I am going to add radar to my cd 33 and would like some advise on mast mounts versus aft pole mounts for the radome unit. Will the mast mount provide better coverage due to height? What are the advantages to a aft pole mount?
Thanks,
larry mace
lmace@gt.com
advise-radome locations
Moderator: Jim Walsh
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Larry DeMers
Re: advise-radome locations
Larry,
I have a stern mounted pole mount and love it. The advantages over a mast mount are; Less work installing it..don'thave to feed the cable up the mast,cut holes in the mast, mount the radar platform up there etc. The cable run is shorter, and the radom is nearby in case I need to remove or adjust it.
Disadvantages to a mast mount; Considerable weight placed high up the mast decreases the righting arm of the boat. WHile you will have a slightly better view of the 12-16 mile range, you will sacrifice tremendously the close-in range. I don't know about you, but my uses for radar are mainly in negotiating buoys and obstacles in fog. The lower platform of the stern mount works great for this. If you increase the range of the radar through mounting it up higher, the signal skips right over the target out in front of you, so this would effect your ability to find objects close in to you, while giving a fine view of the objects out at 16 miles~ ! Now which ones are the most immediate threat to you?
Larry DeMers
s/v DeLaMer
demes@sgi.com
I have a stern mounted pole mount and love it. The advantages over a mast mount are; Less work installing it..don'thave to feed the cable up the mast,cut holes in the mast, mount the radar platform up there etc. The cable run is shorter, and the radom is nearby in case I need to remove or adjust it.
Disadvantages to a mast mount; Considerable weight placed high up the mast decreases the righting arm of the boat. WHile you will have a slightly better view of the 12-16 mile range, you will sacrifice tremendously the close-in range. I don't know about you, but my uses for radar are mainly in negotiating buoys and obstacles in fog. The lower platform of the stern mount works great for this. If you increase the range of the radar through mounting it up higher, the signal skips right over the target out in front of you, so this would effect your ability to find objects close in to you, while giving a fine view of the objects out at 16 miles~ ! Now which ones are the most immediate threat to you?
Larry DeMers
s/v DeLaMer
I am going to add radar to my cd 33 and would like some advise on mast mounts versus aft pole mounts for the radome unit. Will the mast mount provide better coverage due to height? What are the advantages to a aft pole mount?
Thanks,
larry mace
demes@sgi.com
-
Steve Alarcon
Re: advise-radome locations
Larry,
My experience and consideration is that higher is better. Due to the curvature of the earth, a person can see just over three nautical miles when the eyes are at sea level. Imagine the improvement at 30+ feet above the water when the radome is mounted just above the spreaders. As to weight aloft, I mounted a 16nm Ratheon two years ago; I don't have the specific figures with me at home, but as I recall the total weight wasn't more than 10lbs. Windage is not much of a factor when one considers the drag coefficient of modern designs. As to Larry's comment about visability close in, pay attention to your selected radars' vertical degree of visability. My experience is that I can see EVERYTHING in my immediate vicinity if there is some surface capable of reflecting RF!
My experience...Pay attention to quality and get a radar that will "see" as far away as possible. Consider how fast commercial vessel can bear down on you when they are doing 15 kts. That is the issue you need to address while in fog. By the time you paint the image, plot their course, and figure out where you should be they will be on top of you. If you have high speed ferrys like we do in the Pacific North West (35 kts), you can be in real trouble.
As to mounting challanges, Larry DeMers is correct. Mast mounting requires some fore thought. But what the hey, we have boats because we enjoy the mental challange, right? I came up with some unique problem solving (IMHO) during my installation that I would be happy to share. Just let me know.
Bottom line, radar is a safety item. If you are going to commit to it, do it right. Your life, and that of your crew, depends on your decision.
Fair winds,
Steve Alarcon
CD30 Temerity
SEattle
alarcon3@prodigy.net
My experience and consideration is that higher is better. Due to the curvature of the earth, a person can see just over three nautical miles when the eyes are at sea level. Imagine the improvement at 30+ feet above the water when the radome is mounted just above the spreaders. As to weight aloft, I mounted a 16nm Ratheon two years ago; I don't have the specific figures with me at home, but as I recall the total weight wasn't more than 10lbs. Windage is not much of a factor when one considers the drag coefficient of modern designs. As to Larry's comment about visability close in, pay attention to your selected radars' vertical degree of visability. My experience is that I can see EVERYTHING in my immediate vicinity if there is some surface capable of reflecting RF!
