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ivorthediver
20-07-2009, 18:27
I have read odd bits about mine clearance so its not a subject I know much about[ ok I'll say it for you all ..Know change there...]

I have read that the mine clearance was carried out by a towed float that some how "cut" the tether by which it was secured how was this done please

navalis
20-07-2009, 19:00
Mines may be triggered by several means, and how it is cleared depends on the type of mine ... these days minehunters use sonar and remote controlled underwater vehicles to locate mines and then lay a detonating charge next to them.

The more traditional methods ...

The moored mine - the oldest type. Detonates when hit by something. It is designed to float at or just below the water, being held in place by a wire connected to a weighted sinker which is on the bottom. This was swept by use of the 'Oropesa sweep'. This consists of a strong wire, incorporating a serrated edge, which is streamed astern of a minesweeper. The wire will have a float (which should bob along the surface, to show where the end of the wire is); an 'otter' and a 'kite' (boards) attached to the end; these ensure that the wire is kept streamed out at an angle away from the ship and kept at a appropriate depth. The minesweeper would then have to steam into a known mined area with sweep wires extended - snag the wire holding the mine to it's sinker with its serrated sweep - the mine wire would be cut....the mine would then float to the surface. There it could be disposed of by small arms fire.

The moored contact mine has been largely replaced by influence mines -

Magnetic - set off by steel hulled vessel (essentially a large magnet) passed nearby; the trigger being a magnetic needle which closed a circuit as the natural magnetic field was disturbed.

Acoustic - triggered by the noise of ships engines

Pressure - for use in shallow waters; triggered by the increase in pressure as a ship passes overhead.

You may of course, combine several triggers into one mine.....

Magnetic mines can be countered by 'de-gaussing' ships (effectively de-magnetising them) - only using non-steel ships as minesweepers - streaming a powerful electical cable astern of a sweeper to generate a large electric field to set off the mines at a distance from the sweepers.

Acoustic mines - tow a 'sound hammer' to set off mines at a distance.


I believe that these days, minehunting sonar and remote operated vehicles with cameras and the use of detonating charges are the norm.

ivorthediver
20-07-2009, 19:50
Thank you so much for a very good and detailed answer to a complicated question

The reason I asked the question was to see how a wire cable securing the mine was cut ,as I could not envisage in practical terms how this was achieved

Do you have more detail on this please Navalis

davep
20-07-2009, 20:15
on sandowns because we were designed solely for hunting, out remote operated vehicles carried a special cutter for dealing with moored mines, these were basically an oblong box containing a charge and a set of jaws.
the vehicle would be deployed against the mine as normal but rather than dispose of the mine with a charge, the vehicle would be driven so that the cutter connected with the mooring line. then the vehicle would reverse its course leaving the cutter attached to the line. once the vehicle had been recovered the cutter was remotely detonated cutting the cable and letting the mine float free.
time consuming but as the sandowns were designed to operate in deep waters we rarely would be used against moored mines.

ivorthediver
20-07-2009, 20:24
Thanks Davep this is the kind of information that you never hear about and why I stay at the Forum to learn about this very kind of detail ..........any more info would be most welcome


Regards Ivor

davep
20-07-2009, 20:36
i've attached pics of the new rov that we are using now called seafox, smaller and easier to handle than the yellow submarines, first picture is it about to be deployed and the second picture shows it being recovered.
we carry two type of vehicle one the is recoverable and is used to identify targets and one that is used to dispose of the target. the first vehicle carrys a camera and sonar and locates and identifies the target, then it is recovered and the live vehicle is then deployed it is driven into the contact and a shaped charge is used to penetrate and destroy the mine along with the vehicle. its your typical one shot system

navalis
21-07-2009, 08:15
You asked for more detail on how moored mines were swept. As described by davep - modern methods employ remote operated vehicles, but as I outlined, the old way was to tow a cutting wire.

More detail on this old way - A single wire was streamed astern; this had a steel, torpedo-shaped float attached to the end - fitted to this float by a wire was a steel blade which was called an ’otter-board’. The Otter forced the wire outwards from the ship, so that the end of the wire was at an angle to the ship. Also streamed from the ship and attached to the sweep wire is another steel board, known as a ‘kite‘, which is used to keep the sweep wire at a pre-determined depth.

The sweep wire was serrated, having barbs of wire protruding. As the sweeper steamed along, the sweep wire would ‘snag’ the mines mooring line; the forward motion of the sweeper would pull the serrated sweep wire over the mooring line which would then be cut, allowing the mine to float up to the surface.

The method was known as the Oropesa sweep - named after a trawler that was used to carry out trials on the method in World War One.

Francis Stanley
21-07-2009, 08:20
The Oropesa sweeps could also be deployed with explosive cutters down the serrated sweep wire, these cutters had a chisel in a jaw that when activated by a trigger (the Mines mooring wire entering the jaw of the cutter) would fire the chisel and cut the offending mooring wire.

Rob Hoole
21-07-2009, 08:24
The development of naval minewarfare is explained here (http://www.mcdoa.org.uk/MCD_History_Frames.htm).

This article helps describe the work of our MCM forces currently in the Gulf: Hunting in warm waters: UK reinforces expeditionary MCM capability in Gulf (http://www.mcdoa.org.uk/UKMCMFOR%20028-031_IDR_July09.pdf).

More recent news about the activities of RN MCMVs (Mine Countermeasures Vessels) and Explosive Ordnance Disposal (EOD) teams of Clearance Divers here (http://www.mcdoa.org.uk/News_Frames.htm) and here (http://www.mcdoa.org.uk/News_Archives_Frames.htm).

Francis Stanley
21-07-2009, 08:26
Ground Mines could be dealt with by deploying a mine disposal weapon which was basically an explosive charge that when remotely fired would either disrupt the mines circuits or if close enough sympatheticaly detonate it. The other method was of course to send yours truly down with a PE pack, place it on the offending article to make it go bang! (having hopefully gotten out of the water first!)

VirtualF
21-07-2009, 13:17
As a matter of interest do WW1/2 mines still turn up?Considering how many minefields were sown in WW1,such as the "Northern Barrage" and minefield used defensively by the Germans and offensively by the British off the German coast are their still rogue ones about?How did they clear them post war?

navalis
21-07-2009, 13:32
Mines (and other ordnance) from WW2 regularly turn up. See this link for one last year -

http://news.bbc.co.uk/1/hi/england/somerset/7343780.stm


After both wars, there was an extensive mine-clearing effort, which went on for some time, to clear minefields, but despite that ships were lost to 'stray' mines for some years after the end of conflict.

I think most of the mines that turn up these days were originally air-dropped, and buried themselves in the mud or sand at the time, but are then exposed over time.

Francis Stanley
21-07-2009, 14:13
A lot of the swept bouyant mines from both world wars were shot full of holes which did not detonate them but ruptured the bouyancy compartmnets causing them to sink and become no danger to the shipping of that period, however 60 odd years later after rolling around the sea bed fishing boats, oil and gas pipes can find a decaying and sensitive explosive making itself known.

ivorthediver
21-07-2009, 18:14
i've attached pics of the new rov that we are using now called seafox, smaller and easier to handle than the yellow submarines, first picture is it about to be deployed and the second picture shows it being recovered.
we carry two type of vehicle one the is recoverable and is used to identify targets and one that is used to dispose of the target. the first vehicle carrys a camera and sonar and locates and identifies the target, then it is recovered and the live vehicle is then deployed it is driven into the contact and a shaped charge is used to penetrate and destroy the mine along with the vehicle. its your typical one shot system


My thanks again Davep...I have often seen the phrase .."Shaped Charge"..
but what exactly is it and how or what Shape is chosen please

ivorthediver
21-07-2009, 18:18
The Oropesa sweeps could also be deployed with explosive cutters down the serrated sweep wire, these cutters had a chisel in a jaw that when activated by a trigger (the Mines mooring wire entering the jaw of the cutter) would fire the chisel and cut the offending mooring wire.


Thank you Francis,..... do you have any diagrams please

ivorthediver
21-07-2009, 18:23
The development of naval minewarfare is explained here (http://www.mcdoa.org.uk/MCD_History_Frames.htm).

This article helps describe the work of our MCM forces currently in the Gulf: Hunting in warm waters: UK reinforces expeditionary MCM capability in Gulf (http://www.mcdoa.org.uk/UKMCMFOR%20028-031_IDR_July09.pdf).

More recent news about the activities of RN MCMVs (Mine Countermeasures Vessels) and Explosive Ordnance Disposal (EOD) teams of Clearance Divers here (http://www.mcdoa.org.uk/News_Frames.htm) and here (http://www.mcdoa.org.uk/News_Archives_Frames.htm).


Thank you rob I will get to grips with that later

Regards Ivor

ivorthediver
21-07-2009, 18:25
Ground Mines could be dealt with by deploying a mine disposal weapon which was basically an explosive charge that when remotely fired would either disrupt the mines circuits or if close enough sympatheticaly detonate it. The other method was of course to send yours truly down with a PE pack, place it on the offending article to make it go bang! (having hopefully gotten out of the water first!)


Frances you are a "mine" of information, many thanks

ivorthediver
21-07-2009, 18:26
As a matter of interest do WW1/2 mines still turn up?Considering how many minefields were sown in WW1,such as the "Northern Barrage" and minefield used defensively by the Germans and offensively by the British off the German coast are their still rogue ones about?How did they clear them post war?


I was thinking the same thing mate

ivorthediver
21-07-2009, 18:30
Mines (and other ordnance) from WW2 regularly turn up. See this link for one last year -

http://news.bbc.co.uk/1/hi/england/somerset/7343780.stm


After both wars, there was an extensive mine-clearing effort, which went on for some time, to clear minefields, but despite that ships were lost to 'stray' mines for some years after the end of conflict.

I think most of the mines that turn up these days were originally air-dropped, and buried themselves in the mud or sand at the time, but are then exposed over time.


Thanks Navalis.... all a bit worrying ....never know when the next one will pop up

ivorthediver
21-07-2009, 18:32
A lot of the swept bouyant mines from both world wars were shot full of holes which did not detonate them but ruptured the bouyancy compartmnets causing them to sink and become no danger to the shipping of that period, however 60 odd years later after rolling around the sea bed fishing boats, oil and gas pipes can find a decaying and sensitive explosive making itself known.


Yes Frances ...never thought about it that way but a tad nerve racking for the Divers out there

tonclass
21-07-2009, 23:05
I would have given a full explanation on this (being my ex-professional field) but my good friend Rob (Hoole) beat me to it, so have left him to explain all things 'Mine Clearance'

ivorthediver
22-07-2009, 05:15
Thanks Rik,

What do you know about Limpet mines and deterrents please

Bee
22-07-2009, 05:41
Interesting thread,
Thanks all
Bee:)

Francis Stanley
22-07-2009, 07:41
Thanks Rik,

What do you know about Limpet mines and deterrents please

What do you want to know?
This was part of my day job as a Navy Frogperson :)

Francis Stanley
22-07-2009, 08:22
Without giving away current trade secrets the post war period up to present day the threat of a swimmer or diver leaving a limpet mine or Improvised package on the hull of a naval ship has been taken very seriously. The navy developed a security state called Awkward which was meant to be employed when ships were in harbours where a threat was deemed to be likely. (these days they just tend to stay at sea)
These states were designed to ramp up the security depending on the imminence of the threat culminating in full blown ship wide involvement up to and including ships bottom searches. Other deterrents included running the engines and turning props at slow speeds, dragging wires around the vicinity of the ship with small boats. Random deployment of scare charges (1lb of TNT dropped in the water like a grenade) and Armed upper deck sentries.

