Radar - gimballed or fixed mast mount?

[jlavery]

I'm looking to replace the (broken) radar on a 36 foot sailing yacht I've just bought, and I'm looking at the mast mounting options.

I'm considering a gimballed mast mount, to give better, more consistent performance when heeled. However, I'm concerned that the constant movement would eventually damage the cables and cause failure.

Has anyone got experience with these mounts, specifically:

1. Do they give better performance than non-gimballed?
2. Have you had problems with cable breakage?

 

[Zing]

I have a gimballed mount. I don’t like it, it overshoots on the swing and the radar image does nor impress particularly. I do have a tall mast, which makes things much worse. With yours it might not overshoot and be ok. Scanstrut. There Is no damping adjustment and when I asked in an email if it could be modified I got ignored.

 

[prv]

I don’t have any data to support it, but my gut feel is that a gimballed mount is not worth the additional complication.

Pete

 

[Ian_Edwards]

Most ships radars have a narrow beam in the horizontal and a wide beam in the vertical, because the array is long and thin. eg the Raymarine Quantum has a 4.9 deg horizontal beam width and a vertcal beam width of 20deg. So angles of heal (or pitch) up to 10deg shouldn't make too much difference, over that the performance will roll off.
I don't like going to windward with more than 18deg of heal, the boat starts to generate to much weather helm. But by then the radar is well down on performance at 90deg but still ok ahead and astern. When rolling down wind, I see targets come and go as the boat rolls.
So for a Quantum, the answer has to be yes, a gimbled antenna will make a difference. I'm not convinced of the practicalically of something like the ScanStrut offering, especially well up a mast. But if I found a device which I thought was effective, I'd probably buy one.

 

[jlavery]

I have a gimballed mount. I don’t like it, it overshoots on the swing and the radar image does nor impress particularly. I do have a tall mast, which makes things much worse. With yours it might not overshoot and be ok. Scanstrut. There Is no damping adjustment and when I asked in an email if it could be modified I got ignored.

Thanks - that's interesting to know.

 

[jlavery]

Most ships radars have a narrow beam in the horizontal and a wide beam in the vertical, because the array is long and thin. eg the Raymarine Quantum has a 4.9 deg horizontal beam width and a vertcal beam width of 20deg. So angles of heal (or pitch) up to 10deg shouldn't make too much difference, over that the performance will roll off.
I don't like going to windward with more than 18deg of heal, the boat starts to generate to much weather helm. But by then the radar is well down on performance at 90deg but still ok ahead and astern. When rolling down wind, I see targets come and go as the boat rolls.
So for a Quantum, the answer has to be yes, a gimbled antenna will make a difference. I'm not convinced of the practicalically of something like the ScanStrut offering, especially well up a mast. But if I found a device which I thought was effective, I'd probably buy one.

It's the Raymarine Quantum which I will be getting. I was going to check the beam widths. As you observe, with 20deg vertical width, up to 10deg heel should be OK.

My concern is lack of visibility of targets to windward. Of course with a non-gimballed arrangement if you're worried there's nothing stopping you heaving to or coming up a bit to level the boat in order to check to windward. We're looking at cruising situations, not racing.

The ScanStrut or similar would be ideal if it had a lock. Having it constantly moving and working the cables can't be good.

 

[jdc]

I find that I only ever use radar to find small objects when in rather quiet conditions, rather obviously in poor visibility or darkness, but very rarely when heeled over. So I think the OP's question is more theoretical than real.

For big objects such as headlands, they move relative to you only at the speed of your boat, so the occasional view is enough to make a fix, after which one can sail on according to DR in the traditional way so continuous radar look out is not required.

When in poor visibility where there are small uncharted hazards you really should slow down and not bash on as fast as poss, whether upwind or not, so again the angle of heel isn't so critical. In big seas when the boat is rolling heavily the radar will mostly pick up waves anyway and so yacht radars are pretty useless (and golly your stomach will have to be strong - to use radar effectively you can't be steering / cooking / doing the crossword at the same time, you have to stare at it and concentrate for tens of minutes at a time if you are to distinguish random clutter from real targets.)

So the only time one might need the radar when heeled over for extended periods is when sailing is in poor vis amongst shipping on a reasonable length passage, say cross channel. AIS receive has made all the difference here, and radar is much less important than it might have been once. And if able to afford radar, I'm sure you will have fitted an AIS which transmits as well as receives.

 

[Zing]

Flexible cables should be specified. In industry they are routinely used and work fine. Robotic arms cant work without them. The key is to have high filament count conductors.

 

[jlavery]

I find that I only ever use radar to find small objects when in rather quiet conditions, rather obviously in poor visibility or darkness, but very rarely when heeled over. So I think the OP's question is more theoretical than real.

For big objects such as headlands, they move relative to you only at the speed of your boat, so the occasional view is enough to make a fix, after which one can sail on according to DR in the traditional way so continuous radar look out is not required.

