Compass location in C-22 Cruiser

Ken O

Ken O

Member
There is a lot is excellent information in these forums about compass location, much of it thanks to Bob W.:

http://www.c-brats.com/viewtopic.php?t= ... s+location

I'm trying to save some experimenting in regard to relocating the compass on my new used C-22 Cruiser. The compass was located off-center over the V-berth tunnel toward the helm side. It seemed to work fine in this location (as far as could tell when sitting on the trailer). I replaced the wiper motors, and now the compass has a very strong dip and has moved about 20 degrees. This situation exists even with all power off. The new wiper motors are the only change at this point.

Rather than trying to adjust the compass while on the trailer, I'd like to see where people have located their compasses for minimum interference.
Central on the tunnel seems logical, although this older compass (an Aqua Meter model that looks a lot like R2D2) does not have 45 degree lubber lines.

What works on a C-22? Thanks.[/img]
 
I've played around with the position of my compass a few times now. I can see it best between the electronics when it is right of centre on the dash of the boat. But I do find that sometimes there is interference and it does not read right. it sits between the chart plotter and the iPad.

It is difficult to get the right position sitting on the trailer as there is a lot of metal underneath. I found that it was easier to find the right position floating on the water away from trailer, docks and anything else that will interfere with it.
 
Once a location has been established, and the compass has been permanently secured and "swung", you would do well to create a "deviation card". Typically, turn on each offending electronic device separately and notice the number of degrees it has affected the compass. Record this on a 3X5 card and keep it at the helm. If caught in fog as an example, the "deviation" can be added or subtracted from the intended magnetic heading. Be advised however, deviation will likely be different for each offending device that is turned on and for each point of compass heading.
 
My KVH electronic is centered over the tunnel. My wipers are at the bottom of the windows. I have not noticed any deviation. I do the "swing thing" each year, aahhh, except this year. It stay within 1 degree of my heading indicater for the autopilot. I also have a magnetic that is wedged in right beside my C-120. It is there in case I loose all my electronics. Have to admit I hardly ever look at that one.

Harvey
SleepyC :moon
 
If using GPS for comparison, be sure that the Variation in the GPS is correct. There have been some significant changes in the variation and rate of variation thru the most recent years. I assume that an update in software is correcting for that yearly.

I rarely use a compass any more, but it is always nice to have, as a back up. As mentioned in the linked article, I use a Sun Compass to swing mine if necessary.

Barry is correct, you have to do a compensation card for the deviation for each electrical appliance, lights, radios on, and radio transmit, Also it is so easy to put items which are magnetic on the "dashboard" of a C Dory. Years back I bought a great Buck rigging knife--which I wanted to always have clipped on my belt....Nope--huge deviation for the magnet compass. The binnacle was on top of Edson Pedestal steering. Moving from one side of the wheel to the other, standing vs sitting made significant distances in deviation....so the rigging knife had to go...At least not on the belt.
 
Just a funny aside similar to the rigging knife issue. Our sailboat's electronic compass for the autopilot is in the aft berth under a shelf. One day under autopilot my wife goes down below and all of a sudden we make about a 20 degree course change. I correct that and a little while later we swing again. Finally figured out my wife was putting her purse on that shelf above the autopilot compass and every time she moved her purse we would change course!
 
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