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Flush Mount Radar Considerations

Old 08-18-2011, 05:54 AM
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Default Flush Mount Radar Considerations

Folks, still toying around with flush mounting my radome. Had posted on this a while back and not much feedback. Reason to lower from the pedestal is I am always hitting trees when towing.
I pulled into a marina last week and saw about 5 boats where they mounted the radome flush on the hardtop. So it is being done by some, so hoping some of you out there might share experience or knowledge of radar performance loss if I do this.

Here is what the installation instructions state for the Lowrance Broadband 3G radome:
Considerations for direct roof mounting
When deciding a suitable mounting location for the 3G™ scanner, be aware that the vertical radar beam extends to 25° either side of horizontal. With 50% of the power projecting in a beam 12.5° off horizontal. If the radar beams cannot clear the roof lines this could decrease performance of the radar. Depending on the size of the hard top of the vessel it is recommended
not to mount directly on to the surface, instead elevate the scanner to allow the radar beams to clear the roof lines.


What I am confused about is the comment on loss of performance. Does that mean overall performance of the radar unit, or just loss of viewing where signal is blocked from the sides and rear of boat just adjacent to the boat where it does not have a clear view?
I am assuming, that if I forward mount on hardtop, as far forward as possible, I will see any obstructions as I approach them and not worry how far they are to the sides or back as I am navigating, like in the dark or something.
But, will still be able to see storms out in distance.

Right now, my radome is approx. 11" above the hardtop. I can see a plastic buoy within approx. 30 feet to my side as I pass. I think if it is 30' or 75', will make no difference if I get that type of loss by flush mount.

Anyone out there with flush mount experience or knowledge/clarification on what they mean on loss of performance?
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Old 08-18-2011, 07:28 AM
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DO NOT DO IT!!! They ALWAYS work better lifted up off the top. ALWAYS.

They make fold down stuts, that is the way to go if you need clearance.
Old 08-18-2011, 08:12 AM
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I'm getting great radar performance with the Edson pedestal I mention to you awhile back.

All I could say is try it! THe worst that can happen is that is causes loss of coverage in areas where you really want it and you can always go back and put one on.

If your hardtop is plastic or fiber, more reason to give it a try as they are transparent to RF. It's the structure (metal) that will cause the problem. I have a beefy arch with like inch and half or bigger tubes, so I believe I would have been in trouble without the pedestal.
Old 08-18-2011, 06:31 PM
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Birdman, I haven't found a fold down strut. That would be the ticket for sure. Any leads on them?

Also, you say don't do it....but I see lots like this already out there. I want to hear from someone that has done this and what they have experienced with it mounted this way. What I don't want to do is drill holes and mount and then have to put back on the pedestal I have.
Old 08-19-2011, 05:03 PM
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It's fine on the top. Put a few washers in the back of the unit for a down angle while you are running. Should work fine. The extra 6-8 inches the mast or strut provide wont really make a big deal.
Old 08-19-2011, 05:47 PM
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It looks like these guys offer a folding pole solution. They should be able to make a different custom solution for your application, if required.
Old 08-20-2011, 11:37 AM
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Don't do it. Mine is flush mounted because I am on a trailer and I am 13 feet 4 inches tall, flush mounted. Performance is not nearly as good as it should be. On flat calm days, you can really see the difference. Once I head offshore, I have a tough time seeing 23 to 30 foot fiberglass boats over 2 mles away. On another boat with a 12" 4 degree arch and the same radar, no problem. I am looking into a custom flip down.
Old 08-20-2011, 11:45 AM
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Flush mounting will depend on alot of factors, how does your boat sit and run? At what angle is your hardtop, is it forward leaning or aft leaning? If you surface mount you will want it all the way forward on your hardtop. Flush mounting will work fine on some boats and not so on others. You can shim the back of your unit with starboard or washers,etc to get it to lean forward. True, the higher it is, the better off you are, but trailering limits this. The 3g Radar will serve you well.

I opted for a short 6" pedestal with forward lean. Basically to get over my spot light.You can see it in these pic.

Nautical Creations can make you any height you want. Great people to deal with and I do think they have a folding type also.
Old 08-20-2011, 08:10 PM
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Nice setup there dahlbebop!

Reel draggin, let me know if you find a good solution for a fold down. I have a design in mind, but I am sure it will cost $$. Would like to see others out there to see if they might give me some opportunity.

However, while out this weekend, I did some double checking. I think I said mine was 11" tall. Duh, it is 4" tall and 11" wide.

To drop it 4" doesn't seem to make much sense, but I am just skimming trees at 13' 7" on the trailer. The 4" will help, but will not resolve the problem completely. So, thinking rather than doing all this work to try the flush mount, just to live with it unless I can find a fold down. Even if I do find a fold down, likely it will not be flush and give me much gain within the current 4" height.

For now, will just live with this setup since I don't think there is a lot of other choice here.
Old 08-21-2011, 06:27 AM
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I sit at 12'9" on my trailer as she is now with Garmin GPS antenna. I am going to add radar this winter and have the same height problem.

13'6" is NC DOT height for bridges and some are lower than that so keep that in mind. I am also getting another trailer for the boat in September so I will measure again after that to see what I need to do. The fold down might be my only option.