Limpet Mine technology is of course dependent on the organisation deploying it but generally they all follow a similar trend, small enough to be carried by a swimmer, some form of delay firing device and usually some sort of anti removal device.
This could be as simple as a one way thread which would not allow you to unscrew the clamp once fitted down to complex booby traps designed to detonate the devices if removal is attempted. There are various methods of combating this all of which I will not cover for obvious reasons.

The link below is quite intersesting for more info

http://www.munition.eu/naval_mine_en.html

The attached piccy is available on the internet and not classified

Bee
22-07-2009, 08:46
I guess that's very real (having limpet mines attached etc) in regard to threats these days Francis. Ships could do with some kind of force field around them...to prevent rogue divers getting anywhere near. Or some kind of hull detection...where any tampering would immediately set off some form of alarm. But I won't ask you to elaborate on that....just in case there is something.
Anyway thanks for an interesting read.
Cheers,
Bee

Francis Stanley
22-07-2009, 16:27
we could do with a force field to keep a certain rogue diver at bay that is for sure :D

qprdave
22-07-2009, 16:41
Bee

When we did an Awkward exercise there was always a couple of UCs in the SCR listening. In the real world we would have randomly transmitted on the Search SONAR. This would certainly disorientate the divers if not damage them.

ivorthediver
22-07-2009, 17:16
Without giving away current trade secrets the post war period up to present day the threat of a swimmer or diver leaving a limpet mine or Improvised package on the hull of a naval ship has been taken very seriously. The navy developed a security state called Awkward which was meant to be employed when ships were in harbours where a threat was deemed to be likely. (these days they just tend to stay at sea)
These states were designed to ramp up the security depending on the imminence of the threat culminating in full blown ship wide involvement up to and including ships bottom searches. Other deterrents included running the engines and turning props at slow speeds, dragging wires around the vicinity of the ship with small boats. Random deployment of scare charges (1lb of TNT dropped in the water like a grenade) and Armed upper deck sentries.


Limpet Mine technology is of course dependent on the organisation deploying it but generally they all follow a similar trend, small enough to be carried by a swimmer, some form of delay firing device and usually some sort of anti removal device.
This could be as simple as a one way thread which would not allow you to unscrew the clamp once fitted down to complex booby traps designed to detonate the devices if removal is attempted. There are various methods of combating this all of which I will not cover for obvious reasons.

The link below is quite intersesting for more info

http://www.munition.eu/naval_mine_en.html

The attached piccy is available on the internet and not classified

Thank you so much Francis...and I understand your Caution.....

What kind of weight and roughly what kind of size are we talking about here please

qprdave
23-07-2009, 01:21
Thanks Rik,

What do you know about Limpet mines and deterrents please
Q - If a diver was in the vicinity of an sonar dome, and someone inadvertently placed the sonar in operation, would the diver be in any danger or is the sound energy sufficiently attenuated by the water?

A - "Yes the diver would be in danger . SQS source level at 1 yd from transducer is 135 dB. But the sound pressure in water is about 60 times higher than in air for the same dB level (denser medium), so the effective level at 100 yd is 133 dB, which is enough to damage an unprotected ear. An SQS-505 pinging in Halifax harbour could be heard (loudly) in a submarine alongside and generated lots of complaints. Some ships, if divers were working below, word was frequently passed over the public address not to operate the engines or turn on the fathometer. Precautions were definitely taken.".

Bee
23-07-2009, 06:17
Thanks for your answers Dave and for the interesting questions Ivor.
I have another query though...Does sonar affect whales and dolphins?
At various times we have had strandings of both along the shoreline near here and at times this seems to have coincided with naval exercises. Is it possible that higher frequencies are used these days (which could be more damaging), as the older sonar didn't seem to be a problem for the cetaceans?
Regards,
Bee

Francis Stanley
23-07-2009, 07:57
I was involved in a trial involving sound sources and the effects on divers some of the higher pitches and also some of the lower range stuff could make you very ill at ease dizzy and nauseous in some cases but as soon as we faced the same sounds with a neoprene hood the effects were markedly reduced, some modern sonars are so powerfull at close range you would not wish to be in the water with them but others whilst unpleasant would not stop a determined trained diver wearing thick hoods.

qprdave
23-07-2009, 13:41
Does sonar affect whales and dolphins?

Although I have never seen any proven evidence that SONAR does damage wildlife at sea. I am sure it could do. That obviously depends on the range from ship to Whale. Sound is amplified in water and could damage anything in close proximity.

If a ship is steaming along and transmitting, the wildlife would be able to hear it at very long distances (A submarine sonar operator could hear it for hundreds, if not thousands of miles), the wildlife would keep away if it was offending them. Suddenly switching on the SONAR might cause problems.

Bee
23-07-2009, 15:21
Thanks Dave, I think that they probably do suffer damage and that's why they get disorientated and strand themselves...of course I don't think that we'd ever get any official admitting that.
As a species, we've got a lot to answer for....environmentally speaking :(
Regards,
Bee

qprdave
23-07-2009, 15:30
I think that Whaling and polution has a far greater impact on the marine wildlife than some A/B UC2 pinging away and wanting his watch to be over so that he can have a beer

Bee
23-07-2009, 15:35
You're probably right there, Dave....but it would be nice to have a "pinging" system that didn't give them a headache...whilst at the same time provided the A/B UC2 their "off watch" beers :)
Cheers,
Bee

ivorthediver
23-07-2009, 17:25
You're probably right there, Dave....but it would be nice to have a "pinging" system that didn't give them a headache...whilst at the same time provided the A/B UC2 their "off watch" beers :)
Cheers,
Bee


As you say Bee "they" would never admit it for a lot of reasons and pending costs.....but in the order of priorities I suspect Dave is right on this point.

Interesting point though as it must be caused by "something" to make them behave in that manner and ignore their own inbuilt self preservation instincts

Regards Ivor

ceylon220
31-10-2009, 10:46
Picture shows the layout of mines aboard a PORPOISE class submarine,through the open stern door a mine can be seen on the rails that run the length of the submarine inside the casing, the offset periscope is clearly visible.

ceylon220
31-10-2009, 10:49
Ooops!! sorry forgot to upload the picture.

frickerley
05-02-2010, 01:09
I've got my grandfathers testimony of his time as a mine spotting officer and later as commander of a group of minesweepers in the northeast of the UK in WW2, which some of you might find interesting.

(He was a retired merchant navy officer (1st mate) then serving in the home guard when a call went out over the radio -late 1940 - for ex merchant navy officer volunteers to assist the admiralty against a new type of weapon )
the weapon in question was the Magnetic Mine, which you can see an explanation of here:
http://www.chem.ucl.ac.uk/resources/history/people/goodeve_cf/magmine.html
After being commissioned (Lt. RNVR) and receiving around 3 weeks training in portsmouth at the mine warfare school and at the scientific establishment in havant he was sent to the tyne reporting to captain M/S.
Initially it was his job to establish a chain of spotters at vantage points around the docks in the area, to try and observe the fall of these parachute dropped mines in the harbours. a series of OP's were built (42 on the tyne, 26 on the wear and 5 at seaham harbour) with a compass card and an azimuth to take bearings on any mine they spotted during air raids.
Any spotted falling into the harbour were swept for, either by what's called a "Double L" sweep
- a pair of converted trawlers (degaussed) which both towed an L shaped electrical cable (floated on the surface within a sleeve stuffed with tennis balls) at a distance of around 2 cables apart, creating a rectangular field of electrical current, pulsed every 10 seconds, which was sufficient to alter the magnetic field around the mine and trigger it. The sweepers both carried "slave gear" to ensure that both ships would be pulsing the same either positive or negative current.
- In a confined area the M/S trawler could also tow a wooden barge fitted with an electrical coil 22 feet in radius which also pulsed an electrical current down onto the seabed to trigger the mine.
If no mines were triggered by these methods, he would send out pairs of small boats dragging a thin wire along the sea bed trying to snag on the mine. If what was believed to be a mine was found they would try to put a loop around the mine with the wire, and then with lifting gear on the boats the mine (or large rock!) would be lifted to the surface and then inspected from a distance through binoculars to see if the object was indeed a mine.
(A Lt. Cdr Ouvry was the 1st to find and defuse a mine by this method in barking creek)
When the mines landed ashore He would have to lead a party to dig down to the suspected mine, & shore up the hole so the disposal officer could get to work on the mine. The mines themselves were very large - around a ton in weight and had very complicated mechanisms compared to a normal iron bomb. The disposal officer (many of whom were australian RNVR) and his partner at the end of a telephone wire would have a chart showing where the boffins thought the fuse / gain / clock were located behind various access plates. Each screw was numbered and usually taken out in a sequence established by trial & error. The germans booby trapped different screws however to keep their weapon a secret, and only his report of the numbered screws he was removing and the subsequent explosion would alert the boffins to a change in the safe sequence of disposal.
(On one occasion my grandfather had dug down to a mine and secured the cavity using large timbers like railway sleepers, while he was walking back to the safe cordon the mine unexpectedly exploded, sending the timbers flying hundreds of feet away, part of one hit him on the leg & broke it as he laid on the floor, a lucky escape in the circumstances)
Eventually he was made Senior officer, mine watching, for the area between the farne islands and flamborough, helping to decide where & when to conduct sweeps along with the local captain M/S,and also whether or not to keep the harbour closed after a raid, a task made more difficult by the development of multi trigger magnetic mines which would allow up to 17 "triggers" - either ships or sweeps to pass over it before the 18th detonated it, especially around tyne & wear where capital ships were leaving the docks for sea trials.
Following storms many of our own contact mines had wrenched free from their anchors and run ashore and he had to go and dispose of them, on one day defusing 32 between the tyne & seahouses. Many of them were inert when they drifted free due to a safety device, like a plunger, around the mooring wire. when the wire broke away the spring in the plunger shut, making the mine safe, but sometimes barnacles had grown around this area and stopped the plunger from working, so they had to insert a gadget made for triggering the safety device. To dispose of these mines the cover plate was removed, the gain & fuse removed & then paraffin soaked cotton waste was inserted & lit simply burning out the explosive.
When Acoustic mines also started to appear during this period he was also detailed to help to find countermeasures. Initially he was sent out to sea in a trawler along with a ship full of scientists, and detailed into the fore-peak to use a pneumatic drill (for digging up roads) on the stem of the trawler, altering the pitch & revolutions to create sonic values for the scientists to register. They then used this information to create a large watertight bucket about a yard across, with a pneumatic drill inside and a rubber diaphragm that vibrated. this bucket was fitted on 2 arms and hung over the front of the trawler on 2 arms and by altering the sonic values the scientists eventually found the correct ones to cock & explode the mines ( these acoustic mines would be cocked by the 1st ship passing over and detonated by the second one )
The last task he had was to go to sea (once his senior officer finally realised they had an officer with 16 years experience in the merchant navy) and to take command of a pair of mine sweeping whalers ( southern field & southern foam), eventually commanding a mine sweeping group (102). These were double L sweepers for magnetic mines, based in Scapa & sweeping the cleared channel between Scapa and Peterhead.

Francis Stanley
05-02-2010, 09:17
Frickerley
What an interesting post thank you, you must be very proud of your GFather.

