[Public-list] Ignition wiring - Compass location.

[Robert E Johns]

On Apr 28, 2005, at 12:01 AM, Philip Bartlett wrote:

> Two thoughts from someone who spent the winter re-wiring...

> Second, on my boat the compass is still in its original cutout and, 
> before rewiring, used to deviate when the running lights or spreader 
> lights were on because of the unbalanced wiring on the other side of 
> the fibreglass.

My compass has always been on the port bulkhead. This places it away 
from both the engine and the electrical panel which is right in front 
of the compass cutout. The compass cutout is used for the depth 
sounder. (I remember that I had to look around for a model of depth 
sounder that would fit when I replaced the original one.)

I have found that I was able to adjust the compass to as close as you 
can read it (about one degree), and that we did not need a deviation 
table. Before each summer cruise we would swing the compass, usually 
making small corrections. When we first began sailing offshore from 
Provincetown to Maine (usually to Matinicus Rock), it was before we had 
loran or GPS. We found that we were within hearing of the lighthouse 
after 30  hours (120 nm) of sailing by the compass. I know that you are 
not supposed to hold a  course to that accuracy. We sailed the offshore 
leg under autopilot and the method we used was for the person in the 
cockpit to keep glancing at the  compass and if it appeared that the 
average reading was a degree to the left,  make a correction of two 
degrees to the right. Using this technique several times we 
successfully found the Rock in 100 feet of visibility by homing in on 
the sound of the horn. Later, of course, this was no problem after we 
had loran.

I would suggest that if someone is replacing a compass that is located 
in the cutout that he relocate it on the bulkhead instead of leaving it 
in the cutout.

Regards,
		Bob Johns, Wind Call, #397


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