DIY Compass Adjusting

[Davidhoy]

I'm looking for information on adjusting my binnacle compasses (I have dual helms), as I've noticed that they do not agree with each other. I reached out to a professional, but was stunned by the cost. Any suggestions would be most welcome.

BTW, I did a forum search, but my search skills seemed to fail me. I did find some limited info with a Google search, but I prefer the collected wisdom here on CF.

Regards,
David

[GreenWave]

Following as I have a similar issue.
What was the cost estimate you were given?

[Lodesman]

Bowditch chapter 6 describes the process. Bowditch is available online if you google it.

[Davidhoy]

Originally Posted by GreenWave

Following as I have a similar issue.
What was the cost estimate you were given?

It was around $450 per compass.

[psk125]

Follow Lodesman's advice. Post #3.

[SVTatia]

Originally Posted by Davidhoy

I'm looking for information on adjusting my binnacle compasses (I have dual helms), as I've noticed that they do not agree with each other. I reached out to a professional, but was stunned by the cost. Any suggestions would be most welcome.

BTW, I did a forum search, but my search skills seemed to fail me. I did find some limited info with a Google search, but I prefer the collected wisdom here on CF.

Regards,
David

Not sure if you are asking how to adjust for known errors or the procedure to "swing ship".
To adjust the errors you need to locate the adjustment screws and turn it either way.
To me, in the era of GPS, if you check your GPS heading and compare it to the ships compass as you "swing the ship", you could determie the deviation on that heading and either correct it or create a card. I have done it, no big deal.
Unless you really want to be scientific about it, like if the ship's compass is the only one you use (like in the old days), the above will suffice.
This is only good for the hemisphere where you are (either northern or southern), and you'd need to reverse it if you change hemispheres.

[Wotname]

Originally Posted by Davidhoy

I'm looking for information on adjusting my binnacle compasses (I have dual helms), as I've noticed that they do not agree with each other. I reached out to a professional, but was stunned by the cost. Any suggestions would be most welcome.

BTW, I did a forum search, but my search skills seemed to fail me. I did find some limited info with a Google search, but I prefer the collected wisdom here on CF.

Regards,
David

The principle reason for the cost is a professional knows (or should know) everything mentioned in this link https://msi.nga.mil/api/publications....pdf&type=view

Adjusting a compass properly is a complicated business but if you read, understand and follow the process in the link, you can do it properly yourself.

However you can also do a quick and dirty adjustment and you may be satisfied with the result. Refer para 318 on page 13 of the link.
1. Ignore heeling errors.
2. Correct 'A' errors (should be easy)
3. Correct 'B' & 'C' errors

Go sailing.

It is much easier if your compass has built in adjustment screws - if not, you need a selection of small compass adjusting bar magnets and the knowledge of how to use them.

[Wotname]

Originally Posted by SVTatia

.........
To me, in the era of GPS, if you check your GPS heading and compare it to the ships compass as you "swing the ship", you could determie the deviation on that heading and either correct it or create a card. ..........

Presumably you mean GPS track and then comparing this to the ship's compass heading.

If doing this in calm still water at near hull speed, this will give an acceptable (IMO) result.