Radar Head Elevation On Mast

MikeHoncho

MikeHoncho

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Dec 28, 2015
1,890
Laser, Hunter H30 Cherubini Tacoma
I’m excitedly awaiting the arrival of my new radar and mast mount. I’m thinking of mounting it just above my steaming light which is at my spreader elevation putting it 20ft above the deck.
this placement seems to be the common place for a single spreader, 30ft in my marina. Understanding that what and how far I want to see stuff is directly related to the elevation, I sail in the Puget Sound with the greatest expanse being crossing the Strait on occasion. The primary reason for radar is in fog situations with little need for weather or seeing things greater that 5 miles.
I have a 135% Genoa on a fureler and I have electrical all figured out.
So, I know it’s a loaded question but is this height wise and is there other issues I need to consider?
 
Mark Maulden

Mark Maulden

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Jan 25, 2011
2,432
S2 11.0A Anacortes, WA
Probably ok. Your radar should have some instructions pertaining to mounting. To high and you get a circular blind spot close to the boat. To high and there will be a lot of motion causing possible intermittent blips..To low and not much range.
 
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D

dlochner

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Jan 11, 2014
12,393
Sabre 362 113 Fair Haven, NY
Lots to be considered with the location. The line of sight distance to the horizon at 20 above sea level is 6 miles. Putting the antenna on a pole with the radar 13 feet distance reduces the line of sight to the horizon to 5 miles. That is not a lot of difference, for what could be an easier installation.

More weight on the mast will make the boat more tender, the higher it is, the more tender the boat will be. This may or may not be a big issue.

Putting the antenna on the mast offers an advantage when sailing in big seas. In a 6 foot sea a mast mounted antenna will be 14 feet above sea level when in a trough, while a pole mounted antenna will be 7 feet above sea level. Visibility decreases about a mile in the latter case to 4 miles. Higher up has some advantages when sailing in a seaway.

Considering these factors, I installed my antenna on a pole on the transom. The antenna is about 13 feet above sea level. The installation was easier and in my case the mast comes down each year, the pole mount eliminated connecting and disconnecting the antenna each year.

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Don S/V ILLusion

Don S/V ILLusion

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Sep 25, 2008
7,295
Alden 50 Sarasota, Florida
. Assuming your are not using it for navigation or weather watching, keep in mind the primary function is to 'see' stuff close-in. The reason you wont see many radar domes high up on a main mast is distance beyond a few miles isn't the priority.
 
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MikeHoncho

MikeHoncho

.
Dec 28, 2015
1,890
Laser, Hunter H30 Cherubini Tacoma
dlochner said:
Lots to be considered with the location. The line of sight distance to the horizon at 20 above sea level is 6 miles. Putting the antenna on a pole with the radar 13 feet distance reduces the line of sight to the horizon to 5 miles. That is not a lot of difference, for what could be an easier installation.

More weight on the mast will make the boat more tender, the higher it is, the more tender the boat will be. This may or may not be a big issue.

Putting the antenna on the mast offers an advantage when sailing in big seas. In a 6 foot sea a mast mounted antenna will be 14 feet above sea level when in a trough, while a pole mounted antenna will be 7 feet above sea level. Visibility decreases about a mile in the latter case to 4 miles. Higher up has some advantages when sailing in a seaway.

Considering these factors, I installed my antenna on a pole on the transom. The antenna is about 13 feet above sea level. The installation was easier and in my case the mast comes down each year, the pole mount eliminated connecting and disconnecting the antenna each year.

Line Of Sight Calculator

calculators, engineering calculators....
www.calculatoredge.com
Click to expand
I first considered mounting it in a pole but with my day it’s, dingy, solar panels and all of the other crap on the stern was making it a little cluttered. Poles are about 3xs the cost as a mast mount. Appreciate your input.
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,343
CAL 35 Cruiser #21 moored EVERETT WA
Here are the images of two boats.
Mine, is a 35 ft CAL with a mast about a 46 ft. Spreaders are about halve that and the radar is located just above the spreaders.
SV Hadley
Hadley Radar.jpg


Here is a Tartan 34 and the location is about the same height.
Sep 8 - 1 of 1.jpeg


Note that you will need radar cable that will run to the unit and to the location in the cabin or cockpit of the monitor. The cable length may be a limitation
 
MikeHoncho

MikeHoncho

.
Dec 28, 2015
1,890
Laser, Hunter H30 Cherubini Tacoma
jssailem said:
Here are the images of two boats.
Mine, is a 35 ft CAL with a mast about a 46 ft. Spreaders are about halve that and the radar is located just above the spreaders.
SV Hadley
View attachment 186777

Here is a Tartan 34 and the location is about the same height.
View attachment 186778

Note that you will need radar cable that will run to the unit and to the location in the cabin or cockpit of the monitor. The cable length may be a limitation
Click to expand
Any problems while tacking with your Geno?
 