My experience...Pay attention to quality and get a radar that will "see" as far away as possible. Consider how fast commercial vessel can bear down on you when they are doing 15 kts. That is the issue you need to address while in fog. By the time you paint the image, plot their course, and figure out where you should be they will be on top of you. If you have high speed ferrys like we do in the Pacific North West (35 kts), you can be in real trouble.
As to mounting challanges, Larry DeMers is correct. Mast mounting requires some fore thought. But what the hey, we have boats because we enjoy the mental challange, right? I came up with some unique problem solving (IMHO) during my installation that I would be happy to share. Just let me know.
Bottom line, radar is a safety item. If you are going to commit to it, do it right. Your life, and that of your crew, depends on your decision.
Fair winds,
Steve Alarcon
CD30 Temerity
SEattle
alarcon3@prodigy.net
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Al Levesque
Re: advise-radome locations
Another consideration in locating the unit: We have the unit on the mast and noticed some damage to the base and housing adjacent to where the main halyard lies. Earlier in the year we did some sailing in heavy weather and could have left the halyard slack during sail changing. Another time, I noticed that the jib halyard was hooked around the unit on its way down to the tie off point at the bow. Either one of those incidents might have caused the damage.I am going to add radar to my cd 33 and would like some advise on mast mounts versus aft pole mounts for the radome unit. Will the mast mount provide better coverage due to height? What are the advantages to a aft pole mount?
The unit could be protected by adding caging around it, but that adds to cost and weight aloft.
Al
albertlevesque@cove.com
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John
radar height formula
I have the scanner mounted about 18" above the spreaders, about 17 -18' off the deck I guess. I used a typical scanner platform mount made of aluminum. It has never suffered any damage from sails or halyards. I think others have said they noticed some tenderness of the boat with it mounted on the mast. I have never noticed any effect on the boats performance in any way.I am going to add radar to my cd 33 and would like some advise on mast mounts versus aft pole mounts for the radome unit. Will the mast mount provide better coverage due to height? What are the advantages to a aft pole mount?
Thanks,
larry mace
When I first installed it the owners manual said to mount the scanner as high as possible (within reason of course). The total effect of the scanner height and the target height determine the radar "line of sight range". If you want to figure out the potential radar horizon based on the scanners mounted height use the following formula:
Distance (nm) = 2.23 squareroot of h
h = Height of the radar scanner off the water line (in meters)
Example: A scanner height of 2 meters has a radar horizon of 3.2nm
You add the radar horizon figure to the target horizon figure calculated the same way and that sum will give you the distance from you that the target can first be sighted. Obviously the lower the scanner is mounted the more reduced your first sighting of the potential target becomes. Hope that helps you determine what will work for you with your options.
Collision Avoidance:
I use the "EBL" electronic bearing line and the "VRM" variable range marker features on my radar and a Autohelm handheld fluxgate compass to track targets that may pose a collision hazard. It is certainly optimal to plot the findings on a chart and I certainly advocate that practice but when there is limited time to act I don't think you have the time to be plotting when you are possibly on a collision course. If the bearing to the target holds close to the same after a couple of sights its time to take evasive action.
I'd like to hear from others on radar matters, they aren't discussed much.
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Chris Reinke (CD330 Innis
Re: radar height formula
John - This is a very useful formula. I would like to offer one additional item for consideration, and not as contradict to anything you have already noted. The height of the object you are trying to receive a signal reflection from can also be determined by the same formula. My Raytheon SL72 has a 24nm range, but is mounted on a 4m stern pole. The direct line of sight range can be calculated using your formula as only 4.46 miles. However, if I am trying to identify an approaching ship (height of 25m) it will break the visible horizon at 11.2nm, plus the 4.46nm gained by my dome being at 4m high. This provides me with a radar image from 15.6nm.
I was curious, is your antenna dome mounted on a gimbal? I have heard mixed feelings towards mast mounts. One argument for the gimbal is that without it you loose considerable range while heeling and that the effect is magnified as you increase your height. The other argument against the gimbal is that the constant motion will cause fatigue in the antennas dome cable and eventually failure.
Chris
I was curious, is your antenna dome mounted on a gimbal? I have heard mixed feelings towards mast mounts. One argument for the gimbal is that without it you loose considerable range while heeling and that the effect is magnified as you increase your height. The other argument against the gimbal is that the constant motion will cause fatigue in the antennas dome cable and eventually failure.
