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Towed Underwater Metal Detector - What are your experiences & issues
jimkennard
#1 Posted : Tuesday, December 18, 2012 8:15:26 AM(UTC)
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What are your experiences and the issues with towing an underwater metal detector in both fresh water and saltwater for large non ferrous objects? Is it really practical?
jimkennard
#2 Posted : Tuesday, January 1, 2013 12:42:58 PM(UTC)
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What towed metal detector were you using? Was this true for any size steel ship? Old wooden ships would not have much large metal content except for anchors and chain.
Guest
#3 Posted : Sunday, February 17, 2013 12:49:27 PM(UTC)
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I used a towed metal detector and found it almost useless at detecting anything smaller than a steel drum. The torpedo like part is just a weight the sensor part is the loop on top. Unless it was a steel ship that it was towed over the ship and the sensor came within 6-8 feet of the ship very little would register. Using a metal detector is just about as good as using a big magnet on a rope. A lot of steel items that have been immersed for a long time are mostly rust and that gives a very poor signal. In a bobbing boat it is also difficult to keep the sensor at a constant depth. I would go the extra money and purchase a magnetometer and learn to use that.
Guest
#4 Posted : Monday, February 18, 2013 6:23:26 AM(UTC)
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A metal detector has a sensitivity proportionally depending on the mass of metal and inversely proportional to the fourth power of the distance. THis is a physical rule applicable to any insturment using an ACTIVE electromagnetic technology.
A magnetometer has a sensitivity proportionally depending on the mass of ferrous material and inversely proportional to the third power of the distance. This is the rule for a PASSIVE electromagnetic technology detecting a dipole.A target looking like a monopole (e.g. a pipeline) changes the third power to the second power, wwhich makes them detected at even larger distances.
That means that a mag is able to detect targets of given mass at a much larger distance than any metal detector if the material of the target is MAGNETIC, which is mostly the case of old wrecks and their cannons and anchors.

Go there and you will find a PPM unit with a good performance/price ratio : http://users.skynet.be/fa352591/index.htm

Willy
jimkennard
#5 Posted : Monday, February 18, 2013 8:47:28 AM(UTC)
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Hello Old Mossback,
Do you have any experience with an underwater metal detector coil mounted on a towed sled? Looking for non-ferrous objects such as an aluminum aircraft wing.
jimkennard
#6 Posted : Monday, February 18, 2013 8:51:12 AM(UTC)
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Hi Willy,

Your PPM Mag looks great. Congratulations. Look forward to hearing of more results of the Underwater Mag project.

My interest in the boat towed underwater metal detector is looking for non-ferrous objects such as an aluminum aircraft wing.
Rudi
#7 Posted : Friday, November 22, 2013 11:40:09 PM(UTC)

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Hi Jim

It gives good results with towed big loop detector.
http://ebinger.org/index.php/de...ssschleifendetektor.html

mvh
Rüdiger
Sorry, english is not my first language

http://de.groups.yahoo.com/neo/...s/SOB-International/info
classic3009
#8 Posted : Thursday, December 29, 2022 4:36:44 AM(UTC)
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It's great device and very useful for present and future reference work. I'm excited to use this detector for my personal use.



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