Raymarine radar displays affect compasses?

[ste7ve]

I want to install a Raymarine RL70CRC display above my steering binnacle, as you see on plenty of boats. However the Raymarine manual says it should not be installed within 1 metre of a magnetic compass, which ought to rule out such an installation.
Any views on whether there is a problem or not?

 

[JonA]

Cathode ray displays use magnets to direct the electron beam scanning the screen. So, yes there is a problem if too close to a compass.
Jonathan

 

[ste7ve]

It's an LCD display not a CRT.
Maybe there is enough steel in the whole unit to cause a problem.

 

[pvb]

Are Raymarine just playing safe?

As you've said, lots of boats have a radar/plotter display at the helm, and presumably the steering compass still works properly. I'd bet Raymarine are just playing safe, bearing in mind the litigious tendencies of some nations!

 

[Anonymous]

Re: Are Raymarine just playing safe?

[ QUOTE ]
As you've said, lots of boats have a radar/plotter display at the helm, and presumably the steering compass still works properly.

[/ QUOTE ]I wouldn't bank on the compass working properly. I discovered that my compass had been installed with the lubber line moved about 5 degrees out in an attempt to correct deviation due to a large steel hydraulic steering component, only inches away. Incredibly, there are holes present which put the lubber line back onto the keel line so it was not just an error. Having posted this on the Nauticat yahoo group, another Nauticat 42 owner whose boat was built at around the same time, posted that he has exactly the same problem. My boat went right round the world with the compass in that condition! It is a tribute to the electronics.

 

[branko]

I have mounted SL70CRC on the same way and have no problems with compas!

 

[Oldhand]

The RL70CRC has a power consuption of up to 20W, which means there can be one and two thirds amps flowing in the powerlead. This current alone may produce sufficient field to affect a magnetic compass so I wouldn't recommend it being mounted on the steering binacle and haven't done so myself.

Furthermore, you may wish to consider other limitations of binnacle mounting such as:

1.Only the helmsperson can see it and then only if standing behind the wheel. Do you helm from behind the wheel all the time and never "sit out" to watch the trim of your headsail?

2. Only the helmsperson can operate it and if, for example, the operator is concetrating on radar collision avoidance, will he be able to this sufficiently well and helm simultaneously in a choppy sea or gusty wind?

I decided that if my RL70CRC required a lot of attention (and isn't that what its for?), I would have the boat on autopilot or would have SWMBO on the helm, so there was no sense in mounting it on the binnacle and risking upsetting the steering comapss.

 

[hightech]

There is always an amount of magnetism within an LCD based unit and the manufacturer will give a value where no effect is observed. However many people ignore the figures and miunt on top os compass. You just need to plot the effect your unit gives and allow for it accordingly. As the effect will be above and to one side you would get odd affects when the boat is heeled as the field would come into or out of play with differing intensity.

 

[Ships_Cat]

Cannot speak for the Raymarine radar you mention but have plonked compasses right on top of CRT radar displays (like the compass body almost touching the radar case) with no problem, but always checked before fitting by holding the compass in/near its intended relationship and running the radar.

These have not been bottom end radars nor LCD but I would have assumed that a LCD radar of the same quality would be even better.

John

 

[William_H]

In the aeroplane industry we were required to swing the compass for correction after any electrical or radio installation (or even engine overhaul) and corrections were always annotated "radio on" so you should at least check for errors with radar on and off.
This question of errors when the yacht heels is interesting. In theory a radar over or under the compass or indeed an engine under the compass can when the boat is heeled be to one side or the other of vertical in otherwords possibly to North or south of the compass depending on which tack if you were sailing east. Each tack should give different errors. Has anyone ever seen this effect or is it just a possibility that doesn't matter? olewill

 

[snowleopard]

every piece of electrical kit for boats should have a documented 'compass safe distance'. when i installed my engine control panels in the bulkhead below the steering compass i checked the manual - nothing. i called the yanmar agents who didn't know and had never been asked. eventually word came back from japan "no residual magnetism".

 

[Ships_Cat]

Hi olewill

Regarding heeling error my experience is that in yachts of the size that most of us own, once one is heeling much it is normally wavy enuff that the boat and compass yaws/swings so such that the error is not observable against that.

Might be different in tippy boats with little form stability so that they sail on their sides even in the flat, but have no experience of them.

John

 

[Graham_Wright]

Current influence;- if the supply and return leads are adjacent (and they generally are) the magnetis fields cancel out.
This is where the idea of twisted pairs originated.

 

[olavs]

It's common today to mount chartplotter displays on the pedestal itself. only 10-15 cm. away from the compass. Modern pedestals are even designed with a kind of "dashboard" for this purpose. I have not heard of anyone having problems with their compass in such setup.

Manufacturers tend to stay on the safe side. As you may have read, Garmin even states that their GPS-models must not be used for navigation!!