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Old 10-11-2010, 16:02   #1
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Radar Mounting: Mast or Stern Post ?

Hi all, may I request your abundant advice on this topic?

I am installing radar on my Wauquiez 45 Centurion.

I have found a gimballed radar mounting system that could be used either on the mast or on a stern post (custom S\S pole)...

I'm told if on the mast, the radar can be damaged when tacking the headsail or the headsail can be ripped by the bracket... doesn't sound too cool!

Duhh!!! Is is that simple? Am I missing something?
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Old 10-11-2010, 16:16   #2
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I have had Raymarine Ray Dome on my mast for 5 years of coastal and off shore south pacific cruising. The yacht is 46ft and cutter rigged with an overlapping genoa on the forestay and jib on the inner forestay. No problems and good functionality.
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Old 10-11-2010, 16:40   #3
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Pro's & cons for both, but if you lost your mast..........

The windage in the slot isn't good, as well as the weight aloft, chafe on the sails.

Stern pole is in an easier to service location and may be used for other instruments along with a hoist for an outboard.

I'm fabricating a 7' pole for my boat now.
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Old 10-11-2010, 16:59   #4
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The higher the radar, generally the longer the detection range.

The problem with radar on the mast are added windage, the chance to snag the dome with the sail, doing damage to both, the chafe to the sail as a result of rubbing against the radome, and sometimes the long cable runs.

Also, for a given degree of roll, the mast antenna will move further than a lower mounted antenna. I know they make stabilizer platforms but I don't recall seeing one mounted under an antenna on the mast.

The problem with the radar on a stern pole is the lower detection range, the area you're interested in (ahead of you) is partially blocked by the mast, and it takes up real estate that may be better used for a wind generator, wind vane, or davits. I've seen boats with both radar and davits but there isn't much space left on the stern.
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Old 10-11-2010, 17:18   #5
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On previous boat had on pole on stern on one side & wind gen on other side.Did not observe any interference from mast.Will not shoot as far as on mast.On an earlier boat on mast royal pita.Re distance difference have never had problems hitting things miles away.marc
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Old 10-11-2010, 17:49   #6
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I was originally thinking of a wind generator mast on one corner w/a radar mast on the other, ended up looking cluttered. As far as on the mast that depends alot on the rig and exactly where on the mast. on my boat there are two possible locations: just above the forestay and under the steaming light or at the spreaders 10' below the other...this is the ideal place for me. As I only fly a working jib or storm jib on the forestay I have no overlap or chafe problem, Genny's are all flown on the head stay on my boat....but that is my rig forestay about 2/3 up the mast with spreaders down a bit.

In my opinion, a radar mast reduces the distance you can see (on my boat it would be 8' off the water vs 25') while increasing cockpit area clutter. When I mention that radar up high is affected more by heel it is usually pointed out to me that the times I would use it most would be in fog, when I am not heeling much
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Old 10-11-2010, 18:01   #7
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I prefer a pole or an arch. My works quite well and it's not very high.
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Old 10-11-2010, 18:10   #8
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I have mine mounted on the backstays. Was one of those low buck jobs using bimini fittings and tube I already had I got the radar in a trade for work deal.
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Old 10-11-2010, 18:17   #9
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A pacific seacraft that is new to my marina has a single stern pole that has his wind generator, radar and dingy motor lift all incorporated into it. It's nicely done - I haven't seen the owner to find out if it was custom made or something that's commercially available. I'd like to find out because I'd like to do the same aboard my own boat.
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Old 10-11-2010, 18:27   #10
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On the transom it is going to be more out of the way and easier to service. The height difference on the transom versus the mast for a yacht is not going to be much different as far as effective range goes.
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Old 10-11-2010, 18:55   #11
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Quote:
Originally Posted by David M View Post
On the transom it is going to be more out of the way and easier to service. The height difference on the transom versus the mast for a yacht is not going to be much different as far as effective range goes.
Using figures from my ray marine manual and plugging in the two planned heights, on the mast really isn't in the way of anything, a pole on my quarter deck on the other hand is.
8' (2.45m) mast height target height 90.45 (30m) range 7.8nm
22.9 (7m) mast height target height 90.45 (30m) range 16.6nm
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Old 10-11-2010, 19:45   #12
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oops...those measurements are off the deck..formula was for off the water, you can see the difference though

The radar mast is more in the way on my quarter deck than a radome on the mast. With some boats and some rigs it is better to have a separate radar mast even a radar arch, mounting on the backstay is also possible (unless you have a slip backstay like mine) and with some boats mounting on the mast is better. This is not a question of "which is better?" but rather "which is better for my particular boat", as there is no major difference in functionality here, it comes down to personal taste on the part of the boat owner. Some boats have all sorts of high tech gadgets and gizmos and display them quite proudly across the back of their cockpit...while some boats choose to be a bit more subtle about their high tech gear. I have a classic wooden sailboat...for some reason a radar arch just seems out of place.
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Old 11-11-2010, 11:14   #13
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Quote:
Originally Posted by wolfenzee View Post
Using figures from my ray marine manual and plugging in the two planned heights, on the mast really isn't in the way of anything, a pole on my quarter deck on the other hand is.
8' (2.45m) mast height target height 90.45 (30m) range 7.8nm
22.9 (7m) mast height target height 90.45 (30m) range 16.6nm
Eight feet is too low for mounting a transom radar.

Raymarines figures seem highly optimistic because a 3cm radar cannot bend (diffract) much over the horizon. Yes, tall and large vessels coming over the horizon may be seen past the horizon, but you cannot always assume that everything out there is a tall vessel.

Run some of Raymarines figures and see how much smaller their figures are here. Also notice how as you increase height, the distance increases at a substantial decreasing rate.

Distance to horizon calculator....
http://boatsafe.com/tools/horizon.htm

Radar diffraction explained...
http://www.radartutorial.eu/07.waves/wa08.en.html
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Old 11-11-2010, 15:14   #14
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Quote:
Originally Posted by David M View Post
Eight feet is too low for mounting a transom radar.

Raymarines figures seem highly optimistic because a 3cm radar cannot bend (diffract) much over the horizon. Yes, tall and large vessels coming over the horizon may be seen past the horizon, but you cannot always assume that everything out there is a tall vessel.

Run some of Raymarines figures and see how much smaller their figures are here. Also notice how as you increase height, the distance increases at a substantial decreasing rate.

Distance to horizon calculator....
BoatSafe.com

Radar diffraction explained...
Radar Basics
In the following post I pointed out that I had made a miscalculation and the height was really 8' off the deck....the differance in height between a separate radar mast and mounted on the mast (on my boat) is just under 4m compared to just over 7m.
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