? about radar on a sailboat

[mvweebles]

Can the folks who say modern radar have some sort of adjustment to electronically re-level themselves provide a citation? I doubt they even have the ability to sense they are out-of-level let alone compensate for it. There may be some sort of manual intervention you can calibrate for, but doubtful more than a couple degrees to compensate for install error.

I don't understand why anyone would install radar and not a leveling mechanism. Without it, you're at serious risk of erroneous information from your radar which is arguably worse than no radar at all. As another post said, interpreting radar can sometimes be tricky. Why anyone would consciously make that harder is beyond me.

Peter

[mvweebles]

Originally Posted by Jammer

The vertical beam angle on the radars is fairly large, typically 25-30 degrees (-/+ 12-15 degrees from horizontal). The cutoff at the top and bottom of the beam is soft and gradual, not absolute. That's wide enough that typical boat motion has little effect.

As for heel, there are various manual and auto self leveling mounts out there, but they aren't that helpful. Consider a boat on a 20 degree heel. The beam is going to be 20 degrees too high directly off the weather beam, causing degraded performance, but just a little ways forward and aft the effective tilt will be 15 degrees or less. Similar situation to lee except with downward tilt. Straight fore and aft there's no effect on performance from the heel. So the area of degraded performance isn't that great.

The other fact to consider is that it is relatively rare to be hard on the wind in situations where radar matters most. Fog is rarely accompanied by wind. When coastwise navigation is undertaken at night, under sail, it is usually because the wind is on or abaft the beam.

From the installation manual of Navico (B&G). In short, put the radar at a 12.5 degree heel reduces your radar beam by 75%.

Peter

[CarinaPDX]

@mvweebles: radar doesn't "re-level" itself. Modern digital radars do adapt to the different responses from the high side (shooting most of the signal into the air) and the low side (strong sea returns). It is clear that the gain is increased to weather and strong sea clutter removal is applied to lee. I suspect that there is some special handling for when one side's signals are dramatically different than the other, but it could just be the outcome of an adaptive algorithm. I'm not remembering whether it was this radar or the previous, but one of them I tested by angling to one side and stabilizing, then quickly tilting the radar to the other side. The side that went from high to low initially presented a black display upon the change, then adjusted to a normal display. IIRC the other side went white then picked up targets. The fact that each side initially behaved differently in my experiment seems to indicate that the sides were being handled differently. The digital processing to overcome this is very impressive, but it can't completely offset the inferior signals relative to a level scanner.

Greg

[mvweebles]

Originally Posted by CarinaPDX

@mvweebles: radar doesn't "re-level" itself. Modern digital radars do adapt to the different responses from the high side (shooting most of the signal into the air) and the low side (strong sea returns). It is clear that the gain is increased to weather and strong sea clutter removal is applied to lee. I suspect that there is some special handling for when one side's signals are dramatically different than the other, but it could just be the outcome of an adaptive algorithm. I'm not remembering whether it was this radar or the previous, but one of them I tested by angling to one side and stabilizing, then quickly tilting the radar to the other side. The side that went from high to low initially presented a black display upon the change, then adjusted to a normal display. IIRC the other side went white then picked up targets. The fact that each side initially behaved differently in my experiment seems to indicate that the sides were being handled differently. The digital processing to overcome this is very impressive, but it can't completely offset the inferior signals relative to a level scanner.

Greg

Edson manufactures radar mounts that have an angled mount to be used on planing powerboats such as sport fishing boats. This angle is in the 10-degree range. Further, Navico's installation manual specifically recommends that the antenna be angled downward for use on such an application. I would expect that if the software could somehow adapt or adjust to this predictable change in attitude, such installation requirements would be unnecessary.

Bottom line - radar antenna are designed to be installed on a level plane, not heeled. Some adaptivity is inherent, but represents a compromise in effectiveness where the beam strays more than a few degrees from level. To suggest that operating at the outer reaches of that band decreases effectiveness of the gear. If you're going to operate radar on a sailboat, include some sort of leveling mechanism. The self-leveling mounts are easiest, but a manually adjusted one could suffice.

Just because it's common for sailboats to not have leveling mounts for radar does not make it a good practice. Unless you can assure yourself you won't use your gear when sailing, it's just a bad idea. .

