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Go Back   SailNet Community > On Board > Gear & Maintenance > Electronics
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  #1  
Old 09-02-2009
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Radar Dome Placement and Installation

I've asked around and there seems to be a lot of opinions on radar dome installation... up on the mast, the backstay, or on a pole. I've got a solid old 1978 Cal 34, and it seems the cleanest and most economical place for the radar dome is on the mast. Any opinions out there?

Also, for a mast installation, is it OK to just tap a hole and drop the chord to a mast step or is some form of a costly conduit installation required? Thanks for your input. Cheers!
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Old 09-02-2009
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We put ours about 25 feet up from the cabin top on the mast. I personally believe this is the best place for it. There are a lot of opinions on this, but I feel that the mast wins out every time. Do not forget that a radar is line of sight. As such, the higher up you put it, the further it will 'see'. Thus, the benefits of the mast outweigh the negatives.

We ran ours down the mast (inside). Do not be surprised if you have to unstep your mast to get it through unless you have a keel stepped. Even with keel stepped, you may not be able to pull that cord which is as big around as your thumb.

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Old 09-02-2009
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If you live where the masts are taken down each year, then often on a pole is a viable option. That way there is not cutting of the cable and installing a set of male and female plugs so you can unstep the mast.

Just a thought.

My last two boats have had it on a pole and we have liked both very much.

My opinion

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Old 09-03-2009
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I read on one of the other forums a post by someone who had attended a radar seminar given by I think Raytheon. Their advice for sailboats was a stern mounted pole. The reasoning being that while a dozen or so feet higher will give a bit longer range, you will lose detail close in where sometimes you really need it.
Brian
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Old 09-03-2009
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Thanks!

Thanks for the feedback. As always, many things to think about!
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Old 09-04-2009
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I second mitiempo. There is not much interest on very distant targets, I mean 99% of time you want to know what is near you, posing threat. Exceptions for curiosity or tracking showers, there is little advantage of seeing a long range because its drawbacks. The most important, if it's mast installed, keep it as low as practical. Beyond not good short range definition, the real problem will be boat motion. The higher you install, the worse for target discrimination, false pinpoints, wrong reflections, MARPA, etc ...
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Old 09-07-2009
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I have had both mast and pole mounted over time.

Mast mounting has a couple of issues for me. The first is the amount of whip the dome is subjected to. When you're sailing in rough water (and it doesn't have to be big seas, a short sharp chop is probably worse) the radar dome is subjected to a great deal of inertia from mast whip.

Secondly, if something goes wrong with it at sea, you can't reach it easily. If you have tried to go aloft in a rough sea you'll relate to that.

Thirdly, it is in a space where it can get damaged by sails, halyards, etc.

I sailed across the Indian Ocean, a notoriously rough place and three times on a new radar dome, the mast whip unseated the array drive belt and the radar simply lost the image. Not only was the loss of radar a ball-ache but not being able to go up the mast in those conditions meant that I couldn't repair it. Once up there it was easy to fix but getting up there was a life-threatening exercise so I sailed radar-less to the next port before being able to fix it.

I now have a stern pole mount and I have had no problems with the radar. Even if I did, at least I can reach the dome without risking my life and the loss of range is of no consequence, I've never felt disadvantaged because of it. My radar is a 16 mile unit and I often get images out at the 16 mile ring so I don't believe I'm losing range. Anything that is likely to kill you is going to have to get pretty close first so why worry about range?

Also, it's out of the way, nothing gets into that area of the vessel that can damage the dome.

Oh and the other thing I was going to say is that I heard the talk about dropping a cable into the mast and getting it out at the step but what about the chafing of halyards and other stuff inside the mast? If the cable isn't in the conduit then it is sharing space with a lot of tough customers in the mast. And if you have ever tried to feed one into a conduit you'll know how hard that is. And if you have ever priced radar cable then you'll know that messing up the one you have is not clever.

FWIW I'd not go back to mast mounted radar.
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Last edited by Omatako; 09-07-2009 at 07:18 AM. Reason: Adding info
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Old 09-07-2009
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Quote:
Originally Posted by mitiempo View Post
I read on one of the other forums a post by someone who had attended a radar seminar given by I think Raytheon. Their advice for sailboats was a stern mounted pole. The reasoning being that while a dozen or so feet higher will give a bit longer range, you will lose detail close in where sometimes you really need it.
Brian
Being from Maine and cruising from Maine to Canada I find this statement from Raymarine rather odd. I also find it contradictory to their own installation manual that shows a picture of it mounted on the mast of a sail boat with a green check mark next to it for "good location". They also say "Mount the scanner as high as possible above the waterline for better long range performance"

Also a standard 18" radome mounted on a mast, 25' above the water, will actually have the beam HIT the water at roughly 72 feet from the dome. If your mast is set back 12' from the bow of the boat this means that a mast mounted dome can see targets at 0' above the water the water 60' off the bow of your boat. Now add a seven foot boat height, for a typical Sea Ray, and you can see it 42 feet off your bow. The close in argument is not even an argument. If you need to see stuff on radar 42 feet from your bow then you are in some serious trouble.

In contrast a 36 foot boat with a stern pole at 12 feet high could actually get a return from the bow pulpit. Again if you have something 6" off your bow that you NEED to see then you just have not done your job tracking targets...


I have had radar mounted on the mast, a Questus back stay mount and a pole. I currently have it on a pole and HATE IT for performance reasons. Even when I had it on the mast, on three other boats I've owned, I could pick up my boat neighbors in the mooring field with no problems.

