Plastimo Compass Calibration

DougM

.
Jul 24, 2005
2,242
Beneteau 323 Manistee, MI
The Plastimo compass on the pedestal of my Beneteau 323 appears to have lost its calibration.
Even though I have the installation instructions for it, I cannot seem to locate any calibration screws. I did determine the method for removing it from the pedestal which is easy enough, but even if I would have found calibration screws, I fail to understand how it could be properly calibrated while outside the pedestal.
At this point, the compass is at least 20 degrees off from the magnetic setting on the autopilot and the magnetic setting on the gps.
I am not located in an area where anyone has any expertise in compass calibration which exacerbates the situation
Any insight would be appreciated.
 
Sep 25, 2008
1,096
CS 30 Toronto
If the compass was right before and changed, you might have added some magnetic item near the compass or electrical wires. In any case, you need to re-calibrate.

There are 2 bronze slotted head rod in the compass. The shell where it sits in should have 2 plugs covering the holes. One for east-west, one for north-south.

You need to make a brass rod with flat-head and reachable to the slotted rod.

Lifting the compass out of the shell for adjustment is OK but takes more trial and error as it changes when you put it back.

On a calm day, motor slowly (about 2 kts) on a known north-south course (use another compass, auto-pilot, or land marks). Adjust the N-S rod until the compass rose is aligned. Repeat both course north to south and south to north.

Now repeat the course for east-west but use the E-W slotted rod.

You might have to do this a few more times just to get it just right.

If you have an autopilot with flux gate compass may make adjustment a little easier only if the auto-pilot is right.

You can find the instruction on the Plastimo compass web site. Language might be a little challenge to understand but it works.