radome humming noise in the salon/lower helm

vas

vas

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an odd one indeed...

so on Friday with the help of a friend I refitted (hopefully for the last time!) the 24inch garmin radome on the hardop, and bolted it down reasonably tight.

Obvious next step was to fire up the plotter and turn on the radar make sure it works. OK, works fine, np there, but there is a strongish humming sound from the rotating thing inside the radome that obviously travels through the hardtop down the 48mm hollow columns and inside the salon!
Annoying it is, anyone had such an experience and any fancy solutions other than cutting thickish rubber washers and fitting them between the 4mm ss disk that the radome is bolted on?

cheers

V.
 
Unfortunately, noise elimination engineering of this type consists of separating the source (Radome) from the resonator (Saloon). What you suggest is absolutely correct, the idea is to find an insulator that has a different resonating frequency to the radome so mthat the vibrations do not pass as easily. It is a process of elimination however. Or you could leave it switched off
 
Vas, the word "strongish" is interesting ...

Do you hear the sound when engines are running?? ... if not I would not try to eliminate until you manage to reduce engine etc., noise to the point that you once again can hear the radar. You would only use the radar when underway, so unless intrusive then, I would KIS and ignore... if the noise is intrusive underway, then I'd start working on a solution...
 
thanks for the comments,

let me get that straight, of course it wont be audible with engines running, or genny running, or wind blowing, or whatever.
It was just me in the salon, dead calm nothing running but the plotter. Even tried measuring sound level with the soundmeter app on my mobile it was at the quiet library level 20-22db.

The only reason I mentioned it is because I found it rather odd and I'm pretty sure it's a "fault" of setting up a steel tubular construction up there, noise travelling through it and possibly amplified...
BTW, tried this morning and altered radar speed from normal to fast and surprisingly noise was reduced to around 1/3, had to concentrate to hear it, wonder if it's burning more amps to rotate faster or what you're loosing...

Only case it's going to be an issue is at night on a dodgy anchorage (more like with dodgy neighbours) that I'd like to make sure none is coming bumping into me while I'm asleep... IT's going to be a very rare case indeed.
Anyway, I'll have a go at using elastic washers to sandwich the 4mm ss plate the radar is bolted on. Yes I know I should really enlarge the holes on the plate and make sure that the M6 screws do not touch the plate, I'll see what I get and I'll report when I do it.

cheers

V.
 
vas said:
thanks for the comments,

let me get that straight, of course it wont be audible with engines running, or genny running, or wind blowing, or whatever.
It was just me in the salon, dead calm nothing running but the plotter. Even tried measuring sound level with the soundmeter app on my mobile it was at the quiet library level 20-22db.

The only reason I mentioned it is because I found it rather odd and I'm pretty sure it's a "fault" of setting up a steel tubular construction up there, noise travelling through it and possibly amplified...
BTW, tried this morning and altered radar speed from normal to fast and surprisingly noise was reduced to around 1/3, had to concentrate to hear it, wonder if it's burning more amps to rotate faster or what you're loosing...

Only case it's going to be an issue is at night on a dodgy anchorage (more like with dodgy neighbours) that I'd like to make sure none is coming bumping into me while I'm asleep... IT's going to be a very rare case indeed.
Anyway, I'll have a go at using elastic washers to sandwich the 4mm ss plate the radar is bolted on. Yes I know I should really enlarge the holes on the plate and make sure that the M6 screws do not touch the plate, I'll see what I get and I'll report when I do it.

cheers

V.
Click to expand...

If you think the sound travels through the stainless steel tubes why not fill the tubes with expanding foam.
 
@omega2: it's a new old radar, hasn't even worked for an hour but out of warranty.
I wonder if by actually using it the toothed belt will soften and become less noisy?

@bouba: could do, but have to be absolutely sure I don't want to thread another cable though these tubes! Not ready for that yet, so it's going to be my last resort


cheers

V
 
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vas said:
BTW, tried this morning and altered radar speed from normal to fast and surprisingly noise was reduced to around 1/3, had to concentrate to hear it, wonder if it's burning more amps to rotate faster or what you're loosing...
Click to expand...
Looks like a resonance issue Vas. You have changed the frequency of the system by upping the revs, and the resonated noise has reduced, looks like insulating the mountings is the right way to go, as you have already determined. I would look for a closed-cell microcellular polyurethane solution. Closed cell will stop it absorbing water and creating corrosion problems over time, and also maintains properties better than open cell. We used this sort of stuff for mounting dampers on Jaguars. If I remember correctly BASF made the best stuff.
 
every flybridge boat I have had with radar you could/can very faintly hear the radar scanner when its rotating in the saloon with the engines off. I always find it quietly reassuring that its doing something whilst you wait for the magnetron to warm up.
when was it last lubricated? some scanners have a belt drive, some are gear to gear - might be worth a dab of grease/oil the bearings.
If you can't hear it with the engines running and add into that how often will you actually use the radar (few times a year just to check it's working?) = is it worth doing anything about?
 
vas said:
@omega2: it's a new old radar, hasn't even worked for an hour but out of warranty.
I wonder if by actually using it the toothed belt will soften and become less noisy?

@bouba: could do, but have to be absolutely sure I don't want to thread another cable though these tubes! Not ready for that yet, so it's going to be my last resort


cheers

V
Click to expand...
If I was you vas I would check the boat every where for a humming scouser holding a keyboard
 
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