? about radar on a sailboat

[skyhawk]

Are these radars in some way self leveling or self tracking?

Radar on a boat is not really something I've ever really operated.
I was just watching a video of a german guy doing a single handed crossing in a rather small boat. (https://youtu.be/65yvgFBAqrw) and he was monitoring a squall at night with radar.
but his little boat was sailing with quite a keel angle + the boat was pitching quite a lot.

How does the radar high up on a mast and swinging back and forth deal with such a changing angle?
I would have expected for targets such as weather, but especially smaller targets like other boats, to be very intermittent...showing only one in a while when the angle is just right

thanks

[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.

[tkeithlu]

Excellent answer, Jammer. I'd only add that low-to-the-water objects do get missed in one sweep or another from a rolling/bouncing boat, but radar rightfully used should be observed for several sweeps to see if a target is repeated.

[edmundsteele]

Most radars allow you to display an electronic “wake” – just an elapsed time / fading color coded display of previous reflections. I have found this feature useful in detecting small objects that only intermittently get a radar hit as well as highlighting which ones are moving.
Ed

[SaltyMetals]

Not sure i agree w Jammer. I have found that the modern radars have such a narrow beam angle that if you are sailing and heeled over but >20 degrees your radar will be looking at the sky on windward and into nearby water on leeward. I was shocked when i tested it on a well known landmark (one of the forts while exiting the Solent in the UK).

On my new (to me) boat i changed the radar to the new Raymarine doppler Quantum and at the same time mounted it on a self-levelling bracket by Scanstrut. Expensive but problem solved. The radar is no good if you are sailing along in fog or at night thinking there are no obstacles because you have a fixed (non-self-levelling bracket).
Andrew

[Cpt Mark]

Nighttime, crappy weather, delivering a yacht and my 2 crew members were trying to figure out what happened to the blip they saw. They reported they'd seen a target and now it was gone. This was older radar like 15 years ago. I immediately took us to the edge of the channel. The blip they'd seen was a container ship on a collision course. Radar is not infallible. It takes training and lots of experience to learn how to read radar. I'm a former tugboat Captain who dealt with fog and radar entries into marinas we were dredging all the time. I couldn't find that ship on the radar either. Just glad they'd seen it briefly.

[MJH]

Originally Posted by skyhawk

Are these radars in some way self leveling or self tracking?

Radar on a boat is not really something I've ever really operated.
I was just watching a video of a german guy doing a single handed crossing in a rather small boat. (https://youtu.be/65yvgFBAqrw) and he was monitoring a squall at night with radar.
but his little boat was sailing with quite a keel angle + the boat was pitching quite a lot.

How does the radar high up on a mast and swinging back and forth deal with such a changing angle?
I would have expected for targets such as weather, but especially smaller targets like other boats, to be very intermittent...showing only one in a while when the angle is just right

thanks

Since getting AIS on my boat I use RADAR less. You are correct about the angle affects but as someone pointed out a self leveling unit would correct that to a point as long as the movement is not erratic. I tend to use it mainly for fog because there are boats that don't use AIS but they are generally small ones. On my roundtrip to Hawaii I think we used it twice for short periods...it does use power but you can have it ready in standby mode to moderate that.

~ ~ _/) ~ ~ MJH

[Hudson Force]

The gimballed mount for our Furuno was quick and smooth enough in action to account for changes in heel and pitch by sailing or wave action; however, our use of radar in fog or any poor visibility would only seem safe with three in the cockpit. With my wife at the helm and me fixed to the radar screen we could do well in the "Down East" Maine fog among traffic. We were also alerted by our third crew member. Our Schipperke, Zorro, would bark in the direction of vessels often before we could account for them on the radar screen. Of course, this team of three was for close coastal activity with our screen set at a quarter mile among rocks, lobster boats and other traffic.

[ussvdharma]

Most people with radar use a swinging radar mount...basically all it is is a hydraulic or air valve with a piston in the center. The radar is mountedd on the piston and as the boat swings side to side, the piston moves back and forth in the piston slides back and forth in its cylinder..the movement is

reduced a little by the air or oil moving back and forth in the cylinder...easy to make, but most people purchase one.


My opinion, and we all know what an opinion is worth, is that I do not want my radar high on the mast...true it gives somewhat better range, but the radar is truly into its own when entering a channel or harbor, and the higher the radar is the larger the 'cone of silence' is in front of the boat. And heck the storms, etc are so high it does not make a bit of difference where the radar is...just be sure that its 15 degee vertical beam width does not hit anyone on the boat........radar saved me when entering bandaras bay in Mexico...losts of very active storm cells....but my COLOR radar led me around them. Monochrome radar does not give you as much information about the cells as a color radar does.


But then this is just my opinion from over 50 years os solo sailing.
de W7KFI ussvdharma

[sailingfarmer]

radar on a sailboat? good for fog and shipping channels night...

[Ded reckoner]

We have a Garmin radome mounted about 40ft above water level. We bought a Scanstrut self-leveling mount for it. Through a gale with 6ft seas (with an occasional 10ft) in the Gulf of Mexico (in which conditions the Gulf has been called "The Washing Machine"), the radar image was clear and appeared fixed (even as the boat was pitching, rolling, yawing). It was expensive, but I would buy such a mount again.

[waterman46]

We used to have a commercial self-leveling mount, until the day one of the wires from the radar broke inside the cable just below the radar. I repaired the wire by cutting out the bad 1 foot or so, and then I bolted the mount to the mast so it would not move any more. On my boat I won't allow any wiring that is continually flexing.

It is very seldom we are in conditions of low visibility and at same time have much heeling for very long.

[CarinaPDX]

I have a manually-adjusted tilt on my 10-year old Furuno radar (not solid-state). I have tilted the radar when the boat was level in order to observe the effect on sensitivity, and there is no doubt that it is better at picking up objects when oriented level to the water. Modern radars do a lot of processing of the signal, and are able to compensate to a high degree for the fact that there is much less return on the high side (calling for greater sensitivity) while much more return from the sea on the low side. In an ideal world the radar would be gimballed, although without a gimbal they are quite usable and that is how I use mine most of the time. Broken wires from continual flexing is a known issue with gimballed mounts, and was especially bad with the old cable bundles which were a nightmare to fix. Modern radars often have just an ethernet and a power connection which shouldn't be too hard to repair if needed. Radar is no magic bullet - just another tool in the box, and its utility depends on the skill of the operator. Perhaps the latest solid state radars are different, but my experience is that I can, and do, improve on the automatic settings by manually adjusting the radar in use. And just as some boats don't carry AIS and are invisible to that technology some fiberglass and wood boats are invisible to radar (or at least require some tweaking to see). Never rely on a single tool, so have as many tools as you can.

Greg

[smac999]

if the weather / conditions are bad enough you need radar and you are close enough to land you risk hitting it. or you sailing with a big heel or motoring?

[Hermia II]

I have a Scan Strut gimbal between the radar and mast that by gravity keeps the radar "level", it works really well. Having a radar is a very good thing. Please note that if you have one you are obliged to use it to avoid collisions.