SA Minesweeper in DBN Harbour Damaged - Page 3





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  1. #41
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by Olyfboer View Post
    Hi Zulucowboy. MTU stands for Motoren Turbinen Union. It was formed when Maybach, Mercedes and Detroit Diesel combined. The main factory is in the Maybach factory in Friedrichshafen on Lake Constance (Bodensee) on the Swiss border. I did a course on the MTU diesel computer and sensors there. The workshop floor is painted white and the tradesmen working on the engines have a table covered by a white tablecloth with their tools and parts on it. They are dressed in a white doctors coat and wear ties. Very different to the new parts fitters you see here.

    Friedrichshafen is where the Zeppelins were built. There is a Zeppelin museum with pieces of the Hindenburg in it and a mock up of the passenger compartments of the Hindenburg. The rollers for forming the aluminium frames are there too. The Zeppelin company still exists and they still build airships but lifted by helium now.

    If you want to visit Friedrichshafen, don't make the mistake my colleague did. He booked his ticket to Friedrichshaven instead of Frierichshafen and ended up in Denmark. His cringing memory is of looking back after leaving the tourist information office because he couldn't find his hotel and seeing the women curled over with laughter pointing at him.

    Thatís hilarious. Certainly not at the time. Denmark is great too!!

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  3. #42
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by Olyfboer View Post
    Hi Zulucowboy. MTU stands for Motoren Turbinen Union. It was formed when Maybach, Mercedes and Detroit Diesel combined. The main factory is in the Maybach factory in Friedrichshafen on Lake Constance (Bodensee) on the Swiss border. I did a course on the MTU diesel computer and sensors there. The workshop floor is painted white and the tradesmen working on the engines have a table covered by a white tablecloth with their tools and parts on it. They are dressed in a white doctors coat and wear ties. Very different to the new parts fitters you see here.

    Friedrichshafen is where the Zeppelins were built. There is a Zeppelin museum with pieces of the Hindenburg in it and a mock up of the passenger compartments of the Hindenburg. The rollers for forming the aluminium frames are there too. The Zeppelin company still exists and they still build airships but lifted by helium now.

    If you want to visit Friedrichshafen, don't make the mistake my colleague did. He booked his ticket to Friedrichshaven instead of Frierichshafen and ended up in Denmark. His cringing memory is of looking back after leaving the tourist information office because he couldn't find his hotel and seeing the women curled over with laughter pointing at him.
    Very interesting. MTU now make turbofan engines for commercial aircraft too.

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  5. #43
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by JJJ View Post
    I did my National Service in the Navy as an engineering graduate and after officer's training in Gordon's Bay, was stationed in Simonstown from mid 1981 to Jan 83.

    The only minesweeping experience I have was being Officer of the Day - or rather night - in the dockyard. Our office was actually one of the minesweepers which had a broken back, so could not go to sea anymore.

    I distinctly remember the signals coming through on the 50 baud teletext machine at about the same speed as Morse code, possibly slower - takkatakkatakkatakka, etc - and us having to interpret it's importance. Regular reports had to be logged untill bedtime. These were throughout NFTR - Nothing Further To Report.

    But my UCT engineering friend Andy Davies was allocated to IST - Institute for Maritime Technology, together with a late fellow engineering student, nicknamed The Hulk, due to his posture.

    These guys were at the forefront of electronic technology upgrading the degaussing range. Andy once mentioned an IC type where I had to confess my ignorance to him that I do know what a 741 is, but sorry, that thing he is talking about sounds very foreign.

    Regardless, a great time.
    The only minesweeping experience I have was being Officer of the Day - or rather night - in the dockyard. Our office was actually one of the minesweepers which had a broken back, so could not go to sea anymore.

    That was SAS Pietermaritzburg. She was an Algernine Class minesweeper and formerly HMS Pelorus. She led the D Day landings on 6 June 1944, clearing the way of mines to the French coast. I'm not sure which units you served for signals. It may have been before the minesweeping base at SAS Chapman (The Peppermint Palace - so called due to the colour of the building) had a signal office established after the SAS Pietermaritzburg was sunk to form an artificial reef and diver's playground in Smitswinkel Bay.

    But my UCT engineering friend Andy Davies was allocated to IST - Institute for Maritime Technology, together with a late fellow engineering student, nicknamed The Hulk, due to his posture.