Rob Hoole
05-02-2010, 18:19
Hello Frickerley,

What a wonderful post, thank you, and right up my street. Lt Cdr (later Cdr) John Ouvry DSO RN was the first to render safe a German magnetic mine on the mudflats at Shoeburyness in Nov 1939. He and his colleagues were presented with the first RN honours and decorations of WW II by King George VI on the parade ground at HMS Vernon in Portsmouth. Last November, I helped organise the 70th anniversary commemoration of this event together with his son David and grand-daughter Jan (a serving Lt Cdr in the RN) on board HMS Belfast which has the mine on display. HMS Belfast fell victim to a magnetic mine herself a couple of days before Ouvry performed his deed (one of many similar ones) and was put out of action for three years. Details and photos can be seen in the entry for 27 Nov 09 in News Archive 28 (http://www.mcdoa.org.uk/News_Archives_Frames.htm) of the MCDOA website.

You might also be interested in 'Wartime Minesweeping Memories' in the MCDOA website's Dit Box (http://www.mcdoa.org.uk/Dit_Box_Frames.htm). It shows photos and diagrams of the Double L sweep and the Kango SA acoustic hammer. Sadly, Ernest Goodhall, its author, passed away last year but he was a fascinating character and it was a privilege to have known him.

Do look around the website as there are many other references, photos and accounts of the development and use of minesweeping equipment during the Second World War.

ivorthediver
06-02-2010, 19:23
Welcome to the Forum Frickerley,

Well done and full marks on a very good post which as you will already gather is very welcome and appreciated ....and on a subject we have scant information on......

Kind regards Ivor

Don Boyer
07-02-2010, 05:28
Mines are a most scary weapon.

There is a famous story about US ships steaming in the Pacific late in the war....they were avoiding and shooting up mines all the time during the day.

Someone remarked -- "Sure am glad these things aren't out here at night."

Regards.

frickerley
09-02-2010, 22:58
Thanks, I'm glad I was able to share his part of the story with you.

Ouvry did get a mention in his tapes Rob, so he certainly knew of him, though I don't believe he met him personally. I shall have to make the time to visit HMS Belfast, been to the IWM and duxford before, but never got round to her.
It slipped my mind earlier, but I've actually got what I'm led to believe is a parachute ring from one of these magnetic mines sitting on the windowsill.
The pad in the left hand photo is A4 to give you an idea of the size of the object

John Burchell
13-02-2010, 03:34
Minor info you might like to know.
The old degaussing station on Canvey Island has been turned into a museum and will open early this year. Well worth a look if your in the area.

JB ;)

Rob Hoole
13-02-2010, 07:57
Hello Frickerley,

I haven't seen a lug like that before. As you say, it's more likely to be a parachute lug than a suspension lug as the latter screwed into any bomb or mine.

tigercat
27-02-2010, 12:18
Does anyone know anything about the remote control guinea pigs presumably they were merchant ships (?) past there prime used by the Royal Navy to test the efficacity of their minesweeping.

steve roberts
27-02-2010, 12:52
Hi Tigercat. I don't know of any British ships like this,but the Germans certainly had ships for this purpose.They were known as "Sperrbrechers" or obstacle breakers.They were actually manned,but were old Merchant ships,heavily armed with anti-aircraft guns.Used mainly to escort U-Boats from the French Bases.When not in use as such,they operated as part of the Ports anti-aircraft defenses.....Regards Steve.

Rob Hoole
27-02-2010, 14:02
Hello Tigercat,

When the first German magnetic mine appeared in 1939, the Admiralty requisitioned colliers and converted them into mine destructor ships with huge electro-magnets in their holds as a stop-gap measure. The ships involved were ANDELLE, BORDE, BURLINGTON (later SOOTHSAYER, later FAIRFAX), BUSHWOOD, CORBRAE, CORBURN, CORFIELD, QUEENWORTH, SPRINGDALE and SPRINGTIDE. HMS CORBURN detonated a mine off Le Havre and sank on 21 May 1940. HMS CORFIELD sank in similar circumstances in the Humber Estuary on 9 Apr 1941. HMS QUEENWORTH was bombed and sank in the North Sea on 9 May 1941.

Scientists at HMS Vernon quickly developed the Magnetic Sweep Mk 1 (or 'M' Sweep) comprising thirty-four 27 inch-long magnetized bars towed on pendants 40 feet long and spaced 15 feet apart. The 'M' Mk 2 sweep, nicknamed 'the bosun's nightmare', carried seventy 27 inch magnets spaced 10 feet apart across its swept path of 700 feet. This in turn was replaced by the far more successful 'LL' magnetic sweep comprising two buoyant cables of different lengths equipped with strings of electrodes at their tail ends. A petrol-powered 35kW generator set and batteries pulsed the sweep at 3000 amps for 5 seconds each minute.

Towards the end of the war, the Germans laid 'Oyster' pressure mines and experiments were conducted against these using a range of conventional minesweepers, large displacement ships, motor torpedo boats (MTBs) and steam gunboats (SGBs). Barges, honeycomb structures called 'Stirling Craft' and linked flotation tanks called 'Egg Crates' were towed across the mines but all met with unimpressive results. These ground influence mines proved so difficult to sweep that efforts were redoubled on producing minehunting systems that would eventually obviate the need to sweep.

steve roberts
27-02-2010, 14:32
Hi Rob. Thanks for that,your a mine of information(no pun intended) I had never heard of that system...Regards Steve.

Marek T
27-02-2010, 17:14
By the way: what is difference between deperming and wiping?

According to Wikipedia during deperming heavy gauge copper cables are wrapped around the hull and superstructure of the vessel, and very high electrical currents (as high as 4000 amps) are pulsed through the cables while wiping meant a large electrical cable dragged along the side of the ship with about 2000 amps flowing through it.

Was there really any difference between those two methods or is it another example of British/American English differences?

eds3rd
27-02-2010, 19:00
Does anyone know anything about the remote control guinea pigs presumably they were merchant ships (?) past there prime used by the Royal Navy to test the efficacity of their minesweeping.

I am the author of an upcoming book on the subject of mine sweeping boats in the US Navy 1944-1970 "Iron Men in Wooden Boats" I can be contacted at
eds3rd(at)easystreet.net.

Following threads of research in boat minesweeping back to 1915, when Germany stripped Dreadnaughts of their huge guns, and replaced them with 14-18 boat skids holding 50+ foot minesweeping motor launches. These were called "F-Bootes", launched with the battleships massive cranes ahead of the fleet, sweeping mines ahead of the German Fleet in WWI. Their breakthrough of the "North Sea Mine Barrage" - lines of US & British contact mines laid between Scotland and Norway, was intended to deny U-Boats and the Reichsmarine access to the Atlantic. Otherwise, they had to sneak through the English Channel, which the BB Bismarck did in WWII.

The Germans had "Sperrbrechers" in WWI also, but they were limited to using paravanes and other moored mine sweeping techniques to clear the way for the Reichsmarine to the Atlantic. I do not speak German, but Sperrbrecher translates into "bockade breaker" or something akin to that.

The previous posters all had good information on the subject, including the British-developed minesweeping methods. I cannot say that any British minesweeping methods were dubbed as "guinea-pigs", until the advent of pressure mines (oyster mines=German version).

The first German magnetic mine was mis-planted by the Luftwaffe in British tidewater, and was captured immediately by the Brits, and was taken to HMS Vernon for exploitation. (The British had this tradition of naming shore installations "HMS" for Her Majesty's Ship - Vernon was the minesweeping HQ ashore) HMS Vernon, and continued British minesweeping research between the two wars, significantly helped the Allies defeat Germany in mine warfare in WWII.

Following the Magnetic mine in 1939, came mines triggered by Acoustics, and variations of magnetic-acoustic triggering. Then came the pressure mines, triggered by the slight change in water pressure created by a ship crossing over or near an acoustic bottom mine. Literally an unsweepable mine, until a ship of sufficient size passed overhead. As a USN minesweeping sailor in the 1960's, we were told these were outlawed by the Geneva Convention. (I never verified this) Geneva nonwithstanding, it did not stop the Viet Cong from using pressure bladders made from bicycle inner tubes to trigger their river mines, or the Russians from sending acoustic/magnetic/pressure mines to the North Vietnamese Army to plant in the Cua Viet River (USMC - Dong Ha Base supply line)

The USAF towards the end of WWII planted thousands of pressure mines around Japan during "Operation Starvation".

The Japanese (IJN minesweeping forces) were unable to sweep these mines from their harbors, and had to revert to sailing ships back and forth across them, until they detonated. They used skeleton crews, with remote controls from the bridge to the engine room, and (we) nicknamed these vessels as "guinea pigs". Suicide missions at the time.

True, that many countermeasures worldwide were devised in an effort to sweep pressure mines, but the "egg-crates" and other methods were generally unmanned, and towed across minefields using diverter techniques so the towing ship could stay out of the minefields. (Again, I have not done late WWII research, or post WWII research beyond the scope of minesweeing boats.)

Then came the Korean War, with Korea as the proxy for the Soviet Union. They provided North Korea with old and new technology mines and technical assistance "advisors" to help the Koreans plant these mines all around the Korean peninsula.

The IJN Minesweeping forces (never disbanded after WWII) continued to be a major minesweeping force in 1950, continuing the effort to clear US and Japanese planted mines from WWII. They were called upon by Gen McArthur to assist the US Navy in Korea, after the USN lost several ships to mines.

The US Navy copied the IJN "guinea pig" minesweeping concept, using old Liberty ships, remote controlled to the engine rooms, with USN sailors manning these vessels from the bridges. They wore football helmets, padded the bulkheads and overheads with mattresses, and sailed forth. Volunteers who spent at least 30 days doing this (without being killed) were then rotated home - 11 months of their Korean War duty forgiven.

Many other methods were tried to sweep pressure mines such as countermining (concentrated bombing runs over minefoelds), racing fast warships over the bottom mines (racing ahead of the detonations?), and creating large enough wakes nearby to change water pressure significantly enough to detonate), not much was effective. The USN even created what minesweeping seaman called the "Loch Ness Monster". It looked like what we use today on small sportfishing boats, called a "sea anchor", but a much larger nylon funnel like device towed behind a boat. Water entering the larger open mouth in front is compressed by the time it exits the much smaller opening aft, thereby reducing the water pressure. Streaming and retrieving it was another "nightmare", and it was rarely seen to work in Korea. Thus, they reverted to "guinea pigs" - again.

As a final note, when the USN was tasked to sweep North Vietnam waters in the seventies in Operation End Sweep, they created a 1970's version of the guinea pig. They converted an LST with remote controls to the engine room, filled the ship up with styrofoam balls for flotation, in case it detonated any mines, and once again asked for volunteers to sail it. Without researching this, I believe it was the USS Washtenaw County? Not announced at the time, all US Mines laid in North Vietnam contained 28-day sterilizers, which made them inoperable after the time period, so the guinea pig sailings were merely made to placate the N. Vietnamese.

I would be happy to discuss any of these topics with anyone, and would be particularly pleased if others have research that I never intended to cover, since I stopped my lines of research when small boat minesweepers were not involved.

