Magnetic Interference in Ironclad Construction

[Lubliner]

Recently I happened to be reading a Steamship Journal from the 1920's and came upon an article referencing magnetic alignment in the use of iron/steel hulls. My first question arose concerning the handling of ironclads Monitor and Merrimac, and whether the interference of metallic alignment would cause more than compass deviation? Having come upon no mention of any magnetic interference in navigation I began to wonder when this science was 'tweaked' for corrections when iron ship construction began. I found no definite answer but in my search I came upon a couple of worthy sites to share for those interested in the iron construction techniques and their origins.

The Influence of Iron in Ship Construction:1660 to 1830.

maritime.org

Ships Fastenings

A community-based platform for underwater research.

www.maritimearchaeology.com

Thanks,
Lubliner.

 

[DaveBrt]

Recently I happened to be reading a Steamship Journal from the 1920's and came upon an article referencing magnetic alignment in the use of iron/steel hulls. My first question arose concerning the handling of ironclads Monitor and Merrimac, and whether the interference of metallic alignment would cause more than compass deviation? Having come upon no mention of any magnetic interference in navigation I began to wonder when this science was 'tweaked' for corrections when iron ship construction began. I found no definite answer but in my search I came upon a couple of worthy sites to share for those interested in the iron construction techniques and their origins.

The Influence of Iron in Ship Construction:1660 to 1830.

maritime.org

Ships Fastenings

A community-based platform for underwater research.

www.maritimearchaeology.com

Thanks,
Lubliner.

The first documented awareness of iron interference with the compass was in the mid-1500's. Correcting for such was understood and practiced by about 1800. Surely the builders of ironclads were aware of the issue and resolved it -- if they thought it enough of a problem. Correcting such requires "swinging ship," a process that takes a full day for a new type ship; I have never seen any mention of Monitor or an southern warship taking time to swing ship. Such correction only mattered when out of sight of land or in reduced visibility (fog, heavy rain).

 

[Lubliner]

Some 15 years ago I had read a mathematical treatise on the 'discovery' of Longitude, while Latitude was already known. That is beyond my recall but the 1500's does seem to align with memory. Of course the 'swinging ship' problem of say the Monitor Class made me wonder if magnetism could have aided wave action in the handling of those ships. The original Monitor of Ericsson was towed to the site in Hampton Roads so navigation surely was negligible. But ships built in England and purchased for blockade running by the South I have cause to question.
*For example: The paddle-wheel steamer Ruby, reported on January 1, 1863 by Commander Craven of the U. S. Steam Sloop Tuscarora, Ruby is made of iron, draft of 7 feet and about 300 tons;
Flora -- iron screw steamer, 200 tons, draft 9 feet;
Calypso -- Iron screw steamer of 600 tons, draft 11 feet.
These vessels were awaiting opportunity to slip away unseen in the night while in harbor at Madeira, Portugal. The Calypso was verified as successful. These excursions required compass accuracy and especially with their destination of New Providence, Nassau. Yet, I find no mention yet anywhere concerning these vessels as having difficulty in coordinate reports and navigation.

Lubliner.


* [O. R. N. Series 1, Volume 2, page 3 and 4].

 

[Mark F. Jenkins]

I know that eventually, iron/steel balls were attached to the binnacle to correct the compass deviation. I do not know when this practice began, however.

I seem to recall that monitors of the Passaic class had some sort of arrangement where they could mount a compass on sort of a tall tube to get it a distance away from the mass of iron of the ship. I'm not certain how often this occurred or how effective it was, though.

 

[JohnDLittlefield]

I know that eventually, iron/steel balls were attached to the binnacle to correct the compass deviation. I do not know when this practice began, however.

I seem to recall that monitors of the Passaic class had some sort of arrangement where they could mount a compass on sort of a tall tube to get it a distance away from the mass of iron of the ship. I'm not certain how often this occurred or how effective it was, though.

Our current (and new) research vessel has steel balls attached to the wheelhouse compass and is calibrated for their presence. The compass would obviously be off without them. We retain a stand alone compass, on the roof of the wheelhouse about a meter off the deck, in case our wheelhouse compass fails. So, those ideas must have worked since they are still being used today.
We also have an electronic navigation systen that includes a compass.

 

[rebelatsea]

John, your electronic system with a compass will have a compensatory device built into it's innards which acts continuously, as long as it's live of course. My son was shown around the bridge of a cruise liner last year and had it explained to him. These days that is normally off limits, but it's amazing where being a steam engine driver can get you !

 

[DaveBrt]

Our current (and new) research vessel has steel balls attached to the wheelhouse compass and is calibrated for their presence.

The nautical term for those balls is "the Navigator's balls." Though I was navigator on three ships, I never had to swing ship. This procedure is only required if a major change to the bridge is made or if a major new piece of metal machinery is installed in the vicinity of the bridge (such as a new WW2 40mm gun and tub above the wheel house).

 

[Lubliner]

Our current (and new) research vessel has steel balls attached to the wheelhouse compass and is calibrated for their presence. The compass would obviously be off without them. We retain a stand alone compass, on the roof of the wheelhouse about a meter off the deck, in case our wheelhouse compass fails. So, those ideas must have worked since they are still being used today.
We also have an electronic navigation systen that includes a compass.

This makes me wonder. With GPS Navigating systems, which would function as a backup in emergency situations? The GPS due to heavy storm threats (I am thinking of the El Faro) that was lost at sea, Commander Davidson.
I once was interested in terrain vehicle onboard compass, where obviously the gimbal style might work. But at an Army/Navy surplus store I found an electronic beam compass that would prove direction. I don't know if the latter would have worked. Both could be used to advantage.
Thanks for your reply.
Lubliner.

 

[DaveBrt]

This makes me wonder. With GPS Navigating systems, which would function as a backup in emergency situations? The GPS due to heavy storm threats (I am thinking of the El Faro) that was lost at sea, Commander Davidson.
I once was interested in terrain vehicle onboard compass, where obviously the gimbal style might work. But at an Army/Navy surplus store I found an electronic beam compass that would prove direction. I don't know if the latter would have worked. Both could be used to advantage.
Thanks for your reply.
Lubliner.

The intent of retaining the magnetic back up is to be able to dead reckoning navigate if you have lost electrical power. Loss of power to the bridge or the gyro room is possible without the loss of the ship; the magnetic backup provides a means of accurately getting to your destination without them.

 

[Lubliner]

The intent of retaining the magnetic back up is to be able to dead reckoning navigate if you have lost electrical power. Loss of power to the bridge or the gyro room is possible without the loss of the ship; the magnetic backup provides a means of accurately getting to your destination without them.

Great explanation, but there goes the bilge pumps.
Lubliner.

 

[rebelatsea]

I gather the USN has started teaching it's navigators the art of dead reckoning and steering by sights once more. They had deemed it unnecessary in the age of GPS and computers.