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Author Topic: Neodymium magnet fishing  (Read 28488 times)

Ingo Prangenberg

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Neodymium magnet fishing
« on: June 01, 2012, 09:19:57 AM »

I'm writing this post with slight embarrassment, due to the less-than-ethical nature of "fishing" with a Neodymium magnet. My Anthropology Professors in college would have scoffed at this idea and given me an earful.

For those not familiar with a neodymium magnet I have included a definition:
A neodymium magnet, a type of rare-earth magnet, is a permanent magnet made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. This material is currently the strongest known type of permanent magnet.

In Europe some people attach these magnets to a metal wire, throw them in ponds and pull out old war items. These magnets are surprisingly strong and can pull up surprisingly heavy objects.  Due to not being part of a real archaeological, methodical excavation this method creates items that are "orphans", having no record as to their true location.

But, it could be interesting and slightly more ethical if done properly off the reef at Niku. Due to the weight of these magnets they could be attached to a thin metal wire and lowered into the water until they bottom out. The area where the wire enters the water can be recorded via GPS. When the wire has slack the magnet is pulled up again. To drag it would give faster results, but a less exact location of discovery. Any metal items found would be recorded with those rough GPS coordinates. It does not require a large vessel, only a crew of 2 or 3, a $200 magnet and wire and a lot of patience.

The purpose would not be to pull up the wreckage, but to just indicate a possible location to further investigate. Maybe a starting point. These magnets are strong enough to pull objects up that are covered by silt or a thin layer of rubble. They would also be strong enough to pull up aluminum aircraft wreckage that has just small bits of steel (hinges, wires, bolts) attached to them.

This may be a low-budget exploratory tool.

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Monty Fowler

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Re: Neodymium magnet fishing
« Reply #1 on: June 01, 2012, 09:31:00 AM »

That might work with parts of aircraft engines. And other smallish bits. Most of the Electra, if I remember correctly, was made out of aluminum. Some of the instrument faces and such were steel, sure, but overall we're talking aluminum.

LTM,

Monty Fowler
TIGHAR No. 2189 CER
Ex-TIGHAR member No. 2189 E C R SP, 1998-2016
 
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Ingo Prangenberg

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Re: Neodymium magnet fishing
« Reply #2 on: June 04, 2012, 10:28:11 AM »

I think that if all steel parts were listed in an inventory you might be surprised. Electronic equipment, wiring, cables, personal belongings, seat frames, attachment brackets, clips, springs, hinges, locks, etc. come to mind. Also some aluminum or alloy objects with steel screws still attached would also be pulled up.

I'm sure if I knew more about planes the list would be a lot longer. Even if any recovered items don't specifically point towards direct identification of which plane might this may be, it might just give a clue to the general area and what lies down off of the shelf, if anything.

Obviously a ROV is much better and why go backwards in regards to technology available? This low-buck method might have been more useful in finding a possible debris-field in previous years. I for one would have volunteered to sit in a boat for hours to raise and lower a powerful magnet on an electric winch.
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Tom Swearengen

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Re: Neodymium magnet fishing
« Reply #3 on: June 05, 2012, 02:21:44 PM »

Ingo does have a point, ans I thik we covered it in DC. A magnetometer, but with parts of the NC probably around the Electra, it might mask the electra. Another issue is, we know that there are hull parts of the NC somewhere on the reef , or reef ledge (nopefully not on the bottom). As Rich mentioned in another thread, things possible could have shifted. Also, having looked over some of Richie Conroys good work, I noticed that there appears to be a ledge, then a crevasse that might NOT be natural----like something sliding down like a sled on a hill. Ship hull parts, possibly, but 'perhaps' a partically intact 10E.
Thoughts?
Tom Swearengen TIGHAR # 3297
 
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Randy Reid

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Re: Neodymium magnet fishing
« Reply #4 on: June 06, 2012, 12:33:24 AM »

Ingo,

Might be worth trying but a few things to consider:
There is going to be a lot of iron down there and I would guess that some of the remaining pieces of the Norwich City would still
be pretty heavy even after all these years.

What ever you hook onto better be lighter than the heavy displacement of your salvage vessel and your magnet better have a
release point less than your maximum lifting strength. If otherwise you will be permanently anchored to whatever the magnet
attaches to unless you want to lose your gear.

I think if you used a magnet with no more than 40 to 50 kilos lifting strength you would be okay. I can lift and move a hundred
pounds plus and I'm old and weak. Remember even if you get 50 kilos of iron to the surface with a winch, you still have to break
it loose from the magnet somehow.

Another problem would be disposing of all the junk you bring up. You can't throw it back in because you might pick it up again
on the next cast.

Also the area next to the reef would be where I would want to fish and it would no doubt be the lumpiest due to the surf.

A couple of stories for your amusement:
A few years ago I picked up an estimated one ton piece of crawler track from a depth of 100 feet with an electric anchor winch
(no, I wasn't trying to, it just happened). It took a while, winch didn't like it, and the bow of the boat sank about 2 feet beyond the
waterline. The real problem was removing the track from the anchor without sinking the boat or losing the anchor. I was able to
secure the track to the boat with spare rope(line), release the anchor from the track, then cut the line holding the track. Sounds
easy but it wasn't.

Many years ago when I was a teenager working as a skiff man on a seine fish boat, I managed to snag something in the lead of
the net while working off a steep banked island. Whatever it was dislodged from the bank and headed for the bottom pulling the
back end of the skiff and me with it. I poured on the power and managed to keep the skiff afloat until the seiner was able to
close up and take the net lead aboard. We got the net back with a big hole in it and no evidence of what I snagged. You might
want to keep that in mind, I understand Gardner is a steep banked island also.