When in poor visibility where there are small uncharted hazards you really should slow down and not bash on as fast as poss, whether upwind or not, so again the angle of heel isn't so critical. In big seas when the boat is rolling heavily the radar will mostly pick up waves anyway and so yacht radars are pretty useless (and golly your stomach will have to be strong - to use radar effectively you can't be steering / cooking / doing the crossword at the same time, you have to stare at it and concentrate for tens of minutes at a time if you are to distinguish random clutter from real targets.)

So the only time one might need the radar when heeled over for extended periods is when sailing is in poor vis amongst shipping on a reasonable length passage, say cross channel. AIS receive has made all the difference here, and radar is much less important than it might have been once. And if able to afford radar, I'm sure you will have fitted an AIS which transmits as well as receives.

The context for me here is indeed cross channel and similar situations. AIS is all very well, but not a magic bullet. For example in the Fasnet 2015, when we had a French boat 200m to windward at night. They called us saying they needed to bear down on us (we complied) because they'd spotted a fishing boat. The fishing boat wasn't broadcasting AIS.

 

[jlavery]

Flexible cables should be specified. In industry they are routinely used and work fine. Robotic arms cant work without them. The key is to have high filament count conductors.

That's a good point - I'll ask Raymarine.

 

[Graham376]

In theory, gimballed should be better but we've never had a problem spotting targets with fixed mount. If you're cruising, you will want a comfortable angle of heel anyway. Just because the radar's on, doesn't stop visual watchkeeping.

 

[johnalison]

I too find that I seldom need radar except in fairly quiet conditions, and haven't the battery power to run the radar for long periods of sailing without the engine. Although the angles would stay the same, some of the associated movement would be less if mounted lower, as on a stern pole or one of the backstay fittings.

 

[[70521]]

I have a fixed radar on a pole at the transom, it is used about twice a year just to check it still works!

Last week I did the RYA Radar course to find out what I could do with the ancient bit of kit, Noah's dad had the original version. From the "stuff" that was taught on the course I would not waste your time on a swinging gimbal.

A radar rotates about once in three seconds, it sends out a signal 0.01% of the time and listens for the other 99.99%. A radar on a yacht is quite short and thus does not "do detail", unlike longer units.

 

[Deleted member 36384]

Some fixed systems have been modified with a remote controlled actuator to tilt the base at a fixed angle, not gimballing thus giving best of both worlds. The modification obviously requires a mounting plate that can pivot, a trim tab adjuster, a source of power and remote operating device. Alternatively, lead screw adjusters powered by 12V motors are also available as would a simple manual adjustment mechanism, say, compressing a gas strut

I came across the idea on www.morganscloud.com, which is a subscription service for information associated with adventure cruising. Their solution was on a pole mounted radar thingy. Of course it means having to tack the radar thingy if beating to windward.

 

[jlavery]

Some fixed systems have been modified with a remote controlled actuator to tilt the base at a fixed angle, not gimballing thus giving best of both worlds. The modification obviously requires a mounting plate that can pivot, a trim tab adjuster, a source of power and remote operating device. Alternatively, lead screw adjusters powered by 12V motors are also available as would a simple manual adjustment mechanism, say, compressing a gas strut

I came across the idea on www.morganscloud.com, which is a subscription service for information associated with adventure cruising. Their solution was on a pole mounted radar thingy. Of course it means having to tack the radar thingy if beating to windward.

Wow - that's a lot of work! Certainly not intending to go that far.

 

[doug748]

Erik the Viking discusses his set up here, around 10min in:

I always liked the Scanstrut idea but understand it's an arm and a leg job. Eric also has plenty of battery and generating capacity.

.

 

[prv]

Wow - that's a lot of work! Certainly not intending to go that far.

The square riggers I used to sail on had manually adjustable tilt for the radars - climb up a few rungs on the scanner masts and shift a hinged clamping peg into a different slot. The tilt wasn’t often used.



If mounting a yacht radar on a stern pole, rather than halfway up the mast, a simple manual bracket could probably be arranged. The remote-actuated electric one definitely sounds like overkill.

Pete

 

[jlavery]

Erik the Viking discusses his set up here, around 10min in:

I always liked the Scanstrut idea but understand it's an arm and a leg job. Eric also has plenty of battery and generating capacity.

.

Thanks - that's worth seeing. The gimballed Scanstrut mast mount is around £400 more than a standard Raymarine fixed mount.

 

[Beneteau381]

I'm looking to replace the (broken) radar on a 36 foot sailing yacht I've just bought, and I'm looking at the mast mounting options.

I'm considering a gimballed mast mount, to give better, more consistent performance when heeled. However, I'm concerned that the constant movement would eventually damage the cables and cause failure.

Has anyone got experience with these mounts, specifically:

1. Do they give better performance than non-gimballed?
2. Have you had problems with cable breakage?

Overthinking it. Ive had two boats with fixed radar, not an issue. Also to bear in mind, over 15 years sailing these two boats and used in serious anger leas than a handful of times!