Edward Sinclair
USN 1962-1966
eds3rd(at)easystreet.net

Iron Men In Wooden Boats - Small Boat Minesweeping in the US Navy 1944-1970

Rob Hoole
27-02-2010, 19:01
Hello Marek,

This is an excerpt from page 127 of 'Mines, Minelayers and Minelaying' by Captain J. S. Cowie CBE, RN (Oxford University Press, London, 1949):



...In addition to the degaussing of ships by the fitting of coils and girdles, two other methods were used: flashing and wiping. The former involved passing a very heavy current through a large coil placed temporarily round a ship in such a way as to turn her into a permanent magnet with the South Pole down. She then retained this polarity to a sufficient extent to compensate for the normal North-Pole-down magnetization, but only for a limited time ranging from one to six months. The coil and current-generating apparatus, devised by the French, was, moreover, expensive, and this method had only a limited application. Wiping achieved the same result in a rather simpler way, a single electric cable carrying a current of 2,000 or 3,000 amperes being hauled by means of ropes up the ship's side. This could be done very quickly and different parts of the ship could be dealt with separately. Many hundreds of small vessels were so treated, while a similar process known as deperming was used for larger ships, enabling the final degaussing to be carried out with greater accuracy...

Does this answer your question?

tigercat
27-02-2010, 21:26
I have found some more information apparently the Brits converted a ship called the Formigny but abandoned her after some bad experiences

I found this on another site

according to Seedie's List of Awards to the Merchant Navy, Captain Wiliam McCreadie was awarded the OBE in the Birthday Honours List for 1944 - gazetted 10 June 1944 - ship confirmed as FORMIGNY.


I wonder if he was captain at the time

Marek T
28-02-2010, 23:27
Rob - thank you for an answer. A new word appeared - flashing. However I have found a PDF file with nautical glossary, with a following:

Deperming - the process of changing the magnetic condition of a vessel by wrapping a large conductor around it a number of times in a vertical plane, athwartships, and energizing the coil thus formed. If a single coil is placed horizontally around the vessel and energized, the process is called FLASHING if the coil remains stationary, and WIPING if it is moved up and down.

derek s.langsdon
17-07-2011, 14:24
There has been a wealth of excellent information exchanged on this Topic going back to the war years but can someone detail how we have dealt with
and are dealing with mines laid off the Libyan coast? I recall reading that in April HMS Brocklesby blew up one of three mines laid from a small boat by Libyan Gaddafi supportersi and that thereafter Brocklesby completed her missio nand was replaced by HMS Bangor.

Did Brocklesby "sweep" the other two mines from the sea bed ? and were/are the methods used today akin to the old Paravane/Oropesa float and cutter device? i am assuming that these were small mines ,weighted and dropped overboard to float from a wire as of yore, or are more modern devices now being used/available to the Libyans or others ?

derek-L/Norfolk

Rob Hoole
17-07-2011, 15:32
Hello Derek,

No more sweeping these days. It's all hunting with sonar to keep the man out of the minefield. As for Brocklesby's mine disposal off Misrata, see this article (http://www.royalnavy.mod.uk/operations-and-support/surface-fleet/mine-countermeasure/hunt-class/hms-brocklesby/news/royal_navy_clears_mi.htm) on the RN website which includes a video demonstrating the use of the SeaFox unmanned underwater vehicle (UUV) mine disposal system.

Further background information is available in the entries for 5 & 8 May 11 on the Latest News (http://www.mcdoa.org.uk/News_Frames.htm) page of the MCDOA website.

John O'Callaghan
18-07-2011, 10:48
Hi Francis You say that studies have shown that sonar is shielded against by thick hoods.Has this had any effect on selection of:rolleyes: bubblies?
Cheers John O'C.

Francis Stanley
18-07-2011, 12:11
Hi Francis You say that studies have shown that sonar is shielded against by thick hoods.Has this had any effect on selection of:rolleyes: bubblies?
Cheers John O'C.

No, but thick skin helps ;)

derek s.langsdon
18-07-2011, 13:30
Rob/ Thanks for your steer onto those Mine- clearing updates. I obviously did't focus too well on previous exchanges but will catch up on the items you mention with much interest.-- best regards.

derek-L/Norfolk

ivorthediver
30-08-2011, 07:50
Hi Rob,
just been looking at the website you detailed and HMS BELFAST , a very interesting site indeed , thanks for the insite

Regards Ivor

ap1
10-11-2012, 18:43
A bit more on this fascinating subject.

© Crown Copyright/MoD (1999).

MINE COUNTERMEASURES AT SEA

By

John WICKENDEN
(DERA Weapons Systems)

AND

Mike FREEGARDE
(DERA Technical Directorate)

This is an edited version of the article that first appeared in the Journal of
Defence Science Volume 4, Number 1, January 1999.


ABSTRACT

The threat to shipping from sea mines is as real now as it was 50 years ago.
Indeed, with greater emphasis being placed on littoral operations by the
world's navies, the task of countering mines is becoming more complex and
mine countermeasures are poised to take their place among fully integrated
task forces such as the UK's Joint Rapid Defence Force. This new direction
offers many challenges and opportunities. Present capability is a classic
product of DERA research forming the basis for robust in-service equipment
engineered by industry. Current research programmes are the foundation for
capability to match tomorrow's needs.

Mines have been a danger at sea since the time of the American War of
Independence. They are insidious, easy to acquire and to lay in large numbers.
Simple mines are cheap and can be very cost effective, as was seen in
the Gulf campaigns when three United States' ships suffered damage costing
$160M to repair. But in major conflicts the effectiveness of laying large numbers
of mines is probably better measured against the disruption they cause
and the cost of containing their threat than against the actual damage they
inflict.
The significance of mines is thus their potential for causing disproportionate
damage - there has, for example, long been concern over the likelihood
of mines being used against SSBNs, and much of the present mine
countermeasures capability has been developed in response to this threat. The
requirement for dedicated mine countermeasures platforms to clear mines for
SSBNs will remain for the foreseeable future, as well as for clearing-up operations
post conflict.

Increasingly, military engagements around the world are likely to involve
amphibious operations, often in littoral waters where land-based protective
measures will necessitate air support for mine-clearance activities. The UK's
research programme, which embraces several technological areas and is supported
by wide-ranging trials facilities, underpins the procurement of MCM
equipment to meet future operational needs, typically looking five to ten
years ahead to ensure that novel techniques are adequately investigated to
reduce technical risk for industry and to provide informed advice for the procurement
authorities.

The intended purpose of mines can be nullified by avoiding as well as by
clearing them. Whichever tactic is used, the mines must first be detected,
either directly so that their positions are known individually or indirectly by
removing their threat collectively. This review of MCM at sea starts by
describing present capabilities and then examines in turn:

Mine avoidance
Integrated hunting and disposal
High-frequency sonar developments
Future MCM and platform integrated combat systems
Mine sweeping, and MCM in very shallow water and the surf zone.

Computer-based simulation methods feature large in supporting the technical
disciplines required by MCM research and its operational application. The
review concludes that the MCM force of the future will be a capability fully
integrated into the naval forces operating in the battlespace of littoral waters
(FIG1.).

F1124793

Present capabilities

The move to littoral waters is not new to MCM. The UK's MCM platforms,
the HUNT and SANDOWN classes, are very effective in operating against all
manner of mines from deep (200 m) to shallow (10 m) waters.

The HUNTS are multi-role and are also capable of sweeping and remotely removing
mines, and of supporting diving operations against mines.
The SANDOWN class (Fig.2) are single-role minehunters fitted with the variable Depth Sonar
(VDS) 2093 (FIG.3). Both classes have been and continue to be used widely
in distant regions of the world. They have been present at nearly all of the
major conflicts in which the UK has been involved, gaining a reputation
envied by other navies.

F2124794 F3124795

The equipment on-board these vessels ranges from the new to the nearly
obsolete. For instance, the HUNT'S minehunting sonar is still type 193M
Mod 1. This was originally designed by staff at one of DERA's progenitorial
establishments, UDE Portland, in the late 1960s and built by TMS Ltd (formally
Plessey). It has provided sterling service ever since.

Sonar 193 will be replaced in the next few years by a sonar featuring totally
new techniques researched by DERA and now taken up by industry. These
techniques are based on wideband transmissions that provide fundamental
performance improvements to counter the next generation of mines (Fig.4).
The new programme is currently in the project definition stage with two contractors,
Thomson Marconi Sonar Ltd and Lockheed Martin, in competition.

However, this sonar upgrade will not per se make the HUNTS any more
suited to task force missions. For some time, there has been a shift in emphasis
to deployed systems such as Remotely Operated Vehicles (ROVs) carrying
high-grade sonars, remotely operated drones for sweeping and the
Remote Controlled Mine Disposal System (RCMDS) that the UK
has already operated for several years.

All of these systems make embarked personnel safer. This trend is continuing
and the research programme has made significant strides in this field.
But safety is not the only driver: mounting MCM equipment on underwater
vehicles opens up the opportunity for deploying MCM assets from other
vessels such as task force escorts or even submarines. Such platforms
will not be carrying out dedicated MCM missions; they will merely need to
avoid minefields or conduct reconnaissance missions before amphibious operations.


F4124796

Future operations

Future naval platforms will be required to manoeuvre from the open sea into
littoral waters and to police a battlespace for joint operations. These ships
will almost certainly be parts of a Joint Rapid Defence Force and as such
may act as command platforms for an operation. In littoral waters, the mining
threat may be from ground, buoyant, rising or floating mines of many generations.
The threat may appear suddenly and be unpredictable. Unless countered,
mines will restrict freedom of movement and at a minimum will
intimidate and delay naval force power projection.

The civil significance of mines is that 80% of the world's population lives
within a few tens of miles of littoral waters, and the bulk of the world's trade
is dependent on great trading routes. Mines are an effective way of disrupting
trade. Being able to police such waters is clearly important.
Whether mines have been laid for military or civil purposes, avoiding or
countering them requires that first they must be detected. A modern mine
may have a low target strength and be laid on a highly reverberant seabed; it
may be partly or totally buried. There is thus a requirement for high-quality
sonar for all platforms entering littoral regions.

The UK's new platform projects such as the proposed Future Escort (FE),
New Carrier (CVF) and Future Attack Submarine (FASM) call for the
requirements for waging littoral warfare to be reviewed and for MCM to be
integrated into the overall warfare capability to reduce the threat from mines
to the Joint Rapid Defence Force.

F5124797

It is an interesting prospect that the new DERA Trimaran concept (Fig.5)
being mooted for the FE would provide an excellent wide aft end for deploying
Unmanned Underwater Vehicles (UUVs), as well as for the necessary
preparation areas and hangars.
A consideration of littoral warfare is a good vehicle for describing the new
direction of MCM and how research can advance technologies for both traditional
MCM techniques and for equipment that is more suited to littoral
warfare.

Mine avoidance

If a main force is operating in littoral waters, protecting it effectively from
the hazards of enemy minefields requires sonars that are capable of making
detections with very low probabilities of false alarms. This drives the requirement
for either high quality MCM-like sonars to be fitted directly to the hulls
of escorting platforms or the ability to deploy UUVs, carrying similar high frequency
sonars, running ahead of the task force. DERA has designed and
demonstrated an organic, physically attached, HF active mine-avoidance
sonar based on the wideband sonar demonstrated for upgrading the HUNT
class.

In addition to bandwidth, this sonar affords a large aperture and wide
field of view. An important feature is the provision of a certain element of
classification. The sonar is capable of discriminating echo structures from
mines, non-mine objects, clutter and seabed reverberation by using long range
detection techniques rather than the usual higher frequency, shorter
range, techniques of MCM sonar. This means that an element of automatic
processing can be applied to reduce false alarm rates and thus minimize disruption
to missions.

