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Old 02-09-2019, 08:27 AM   #1
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Radar on trawler

We have a 36 ft Nova Sundeck and are liking to add Garmin Radar to it. If I follow Garmin’s specifications I would have to add more than 18” mount to my arch. That seems extremely high especially when I look at pictures of other boats like ours and they are not using as tall of a mount. Any suggestions are appreciated.
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Old 02-09-2019, 09:20 AM   #2
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Welcome to the forum!
A picture of your arch or a link to a sister boat would be helpful.

Ted
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Old 02-09-2019, 09:31 AM   #3
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This is a picture of our 36’ Heritage East.
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Old 02-09-2019, 09:59 AM   #4
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I'm not sure what Garmin's reasoning is (have you asked them?), but the higher it is the more range you have.
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Old 02-09-2019, 10:17 AM   #5
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The small issue you will have with lower height has to do with metal from your enclosure frame blocking the signal at closer range. While elevating the radar antenna allows the unit to have a direct line of transmission for objects closer to the boat at water level, there is a down angle limit as to how far down the radar can see. Unless you tilt the radar forward, at that height objects at water level will start to disappear between 100 and 200' away.

Do you plan to use the radar at short range? If not, elevating it 18" won't have much effect. Of a bigger issue will be whether you use it while on plane. I imagine the bow rises significantly on plane. This will likely greatly increase the distance at which you lose objects at water level.

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Old 02-09-2019, 10:55 AM   #6
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Originally Posted by caltexflanc View Post
I'm not sure what Garmin's reasoning is (have you asked them?), but the higher it is the more range you have.


The person I spoke with at Garmin pretty much quoted directly from the install manual. I would have felt more confident in his response if he knew the configuration of our boat and also knew that no one else on a boat similar seems to have a radar mounted that high.
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Old 02-09-2019, 11:01 AM   #7
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The small issue you will have with lower height has to do with metal from your enclosure frame blocking the signal at closer range. While elevating the radar antenna allows the unit to have a direct line of transmission for objects closer to the boat at water level, there is a down angle limit as to how far down the radar can see. Unless you tilt the radar forward, at that height objects at water level will start to disappear between 100 and 200' away.

Do you plan to use the radar at short range? If not, elevating it 18" won't have much effect. Of a bigger issue will be whether you use it while on plane. I imagine the bow rises significantly on plane. This will likely greatly increase the distance at which you lose objects at water level.

Ted


We are heading out on the Great Loop in one month. Most of our trip will be navigating the ICW, so our use is mainly short range. Our top end is 7-8 knots, so our bow does not rise much (if at all).

Do we really have to worry about radiation with these new units? I’ve looked at numerous pictures of similar boats and can find none that have a highly elevated mount.
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Old 02-09-2019, 12:06 PM   #8
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We are heading out on the Great Loop in one month. Most of our trip will be navigating the ICW, so our use is mainly short range. Our top end is 7-8 knots, so our bow does not rise much (if at all).

Do we really have to worry about radiation with these new units? I’ve looked at numerous pictures of similar boats and can find none that have a highly elevated mount.
Did the great Loop in 2017; wonderful trip!
Majority of your trip would have short range (<4 miles) radar requirements when needed. Elevation for radiation isn't an issue on the arch. What is your air draft (bridge clearance), or does the arch fold down? If you do elevate the radar, I would angle it a couple of degrees forward of level to give you better close range forward of the bow. While it's unlikely you will be cruising much if at all at night, sometimes fog or heavy rain can catch you. Being able to see channel buoys closer to the boat as you pass them is a big plus.

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Old 02-09-2019, 12:23 PM   #9
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Ted, our air clearance is 16’. The arch does fold down but is not preferred. Could have used radar last weekend, heavy sea fog made visibility a challenge (and a learning experience). This trawler is new to us (though vintage), as is salt water navigation. Purchased specifically for the Loop. Will be happy to get this radar installed!
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Old 02-09-2019, 12:52 PM   #10
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Quote:
Originally Posted by dkris60 View Post
We have a 36 ft Nova Sundeck and are liking to add Garmin Radar to it. If I follow Garmin’s specifications I would have to add more than 18” mount to my arch. That seems extremely high especially when I look at pictures of other boats like ours and they are not using as tall of a mount. Any suggestions are appreciated.
Many radar installations are not executed IAW the manufacturer’s instructions. This may explain some of your observations. I find it amusing that many boats have their satellite TV receiver mounted for great performance, but the navigation radar is relegated to a much lesser mounting location.

My last 2 installations (Raymarine and Navico) required a pedestal to elevate the scanner sufficiently. One of those was on an arch, in close proximity to rod holders and other antenna mounts. The pedestal put the scanner over those potential interfering items. Both units worked very well in fog. I think you want the scanner to be high enough that it is not affected by energy reflected from all of the other things we mount up there.