Chris
I have the scanner mounted about 18" above the spreaders, about 17 -18' off the deck I guess. I used a typical scanner platform mount made of aluminum. It has never suffered any damage from sails or halyards. I think others have said they noticed some tenderness of the boat with it mounted on the mast. I have never noticed any effect on the boats performance in any way.I am going to add radar to my cd 33 and would like some advise on mast mounts versus aft pole mounts for the radome unit. Will the mast mount provide better coverage due to height? What are the advantages to a aft pole mount?
Thanks,
larry mace
When I first installed it the owners manual said to mount the scanner as high as possible (within reason of course). The total effect of the scanner height and the target height determine the radar "line of sight range". If you want to figure out the potential radar horizon based on the scanners mounted height use the following formula:
Distance (nm) = 2.23 squareroot of h
h = Height of the radar scanner off the water line (in meters)
Example: A scanner height of 2 meters has a radar horizon of 3.2nm
You add the radar horizon figure to the target horizon figure calculated the same way and that sum will give you the distance from you that the target can first be sighted. Obviously the lower the scanner is mounted the more reduced your first sighting of the potential target becomes. Hope that helps you determine what will work for you with your options.
Collision Avoidance:
I use the "EBL" electronic bearing line and the "VRM" variable range marker features on my radar and a Autohelm handheld fluxgate compass to track targets that may pose a collision hazard. It is certainly optimal to plot the findings on a chart and I certainly advocate that practice but when there is limited time to act I don't think you have the time to be plotting when you are possibly on a collision course. If the bearing to the target holds close to the same after a couple of sights its time to take evasive action.
I'd like to hear from others on radar matters, they aren't discussed much.
-
John
Radar Formula explained
Chris,
I'm going to try and clarify some of my previous comments a little because maybe I wasn't clear enough. I note you stated that the target height reflection signal can be determined by using the same formula. Yes, you are absolutely correct and you will note that I mentioned that in the paragraph just after the formula.
Your figures that you use are correct. By adding the 4.46 "nautical" miles of the vessels radar (scanner) horizon to the 11.2 "nautical" mile target radar horizon you will have a total "radar line of sight range" of 15.66 nautical miles. That is the point at when the target would begin to appear on your radar display head.
The "direct line of sight range" of 4.46nm that you refer to is not the "direct line of sight range", it is the "radar scanner horizon". You must add that range (mileage) to the "target radar horizon" range (mileage) to get the "direct line of sight range".
For example: (using your numbers)
1) radar scanner height = 4 meter
2) after application of formula the "scanner
radar horizon" is then 4.46 nautical miles
3) target (ship) height = 25 meters
4) after application of formula the "target radar
horizon" is then 11.2 nautical miles
5) add the scanner horizon range and the target
horizon range to get the "direct line of sight
range" which in this example would be 15.66
nautical miles.
6) the "direct line of sight range" (15.66 nautical
miles in this example) would be the point at when
you would first see the target on the radar display
screen.
I hope this helps everybody understand this crazy stuff.
Chris, in essence we are in mutual understanding of one another.
As I said in my other post I mounted the scanner on a fixed platform. The problem with radar scanner mounting is that everything is a compromise. You have to pick your poison and live with the consequences. The gimbal is great, but like you said the cable is really vulnerable. Plus, the gimbals are really expensive. I've been served well with the fixed mount and haven't hit anything yet. I think if I were to install a new radar I'd again install on the mast with a fixed mount. Why? Because it allows me to have the wind generator on a pole at the stern. On the mast I get a better radar horizon (longer) thus I see targets further off than I otherwise would. The mast is aft of the scanner rather than in front of it, radar generally has clearer less obstructed view. All things considered I think the mast mount with a gimbal is the best way to go. But I share very much in your comments about cable wear with the gimbal. The heeling effect on scanner height is a reality but to what degree I sure do not know. That is for an engineer to calculate. I don't think it would be any concern regarding a 25m height ship target but small stuff could be missed with the boat well heeled over. I've not had a problem however.
John - This is a very useful formula. I would like to offer one additional item for consideration, and not as contradict to anything you have already noted. The height of the object you are trying to receive a signal reflection from can also be determined by the same formula. My Raytheon SL72 has a 24nm range, but is mounted on a 4m stern pole. The direct line of sight range can be calculated using your formula as only 4.46 miles. However, if I am trying to identify an approaching ship (height of 25m) it will break the visible horizon at 11.2nm, plus the 4.46nm gained by my dome being at 4m high. This provides me with a radar image from 15.6nm.
I'm going to try and clarify some of my previous comments a little because maybe I wasn't clear enough. I note you stated that the target height reflection signal can be determined by using the same formula. Yes, you are absolutely correct and you will note that I mentioned that in the paragraph just after the formula.