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Old 08-21-2011, 06:43 AM
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Keep in mind guys that the Br radars scanner is about halfway up in the housing, so it is already elevated a little anyway. Here is a picture of Nauticalcreations fold down. The picture is upside down,sorry

Old 08-21-2011, 07:55 AM
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I like the fold down from Nauticalcreations. I will probably add that when fishing slows this winter. Having the unit up and at an angle works way better.
Old 08-22-2011, 05:23 AM
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Yeah, was thinking that height sounded familiar with the bridges. Need to start looking at them and see their height. Also was trying to see the height on some of the tractor/trailers and see how high they normally run.

That bracket seems to only fold from a horizontal to a vertical position. I think that would be a problem in that the radar on it's vertical position is just as tall if not taller? Unless it is pushed far to forward on hardtop and the radome extends off the edge to get more fold down opportunity.

Here is kinda what design would seem to make sense. It would just swing forward and down and lock with a pin in either up or down position: Rough drawing:
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Last edited by roberth; 08-22-2011 at 05:55 AM. Reason: Add pic
Old 08-22-2011, 06:06 AM
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I don't know if this will work for something as heavy as a radome but I have my GPS mounted for quick-release.

I installed bolts in my consoles facing up and fixed them into place with acorn lock-nuts. To hold down the units I use wing-nuts. I have similiar situations inside the consoles as dead-mounts for concealed storage. The dead-mounts also provide a handy place to keep spare wing-nuts. Due to Murphy's law, that much redundancy means I have not lost a wing-nut in the 10 years I have used the set-up!


For something as heavy as a radome you will obviously want heavier bolts than I am using as well as lock-washers. The wing-nuts should be strong enough if you crank them down with pliers. You might also want to add M/G plywood, Starboard or similar material around the nuts to reduce the stress around the holes.

The bigger challenge will be the cable. Unless your unit has a quick-connect you will want it long enough to reach between the storage location and the useful location. You can probably fasten the extra coil near the mount or rig a box to stuff it into. I know next to nothing about radar so I don't know what impact that might have on performance.

Good luck!

Last edited by Kamper; 08-22-2011 at 06:22 AM.
Old 06-23-2012, 06:47 PM
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Well, thought I would post back my results for others that might consider flush mounting radar.

Since my hardtop (fiberglass) actually has some curve to it from center out to front and sides, I did not need a wedge or shims. I just moved it forward enough until I got the degree angle I wanted.

I ran trials this weekend, rough conditions due to wind. I have to say, I am every bit impressed as I was when it was up 4" more. I did not lose any quality of performance!

I can spot the small bouy's just up in front prior to any collision, so know for sure what is in front. From the sides, I lost only a few feet of distance, but can guestimate the buoy was approx. 25-30' out and I could see it.

From the rear, I can still see my prop wash and the bouy out approx. 75-100', which is not that important, but was delighted to see rearward that close in when most all the hardtop is aft of the radome.

Perhaps the new technology radar is able to perform in this area better than those in the past, dunno as I am not technical in that area, or maybe I got lucky in how my hardtop curves some, but in the end, I am able to get under my power line in the driveway and also the one in the street as well as some of the trees that I could not pass under before due to large limbs.

Hard to believe just 4" would clear the impacts that would cause me some damage.
Old 06-23-2012, 08:39 PM
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Perhaps the radar signal simply passes though the fiberglass hardtop material and does not significantly restrict the vertical beam width as the installation diagram implies?
Old 06-24-2012, 04:40 AM
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Thanksfor the update!

FWIW - Public roads are expected to have a minimum clearance level that I believe is 13.5 feet (road experts please feel free to correct this number). If there is less than this clearance there should be advisory signs at the last turn-off before the obstacle. Of course, as you have learned, trees grow where they want and probably wouldn't read the signs anyways...
Old 06-24-2012, 05:38 AM
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Not sure if you can link out to this Facebook video or not - but there is a post on the Lowrance FB page of a motorized mount someone did - it's sweet! Would do the trick

https://www.facebook.com/photo.php?v=10151319170165165
Old 06-24-2012, 11:23 AM
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In my considerations of mounting a 3G on my hardtop, I have decided when I do install one, I am going to flush mount it.
However, I have a friend with mad metal working skills who suggested this:

Mount a plate with a pipe welded to it on the top of the T-top with the pipe going down through the top about 6".
Then use an inner pipe 12" long with an upper plate to mount the radome on. Lower the radome down when traveling raise the pipe up when fishing. He had suitable suggestions for securing the pipe so it did not move when raised or lowered.
Pipe length is only limited by individual boat's clearance below the hard top. Wireing would be run through the inner pipe. LOL, he suggested we could raise it 4' if I wanted.

This would actually work on my boat as the forward part of the top is not an area where anyone would hit their head on the pipe, nor would it obscure vision when the radome was down. Cost factor is minimal,, he supplies the material and fabrication. I buy him lunch when he does these kind of projects for me. Don't know what someone else's labor cost would be, but it's a rather simple project that could be easily installed by the boat owner.

Maybe his idea might help someone deal with the height problem.

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