F6124798 F7124799

A similar wideband sonar has also been adapted to fit on to the jointly developed
UKFrench Remote Minehunting Experimental Platform (Figs. 6 and 7).
This platform was built to determine the optimum characteristics for both
shallow and deep remote operations and to explore the performance envelopes
of two variants, one being fully autonomous and battery powered and
the second powered down the cable. The project was brought to a successful
conclusion in 1997, providing for the first time a capability to reach ahead of
the mother ship, to operate at depth, to provide a stable operating platform
and to be able to carry high-grade sonar.

The UK/French system is an example of a large fully capable UUV that
would most probably be deployed from a surface ship and operate a few kilometres
from the mother platform. A similar system would be appropriate both
for future MCM missions and for organic mine avoidance or reconnaissance
operations from task force participants. The first role would of course call for
some complementary means of disposing of mines.

The UK's current disposal system is based on the French ECA PAP 104 Mk5,
which is deployed from the MCM vessel, transits to the site of the mine,
identifies it, lays a disposal charge alongside and withdraws. The charge is
then detonated acoustically from the mother craft. However, the operation is
very time consuming and not well suited to remote minehunting.

Many countries are considering new disposal systems based on one-shot technology:
small UUVs, about a metre long, are launched from the host platforms,
transit to the mine and, having located it exactly, immediately fire a
directed-energy explosive charge at it, destroying both the mine and the
vehicle.
Again, this research concept is not entirely matched to remote minehunting-
the drawback is the time taken for transiting and keeping up with
the remote hunting vehicle operating well ahead of the mother platform. An
alternative would be for the hunting UUV to carry its own means of disposal-
the concept of remote integrated hunting and disposal.

F8124800

Integrated hunting and disposal

The concept here is that of a hunting UUV carrying several one-shot vehicles
each bearing either a shaped charge or semi-armour-piercing weapon (Fig.8),
the idea being that the transit time would be minimized for the single shots,
which could then prosecute the mine more effectively. Reducing transit time
also favours a reduction in on-board power requirements and therefore cost.
At present, an off-the-shelf commercial one-shot vehicle is being integrated
with the UWFrench experimental platform in preparation for concept evaluation
trials in 1999.

In the longer term, the concept of integrated vehicles is for UUVs to carry
very capable high-frequency sonars and multiple one-shot weapons. The complete
system would then be suitable for both traditional MCM purposes
deployed from conventional MCM vessels, or for task force platforms using
the UUV-based sonar for mine avoidance and reconnaissance purposes.

High-frequency sonar developments

The aims of the present research programme into fundamental high-frequency
acoustics are to enhance the area search rate and to increase the probability
of detection and classification in all environments. The relationship between
sonar design and environmental factors is very important and DERA maintains
a suite of very sophisticated models to aid design, optimize systems in
real time during missions and for procurement acceptance purposes. The programme
is currently investigating new high-resolution algorithms to enhance
azimuth resolution, especially for aperture-limited systems as envisaged for
UUVs. The ultimate approach is seen to be synthetic aperture sonar which, if
successful, would provide 'image-quality' data at long ranges, similar to
those of existing short-range side-scan sonars available today.

It is well known that side-scan sonar provides good resolution and that minelike
objects and seabed characteristics can be extracted from the data in conjunction
with the Image Analysis Centre at Heriot Watt University,*
(*The Image Analysis Centre is a joint venture between DERA and Heriot Watt University)

DERA has developed an automatic processing system based on fractal techniques
that not only segments seabed textures but also picks out mine-like objects
and assigns positional error ellipses to the data. The algorithms have been
transferred to industry for use in the Route Survey Data Base (RSDB), built
by Logica Ltd, which has now entered service with the RN and the
Hydrographic Service.

The concept for the future is that MCM operations will be carried out with
knowledge of earlier missions detailing the positions of mine-like objects and
seabed types, and any other relevant information such as seabed stability and
the probability of mine burial. Synthetic aperture sonar linked to this capability
would be a powerful combination offering the prospect of an automatic
system based on a UUV for minehunting, surveying and reconnaissance.

Future MCM and platform-integrated combat systems

A route survey database or, more properly, a minewarfare database, has
another potential benefit:
UUVs on a reconnaissance task would be primed with information from
the database; this data would be reduced and simplified, and returned
updated. The amended data would then be geo-coded and overlaid on
high-definition charts. A comparison could then be made with data from
earlier surveys or even other sources such as magnetic sensors.

This facility could be important for combat management, the resultant multilayered
database forming the first node of a distributed combat management
system and the means to fuse and filter data for the first level of a command
structure. Integrating MCM combat management systems into mainstream
platform combat systems is an issue to be tackled if a task force is to be
regarded as being fully proficient in MCM terms.

Mine sweeping and hunting are often complementary. They provide operational
flexibility and can compensate for each other's shortcomings in some
situations-for example, where the seabed is strewn with rocks, hunting is
almost impossible, while sweeping can be a better option, particularly for
certain types of mines. However, hunting would generally remain the preferred
method for guaranteeing clearance, especially after operations.

For circumstances where hunting is the poorer option, the UK also maintains
sweeping capabilities on the HUNT class, the ships at present being fitted with
both a mechanical sweeping system and the Combined Influence Sweep
(CIS), which is fitted with magnetic and acoustic influence generators. At
present, the HUNTS' sweeping systems are being reviewed and possibly updated
to remove and mothball the mechanical sweeping system and replace CIS
with a Remote Influence Minesweeping System (RIMS). A feasibility study
is expected to start in 1999.

RIMS would fit well with the future concept of MCM operations. The system
could be controlled not only from dedicated MCM vessels but also from task
force participants or ships taken up from trade. In peacetime, remote drones
could, if fitted with sonars, be used for other tasks such as surveying; for
amphibious landings, they could efficiently pioneer clearing paths for landing
craft, especially when air superiority may not yet have been secured.

F9124801

Influence sweeping is carried out using either Mine Setting Mode (MSM)
(Fig.9), or Target Setting Mode (TSM). The first assumes awareness of the
types of mines to be swept, including particularly their sensors and algorithms,
and generates influences accordingly. TSM assumes little or no such
knowledge but instead mimics the vessel that intends to transit the swept
path, a method that requires full knowledge of own-ship's signature. Remote
sweeping depends on research for its understanding of these requirements for
influence generation.

Novel sweeping methods and systems concepts are studied to ensure that a
leading capability is sustained. A key contribution to maintaining a mine encounter
model is the Total Mine Simulation System (TMSS), which can
test different sweeping concepts and also provide operational advice to the
Mine Countermeasures Fleet. TMSS was pioneered by DERA and the basic
programmes were then shared with collaborating nations under TTCP. All
these nations now contribute to the further development of TMSS, the UK
continuing to update and retain the master model.

Very shallow water and surf-zone MCM

So far in this vision of the future, research has provided answers for protecting
a task force from mines in littoral waters, enabling reconnaissance to be
carried out to find suitable landing areas and can provide lead-through mine
sweeping by mimicking landing craft. What then remains is safely getting the
landing craft up a beach or into a harbour. The United States has expended a
great deal of effort in this area following their difficulties in landing marines
on the beaches of Kuwait during the Gulf War. Many systems are being
tested under their Advanced Concept Technical Demonstrator (ACTD) programme,
details of which can be found under ONR's world wide web page on the Internet.

The UK's research programme is considerably more modest
and is focused more on reconnaissance rather than on breaching.
The mine threat in very shallow water and the surf zone is likely to be very
different from that in deeper water. There will almost certainly be many antitank
and anti-personnel mines, as well as the normal ground mines. There
may also be all manner of obstacles, debris and barbed wire. To sense the
presence of mines in this environment is no trivial task.

F10124802

Detection from the air may be possible using unmanned air vehicles or sensors
deployed from specially designed underwater vehicles. Non-acoustic sensors
might be more effective than acoustic sensors. DERA has developed an underwater vehicle
(NASP-Non-Acoustic Sensor Platform) FIG.10), specifically to investigate
self noise and other integration issues associated with deploying an assembly
of non-acoustic sensors, such as magnetic, laser stripe and olfactory sensors,
from a UUV. The vehicle and sensors were successfully demonstrated in
1998, which is believed to be the first time such sensors have been deployed
from a UUV rather than from a towed body.

The ability to reconnoitre right up into the very shallow water and surf zone
will enable a path to be identified for landing craft. Destruction of mines and
obstacles in this path, however, will require a brute force approach. One
possibility is to adapt the UK army's Giant Viper breaching system for use in
water from landing craft. Explosives are being characterized in this environment
to determine the efficacy of such an approach (Fig.11).

F11124803

The Future of MCM

The most technically advanced mines and methods of using them undoubtedly
require the most advanced techniques to counter them. But mines of earlier
generations can still be very effective, as has all too clearly been demonstrated
in recent conflicts. These older mines are available in large numbers on the
world's markets, so that nations of modest means and disproportionate political
ambitions can be capable of creating threats that cannot be overlooked.
Clearing mines successfully is a very precise art; for the bulk of countermining
operations, there is no substitute for a dedicated MCM capability featuring
specialized equipment and highly trained personnel.

But the equipment used must be up to the task; in the right hands, it must be
capable of dealing with all types and generations of mines in increasingly
difficult environments. Many of the technical advances described and foreseen
are equally applicable to upgrading and enhancing the present capabilities
of the HUNT and SANDOWN classes. In addition to providing the
versatility central to supporting the likely shift in the character of many military
operations, research programmes are conscious of the need that will arise
in the medium and longer term to consider replacements for present MCM
vessels.

A separate and dedicated MCM force is no luxury. Nevertheless, particularly
for naval engagements in littoral waters, there is a strong case for fully integrating
a MCM capability into the main force. This may mean not only adding
UUVs and other future equipment of the sort described but could also
mean embarking MCM specialists on-board platforms such as the FE.

In a future capability, high-quality data will be gathered by remote platforms and
must be streamed back to the command centre, perhaps on a carrier of a joint
task force. The commander of such a force must be able to integrate the
MCM battlespace picture derived from a wide range of sources, platforms
and sensors. This will call for a highly automated communication system and
for tactical aids for planning and carrying out MCM tasks.

Rob Hoole
10-11-2012, 19:00
Thanks Andy,

I worked with John Wickenden and Mike Freegarde for several years in various guises.

ap1
10-11-2012, 19:18
Rob, when did you leave the R.N.?

Rob Hoole
10-11-2012, 21:29
Rob, when did you leave the R.N.?

Oct 2002. See my public profile.

ivorthediver
11-11-2012, 09:59
Thanks Andy,

Did you not know of our Robs activities then .....not like you .

I bow with great esteem to our friend and fellow diver , and the regard he maintains for lads beneath who more often than not are over shadowed by those in clear view :o

Excellent article Andy .....

Just out of interest .......and certainly no slight intended...... are you and Harry in competition to see who can do the longest " wallpaper" job :rolleyes::):)

ap1
11-11-2012, 22:34
Thanks Andy,

Did you not know of our Robs activities then .....not like you .

I bow with great esteem to our friend and fellow diver , and the regard he maintains for lads beneath who more often than not are over shadowed by those in clear view :o

Excellent article Andy .....

