Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 24-12-2013, 16:15   #1
Registered User
 
neelie's Avatar

Join Date: Oct 2007
Location: On the boat
Boat: Valiant 50
Posts: 514
Radar: Pole or Mast Mount?

I'm sure this has been discussed ad nauseum in the past, however, the search function does not reveal anything.

Apart from a reduced line of sight range of say 4 miles with a 10 ft high antennae instead of say 8 miles for a 30 ft high antennae why else would one choose to mount the scanner halfway up the mast?

I'm thinking that I can live with a reduced range of 4 miles to a low atoll - worst case! An oil tanker would still appear at 20 miles.

I am seriously contemplating changing from my mast mount to a pole mount.

Should I or shouldn't I?
__________________

__________________
The light at the end of the tunnel are no longer the headlights of the oncoming train......yippee
neelie is offline   Reply With Quote
Old 24-12-2013, 16:36   #2
Registered User
 
tryrsh's Avatar

Join Date: Sep 2011
Location: Indiana
Boat: Beneteau 411
Posts: 62
Mines on a pole but I never turn it on... Good chart plotter with up to date maps and a couple iPads running Garmin Blue Carts and an AIS linked to all three, I have no use for or reason to turn my radar on... Well, I have in fog near shore but that's rare in my type of cruising. Anybody else feel this way or is it just me?
__________________

__________________
tryrsh is offline   Reply With Quote
Old 24-12-2013, 17:00   #3
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,462
Re: Radar: Pole or Mast Mount?

Arch? Mount yer solar panels up there as well?
__________________
Delancey is offline   Reply With Quote
Old 24-12-2013, 17:01   #4
Registered User

Join Date: Aug 2013
Location: Gosport, UK
Boat: Elan Impression 434
Posts: 44
Re: Radar: Pole or Mast Mount?

I'm new to it all, but I think the same - AIS is amazing. Radar I'll be using for fog/night and close in small stuff without AIS. And due to the power consumption I'll likely power it up manually only every few mins.
__________________
Charliemciver is offline   Reply With Quote
Old 24-12-2013, 17:17   #5
Senior Cruiser
 
Randyonr3's Avatar

Cruisers Forum Supporter

Join Date: Nov 2007
Boat: Beneteau FIRST 42
Posts: 1,836
Re: Radar: Pole or Mast Mount?

Have had both types.. the mast mount showed a large "dead" spot to the rear of the boat where the pole mount gives you a pretty clear shot 360 degrees.. don't have an AIS, and not sure I'm putting one on befor we leave this time..
__________________
Randyonr3 is offline   Reply With Quote
Old 24-12-2013, 17:43   #6
Registered User

Join Date: Jan 2009
Location: where ever my anchor is
Boat: 28' Bristol Channel Cutter - Angelsea
Posts: 215
Images: 3
Re: Radar: Pole or Mast Mount?

What about the vessels who don't have AIS. I can't believe someone said that. I held an all oceans license which required radar certification. If I only had one electronic aid to navigation it would be radar. The question from the OP was wether mast or dedicated mount was best for radar.
Mounting on the mast gives more weight aloft. Not good. But it also increases the range. Good. But how much range do you need. Basically not much more than a dedicated mount. Motor yachts have to use a dedicated mount and do fine. As far as other vessels go you should be able to see them 10 miles out. Plenty of time for collision avoidance. Islands are good for a much longer range if you use topographic maps, or charts with topography and make appropriate calculations.
__________________
Gary Shanti's blog
"two wrongs don't make a right, but three lefts will get you back on the freeway"
seacap is offline   Reply With Quote
Old 24-12-2013, 19:16   #7
Registered User

Join Date: Nov 2011
Location: Montegut LA.
Boat: Now we need to get her to Louisiana !! she's ours
Posts: 3,421
Re: Radar: Pole or Mast Mount?

No matter which you choose, pole or mast mount, you will have one of the best tools you can have on a vessel! I know all of the new stuff available today, AIS and such ! But when ya get caught in the REAL fog! nothing will give ya that comfy feeling like a good radar!! Im sure that haveing AIS is nice but if I could only have one extra piece of navagation gear besides a compass, I would want to have a working radar !But then Im Old and learned my sailing In the PNW, and as some of yall know it gets foggy up there sometimes ! ( it also helps down here in the Gulf with all the metal out there!!LOL) Just my 2 cents
__________________
Bob and Connie
bobconnie is offline   Reply With Quote
Old 24-12-2013, 20:25   #8
Registered User
 
gamayun's Avatar

Join Date: Aug 2013
Location: Oakland, CA
Boat: Freedom 38
Posts: 1,231
Re: Radar: Pole or Mast Mount?

