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Japanese Midget Submarines in Pearl Harbor

Discussion in 'Pearl Harbor' started by kimfdim, Aug 13, 2008.

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  1. OpanaPointer

    OpanaPointer I Point at Opana Staff Member Patron   WW2|ORG Editor

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    Drop "Silly"?
     
  2. Takao

    Takao Ace

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    Why doe you think search radar is mounted high on the mast, and not on the superstructure...Because the superstructure would create a blind spot.
    IIRC, the USN found this out on the North Carolinas when the SG antennae was mounted too low.
     
  3. wm.

    wm. Well-Known Member

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    Weren't aircraft engines made from steel?

    And I think magnetic force varies in proportion to the cube of the distance.
    This means a magnetic charge from 1m away will be a million times stronger than the same from 100m away.
     
  4. Takao

    Takao Ace

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  5. wm.

    wm. Well-Known Member

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    Captain Outerbridge said the Condor was doing a magnetic sweep out in the channel, sweeping with her magnetic sweeps.
    And he proceeded to her position, as close as we could get to her without fouling her sweeping gear.

    So it was an external gear, so much external it could have been easily damaged, but why external?
    A short wire and a parallel long wire are very inefficient, lots of wire spooled on the ship hull would generate hundreds of times stronger field.

    And why they were sweeping so feverishly, according to the internet the Japanese didn't have any magnetic mines.
    What about the much more probable conventional mines, nobody swept for them?

    MAD units could have been installed on ships, but it seems they weren't.
    The reason was ships are slow and MADs were very short range, (fast) planes were much better at MADing.
     
  6. OpanaPointer

    OpanaPointer I Point at Opana Staff Member Patron   WW2|ORG Editor

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    Condor was doing a routine sweep of the approaches.

    We could thank the British for the technology, btw.
     
  7. wm.

    wm. Well-Known Member

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    So it was the so-called Double L sweep, a quite ingenious device. It required two minesweepers, a single minesweeper was much less effective.

    But why were they doing it if the Japanese didn't have any magnetic mines?

    btw was Condor a wooden ship? She had to sail over mines before detonating them.
     
  8. RichTO90

    RichTO90 Well-Known Member

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    Yep, she was built as a wooden fishing vessel in Tacoma, Washington in 1937 and not taken over by the Navy until October 1940.
     
  9. OpanaPointer

    OpanaPointer I Point at Opana Staff Member Patron   WW2|ORG Editor

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    "We tap dance in mine fields." (Seen on minesweeping helos clearing Suez "a few years ago".)
     
  10. Takao

    Takao Ace

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    I'm not sure how you came to the conclusion that they were sweeping "so feverishly?" The Condor was performing a routine sweep of the channel.

    The Japanese didn't have magnetic mines, but they were researching them. Further, the Germans had them, and there was known technological trading going on between Japan and Germany at the time. Further, the possibility could not be discounted, since German raiders had been active in the Pacific and could easily have delivered a cargo of magnetic mines to Japan.

    Actually, they were...The US version was called Ship(or Ship's) Magnetic Submarine Detector(SMSD). They were standard fit on most new destroyers in 1941-42, however they performed abysmally in practice and fell into disuse during 1943.

    Sorry, but that is incorrect. Ships had much better sensors for detecting submarines - ASDIC/SONAR and hydrophones - aircraft, on the other hand, had no sensors to detect submerged submarines.

    An ingenious device? You didn't think so earlier...
    You thought it was "inefficient."

    That was for sweeping a large area, common British practice was two use two or three minesweepers when sweeping for magnetic mines...We are talking about a narrow ship channel.
     
  11. OpanaPointer

    OpanaPointer I Point at Opana Staff Member Patron   WW2|ORG Editor

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    Found it.

    [​IMG]
     
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  12. OpanaPointer

    OpanaPointer I Point at Opana Staff Member Patron   WW2|ORG Editor

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    Google Earth shows the Channel to be about 1000' feet wide. USS Nevada was 583' long, beam 95 ft 2.5. That left 417' of clearance total if she was sunk perfectly sideways. I suppose young IJN pilots might have dreamed about "blocking the channel and bottling up the US Fleet", but it just wasn't going to happen. Even if she had been handled so badly as to be at her maximum blockage angle there were IIRC, over a dozen dredges in the harbor that day. The way would have been open quickly.
     
  13. wm.

    wm. Well-Known Member

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    What was the designation of that unit? There nothing about it in any available declassified technical reports concerning themselves with MAD.
    Especially you yourself denied their existence:


    I was refering to MAD only. The truth is airborne MAD was/is much better than shipborne MAD.



    I said nothing about it because I didn't even know it existed. I saw the light thanks to Mr. OpanaPointer.
    Double L sweep overcame the obvious limitations by employing two minesweepers with synchronized devices.
    That they use
    had nothing to do with anything, but the synchronization did the trick.


    Double L sweep overcame the obvious limitations by employing two minesweepers with synchronized devices.
    Wire spooled on the ship hull would be better but the mines would detonate too close to the ship for comfort.
    Double L sweep was designed to detonate mines far away from the ship.
    The letter "L" denotes that if I'm not mistaken.
     
  14. Takao

    Takao Ace

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    Ship Magnetic Submarine Detector or Ship's Magnetic Submarine Detector Type 1, I have seen both used.

    Yes, I denied it's existence, because up until last night, I did not know it existed. While researching another matter, I was reading "Destroyer Weapons of World War II" by Peter Hodges and Norman Friedman, and came across a 2-sentence mention of the Ship Magnetic Submarine Detector(SMSD). After some time Googling, I found very little on the SMSD - The September War Diary of the USS Palmer(DMS-5), which mentions it being installed on September 2, 1942; the January, 1943, War Diary for the USS Carmick(DD-493), which mentions calibrating the ship's magnetic compasses and Ship's Magnetic Submarine Detector; and a photo caption for the USS MacKenzie(DD-614);
    Destroyer Photo Index DD-614 USS MACKENZIE
    and also a mention in an interview on the destroyerhistory.org website - http://destroyerhistory.org/flushdeck/ussgamble/index.asp?pid=51507

    Other than that, I have found nothing else on this device.

    Don't think so...
    Ship's have better and more effective ASW sensors than SMSD/MAD. Hence, SMSD falling into disuse.

    synchronization allowed for better coverage of a wider area. Again, we are talking about a narrow shipping channel.

    Technically speaking, L stands for Longitudinal. However, from the sailors using the term, L stood for Leg(the two wires, short Leg, and long Leg).
     
  15. wm.

    wm. Well-Known Member

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    "until last night, I did not know it existed", "I have seen both used".

    Is there anywhere a picture of the detector?
    I think, to work at all it had to be mounted on a long arm, as far as possible from the ship.
    And a dedicated crew member. They were complicated, requiring 3D gyroscopic stabilization, and constant attention devices.
     
  16. OpanaPointer

    OpanaPointer I Point at Opana Staff Member Patron   WW2|ORG Editor

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