Your figures that you use are correct. By adding the 4.46 "nautical" miles of the vessels radar (scanner) horizon to the 11.2 "nautical" mile target radar horizon you will have a total "radar line of sight range" of 15.66 nautical miles. That is the point at when the target would begin to appear on your radar display head.
The "direct line of sight range" of 4.46nm that you refer to is not the "direct line of sight range", it is the "radar scanner horizon". You must add that range (mileage) to the "target radar horizon" range (mileage) to get the "direct line of sight range".
For example: (using your numbers)
1) radar scanner height = 4 meter
2) after application of formula the "scanner
radar horizon" is then 4.46 nautical miles
3) target (ship) height = 25 meters
4) after application of formula the "target radar
horizon" is then 11.2 nautical miles
5) add the scanner horizon range and the target
horizon range to get the "direct line of sight
range" which in this example would be 15.66
nautical miles.
6) the "direct line of sight range" (15.66 nautical
miles in this example) would be the point at when
you would first see the target on the radar display
screen.
I hope this helps everybody understand this crazy stuff.
Chris, in essence we are in mutual understanding of one another.
As I said in my other post I mounted the scanner on a fixed platform. The problem with radar scanner mounting is that everything is a compromise. You have to pick your poison and live with the consequences. The gimbal is great, but like you said the cable is really vulnerable. Plus, the gimbals are really expensive. I've been served well with the fixed mount and haven't hit anything yet. I think if I were to install a new radar I'd again install on the mast with a fixed mount. Why? Because it allows me to have the wind generator on a pole at the stern. On the mast I get a better radar horizon (longer) thus I see targets further off than I otherwise would. The mast is aft of the scanner rather than in front of it, radar generally has clearer less obstructed view. All things considered I think the mast mount with a gimbal is the best way to go. But I share very much in your comments about cable wear with the gimbal. The heeling effect on scanner height is a reality but to what degree I sure do not know. That is for an engineer to calculate. I don't think it would be any concern regarding a 25m height ship target but small stuff could be missed with the boat well heeled over. I've not had a problem however.
John - This is a very useful formula. I would like to offer one additional item for consideration, and not as contradict to anything you have already noted. The height of the object you are trying to receive a signal reflection from can also be determined by the same formula. My Raytheon SL72 has a 24nm range, but is mounted on a 4m stern pole. The direct line of sight range can be calculated using your formula as only 4.46 miles. However, if I am trying to identify an approaching ship (height of 25m) it will break the visible horizon at 11.2nm, plus the 4.46nm gained by my dome being at 4m high. This provides me with a radar image from 15.6nm.
I was curious, is your antenna dome mounted on a gimbal? I have heard mixed feelings towards mast mounts. One argument for the gimbal is that without it you loose considerable range while heeling and that the effect is magnified as you increase your height. The other argument against the gimbal is that the constant motion will cause fatigue in the antennas dome cable and eventually failure.
Chris
I have the scanner mounted about 18" above the spreaders, about 17 -18' off the deck I guess. I used a typical scanner platform mount made of aluminum. It has never suffered any damage from sails or halyards. I think others have said they noticed some tenderness of the boat with it mounted on the mast. I have never noticed any effect on the boats performance in any way.I am going to add radar to my cd 33 and would like some advise on mast mounts versus aft pole mounts for the radome unit. Will the mast mount provide better coverage due to height? What are the advantages to a aft pole mount?
Thanks,
larry mace
When I first installed it the owners manual said to mount the scanner as high as possible (within reason of course). The total effect of the scanner height and the target height determine the radar "line of sight range". If you want to figure out the potential radar horizon based on the scanners mounted height use the following formula:
Distance (nm) = 2.23 squareroot of h
h = Height of the radar scanner off the water line (in meters)
Example: A scanner height of 2 meters has a radar horizon of 3.2nm
You add the radar horizon figure to the target horizon figure calculated the same way and that sum will give you the distance from you that the target can first be sighted. Obviously the lower the scanner is mounted the more reduced your first sighting of the potential target becomes. Hope that helps you determine what will work for you with your options.
Collision Avoidance:
I use the "EBL" electronic bearing line and the "VRM" variable range marker features on my radar and a Autohelm handheld fluxgate compass to track targets that may pose a collision hazard. It is certainly optimal to plot the findings on a chart and I certainly advocate that practice but when there is limited time to act I don't think you have the time to be plotting when you are possibly on a collision course. If the bearing to the target holds close to the same after a couple of sights its time to take evasive action.
I'd like to hear from others on radar matters, they aren't discussed much.