Just out of interest .......and certainly no slight intended...... are you and Harry in competition to see who can do the longest " wallpaper" job :rolleyes::):)

Of course I knew of Rob's activities!

I asked him a simple question; one that is not evident from his public profile.

Rob Hoole
12-11-2012, 11:09
Of course I knew of Rob's activities!

I asked him a simple question; one that is not evident from his public profile.

Hello Andy,

My response to your question was unintentionally curt. I only added the bit about looking at my profile to help put my RN career in perspective in case you had not read it. I'm sure that Ivor, like me, meant no offence.

ap1
12-11-2012, 18:45
Hello Andy,

My response to your question was unintentionally curt. I only added the bit about looking at my profile to help put my RN career in perspective in case you had not read it. I'm sure that Ivor, like me, meant no offence.

Rob, rest assured. I pay a great deal of attention to the minutiae of very interesting people like yourself, from the outset of their appearance on the forum.

I spend hours reading about their exploits, and enjoy every minute of it.

However, there are certain people who, unfortunately, totally misconstrue the most innocent of intentions of some of the 'posters' on this Forum.

ap1
12-11-2012, 21:45
© Crown Copyright/MoD (1986).

SINGLE ROLE MINE HUNTER

BY

A. P. MARTIN, C.ENG., M.I.MECH.E, F.I.MAR.E., R.C.N.C.

(Sea Systems Controllerate)

Background

In September 1980 the Admiralty Board endorsed a new Mine Countermeasures
(MCM) 'Concept and Numbers Policy'. Amongst other matters
the policy recognized the high unit cost of the HUNT Class MCMV and
identified the need for a cheaper vessel to complement it. Such a vessel
would have to meet the same principal MCM threat as the HUNT Class but
cost savings were to be sought through less sophistication, reduced versatility,
and possibly the acceptance of a somewhat higher degree of risk from the
mines to be hunted.

The HUNT Class MCMV is equipped for both minesweeping and minehunting,
and in addition is employed in a secondary role as a patrol craft. The
requirement to provide a cheaper vessel has led to the concept of a craft
equipped primarily for minehunting as being the most effective form of
active MCM and accordingly the craft has been designated as a Single Role
Mine Hunter (SRMH).

Four contenders were identified as being types of vessels which warranted
further study, these being:

(a) A single role version of the HUNT Class.
(b) The tripartite Belgian/Dutch/French mine hunter.
(c) A large hovercraft.
(d) A new design of displacement craft specifically designed to fulfil the
Navy Department requirements.

After investigations and early feasibility studies it was concluded that only
a purpose-designed vessel would be capable of meeting the requirements,
rectification of the shortcomings identified in the alternatives being such that
it was unlikely that these could compete on a cost basis. The proposal to
proceed on the basis of a purpose-built design was ratified and the vessel as
currently defined is as a result of the decision. The first of the class will be
H.M.S. Sundown. A model is illustrated in FIG. 1.

An artist's impression of the SRMH, together with additional information
relating particularly to the weapons and AI0 fit, can be found in an article
by Wright'. The application of the magnetic target in the case of the SRMH
main engine was discussed by Robson .

Design Basis

It was decided that deeper feasibility studies should be undertaken by a
member firm of British Shipbuilders as part of the policy of greater involvement
by industry in the design and procurement of defence equipment. The
shipbuilder concerned had in the past conducted design studies into a mine
hunter of similar size as a private venture and also had considerable expertise
gained in the design and construction of the HUNT Class.

The requirements call for all applicable Government and British Standards
to be observed in addition to MOD Standards. It was implicit, however,
that the use of proven commercial equipment rather than new design be
considered in the quest for low cost; the shipbuilder was tasked with
challenging standards where it could be shown that their application would
increase costs, and was required to employ value engineering solutions to
problems arising during the design process.

F1124836

The application of these constraints has led to a straight-forward approach
to systems, using fundamental principles as described below. The design has
evolved around an Upkeep by Exchange (UXE) policy of providing adequate
dedicated removal routes for machinery items in order to reduce downtime
and maximize hull availability. Emphasis has been placed on availability for
the proposed mission pattern, support being provided from Forward Support
Units (FSU).

Design Details

The emphasis on minehunting and the consequent absence of minesweeping
gear has had a considerable influence on the design and has led to a
quarterdeck area dedicated to the primary role. The various design investigations
have resulted in a vessel of 50 m length at the waterline and
10.5 m beam. These dimensions represent the best compromise between the
requirements for seaworthiness and ship motion for the envisaged operational
areas on the one hand and the avoidance of problems associated with
pressure signature on the other.

In view of the vessel's size, attention has been paid to crew comfort in
adverse conditions and has resulted in accommodation and operational spaces
being concentrated in the middle third of the vessel. The view from the
bridge also received attention at an early stage. The general arrangement is
shown in FIGS. 2 and 3. Accommodation is provided for a total of 40 men
including 7 officers and 9 senior rates.

In view of the method of operating the ship using advanced minehunting
techniques, the allowable magnetic signature has been considerably relaxed
compared with ships of the HUNT Class. Strict attention has been paid to
the allowable magnetic signature of individual equipments and the overall
signature prediction has been closely monitored by use of a mathematical
model. The ship's signature will be controlled by a degaussing system whilst
in service.

F2124837 F3124838

Method of Propulsion

The staff target for the ship calls for a high degree of manoeuvrability
coupled with the achievement of signature targets for noise and magnetics.
The various propulsion options investigated are shown in FIG. 4. The more
demanding of the operations associated with minehunting which have a
heavy influence on ship design comprise the ability to hover at a set point
after coming to rest, circling around a set point at a given radius, and the
ability to cover a given track within prescribed limits. It soon became
apparent that these varied requirements could only be met by active rudders
or Voith Schneider Propellers (VSPs) and that electric propulsion, particularly
at minehunting speeds, would be the most effective method of reducing
noise. Propulsion by diesels would offer the best method of achieving the
high speed and transit conditions.

F4124839

The operating principle of VSPs is shown in FIG. 5 and their capability of
thrust in any direction caused them to be nominated for the SRMH.
A bow thruster has been incorporated into the design since it appears
unlikely that desired directional control could be achieved in high seas and
wind states at slow speed by VSPs alone.
Observing that two alternative methods of propulsive power are utilized,
both driving into each propulsor, the drive system adopted involves the use
of synchronizing self shifting (SSS) clutches and is shown in outline in FIG.
6. Fluid couplings are incorporated between the motive power and clutch in
each case as an aid to starting, and a torsional vibration de-coupler for the
main propulsion diesels. The drive from the propulsion electric motor to the
main shaft is by belt as a means of avoiding the generation of discrete tone:
which would arise if a geared drive were used. Each machinery set is raft mounted
to reduce underwater noise transmission and as an aid to meeting
the desired shock capabilities.

F5124840 F6124841

Drive from the raft-mounted propulsion package is transmitted to the VSP
by way of an internal shaft. This is mounted in bearings supported from
internal bulkheads and connected at each end by cardan shafts incorporating
flexible couplings to cater for movements likely to be encountered under
shock conditions.

F7124842


Electrical power both for silent propulsion by electric motor and for ship's
services is provided by three radiator-cooled diesel generators, each of
250 kW output, fitted high in the ship to reduce water-transmitted noise.
The generators are connected to a single switchboard and arranged so that
when on silent drive one generator is normally employed for propulsion and
one for ship's services, with the remaining set standby for either duty as
shown in FIG. 7.

The slow speed drive (SSD) power has been selected to
meet the most demanding requirements foreseen whilst minehunting. In the
most favourable conditions the power requirements of the SSD are minimal
and the generator sets can be run in continuous unattended parallel operation.
By this means the loads associated with ship's hotel services and propulsion
nlay be shared, thus avoiding the problems associated with low power
running on turbo-charged diesel engines.

Auxiliaries and Ship's Services

In order to reduce cost and to control the ship's acoustic signature,
advantage has been taken of the short mission times to eliminate all inessential
items. Of those systems remaining only those necessary for the primary task
will be operated during minehunting and whilst on slow speed drive.
Machinery to be run while minehunting is mounted on a common raft in
the Auxiliary Machinery Room, as an aid to noise reduction.

(a) Fuel System. Design of the fuel system has drawn heavily on the
experience gained during hostilities in the Falklands and has resulted
in the development of the system shown in FIG. 8. Fuel is stored in
two deep tanks and transferred as required to a central service tank
via a filter and coalescer. Clean fuel is then drawn from the service
tank by duplicated fuel supply pumps and directed to header tanks
for the diesel generators which constantly overflow into the main
engine header tanks which in turn overflow back into the service tank.

Because the header tanks are thus never less than full the use of this
cascade system reduces the maximum amount of fuel stored at elevated
levels. The fire risk is consequently reduced, whilst ensuring that in
the event of electrical power loss a sensible minimum of fuel is available
for use until power is restored. Flexibility has been incorporated into
the system by various emergency and cross connections, and a hand
pump is fitted to assist in initial start-up and emergency situations.

F8124843


(b) Lubricating Oil Systems. Storage of lubricating oil has been reduced
to the minimum required for changing and replenishment, allowing
for the ship's envisaged operating cycle. Contaminated oil is stored in
a dedicated tank and will be discharged at a suitable disposal point on
return to harbour.
(c) Compressed Air System. The system as designed allows adequate stored
air for use whilst minehunting and it is not intended to run air
compressors whilst on task unless absolutely necessary. All air is to
the purity standard required for diving, and dedicated bottles will cater
for diesel engine starting if system pressure is low.
(d) Sullage System. To reduce complexity the ship will not be fitted with
an oily water separator, and separate sullage holding tanks are provided
since the area of operation will preclude the discharge of oily waste
overboard. Discharge on return to harbour will be through a deck
connection.
(e) Fresh Water. No provision has been made for the production of fresh
water but space exists for the installation of an R 0 plant later if
absolutely necessary. Sufficient fresh water for the ship's duty cycle is
stored and allows for the expected daily consumption. Hot water will
be supplied by individual electrical calorifiers at user points.
(f) Sewage System. The design incorporates a vacuum sewage collection
and holding system utilizing fresh water flushing, thus avoiding the
necessity to run sea water pumps whilst minehunting. The use of a
vacuum system which does not rely on gravity provides maximum
freedom in the layout of accommodation. Discharge of sewage holding
tank contents whilst alongside will be arranged via a dedicated sewage
discharge pump.
(g) Air Conditioning System. Accommodation and operational spaces will
be air conditioned to temperate conditions by a duplicated direct
expansion compressed gas system and the resultant cool air distributed
throughout the conditioned spaces by trunking and fan. To avoid the
use of pumps no chilled water system is fitted.
(h) Fire Fighting Systems. Fire fighting for the ship will be by fixed two shot
Halon systems for machinery spaces, backed by sea water and
AFFF systems. A fixed pressurized tank is fitted for magazine protection
and by this means it has been found possible to dispense with the
need to run pumps during minehunting operations. In case of fire the
necessity to start pumps, with attendant noise risks, will be by command
decision.
(i) Refrigeration and Deep Freeze. To avoid unnecessary cost and complication,
self-packaged free-standing cabinets have been incorporated
for both cold and cool storage.
(j) RAS. The ship will be fitted for replenishment at sea of fuel, fresh
water and dry provisions, with a helicopter pick-up point on the top
deck.