You may be pleased with “going the extra mile” on your install. It is an infrequent occasion to install a new set, and unless you have special needs for clearance why not get all the performance your new radar can provide via proper installation?

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Old 02-09-2019, 01:01 PM   #11
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Originally Posted by dkris60 View Post
Ted, our air clearance is 16’. The arch does fold down but is not preferred. Could have used radar last weekend, heavy sea fog made visibility a challenge (and a learning experience). This trawler is new to us (though vintage), as is salt water navigation. Purchased specifically for the Loop. Will be happy to get this radar installed!
Have you measured your air clearance? Depending on how you mount the radar, it's going to get close to the advertised 19' 6" limit. This assumes you will not go west of the Oswego canal on the Erie canal which has a 15' 6" limit.

If you haven't done it, strongly encourage you to measure it yourself! This is easy to do by passing under a fixed bridge with a friend on the bridge. Lowering a tennis ball attached to a string till it hits the highest point is a good safe way. Then lower the string till the ball touches the water and calculate the difference.

Bridge heights are subject to water levels. If the water level is up, you really want to know if it's a go or a no go!

Ted
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Old 02-09-2019, 01:20 PM   #12
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If it's a 4kw radar it'll be fine right on the arch if you won't be exposed to the beam, if you're lower than the beam by a safe distance your fine. That said it certainly won't hurt to have it higher for safety though it won't do much for range on a small set. You said the arch folds, can you put a higher mount up there and still fold the arch for bridges and such?
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Old 02-09-2019, 01:56 PM   #13
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Quote:
Originally Posted by O C Diver View Post
Have you measured your air clearance? Depending on how you mount the radar, it's going to get close to the advertised 19' 6" limit. This assumes you will not go west of the Oswego canal on the Erie canal which has a 15' 6" limit.

If you haven't done it, strongly encourage you to measure it yourself! This is easy to do by passing under a fixed bridge with a friend on the bridge. Lowering a tennis ball attached to a string till it hits the highest point is a good safe way. Then lower the string till the ball touches the water and calculate the difference.

Bridge heights are subject to water levels. If the water level is up, you really want to know if it's a go or a no go!

Ted


Ted, I have not measured myself, but your idea is a good one! Will do.
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Old 02-09-2019, 02:07 PM   #14
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If it's a 4kw radar it'll be fine right on the arch if you won't be exposed to the beam, if you're lower than the beam by a safe distance your fine. That said it certainly won't hurt to have it higher for safety though it won't do much for range on a small set. You said the arch folds, can you put a higher mount up there and still fold the arch for bridges and such?


It is a 4kw Radar. Folding the arch is a real pain and would strongly prefer not to as it opens a “can of worms”. Thinking of a compromise solution; using a raised mount (less than 18”) that is hinged.
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Old 02-09-2019, 02:24 PM   #15
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Or find a solution to easily move the radar install if height becomes an issue.

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Old 02-09-2019, 02:40 PM   #16
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It is a 4kw Radar. Folding the arch is a real pain and would strongly prefer not to as it opens a “can of worms”. Thinking of a compromise solution; using a raised mount (less than 18”) that is hinged.
I had a friend that made one with a SS hinged sailboat mast step, seemed to worked fine and looked professional.
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Old 02-09-2019, 02:59 PM   #17
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It is a 4kw Radar. Folding the arch is a real pain and would strongly prefer not to as it opens a “can of worms”. Thinking of a compromise solution; using a raised mount (less than 18”) that is hinged.
Adding 18" or even 24" more to your 16' will add only a very minimal amount of additional range. More importantly is mounting the radar high enough to keep other items on your boat out of the beam.

Ken
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Old 02-09-2019, 03:26 PM   #18
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We have about an 8” extension above out radar arch for the dome. It seems to work fine. I measured our air draft by taking a 12’ straight edge and taped a Sharpie to the end of it. Held it level with the top of the radar dome and made a mark on a piling next the boat. Then just measured down from the mark on the piling to the waterline.
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Old 02-09-2019, 03:32 PM   #19
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I actually made a shim out of 2” Starboard to bring the radar dome up almost level so that it was not pointing down into the water since we don’t get up on plane. Most mounts have an angle on them to point the dome down so when you are on plane the dome is level. Here are before and after photos without the shim and with the shim. Also before and after the hardtop install.
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Old 02-09-2019, 04:00 PM   #20
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It's interesting you added a wedge to level the dome. I was thinking of ding the same. Also a good idea on measuring for clearance. I'm curious what is your clearance? Boat looks nice with hardtop.
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