[ARC5] Degaussing Field and B-18's

[J. Forster]

Not really, but I would note that degaussing in WW II was different than
it is now.

If you want to degauss a picture tube, tool, or erase a mag tape today you
use a decaying AC field.

That may also have been the case with some ships in WW II if the came up
to a degaussing station, but for the sub I've seen it is clearly not so.
The sub had coils with adjustable currents, essentially to null out any
field when seen from a distance.

Think of like a set of Helmholtz coils to cancel the local earth's
magnetic field for a science experiment.

Aside: I strongly suspect that the sub's coil currents were adjusted as
the sub's Lat and Long changed, but I don't know. I will inquiure.

FWIW,

-John

================



> This discussion has caused me to become very interested in the subject of
> degaussing in general.
> Can anyone recommend some sites to visit regarding the degaussing of ships
> and aircraft, particularly during the WWII period?
>
> 73,
> Rick
>
>
> On Jan 4, 2012, at 4:13 PM, Clarke, Tom AIR4.0P NATOPS wrote:
>
>>
>>> I recall reading that the degaussing for ships in WWII was a pretty
>> quick
>>> and dirty affair.  They ran up to a dock and slapped a wire on the
>> hull
>>> and that was that.   Would doubt if the subs would use anything
>> different.,
>>
>> Well, I have here a rather poor quality pic of the DeGaussing
>> Switchboard
>> on the sub Lionfish at Battleship Cove. The plaque says it sends DC
>> voltage through vertival and horizontal coils throughout the ship.
>>
>> Hence my question- how do you adjust the thing?
>>
>> ---------------tom sez------------------------
>>
>> I am not sure how it is done on a sub, but when I was on a Minesweeper
>> (MSC-195) we would go through the degaussing range at Norfolk or
>> Charleston to measure the ships magnetic signature.  Adjustments were
>> then made to the controller for the degaussing coils in the ship and we
>> would run thru again until the signature was acceptable.
>>
>> The controller was a box full of saturable reactors and mag amps that
>> varied the current in the coils around the ship.  There was a device
>> referred to as a "Total Field Magnetometer" up on the mast of the ship
>> that measured the field around the ship and adjusted the coil currents
>> as necessary.
>>
>> Somewhat similar to the MAD head on a patrol aircraft. Since the idea is
>> to measure the magnetic field of the earth for disturbances caused by
>> the presence of a large chunk of ferrous metal, the system needed
>> calibration to remove aircraft disturbances.  Any P-3 or P-2 folks on
>> here will remember, fondly (or not!), MAD Comps, where we would pitch
>> the aircraft up and down and do rolls without yawing.  Only the
>> heartiest in the back would remain free from airsickness! Fun for the
>> front office, though!
>>
>> 73 Tom/W4OKW
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