Control

To meet the manoeuvrability targets the optimum controls for both ship
and machinery are necessary. It was recognized at the outset that the targets
for hovering, circling and track keeping would be so demanding as to rule
out manual ship control and hence the controls have developed along the
lines shown in FIG. 9.

Three separate modes are employed while in slow speed drive, viz. fully
automatic, computer assisted manual, and manual. In each case ship data
will be displayed on a VDU mounted on the helmsman's console, the
necessary inputs in the fully automatic mode being derived from the various
sensors associated with the Action Information Organization (AIO) fit for
the ship, e.g. radar, SATNAV, radio fixing, etc. The optimum form of the
controls is still being studied.
While on diesel drive control will be by direct throttle controls and this
also is shown in FIG. 9.

F9124844

The SRMH is fitted with a Ship Control Centre (SCC) in which is mounted
the main switchboard and machinery start/stop and surveillance panels. In
all modes the primary control position will be the helmsman's console on
the bridge, and watchkeeping in the SCC will be for monitoring rather than
traditional throttle watchkeeping.

Selection of Equipment

In accordance with government policy on maximizing competition and
devolving work to industry, the lead shipbuilder has been tasked with seeking
competitive tenders for all equipments and in some cases this has led to
proposals from contractors hitherto unknown in defence circles. This is seen
as a vital step in achieving low unit production costs (UPC) for the ship.
Detailed information on the equipment likely to be selected is not yet
available, for reasons associated with the present stage of the contracts.

Conclusion

The single role concept, simple approach, and maximum competition have
combined to form a cost-effective solution to the problems of detection,
classification and disposal of mines, and should prove a versatile and
worthwhile addition to the R.N., seeing service into the 21st century.


References

I. Wright, R.: The Single Role Mine Hunter; Naval Electrical Review, vol. 37, no. 4, April 1984, pp. 1-6.

2. Robson, P. G.: Diesel engines for low-magnetic signature applications in MCM vessels;
Journal of Naval Engineering, vol. 27, no. 3, June 1983, pp. 437-441.

ap1
13-11-2012, 16:22
© Crown Copyright/MoD (1981).

HOVERCRAFT IN MINE COUNTER MEASURES

BY

D. K. BROWN, M.ENG., C.ENG., F.R.I.N.A., R.C.N.C.
AND
C. M. PLUMB, BSc., C.ENG., M.I.MEcH.E., R.C.N.C.

(Ship Department)


This article was first presented as a paper to the High-Speed Surface Craft
Conference in June 1980. For security reasons, some of the recent studies and
trials were treated very superficially. The current area that is being examined is
the minehunting field. Trials last year demonstrated that a 193M sonar could
operate successfully under a hovercraft and that sonars could be towed behind
hovercraft without peformance degradation.
Hovercraft fitted with hull-mounted and/or towed sonars could perform
minehunting roles. As sonar search speeds increase, the hovercraft offers unique
qualities of low noise signature and good endurance. Sonar operating speeds are
rising and, if recent articles are to be believed, foreign towed-sonar speeds are
making major advances, bringing the high-speed minehunting hovercraft nearer
to a reality.

Introduction

Hovercraft exhibit a number of characteristics that are attractive for mine
countermeasures (MCM) operations. Considerable experience has been
gained through trials and studies to identify and quantify the important
parameters. As part of the studies, a survey of current and potential
hovercraft designs was made to determine the characteristics of a craft needed
for the role. The SRN 4 was identified as the design with the greatest
potential and most studies have been directed towards using a craft of this
size. However, for the support of MCM forces and in some MCM associated
roles, smaller hovercraft also offer potential advantages over more conventional
vehicles.
The air cushion that supports the hovercraft also isolates it from the water
making such craft extremely resistant to underwater explosions and also leads
to extremely low underwater noise levels. These characteristics make the use
of hovercraft in MCM attractive and a long series of R.N. trials and studies
have been carried out with the aim of overcoming the many problems and
realizing the potential of the MCM hovercraft-MCM(H).

Trials and Studies

Early Trials
The Interservice Hovercraft Unit was formed in September 1961, only two
years after SRN l's historic crossing of the Channel. The initial aim of the
Unit was to evaluate hovercraft in a wide range of roles for all three Services.
It was soon clear that the Unit needed its own craft and in 1964 one SRN 3 (35
tonnes) and three SRN 5s (7.5 tonnes) were accepted.

After a number of trials in other roles and basic studies into craft
performance, the hovercraft became active in mine countermeasures during
1972. By that time the Unit had been equipped with SRN 6 craft and one of
these was used for a series of trials both in calm and moderate weather towing
a drogue to simulate sweeping gear. Control and track-keeping was measured
at various headings relative to wind. On the successful conclusion of these
trials, the craft was fitted with a Sweep AP Type H (Pipe Noise Maker)
lowered into the water by a simple davit. The next device to be tried, in May
1972, was a team sweep intended to be deployed between two SRN 516 aimed
against snag-line or antenna-operated mines. This sweep, developed by the
staff of Captain MCM was the first equipment specifically designed for
hovercraft.

Later that year, the SRN 3 was modified to lay and recover dan buoys using
a gantry and hydraulic winch at the bow. Dan buoys were carried in the cabin.
SRN 3 was also used for track-keeping tests towing a simulated sweep.
Considerable importance was attached to the capability of the hovercraft,
which is almost invulnerable to mine explosion, to tow damaged MCM craft
clear of a minefield. In January 1972, after early tests with lighters, a SRN 6
towed a 355-tonne coastal minesweeper at 3 knots in calm conditions. During
the following year, a variety of towing trials showed that the operation was
still possible in moderate sea conditions.

Trials of equipment are the most spectacular part of a development
programme but they must be backed by a careful series of measurements.
These included static pulling tests, detailed measurements of track keeping
under various conditions, and also measurements of acoustic, magnetic, and
pressure signatures.

The BH 7 Craft and Trials

In September 1970, the Unit accepted the BH 7, a craft specifically
designed for a range of military roles.

Weight (gross) 50.7 tonnes
Pay load 14.2 tonnes
Length 23.9 metres
Maximum speed 60 knots

She was propelled by a single Proteus engine (2840kW) driving a 3-5-metre
lift fan and a 6-4-metre propeller. This larger and more capable craft was used
to carry out a much more realistic range of trials and was also able to play an
important part in MCM exercises.

BH 7 was easily able to tow 'damaged' minesweepers and, towing a drogue,
could maintain control in up to wind force 6. In navigation trials she was able
to hold course, thanks to her rotatable propeller pylons, to a 15-metre
standard deviation in force 4 and to 25-metre standard deviation in force 5.
Later, BH 7 was fitted with some special light-weight sweeping gear,
developed in the United States for use from helicopters. This gave the craft
some capability for cutting moored mine cables and for sweeping magnetic
mines. In addition a small towed minehunting sonar was used. Once again,
this practical activity was supported by the usual range of precise
measurements of signatures, towing pulls, control responses, etc.

The Hovercraft Unit had long been developing the facilities and experience
necessary to operate the craft for considerable periods away from base. For
BH 7, the mobile base comprised twenty men with two caravans, a support
lorry, and a Land Rover. Normal commercial fuel supplies were used. So
equipped, the Unit was ready to take its part in major exercises.
In his history of the IHU, Brian Russell tells the story of several such
exercises but in this article a brief account of one, 'Scotch Broth', in early
1973 must suffice. Three SRN 6 were carried to the temporary base at
Greenock while BH 7 made her own way at a passage speed of 31 knots.
After a work-up period, the tactical phase began on the 5th of February. One
of the SRN 6s was used as a logistic support vessel throughout, carrying

F1124850

stores, NAAFI goods, spare sweep components, etc. to and from shore bases,
the command ship at Campbeltown, and the MCMVs at sea. The other SRN
6s were mainly used for snag-line sweeping though they also used the pipe
noisemaker.
BH 7 used her light-weight sweeps and also laid a chain of dan buoys for
navigational purposes. She also gave a series of demonstrations to senior
officers and towed a 'damaged' minesweeper out of a simulated minefield.
Since then, BH 7 has continued to develop equipment and techniques for
mine countermeasures. More recently she has been used for an elaborate
series of trials to study the acoustic environment and sonar operating
conditions under a craft.

Precursor Sweeper Designs

In 1975, a contract was placed with a joint design team from British
Hovercraft Corporation and Vosper Thornycroft for a series of design studies
for a precursor sweeper, to sweep ahead of the conventional MCM force,
disposing or locating any anti MCM devices. The study team produced eleven
new designs and also considered the VT 2 and SRN 4 craft for this task. They
were all designed to operate the same light-weight sweep used in BH 7 but it
was found that the SRN 4 was big enough to carry and operate the same full size
sweeps as a conventional minesweeper.

In the relatively small numbers required, it has since appeared that a craft
of SRN 4 size is the most promising solution. Already developed and proven
in commercial service, there would be less need to build a prototype if a SRN
4 were used as a MCM(H). However, the need to optimize a number of the
characteristics of the present commercial craft, before its use for MCM tasks,
might make a prototype desirable. This size of craft has the advantage of
being able to carry and operate all existing sweeps. As part of the design study
investigation, a wide-ranging series of detailed trials were carried out to
document the performance of the SRN 4 in MCM.

The main particulars of the SRN 4 are:

All-up weight (commercial role) 220 tonnes
Length 39.7 metres
Beam 25.5 metres
Pay load 106 tonnes
Sweep-deck dimensions: Length 24 metres
Width 10 metres
Power 4 Rolls-Royce Proteus
each 2835kW max.
continuous rating.
Propeller diameter 5.8 metres

Should it be decided to pursue the use of hovercraft for MCM tasks, a craft of
this size remains the most likely option to be adopted.

Explosion Trials

Some early trials with VA 3 had indicated that hovercraft had considerable
resistance to underwater explosions and, when SRN 3 reached the end of her
useful life in 1973, it was decided to carry out a further series of explosion
tests. Most of the useful equipment was removed and the craft was moored to
a buoy while hovering but unmanned. Seven mines were exploded, one after
the other with the last one just clear of the craft perimeter. To most people's
surprise, as the spray settled, the craft was seen still hovering and with only
minor damage to the skirt and superstructure from fragments of mine casing.
The commercial radar and radio sets were still functioning and the instrument
readings showed that the crew would have been in no danger had they been in
strong seats with lap straps. After the trial, the crew re-boarded their craft
and brought it back to base.

A similar trial, with less severe loading, has since been carried out against
the VT 2 and, in this case, the crew did remain onboard. There is little doubt
that a hovercraft can withstand any mine explosion provided that the
explosion plume is clear of the craft.

Performance of a Large Hovercraft in the MCM Role

Speed
The power requirements of a craft will depend on the maximum speed or
the towing load requirements. A future MCM(H) design would need to
reflect the operating profile before the power requirements can be decided.
There are obvious advantages for MCM vessels having a high passage
speed capability in order to achieve maximum time on task. A large
hovercraft with a speed of about 7G knots can spend almost all its operational
time on task, whereas the conventional MCMV will spend a far greater
proportion of its time reaching the area of operations. In addition, the block
speed (allowing for refuelling), over larger voyages, of about 40 knots allows
rapid deployment from one area to another as the threat changes.
The speed of a hovercraft varies considerably with all-up weight and with
wind and sea. As an example, the SRN 4 MkII, in calm weather, has the
following range of speeds in calm water:
All-up weight (tonnes) 160; Speed (knots) 80
All-up weight (tonnes) 200; Speed (knots) 70

In bad weather, speed is affected both by wind and sea and hence the
maximum speed depends on direction relative to the weather. It is proper,
and pessimistic, to define weather in terms of Coastal Code rather than Sea
State as the former definition assumes a higher wind speed for given wave
height, i.e. in the open sea, with fully developed waves, the hovercraft speed
in any given wave height will be greater than shown below.