Are you sure the range of radar on a 10-ft pole is 4 miles? I don't remember the formula but thought it was a little more, like 6 miles on an 8-foot pole, which is what I have. Also, why are you thinking of changing the setup you already have? Is there a problem with it on the mast? Having been in fog with 1/4 mile visibility right outside the Golden Gate Bridge, I was happy to have my radar. The pole was the only consideration for me because I have a carbon fiber mast and can't drill into it for the mounting holes. The radar is 3G, so it doesn't have the same radiation and power concerns as the other type, but I still don't keep it on when visibility is good. How close the radar is to your head is something to consider.
__________________
gamayun is offline   Reply With Quote
Old 24-12-2013, 20:58   #9
Registered User
 
neelie's Avatar

Join Date: Oct 2007
Location: On the boat
Boat: Valiant 50
Posts: 514
Re: Radar: Pole or Mast Mount?

Quote:
Originally Posted by gamayun View Post
Are you sure the range of radar on a 10-ft pole is 4 miles?

Pretty sure (+/- 0.5nm) and that's to target of zero height. Of course if your target is a Walmart container vessel from China stacked 200 ft high with Christmas goodies then your radar will pick it up at 24 miles or so.


I don't remember the formula but thought it was a little more, like 6 miles on an 8-foot pole, which is what I have. Also, why are you thinking of changing the setup you already have?

Since I am changing the radar to a B&G 4G plus installing wind generator - I was thinking that mounting it on a pole would have more advantages than disadvantages. (Kato Marine do a wind gennie / radar combo pole.)


Also, the attraction of the 4G is its ultra short range capability - hence a scanner mounted high up is not an advantage.

Is there a problem with it on the mast? Not really - apart from weight high up and more difficult to access.

Having been in fog with 1/4 mile visibility right outside the Golden Gate Bridge, I was happy to have my radar. The pole was the only consideration for me because I have a carbon fiber mast and can't drill into it for the mounting holes. The radar is 3G, so it doesn't have the same radiation and power concerns as the other type, but I still don't keep it on when visibility is good. How close the radar is to your head is something to consider.

I read somewhere that the new generation radars don't transmit a lot of energy - having said that I wont be placing my testicles in front of the scanner to prove my point.

Answers in green....
__________________
The light at the end of the tunnel are no longer the headlights of the oncoming train......yippee
neelie is offline   Reply With Quote
Old 24-12-2013, 21:09   #10
Registered User
 
WindLove's Avatar

Join Date: Nov 2013
Location: Wherever Sarah takes me but based in VA/Chesapeake
Boat: Bavaria 36
Posts: 69
I think installation on a mast is preferable. Why have an additional structure with a lower line of sight. Radar and AIS are not things to compare and choose your favorite. They are two very different tools for two very different needs. You should try to have both.
__________________
Even if you’re on the right track, you’ll get run over if you just sit there..
WindLove is offline   Reply With Quote
Old 24-12-2013, 21:20   #11
Registered User
 
markpierce's Avatar

Join Date: Aug 2010
Location: Central California
Boat: M/V Carquinez Coot
Posts: 3,413
Re: Radar: Pole or Mast Mount?

I don't like the idea of my eyes/body scanned by low-mounted radar. Mine is on the mast.

__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 24-12-2013, 21:29   #12
Registered User
 
rgleason's Avatar

Join Date: Mar 2012
Location: Boston, MA
Boat: 1981 Bristol 32 Sloop
Posts: 9,369
Re: Radar: Pole or Mast Mount?

Written some time ago


Our backstay mount radar is on a gimbal 12' above water. The maximum range for a similar height object is
1.22nm x sq root height of radar + 1.2nm x sq root ht of target
1.22nm x sq root of 12' + 1.2nm x sq root of 12'
1.22nm x 3.464 + [/FONT]1.22nm x 3.464
4.22nm + 4.22nm = 8.4nm
Therefore we will only be able to see about 8 nm Miles over the curvature of the earth!
PURCHASING a 24nm or 36 nm RADAR and suffering the added weight (aloft or on the stern), windage due to size, and battery depletion is pure insanity.


I wrote some time ago, the following:

Our backstay mount radar is on a gimbal 12' above water. The maximum range for a similar height object is
1.22nm x sq root height of radar + 1.2nm x sq root ht of target
1.22nm x sq root of 12' + 1.2nm x sq root of 12'
1.22nm x 3.464 +
[FONT=Arial]1.22nm x 3.464
4.22nm + 4.22nm = 8.4nm
Therefore we will only be able to see about 8 nm Miles over the curvature of the earth!
PURCHASING a 24nm or 36 nm RADAR and suffering the added weight (aloft or on the stern), windage due to size, and battery depletion is pure insanity.


