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.

Welcome to the forum!
A picture of your arch or a link to a sister boat would be helpful.

Ted

This is a picture of our 36’ Heritage East.

I'm not sure what Garmin's reasoning is (have you asked them?), but the higher it is the more range you have.

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

caltexflanc said:

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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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.

O C Diver said:

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

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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.

dkris60 said:

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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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.

Ted

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!

dkris60 said:

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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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?

Best Wishes

dkris60 said:

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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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

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?

O C Diver said:

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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Ted, I have not measured myself, but your idea is a good one! Will do.

Fish53 said:

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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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.

Or find a solution to easily move the radar install if height becomes an issue.

>>>>>>>>>>>Action

dkris60 said:

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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I had a friend that made one with a SS hinged sailboat mast step, seemed to worked fine and looked professional.

dkris60 said:

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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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

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.

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.

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.

A friend of mine has a milling machine and he did the wedge for me. My air draft with the anchor light down is 16’6”. With the anchor light up it is 17’6”. Thanks we love the hardtop.

Don't forget to make sure your anchor light is above the dome (not obstructed). I wish I had a dollar for every time a radar was installed directly in front or behind the existing light. Even saw the Coasties RHIB with a dome directly in front of the all-around white.

High Wire said:

Don't forget to make sure your anchor light is above the dome (not obstructed). I wish I had a dollar for every time a radar was installed directly in front or behind the existing light. Even saw the Coasties RHIB with a dome directly in front of the all-around white.

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For sure!!!

I think we are beating this subject to death! You are correct to question the best height of the scanner but as some others have pointed out, mounted directly on the arch seems to work for most folks. If it were me, I'd buy the set of my choice, mount it to the arch, (leaving a couple extra of feet of cable) and take the boat out and actually see how close it scans. (Thinking of the great Loop trip.) If not scanning close enough, mount the scanner higher with a slight down angle until you can see both close and distant to your satisfaction. (Use a box, etc., temporarily attached until you achieve your desired range.) when you are happy with the scan, measure the height of the "box" and buy/build a mast that accommodates that height.

I'm surprised there is not an adjustable mount that lets you tweak the angle...

Comodave said:

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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Dave,

Looks like you could do better to add some height to the dome. The angle were it intersects with the top of your Bimini is too shallow, and you'll loose images close in. Just the way it looks, but worth being sure. With that guess you won't see much for several hundred feed.

I could argue to see the crab traps go by you'd want less than 100 feet, as well as small boats, pilings, etc.

Fish53 said:

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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If it's one of the new digital radars, they don't have magnetrons and no risk. And they work quite well for short range, like the loop would require. Love mine. (Simrad 4G Broadband).

There are some good visuals at the link below, on pages 8 and 9. Various radars will have different vertical (and horizontal) beam widths. Your Garmin would appear to be less vertical beamwidth than this Navico product, but the theory as it pertains to mounting and obstructions is the same.

https://www.navico-commercial.com/Root/SimradProSeries_docs/RADAR_3G_4G_IG_988-10113-003_EN_W.pdf

Seevee said:

Dave,



Looks like you could do better to add some height to the dome. The angle were it intersects with the top of your Bimini is too shallow, and you'll loose images close in. Just the way it looks, but worth being sure. With that guess you won't see much for several hundred feed.



I could argue to see the crab traps go by you'd want less than 100 feet, as well as small boats, pilings, etc.

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I would agree. Thanks for your input.

IRENE said:

There are some good visuals at the link below, on pages 8 and 9. Various radars will have different vertical (and horizontal) beam widths. Your Garmin would appear to be less vertical beamwidth than this Navico product, but the theory as it pertains to mounting and obstructions is the same.



https://www.navico-commercial.com/Root/SimradProSeries_docs/RADAR_3G_4G_IG_988-10113-003_EN_W.pdf

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Great link. Thank you,