# Finder's Bar question



## Anabasis (Jan 31, 2018)

I am following up my adjustment question with another one.

Have any of you ever flipped the Flinder's bar when you crossed the magnetic equator?

I don't do it, and I've never seen it done.

Frankly, from what I've seen over the years, most sailors think of the magnetic compass and it's adjustment akin to magic or voodoo and avoid changing anything.

I remember as a 2nd mate having to mediate between a drunk Master and CM who were arguing about whether magnetism was purely horizontal or had a vertical component. I can't even remember which one was right at this point.


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## Laurie Ridyard (Apr 16, 2014)

Anabasis said:


> I am following up my adjustment question with another one.
> 
> Have any of you ever flipped the Flinder's bar when you crossed the magnetic equator?
> 
> ...


The Earth 's magnetic field is similar. to a that of a bar magnet 

Whilst, for convenience sake, the force is given horizontal ad vertical components; it is contant, following an arc.

The horizontal component is at it's strongest equidistant from the magnetic poles. and non-existent at the magnetic poles. 

ATB

Laurie


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## Anabasis (Jan 31, 2018)

Laurie Ridyard said:


> The Earth 's magnetic field is similar. to a that of a bar magnet
> 
> Whilst, for convenience sake, the force is given horizontal ad vertical components; it is contant, following an arc.
> 
> ...


That's what I told them, with diagrams. I was a bit unclear I think. I meant I didn't remember if the CM was correct, or if it was the Master.


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## Mad Landsman (Dec 1, 2005)

The Angle at which the magnetic field of the earth varies according to latitude and is known as the 'dip angle'. 
The dip angle can be, and is, measured using what is effectively a compass with the pivot in the horizontal and another normal compass in the base. It is set with the dip needle parallel to longitude. 

The dip angle does not normally affect ships because the effect is most felt near to the poles and would be allowed for. 
It does however affect magnetic compasses used in aviation because a false reading can be given if the aircraft banks at high altitude.


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## Michael Taylor (Aug 31, 2008)

Today we have the north end marked with an engraved arrow. During Civil War times one US manufacturer of magnetic compass so marked the lubber line to the East as the direction of the Holy Land. Useless piece of information but you never know when it might be needed!


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## saudisid (Mar 17, 2014)

*Flinders Bar*

Used to correct for induced magnetism in vertical soft iron.
Most soft iron is above and abaft compass so Flidners bar placed infront and below. From when I was up for Masters in the 70's it was made up of 1 x 6" 1 x 3" 2 x 1.5" bits of soft iron to make nominal 12 " bar.
Alan


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## 8575 (Sep 8, 2006)

Michael Taylor said:


> Today we have the north end marked with an engraved arrow. During Civil War times one US manufacturer of magnetic compass so marked the lubber line to the East as the direction of the Holy Land. Useless piece of information but you never know when it might be needed!


That is a fabulous tale Michael; I've always liked the quirky things that people do.

According to some press reports in UK the poles might be starting to 'swap ends' (as they do roughly every 200,000 years) but given that it takes thousands of years I doubt it'll affect any of us.


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## Ken Wood (Sep 6, 2006)

When I took my Master's, we were warned that one particular examiner had no idea about heeling error, so when he asked if the compass in the exam room had heeling error, we would tip it over to an angle, peer at it for a few seconds and reply "no". "Correct" was his answer!


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## garry Norton (Jun 8, 2009)

The Flindlers Bar is to correct the soft iron effect of the ship so does not need to be corrected when you cross the magnetic equator similar to the Kelvin balls


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