Captain Larry-DH

Captain Larry-DH

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Jun 14, 2010
2,235
Robertson & Caine 2017 Leopard 40 CT
I think 10-20 feet is about right for most coastal sailing boats. It’s the close stuff that matters most. Bigger ships have tall hulls and can be picked up beyond the horizon.
 
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jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,343
CAL 35 Cruiser #21 moored EVERETT WA
I have not had any problem. The new sail has a bit of extra cloth in the area to manage any chafe. You need to be sure that your halyards are clear and have a fairlead if it has been windy. But I do that all the time, it is ingrained. With the halyards running in the mast half of the problem is solved. :biggrin:
 
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capta

capta

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Jun 4, 2009
4,882
Pearson 530 Admiralty Bay, Bequia SVG
When you look at most commercial small craft (fishing boats and ferries, etc) they normally mount the radar right onto the pilot house roof, and they need radar a lot more than we pleasure boaters.
We have a 48 mile radar and a 12 mile radar, and the 48 is grand for watching approaching squalls, but rarely needs to be on anything farther than 12 miles. Any vessel of consequence to you is going to have some freeboard and that should at least double your range of contact.
I'd go for the pole for ease of installation and repair, and I do believe if you tack a lot, a mast mounted one will, in time, wear on your headsail. Our staysail stay sure does.
 
sailme88

sailme88

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Jan 19, 2010
1,254
Catalina 34 Casco Bay
I've had radar on mast(s) and on stern towers.... I'll stick with the stern tower every day. Of course it goes without saying that others will have different opinions and that's the beauty of this site and this country.

REASONS:

Aloft on the mast... yes greater distance. BUT you're not going to hit something that is far away. So, when you are set on a range scale of... 1/2 mile there is NO difference.
Then there is the stability issue. On the mast it's like a pendulum. My mast mounted returns on many occasions had tails.. Then there is service... got an issue either the radome is coming down or the mast.
At our club we step and unstep the majority of members masts. Those that opt for mounting below the spreaders rue the day they did that as the balance point gets shifted and many have moved to the stern tower upon a radar upgrade.

On the transom or backstay:

Less movement in rough seas so smaller of no tails. Service can be done from a step ladder. No need to reinforce the Genoa leach ( because contact WILL happen). Greatly eases stepping and unstepping the mast. If not knowing what is over the horizon is of little consequence, not needing to go to a sail loft to repair your headsail and not needing a rigger to go up the mast for radar repair appeals to you... then look at a stern tower.
 
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Rick D

Rick D

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Jun 14, 2008
7,178
Hunter Legend 40.5 Shoreline Marina Long Beach CA
I have had two mounted on poles FWIW. I can see a freighter out 16 miles easily and Catalina at 24 miles. I am SO glad it was stern pole mounted since I had to service the radome three times before I mounted a new B&G radar, which was also a whole lot easier. There are pros and cons of all; your money, your boat, your choice. Good luck!
 
nightowle

nightowle

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Aug 28, 2006
578
Bavaria 35E seattle
It surprises me that the darn radar pole can cost more than a radar unit itself!
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,343
CAL 35 Cruiser #21 moored EVERETT WA
When you look at old radar format, the further it is from your head the less radiation exposure. So avoid a short pole.
 
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sailme88

sailme88

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Jan 19, 2010
1,254
Catalina 34 Casco Bay
nightowle said:
It surprises me that the darn radar pole can cost more than a radar unit itself!
Click to expand
It is very costly when you go with Seaview or Edson. BUT, a 96x3" section of stainless tube can be had for about $160.00.
What this says is find a good machine shop and have them make up a mounting plate with hinge that will support that 3" tube. Couple of struts and you'd probably be out of it for $5-600.00.
 
shemandr

shemandr

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Jan 1, 2006
7,403
Slickcraft 26 Sailfish
Why the difference with digital radar? Doesn't it still transmit EMR?
 
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