Peter

[skyhawk]

thanks everyone. Makes sense.
Seems like the failed wire issue that was mentioned...maybe just have the wiring on some sort of preventive replacement schedule

[Moonshine36]

Looking at replacing an older radar on a Mason 44 Sailboat. it's currently mounted about 30 feet up the mast and the display is in the cabin, so to use the radar someone needs to be in the cabin and relaying information to the person on the helm. Chart plotter with AIS at the helm station. SO radar use really is not possible when you really need it.
Question, would you replace it on the mast, mount it on the backstay or a separate mounting pole on the transom ?
Ken

[Sailmonkey]

If it’s never caused you any sail handling problems on the mast, I’d be inclined to leave it up high on the mast.

[Cheechako]

I looked into a leveling radar bracket in the past. I concluded you dont really need it. The radar works fine without, sure you may lose some coverage temporarily , but boats don't just stay on one tack or stay level ...they rock and roll. A swinging radar antenna is not going to be superb either. Not to mention wire chafe and wear etc.
Leave your radar high up, and use it.
I find radar a great thing.
-It has helped me enter a port blind at night in late arrival.
-Helped me find and get through a blind harbor entrance in very rough water heading straight into a lee shore.
-Allowed me to spot and dodge water spouts in the Gulf Stream.
-Locate and track huge thunder cells at night.
-And of course spot tankers at night still 15 miles off or more.

[SaltyMetals]

Firstly you do not say what yr MFD is in the cockpit but i 100% agree with the OP that it makes much more sense to have the radar output being readable in the cockpit. I changed the MFD in the cockpit of my boat (jeanneau 43ds 2004) so i could add AIS and read the result in the cockpit on my new MFD (Axiom 9). That left me with the radar only being readable at the chart table bec the new MFD in the cockpit did not talk the same language as the old 2004 radar (all Raymarine equipment). So I upgraded the radar to the Quantum Raymarine. Get the Quantum 2 if you have a MFD which runs on Lighthouse 3 software.

So where do you put it? On my previous boat i thought i was being clever and mounted it on a strut on the transom arch. Mistake. Could never get more than about 12-15 nm range on a unit which should have been giving me 24 nm range. It should best be mounted halfway up the mast at just above the first spreaders. Finally, i was shocked one day on my previous setup that when sailing out of the Solent to Itchenor my radar could not see the forts. For those who do not know the area these are absolutely massive constructions built in Napoleonic times to protect Portmouth naval dockyard. The reason my radar could not see them was because i was heeled about 20 degrees so on my leeward side my radar was looking at the water while to windward was looking at the sky. So in my new installation i have used a Scanstrut self-levelling bracket to hold my new Raymarine Quantum. Magic.
I know Scanstrut is not cheap but why have a radar if it cannot identify critical objects when you are sailing and heeled over?
Andrew

[CarinaPDX]

If it is working in the current location I don't see the point moving it - unless you are the sort that is looking for excuses to work on your boat. What you need to do, assuming that it is not an old CRT display, is move the display to the helm - it is much more useful there.

Greg

[Cheechako]

Having it at the helm would be nice. Mine never were, but I mounted them either: so I could see it from the companionway, or in one case, on a swing arm so it was right in the companionway.
Both these options work just fine. Whether you are looking at ship location, thunder cells or etc. I found no issue leaving the helm for a few seconds when necessary.

The negative to being outside is it's difficult to see the screen well at times, as well as the weather attacking the unit's connections or possible theft. Disconnecting many times to store it inside could be an issue?

[CarinaPDX]

Being tiller-steered the watch sits in the front of Carina's cockpit so not the same issue as with a wheel. My first LCD radar was mounted on a swing arm in the companionway, where it could be in the passage but under the hatch and even behind a plexiglas drop board if needed; it could also be swung to face inside for viewing below decks. My current radad is mounted to the outside of a drop board. In both cases it was easy to see and control while at the helm. While wheel steering may require more effort, or at least a different effort, the utility of having it right in front of the helmsman is great.

Greg

[Moonshine36]

SaltyMetals,
To answer your questions, about 2-years ago I put a Raymarine Axiom Pro 12 MFD in the cockpit. The current radar is a Furuno Model 1730, so yes, about 30-year old CRT. (or small boat anchor). I am looking at replacing the system with Raymarine Radar (either the Quantum 2 Doppler or the Quantum CHRIP system). In addition I am looking at moving the Axiom MFD to the chart table to do all the work and processing there and placing a slave MFD in the cockpit location.
Ken

[SaltyMetals]

Moonshine, just a note that if you are going to change to the Raymarine Quantum you cannot use the Quantum 2 if yr Axiom is running on Lighthouse II. You can use the Quantum on LH II or the Quantum 2 on LH III. The Quantum 2 is better than the Quantum and worth getting if you have the correct LH software.
Andrew

[Moonshine36]

Good to know, thank you