Even in Maine, where fog was invented, I have yet to find more than 4 or so days out of the last 20+ years where the visibility was less than 75 feet. If you have not acquired a target by the time it gets that close you're just not doing your job.

As someone who has spent literally thousands of hours operating radar in the fog, as both a commercial fisherman and a pleasure boater, there is NO question that a mast mount, 22-25 feet up, would be my preferred placement. Eventually I will remove my pole and place my dome on the mast but the boat came this way and the radar pole has been painted around with Awlgrip. I clench my teeth every time I am in 6+ foot swells, and fog, and keep loosing targets and having to re-acquire them due to the low dome height when in a trough. I rarely if ever had this problem with domes mounted on the mast.


If you only sail in protected foggy bays with no swell or chance of a sea a pole mount can suffice but if you venture into the open ocean, at night, or in the fog, a higher dome placement will track and keep targets on screen far better.


It's not all just about radar either.....


Things to do when in fog to be a good boater and to be courteous to others.

Radar Reflector
= BUY ONE AND USE IT!!!! Just because you choose not to have radar does not mean you should choose to be invisible or nearly invisible to the rest of the world who may be practicing good collision avoidance.

VHF = USE IT and by that I mean turn the thing on and monitor VHF 16 or at least scan 16 and the shipping channels. PLEASE! The rest of us don't have your cell number on speed dial. "Vessel rounding 2KR what are your intentions, over?........." Silence..........=not smart

Running Lights
= When the visibility drops use them. They do help and can add another 50-100 feet of warning.

Fog Signals = Wal*Mart sells sports air horns for $6.00. Please get one and use it when applicable.

Slow Down = A single sailboat traveling at 6 knots is covering 10.1 feet per second. In 100 feet of visibility the collision time to a fixed object is roughly 11 seconds from your first physical sighting. Of course you should have acquired this target LONG before 100 feet!! Now take two sailboats converging, each traveling at 6 knots, your collision time in 100 feet of visibility, from your first physical sighting, becomes just 5 seconds. You had better acquire your targets LONG before the stated by Raymarine "close in performance" even matters or you'll be in a heap of trouble..

A power boat traveling 30 knots, on a collision course, will collide with a sailboat doing six knots, at 100 feet of visibility, in under two seconds from the first sighting! You will NOT have enough reaction time to avoid a collision with a clown like this other than to have radar and been tracking him far ahead of the "close in performance". Think people don't go fast in the fog? Think again..

Some photo examples of what these reckless boaters look like:

There really is a boat here 200+ feet off my stern. No radar, no reflector, no running lights, no horn signals and not even a VHF response. "Dumb dee dumb, sailing awayyyy, dumb dee dumb, doh', a boat, how'd that get there?"

Here's a radar shot of that boat when it was actually showing up. It's the red spec just above the 18 foot spot off my stbd stern quarter. The two targets ahead and to port and stbd were two J Boats traveling together both of which had reflectors when they went by. SOME BOATS JUST DO NOT SHOW UP ON RADAR!!! The guy behind me owns one!


1st class clown (see speed above), no radar, no lights, no horn signals, no reflector and also not showing up well, and not monitoring VHF!


For reference this is 400 feet of visibility from a few weeks ago (400 feet is generally fairly decent vis for Maine fog):


And here's the screen shot with the cursor just over the closest radar image at 411 feet (upper left corner measures distance).:




It scares me how many people are just plain dangerous and have no clue they are being so reckless. If they succeed once they do it again only this time with a greater level of comfort and confidence.

So in summary I'd still opt for mounting the dome on the mast..
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Last edited by Maine Sail; 02-03-2011 at 10:02 PM.
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  #9  
Old 09-07-2009
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Originally Posted by Omatako View Post
My radar is a 16 mile unit and I often get images out at the 16 mile ring so I don't believe I'm losing range.
Figuring a 12 foot high dome, unless your tracking very high ships or large and tall land masses, you are getting AMAZING results.

With a 12' dome and a 20' tall target you can see it at 9.52 miles. If that target is 30 feet tall you can see it at 10.73 miles. A 90' high target can be seen at 15.54 miles. Of course if you are in 10 foot swells or seas every time you hit the trough your dome height becomes essentially 2' not 12'. If the other boat goes in a trough at the same time you may loose a target and have to re-aquire it at the top of a wave...

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Old 09-07-2009
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I have had only mast mounted radars and generally feel that this is the best location. Having said that I have an issue with mine that came up after installing a furling unit on our staysail stay. I now get an intermittent echo (quite often a double) directly off the bow which is disconcerting and a major distraction to say the least. Our radar is mounted at the first spreaders, well below where the staysail furling attaches to the mast. I did not have this echo with just the headsail furling unit. Anyone else have this problem?

Main- amazing resolution with your Garmin on the plotter. I'm thinking of adding a second radar on a pole and running it to the 3210 in the cockpit, hoping that the offset pole will eliminate the echo off the bow. What do you think?

I'm sure I am not the only one that has a narrow rip rap lined channel (app. 50') leading into my marina. With my mast mounted radar, set on the lowest scale, the cone overlaps both sides of the channel by about 50% rendering the image all but useless, except you can kind of guess at the middle. Our radar is about 18'-20' up. On our power boat the radar is app. 10' off the water and we can see the channel clearly (same Furuno 4KW units). I guess like everything else radar mounting is a compromise.
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