Although I remain unconvinced the Electra is anywhere near Gardner, wouldn't it be something if your method brought up a
tailwheel assembly? or a cast iron cylinder? Smoking gun for sure if it is the right tailwheel.

Randy

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Ingo Prangenberg

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Re: Neodymium magnet fishing
« Reply #5 on: June 06, 2012, 06:16:39 AM »

Thanks Randy for the reply.

The magnet could certainly not be too strong, but it wouldn't have to be either, since any steel parts on the Electra would not have been too large anyway. Maybe a 20 pound Neodymium?That way if it did connect with an item too heavy it could still be released.

Now, one thing I wouldn't expect in the vicinity of the possible Electra site would be steel Norwich City parts. If the wreck is South of the area in which the search is planned to take place and the currents are moving south, wouldn't the heavy wreck parts from the Norwich City lie even farther South?

As an open offer to Ric: Being a school teacher, I have the entire summer off and will gladly work for free for two weeks, sitting in a skiff with a magnet. A chicken dinner and a couple of pints of Pale Ale is all I need, I'll bring the tent though. My resume is on the way.  ;) 
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Bill Mangus

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Re: Neodymium magnet fishing
« Reply #6 on: June 08, 2012, 07:51:30 AM »

Does anyone know if a magnet such as this has been used at the Seven Site?  May also be useful at the as yet undesignated "Camp Zero."
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Ingo Prangenberg

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Re: Neodymium magnet fishing
« Reply #7 on: June 08, 2012, 08:44:34 AM »

I seriously doubt a magnet has been used at any time during this expedition, due to it not being a
"proper" applicable archaeological method. On the other hand, I guess it is a bit like a shovel-testing procedure for a general area, not too precise, but used as an indicator for further inquiry.

In regards to using a Neodymium on land, it could be worthwhile to run a Neodynium through previously excavated deposit mounds. No harm done there. If the mesh size of the screen is 1/4 inch a Neodymium may attract smaller items.

Pulling a Neodymium through the undergrowth may be of good use though after all. It will pick up any metal that your eyes have easily missed, even those caught under a layer of leaves or a couple of inches of coral rubble. Once again, almost like a shovel test. In this case I would recommend a larger magnet. If they are strong enough to pull a machinegun out of a German lake, what might they find on Niku?

Just a metal wire and a magnet. Seriously low tech and low budget, but the possibility of finding a new site.

Take a look on Youtube for "Magnet Fishing". Careful though, its addictive.  :)

 
« Last Edit: June 08, 2012, 09:25:49 AM by Ingo Prangenberg »
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John Ousterhout

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Re: Neodymium magnet fishing
« Reply #8 on: June 08, 2012, 09:25:08 AM »

There are variations to consider. For example, using a "stud finder", which is actually a nail finder, capable of pointing to the nearest small ferrous object from a distance of a foot or so.  The simplest ones are literally a small magnet on a pivot in a holder.  More sophisticated ones are practically miniature metal detectors.
Another example - wheeled magnetic nail sweepers, as used around construction sites to pick up nails and screw from the dirt before they puncture a tire.  Available in various strengths and lengths.
I'm sure there are others.  Since they're cheap and don't take much space, including a variety on the next expedition would be reasonable.
Cheers,
JohnO
 
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Malcolm McKay

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Re: Neodymium magnet fishing
« Reply #9 on: June 08, 2012, 09:03:17 PM »

Somewhere in the TIGHAR documentation is reference to the use of a metal detector on Nikumaroro which is a very useful thing when dealing with this sort of site. Standard procedure is basically to sweep, mark the spot, plot these on the plan and then excavate if considered necessary. The problem with a magnetic recovery is that if it picks the object up then it removes it from its context and this can then lead you into missing a non-ferrous object that might be related to it. The first principle of archaeology is with minimal disturbance to note the position of artifacts in relation to other artifacts which then leads to you being able to discern a broader and more accurate picture. Removal for off site analysis is the last step.

Dragging a magnet off the reef might retrieve something but unless that object was clearly identified in a manner that related it to the wreck (if it exists) then you are simply left with a chunk of unidentified metal and another puzzle. Also a magnet might detach a ferrous object with no clear identifying marks from a non-ferrous object that is clearly marked or identifiable as coming from the wreck you are seeking. If that occurs then you have really missed what could have been a crucial find. The TIGHAR approach using an ROV is much better and safer both for identification of objects of interest and importantly being non-destructive in their recovery or examination, depending upon the search strategy adopted.     
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Chris Johnson

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Re: Neodymium magnet fishing
« Reply #10 on: June 09, 2012, 02:53:34 AM »

Excellent points there Malcolm.  Context is very important in this, how does object X relate to feature Z.
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Chris Johnson

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Re: Neodymium magnet fishing
« Reply #11 on: June 09, 2012, 02:56:01 AM »

The fishing lines a good idea for retrieving stuff but dosn't help in the understanding of whats gone on.
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John Ousterhout

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Re: Neodymium magnet fishing
« Reply #12 on: June 09, 2012, 11:53:14 AM »

Anything that a magnet could pick up could also be sensed by a suitable magnetometer (aka; metal detector).  The common image of a metal detector is as a hand-held device, but one could be made that was suspended on a line so it could be used for "fishing".  It would tell the operator if it was near a metal part, without disturbing it.  Would it be useful to know where metal objects are to be found, for later, more expensive, investigation?
I recall reading that the currents are quite strong around Niku.  Anything dangling from a line would be drawn a long way downstream, making its location hard to know, and in danger of getting hung up on the reef itself.  Then again, losing a magnetometer head would be less costly than losing an ROV.  Hmmm, do any ROV's have built-in magnetometers?
Cheers,
JohnO
 
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