Sent from my SCH-I545 using Cruisers Sailing Forum mobile app
__________________
rgleason is offline   Reply With Quote
Old 24-12-2013, 21:35   #13
Registered User
 
rgleason's Avatar

Join Date: Mar 2012
Location: Boston, MA
Boat: 1981 Bristol 32 Sloop
Posts: 9,369
Re: Radar: Pole or Mast Mount?

Long thread here http://www.cruisersforum.com/forums/....php?p=1013621
B&G Zeus MFD - Has Anyone Tried it ? Sorry for double post. On cell

Sent from my SCH-I545 using Cruisers Sailing Forum mobile app
__________________
rgleason is offline   Reply With Quote
Old 24-12-2013, 22:27   #14
Registered User
 
gamayun's Avatar

Join Date: Aug 2013
Location: Oakland, CA
Boat: Freedom 38
Posts: 1,231
Re: Radar: Pole or Mast Mount?

Quote:
Originally Posted by rgleason View Post
Long thread here B&G Zeus MFD - Has Anyone Tried it ? - Page 2 - Cruisers & Sailing Forums
B&G Zeus MFD - Has Anyone Tried it ? Sorry for double post. On cell

Sent from my SCH-I545 using Cruisers Sailing Forum mobile app
I have the B&G Zeus 7" display. I'm very happy with it, but have had some "manufacturing warranty" defect with it interfacing with the radar. Not sure if the trouble getting it fixed is the manufacturer's or Johnson Marine in Santa Cruz. The people at Johnson Marine seem genuine in addressing the problem, but there hasn't been much progress. To get the most out of the MFD, which has some great sailing features, it needs to have the speed-depth-wind combo hooked up, which I haven't done yet. I also have the 3G dome because of that line of sight calculation -- no need to buy more than it would ever be able to function at.
__________________
gamayun is offline   Reply With Quote
Old 24-12-2013, 23:11   #15
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: Radar: Pole or Mast Mount?

Neelie,
Merry Christmas!!

1) Really???
Quote:
Originally Posted by neelie View Post
the search function does not reveal anything.
My search using radar and mast mounting, turned up quite a bit...including the definitive answers you were seeking, from just a few months ago!!

Please read this posting / thread for all the detailed answers to your questions....
"Radar dome location??"
Radar dome location??





2) Brief / specific answers:
Quote:
Originally Posted by neelie View Post
Apart from a reduced line of sight range of say 4 miles with a 10 ft high antennae instead of say 8 miles for a 30 ft high antennae why else would one choose to mount the scanner halfway up the mast?
As detailed in the above linked thread, the 1st / primary advantage is NOT increased range, but rather the ability of the radar to actually work when at sea, in a heavy sea....a low-mounted radar is prone to having its beam blocked by the waves/sea!!!
(and fyi, there's no need to mount it "halfway up the mast", as typically 1/3 the way up a 65' mast is plenty...also, while your "4 nm" figure is accurate, the radar horizon from a 30' height is only approx. 6.9nm, not 8nm...)

Secondarily, the increased scanner height (of "mast-mounted radars") can provide some advantage in target acquisition, especially when looking for smaller targets that are either low to the water and/or when in heavy seas....

Another advantage is that it keeps the radar scanner from shading solar panels, etc. and/or cluttering-up the aft-end/transom....




I'm thinking that I can live with a reduced range of 4 miles to a low atoll - worst case! An oil tanker would still appear at 20 miles.....
......Since I am changing the radar to a B&G 4G plus installing wind generator. Also, the attraction of the 4G is its ultra short range capability - hence a scanner mounted high up is not an advantage.
----Not sure your B&G 4G radar is really going to detect much shipping at 20 miles....but even if it can, I doubt it'll be an oil tanker (typical superstructure radar cross-section is NOT 200' high, but closer to 100' high), so don't expect to see "oil tankers" too much beyond 16 nm or so, from a 10' high radar scanner (especially one that isn't designed for long-range..)
But....this is a pretty moot point as detecting shipping at ~20 miles is really not a requirement for most cruisers...

----And, unless you'll be doing "zero-visibility" docking, and require perfect target resolution at distances of 50', having the scanner mast-mounted (at say, 25' or so) shouldn't be an issue/disadvantage...




apart from weight high up and more difficult to access.
---- most modern radar scanners are very reliable.....and the reduction of a few pounds of weight aloft on a Valiant 50, would be unnoticeable...




I am seriously contemplating changing from my mast mount to a pole mount.
Should I or shouldn't I?
I would NOT....and depending on where you're sailing/cruising, I'd not recommend this for you either...
Just my opinion here...but you did ask!!



neelie, I do hope this helped...
Fair winds...

John
s/v Annie Laurie
__________________

__________________
ka4wja is offline   Reply With Quote
Reply

Tags
mast, radar

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 22:06.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.