version I have now is mounted the same way.
BTW, I am not entirely convinced it really works any betetr than the outboard itself as a radar reflector..............
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Old 01 May 2007, 23:10   #5
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I have the big brother to the one you bought. I have had a couple of those smaller ones that mount to a little leg... Neither lasted a season as that bracket just wasn't up to the pounding it took on a RIB. I believe those smaller jobs are meant for sailboats where they can be tied to the rigging. I agree it needs to be attached at both ends. For some reason, I was under the impression that these are to be mounted vertically for best results...

The larger odel is about 4" wide and attaches with four bolts. This one las lasted about 5 years.

As for whether they help or not, I can tell you that friends with radar tell me that my boat casts a shadow about the size of a 60 foot steel boat. I have it mounted to a platform on the top off my A-frame. The higher it is , the better it will work. I've attached a lousy pic... it's cropped form a larger one...
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Old 02 May 2007, 05:50   #6
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Quote:
Originally Posted by Ribshop View Post
Hi Chris,
The higher you can get it, the better. We normally try to fit them across the top bar of the A frame. Hope this is of use, if you need more info, just PM me, e-mail us or give us a call.

Thanks
So they can be fitted horizontally? that might be useful
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Old 02 May 2007, 09:51   #7
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I wouldn't bother fitting horizontally, as you will get as much return off the A frame horizontals as you would from the reflector. Always mount vertically, as high up as possible for best results.

Chances are with a substantial A frame, that will acount for about 80% of the return the interrogating radar receives back. They are of most use when you are bow on to the interrogating vessel, as the engines will give most of the return when "pinged" from behind, so to speak
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Old 02 May 2007, 12:33   #8
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If you use cable ties put quite a few on; I originally fixed one to Evolution with 2 on each end and it fell off (into the boat fortunately). Gone for 4 each end now and it seems to stay put....
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Old 03 May 2007, 06:32   #9
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we have them on the boats in order to comply with Solas regs that say you must have a reflector if practical to fit one. Cable ties each end and big one around the tube itself onto A frame. Not had a problem with them moving fitted like that. In very thick fog we had a conversation with a merchant vessel who we called up on vhf before crossing a busy shipping lane as we knew he must be somewhere near our crossing point and he confirmed he could see both boats on the screen-but whether that was from the reflectors or the 4 cylinder engine blocks, or the loose change in m'pocket is a matter of some conjecture
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Old 03 May 2007, 07:25   #10
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OK - Lets bring in a bit of science. The effectiveness of a radar reflector if very much determined by the angle of orientation. This has seen particular high profile of late due to the sad incident of the Ouzo (link below).

http://www.maib.gov.uk/cms_resources/Ouzo_.pdf

The important issue is that radar reflectors are mounted in the "catch rain" position- any other orientation will severely com Lets think this through and we'll all see why.

A wave will always reflect from a flat surface at the same angle at which it arrived. Therefore if you place two reflectors at right angles, the wave will always go back directly to where it came from. See the image below. This is exactly what we want as it gives a big radar return to vessel looking for obstacles. Now given that we operate in a three dimensional world then we need three surfaces all at right angles) hence the shape of a traditional reflector.

If you mount the reflector with the vanes being either vertical or horizontal then this will give a strong reflection for radar coming from over head (e.g. an airplane) but will be naff all use for something loosely alongside you (e.g. another ship). In order to give a strong radar return to another ship then you MUST have it is the "catch rain" position (i.e. with the vanes at 45 degrees to either the horizontal and vertical)

Here ends the physics lesson

Andrew
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