# Magnetic compass adjustment



## Anabasis (Jan 31, 2018)

Has anyone here ever had to adjust the compass underway without the aid of a professional compass adjuster?

In the US MM, we tend not to do it but I am wondering if anyone else does it as a matter of course.


----------



## James_C (Feb 17, 2005)

I've never adjusted it at sea (would never do it unless an emergency) but I spent some years on RoRo/Container ships and we'd often do a compass swing every few months so as to construct a more upto date deviation card.


----------



## 5036 (Jan 23, 2006)

I have swung many using the technique of steaming in a slow circle for binnacle compasses and most flux gate compasses can be swung by completing two slow turns in calibration mode. I have also checked many using transits and bearings from a GPS position but never actually adjusted one, I would always leave that to the professional.

I have sorted a few by removing magnetic material and/or magnets themselves from the vicinity of a compass, many owners are blissfully unaware of these effects.


----------



## Alistair Macnab (May 13, 2008)

*Magnetic Compass Adjusting...*

I always remember the difficulty I had with the Magnetism course at the Royal College in Glasgow. Getting close to exam time, I confessed to the lecturer that it was all 'magic' to me and that I just did not understand it.
"Never mind" he said. "All of a sudden the penny will drop and you will know all about magnetic compass adjusting."

You know, he was absolutely right!

We ran from Cape Town to Otaru on Hokkaido every six months. We employed a professional compass adjuster in Capetown once a year. At least I knew what he was doing and it was no longer 'magic' but a very necessary operation on a ship with no gyro.

Alistair.


----------



## mikeharrison (Aug 8, 2008)

Anabasis said:


> Has anyone here ever had to adjust the compass underway without the aid of a professional compass adjuster?
> 
> In the US MM, we tend not to do it but I am wondering if anyone else does it as a matter of course.


I have done it in a emergency on a deep sea Tanker. We sailed into some stormy weather on that ship and started getting strange magnetic compass errors. The cause turned out to be that the AB who had been painting up on the Monkey Island had left his (magnetic) pot of paint hanging off one of the Kelvin spheres on the magnetic compass binnacle. I corrected out the residual errors.

Apart from that, in my experience , a well corrected magnetic compass should stay corrected during a worldwide voyage and my inclination was not to fiddle with the magnetic compass at sea but to take regular compass errors to check that all was well.
Regards, Mike


----------



## woodend (Nov 23, 2009)

Exactly the same as Alistair deviation and the deviascope was a black art until the penny dropprd with a loud clang.
I was dropped into actually doing it by our Captain. He was ashore for an exrended lunch at 'The Club' in Warri, Nigeria. It was 1964 and the start of the oil exploration boom. Apparently a small American seismic boat had been in collision and had her compass was knocked down'. She was stuck alongside until the only compass adjuster could get from Lagos or she could get to Lagos. My Second LMate has just got his Masters ticket a few months ago I am sure he can do it says o9ur Captain. Someones ears *****ed up obviously and the next thing I am sent for. Over a beer4 at the Warri Club I am persuaded / told to fix it. Anyway the next thing the seismic ship is tied up to a buoy and a launch aquired to tow her round for a full swing. It took two round turns and I got a 'card' that I was happy with. Exemption for the trip was obviously granted by someone and she started work and then eventually managed the trip to Lagos anyway without mishap and if I remember rightly I got a case of beer and a bottle of whisky. I was never told what the old man settled for. I am not sure if I had any magnets left over it is a long time ago.(Pint)


----------



## Binnacle (Jul 22, 2005)

Anab asis said:


> Has anyone here ever had to adjust the compass underway without the aid of a professional compass adjuster?
> 
> Lying off the Bluff NZ awaiting a berth the OM decided that we would adjust compass as we were going on time charter on the Aussie coast for a lengthy time. "Old Paddy" a very competent ship master of the old school headed up to the monkey island and instructed me to remove the compass bowl and lay it on the deck and reverse the heeling error magnet. After that as Paddy was going to use the sun, I had to alter the chart room clock so that when working out the sun's bearing the local hour angle was easily obtained by deducting the clock reading from twelve when he shouted down the speaking tube.. After more than a few swings of the ship's head Paddy was satisfied that the deviation card he had made out was suitable for navigating in the southern hemisphere. I never knew how the adjustment went as I was landed to hospital in Invercargill.


----------



## garry Norton (Jun 8, 2009)

While in the Marine Department in the British Solomon Islands when we did a annual survey of local vessels we swung their magnetic compasses and corrected them with magnets as we were near the magnetic equator and laid the magnets encased in lead pipe on the cabinets around the steering cabinet.Most of our local vessels were wooden overgrown boats and the few larger vessels had binnacles.On my leave I tried to do the compass adjustor course in N.Z. but they had stopped doing it.It was done the same way as you did it for Master Certificate and off Honiara Tulagi Island has several points of north magnetic and North East magnet and these can be used sighting along the wheelhouse doors and also lining up astern.


----------