    The Institute for Maritime Technology (IMT) and Institute for Maritime Medicine (IMM) were right next to each other. The one a leader in the engineering field and the other a leader in the maritime medical field. I'm not sure what the situation is now.
    Last edited by Olyfboer; 2020/07/13 at 10:35 AM. Reason: Factual
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    OT, but in response to yours:

    My duty in the dockyard was as a relief for some slightly senior officer who usually could not be "available" for his at very short notice. Mmmm.

    Our regular roster was at SANAD, up the mountain.

    When you were driven into the ammunition area checking on the guys patrolling there you had to remember to keep your arm inside the car when the handler walked up to your window. Those dogs weren't pets.
    Last edited by JJJ; 2020/07/12 at 11:14 PM.
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Just watched the Movie Greyhound with Tom Hanks, for the Vlooties, it is a must watch. If you were at MCM, Hub, PP, PK, PS, Mama, JVR, SvdS, life begins at 40 Knots, you will love it.
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by Olyfboer View Post
    As stated before, all steel hulled vessels have a permanent magnetic field that is generated during construction. After construction and periodically, this field is read to determine it's characteristics. This can be done by wrapping the vessel in cables and sensing the magnetic field. Once the field has been determined, calculations are made and an opposite magnetic field is applied for a calculated time. This is called de-perming.

    Attachment 579282

    Another way of detecting the permanent magnetic field is to have a berth or de-gaussing range the vessel can be moored or sail over. The SA Navy had/has a berth in Simon's Town harbour and a range in False Bay.

    Attachment 579284

    The results of de-perming are that the magnetic signature of the vessel is far less and less likely to set of magnetic influence mines.

    Attachment 579285

    Some navies have gone to extreme lengths to avoid magnetic signatures such as the Soviets building a submarine with a titanium hull and the Germans building submarines with a stainless steel hull. The titanium hull also allowed a very deep diving depth below the capabilities of Western torpedo's but six submarines with these hulls helped bankrupt the Soviet economy.

    Modern magnetic countermeasures are active systems which use magnetic maps, the vessel's gyro compass and GPS as inputs. More about this system in the next post.
    I also did a stint in the 2nd generation minehunters the Navy had at the time. Due to the arms enbargo the ships were officially Postoffice Cablerestorers with advanced minisubs and very fancy sonar equipment.

    We spent most of out days at sea on the de-gaussing range just off Smitswinkel bay.

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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Keep it coming Olyf, brilliant information.
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by Olyfboer View Post

    That was SAS Pietermaritzburg. She was an Algernine Class minesweeper and formerly HMS Pelorus. She led the D Day landings on 6 June 1944, clearing the way of mines to the French coast. I'm not sure which units you served for signals. It may have been before the minesweeping base at SAS Chapman (The Peppermint Palace - so called due to the colour of the building) had a signal office established after the SAS Pietermaritzburg was sunk to form an artificial reef and diver's playground in Smitswinkel Bay.
    During my stint at Chapman, the PMB was converted into staff quarters.

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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by The Condor View Post
    During my stint at Chapman, the PMB was converted into staff quarters.
    I just loved to walk around in the PMB, what a great ship, stayed in the PMB for a week, when the Durban was in the drydock. Also walked around in the PK, when she was still out of commission. Just behind the wheel house/officers boardroom the SA Navy's Cock of the Fleet trophy was still displayed in a glass cupboard. I think I am wrong but I had an idea that it was made from sterling silver. Should have taken/stolen it as a good sailor would have done like we did with the victuals.
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    I was also on the PMB for national service 87/88 and must admit it was a bit shagged out then ( had better accommodation in basics ) The PMB was originally the HMS Pelorus which was one of the lead vessels in the D-Day invasion which if it was still in the UK it would have been preserved as a historical ship , but no our government decides to sink it .

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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by Andrew Rodrigues View Post
    I was also on the PMB for national service 87/88 and must admit it was a bit shagged out then ( had better accommodation in basics ) The PMB was originally the HMS Pelorus which was one of the lead vessels in the D-Day invasion which if it was still in the UK it would have been preserved as a historical ship , but no our government decides to sink it .
    There was no way the PMB could have been preserved. They had to wait for very calm weather to tow it out to Smitswinkel bay to be sunk as it was in danger of breaking up if the weather was worse than calm. Had she not been sunk as a reef she would have sunk alongside. There is just no way the SA Navy would preserve a ship. There is no budget for that and the Navy's mandate is defence, not preservation of history. The only vessel that is planned for a museum is the SAS Johanna van der Merwe or SAS Assegaai as she was renamed. This is being done with private funds. The SA Navy has provided a dry docking space until that time.
    Last edited by Olyfboer; 2020/07/14 at 02:11 PM. Reason: Spelling
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  17. #52
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    We have seen that all steel hull vessels have a permanent magnetic field induced during building.
    We have seen that this can be measured on a degaussing range and minimised.
    We have seen that this lessens but doesn't negate the magnetic field.
    We have seen that the compass heading of a ship influences the ship's magnetic field.
    We have seen that the geographic position a ship influences the ship's magnetic field due to the Earth's field differing geographically.
    The pitch and roll of the ship also influences the magnetic field.
    Therefore the magnetic field is dynamic and changing by the second.


