Silva Compass installed on centreboard Cover

[Peter Cockerton]

Never really used this before as whenever I have wanted to get a compass heading my chart plotter has been the source.

The other day whilst out on the Rutland water it occurred to me that I don't really know how to read this Silva compass, the bearing obviously changes depending on the position you set the dome and the red markers.

Do you have the markers set in line with the direction of travel of the boat, that would make the most sense, if this is true why does the dome rotate, is it do with helming position.

On other boats where the compass has been mounted on the cabin bulkhead the heading line relative to north has always been fixed, this makes sense to me, the dome obviously rotates for a reason, anyone have an explanation ?

Peter Cockerton

[Graham W]

Peter,

My Silva looks like the attached photo and as far as I'm aware, it has no moving external parts.  If you have the same model, you're saying that your dome can be rotated?  Normally, the compass should indicate the direction in which the bow is pointing.  In the photo, it's about 210°.

I don't think I've ever used my compass and wouldn't trust it anyway since Reg pointed out that switching on the nearby GPS causes it to swing by more than 10°.

[Peter Cockerton]

Hi Graham

Thanks for your views on this post. Found an installation guide for this model of compass and the dome is designed to rotate to align the lubber lines with the fore and aft of the boat centre line. Once the plate fixing screws are tightened (when alignment complete) the dome should then not move. Guide suggests checking alignment periodically and adjusting as required.
A different model to this one has three lubber lines which can be used if the viewing position of the compass is offset when helming.

Thanks for post

Peter

[Colin Morley]

Be aware that a chart plotter that is turned on will affect the compass direction

[Tim Riley]

When looking at fitting my Garmin onto the centreboard cover I noticed the compass swing without it even being turned on. After consultation with that wise old BRe sailor Reg I moved the compass onto the back of the cabin. On my previous bayraider I had the plotter mounted at the stern just behind the round hatch on one side. An easy position to wire to and well protected from damage but a bit difficult to see sometimes.