    Modern warships need to negate the magnetic field, not just reduce it. Modern torpedo's do not strike a vessel. They sense, among others, the magnetic field and explode under the vessel in order to break the vessels back. Therefore it's essential to have a neutral magnetic field to counter this part of a torpedo's sensors.

    Click image for larger version. 

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    https://www.youtube.com/watch?v=RV8MF-440xg

    The way this is done is by having coils throughout the ship on three axis - Vertical, horizontal and longitudinal as illustrated. The current applied to each coil is controlled by a computer and the variables of position, compass heading, pitch and roll are obtained from the magnetic map, GPS and inertial sensing gyro compass.

    Click image for larger version. 

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    Once the permanent magnetic field of the ship has been initially read on a degaussing range after construction, it becomes the baseline magnetic field and a permanent degaussing counter current is applied to negate it by the computer. The variables that influence the field like position, compass heading, pitch and roll are constantly sensed and input into the computer which applies a varying counter current in all three axis to keep the magnetic field of the vessel neutral.

    The modern stealth frigates South Africa bought from Germany have such an active degaussing system. Pic of SAS Spioenkop.

    Click image for larger version. 

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  19. #53
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Very interesting to know
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Is degauzzing done by pushing a button or creating an opposite magnetic field. Where does this magnetic field get discharged to eg static electricity is discharged to earth, how is it done on a ship.
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Just a correction. The PMB was sunk just off the Millers Point launch. We dive regularly on the wreck. Will see if I can get some recent photos. At this stage the wreck isnít in a good state. Some fellow divers also placed a plaque commemorating the D-day invasion link.

    Photo credit Richard Dark.

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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by hunter26 View Post
    Is degauzzing done by pushing a button or creating an opposite magnetic field. Where does this magnetic field get discharged to eg static electricity is discharged to earth, how is it done on a ship.
    On a ship without an active system, the field is sensed and neutralised by applying an opposite field for a calculated time.

    On an actively degaussed ship, the field is applied as the attitude of the ship changes. The axis coils are giant electromagnets. By constatly varying their strength dependent on the vessels geographical position, compass heading, pitch and roll, the vessel is kept magnetically neutral.
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by Olyfboer View Post
    On a ship without an active system, the field is sensed and neutralised by applying an opposite field for a calculated time.

    On an actively degaussed ship, the field is applied as the attitude of the ship changes. The axis coils are giant electromagnets. By constatly varying their strength dependent on the vessels geographical position, compass heading, pitch and roll, the vessel is kept magnetically neutral.
    Thanks, I'm guessing all done by computers... Bit of a bugger if the computer fails.
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Quote Originally Posted by hunter26 View Post
    Thanks, I'm guessing all done by computers... Bit of a bugger if the computer fails.
    The military specifications of computers, like those used in aircraft, are stringent. That German built stealth frigate of the SA Navy pictured above has 6 computers located throughout the vessel. They monitor and/or control over 6000 points using the same PLC's that are used in Airbus aircraft.

    Any one of those 6 computers can be designated as the primary and keeps all the others updated at all times via a redundant ethernet system. Should all 6 fail simultaneously, there are two points where a laptop can be plugged in to run the vessel. Due to computers, the enormous engine rooms, generator and switchboard rooms of the vessel are completely unmanned. Should computer systems start failing there are several levels of degradation right down to manual control of the vessel.
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Thank you Olyfboer and other contributors for a fantastically interesting thread.

    Any news on the SAS Durban?
    Last edited by Changa Bulanga; 2020/07/25 at 07:47 AM.
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    Default Re: SA Minesweeper in DBN Harbour Damaged

    Watched a series on TV on abandoned buildings. One series showed a Russian submarine base that was used to degauze the electromagnetic fields from the subs. Can't remember if this was during ww2 or the cold War.
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