Table 1124859

Seakeeping

The three aspects of the seakeeping of any craft in bad weather are
survival, craft performance, and crew efficiency.
Model tests have shown that a large hovercraft cannot be overturned or
overwhelmed by the most severe seas likely to be met in U.K. operational
areas, in either the hover or the raft mode. These model tests have been
confirmed in slightly less severe seas by service experience with smaller
hovercraft (SRN 5 and SRN 6). The British Rail SRN 4 which was recently
lengthened showed no signs of damage from wave impacts when cut in half
and inspected. With four engines, it is almost inconceivable that the craft
should be reduced to the raft mode but even so the craft is safe.

FIG. 2 shows the performance of the craft in various wind and sea states.
Speed in rough seas will cause vertical motions and these are shown in terms
of r.m.s. accelerations in FIG. 3. Crew performance is governed primarily by
the frequency and magnitude of the vertical accelerations caused by the
passage of the craft over waves. At the maximum attainable speeds in rough
weather accelerations will be high and it would be expected that the crew
would be exhausted in about twenty-four hours.

F2124851 F3124852

The long-term tolerance of human beings in such motion is ill defined,
varying from person to person and day to day, and is also a function of
frequency as well as acceleration. However, in the critical frequency bands
r.m.s. accelerations of about 0.08g are generally acceptable for prolonged
periods. FIG. 3 shows that the accelerations at the speeds shown lie only
slightly above this value. While at hunting speeds (5 knots) and sweeping
speeds (10 knots) the motion will be less severe. Such trials give confidence
that the crew of a SRN 4 could operate sweeps or hunting gear over periods of
days in any weather in which conventional MCMVs can operate, i.e. about
2.4 metre seas.

Commercial hovercraft are designed for half-hour trips across the Channel
and, in consequence, little has been done in their design to reduce noise and
vibration levels which would cause rapid crew fatigue if these craft were used
for longer missions. However, studies indicate that comparatively cheap and
simple treatment (some strengthening and insulation) could reduce these
levels to an acceptable value.

To maintain the operational efficiency of the crew under adverse weather
conditions, the design must be directed to providing work stations that are
comfortable. The crew will normally be seated in order to reduce the danger
of injury if a mine explodes. Because of the likely severity of craft motion,
attention to seat design is necessary. A low background noise level is
desirable even though the crew on duty will be wearing lightweight protective
helmets incorporating head sets linked to an I/C system. Those off duty may
require protection from noise to allow them to sleep.

Control

The control of a MCM craft is of great importance during operations. Trials
were undertaken on a commercial SRN 4 to assess the characteristics of a

F4124853 F5124854

large hovercraft. The SRN 4, with four propeller pylons, each of which can be
rotated to alter the direction of thrust is inherently highly controllable. The
fore and after pylons can be moved together or in opposition (FIG. 4). Trials
were carried out towing a drogue to simulate sweeping gear in various wind
and sea states. In one example, the craft at 10 knots was able to hold a defined
course with a standard deviation of about 4 metres in 2-metre waves and a 22-
knot wind (FIG. 5), a much better result than that obtained by conventional
ships.
Under the weather conditions outlined above, the craft was quite
controllable with only three engines running and, in more moderate
conditions, two would suffice giving a considerable increase in endurance and
ultimately in engine life. The best track keeping was achieved with the craft
trimmed level +/- 0.25 degrees compared with the more normal free-running true level to + 0.5 degrees.
It seems likely that for prolonged operation some form of automatic control
would be desirable.

Signatures

Mines can be actuated by the acoustic, magnetic, and pressure signatures of
the MCM craft, either singly or in various combinations. The signatures of a
commercial SRN 4 have been measured and, though the detailed results are
confidential, it should be borne in mind that these general statements are
based on measurements of a full-scale craft and not on measurement of tests
on models.

Acoustic

The acoustic signature of the SRN 4 compares very favourably with any
existing conventional MCM craft in any condition and the underwater
noise levels vary little, if at all, with speed or when the craft turns. In a
normal MCM operation, the craft is turning for some ten per cent. of the
time during which all conventional craft become very much noisier.
The hovercraft is inherently quiet due to its air cushion and cannot
become noisy due to propeller damage or 'shorts' across the flexible
mountings of machinery as can happen to conventional craft. In
consequence, there is no need for repeated monitoring of acoustic levels in
hovercraft.

Magnetic

The magnetic signature of a SRN 4 in commercial form is quite low since
the craft is built of aluminium and the main ferrous components of the
machinery are carried high above the water. Some high spots in the
signature have been identified and could be reduced in a military craft
either by degaussing or by replacing ferrous components with other
materials.

Pressure

The pressure signature of a hovercraft is very low in all normal operating
conditions.

F6124855

A Possible MCM Hovercraft based on SRN 4

To confirm that all the characteristics needed for a MCM(H) could be
accommodated in a large hovercraft, a study of SRN 4 in this role was
undertaken.
A possible layout of this craft as a minesweeper is shown in FIG. 6. The
winches, reels, etc. needed for minesweeping of moored mines and the
generators, etc. for influence sweeping of acoustic and magnetic mines fit
easily into the spacious vehicle deck. Adequate space remains round the side
for crew accommodation, galley, and for the operation and navigation spaces
needed in MCM work.

In a refinement of this fit, the MCM equipment can be mounted on pallets
so that a rapid change can be made from MCM to one of the alternative roles
listed subsequently. Care would, however, be required in breaking and remaking
joints in the hydraulic system. The generator required for the
magnetic sweep would be a light-weight gas turbine.

Overhead runways in the covered minesweeping deck should make the task
of getting sweeps in and out both less arduous and more comfortable than on
the conventional open quarter deck. The towing pull developed by the SRN 4
is adequate to tow any known minesweeping gear at the maximum design
speed of the sweep (FIG. 7).

124856

Should airborne noise levels in the crew's quarters or operational spaces
prove unacceptable it would be possible to mount insulated rooms, perhaps
containers, clear of the main structure.

Many modern mines are virtually unsweepable and must be located and
destroyed using minehunting sonars. Conventional craft will usually detect
and classify a mine using a sonar mounted below the hull and the same sonar
will be used to assist in the destruction of the mines. Drawings have been
published showing such a set, the 193M, carried on a retractable strut within
the cushion of the hovercraft. Tests in support of such an arrangement have
been carried out with encouraging results.

Endurance

It is hard to put precise figures on the endurance of any warship in an
operational scenario as fuel consumption varies so much with speed, use of
helm, bottom condition (for a displacement craft), etc. In consequence, the
endurance of warships is compared on a very simple basis, e.g. 5000 miles at
18 knots. While such a simple definition is just adequate to compare the
characteristics of two similar ships, it is quite inadequate to compare a
conventional MCM craft with a hovercraft.

Hovercraft power requirements are much more dependent on craft weight,
sea state, wind force, and towing pull than are those of ships. Statements on
endurance should be precise in defining all these parameters and yet the
complications involved in such considerations make the figures difficult to
understand let alone compare with surface ships. TABLE II gives a few typical
figures for a large hovercraft:

Table 2124860

With the ever-rising fuel costs, there is interest both within the MOD and
commercially in improving fuel consumption.
The SRN 4 is an elderly design and, though updated over the years, is still
much less efficient than a new design would be. Wheeler2 has indicated the
improvements that could be made by lower specific fuel consumption of more
modern engines, better skirt design, and by better aerodynamics. Some
indication of what these factors could mean to SRN 4 MkII towing a small
minehunting sonar into wind in Coastal Code 4 is given in TABLE III.

Table 3124861


Since there seem to be no problems in refuelling hovercraft at sea, it may be
concluded that the fuel endurance of hovercraft is quite adequate for MCM
operations.

Availability, Reliability, and Maintainability

A MCM(H) should have high availability, high reliability, and the
minimum of maintenance which can be undertaken easily. The only data
available on a hovercraft of the size likely for a MCM(H) is that of the
commercially operated SRN 4.

This craft has been in service since 1968 and has now achieved a high
standard of availability. Commercial craft achieve about 1500 hours of running
each year in cross-Channel service with up to 14 hours each day during the
peak of the holiday season. Hoverlloyd achieves 290 days of operations per
craft per year with a maintenance load which, though significant, permits a
commercially profitable operation.

About one per cent. of cross-Channel trips are cancelled due to mechanical
problems. The two per cent. or so of passages cancelled due to weather is a
measure of the lower tolerance of passengers to motion.

In wartime, a hovercraft could operate from almost any large, flat beach.
The craft could be fitted with built-in jacks to raise it for skirt maintenance or,
on a soft beach, a hole could be dug under the area concerned. Skirt damage
can be repaired quickly by riveting on a new piece of material. The
configuration of the craft makes mechanical work comparatively simple, e.g.
an engine change takes about five hours.
A permanent base would require a concrete ramp and large apron but a
hangar would not be essential as commercial craft are normally maintained
in the open. The site of such a permanent base would not be easy to find as
a number of large hovercraft would not be popular neighbours.

Both for the temporary base (beach) and the permanent site, good access by
road is desirable though, perhaps, not essential for the temporary base as the craft
themselves could carry all the vehicles needed to set up the base.
Costs

The cost of hovercraft operation is very dependent upon usage and on fuel prices.
The envisaged breakdown of life costs (September 1979) is .shown in FIG. 8.

F8124857

Alternative Roles

In most discussions, the 'conventional' warship is held to be much more
flexible in: operational usage than the more specialized 'Advanced Naval
Vehicle'. While there is, at present, a good deal of truth in such a view when
applied to frigate-sized ships, it does not seem valid when applied to MCM
vehicles.
The large, open deck and good weight-lifting ability of a large hovercraft
make it adaptable for a wide range of roles both in support of mine warfare
operations and in logistic support. Some examples are:

(a) It could tow damaged ships up to the size of a destroyer out of a
minefield.
(b) It could carry stores, personnel, and, as already stated, the vehicles for
a forward support unit to the operations area-and all this at a transit
speed of up to 70 knots.
(c) The hovercraft could mark quickly with buoys the edge of suspect
areas, at little risk to itself, so that shipping may be diverted until the
area can be cleared.
(d) Hovercraft could be valuable in minelaying operations as they could
take short cuts over sandbanks and even, in some cases, over 'friendly'
minefields.
(e) In the logistic role, a large hovercraft could carry loads such as;
4 Scorpion tracked vehicles and six trucks, or 7 trucks and 250 men.
Main battle tanks could be carried if the decks were suitably strengthened.
Over a route of thirty nautical miles, a single large hovercraft could carry 1500
tonnes in twenty-four hours.
Because the hovercraft does not need to use ports or stick rigidly to mine-free
routes, it would be able to operate much more flexibly than conventional
craft.

MCM Support Hovercraft

Exercises carried out since about 1972 have shown the value of the small
hovercraft owned by the Hovercraft Unit in-carrying urgently needed spares
and personnel to conventional MCM craft. The new HUNT Class MCMVs just
coming into service are extremely capable ships but their cost is likely to limit
the numbers that are procured. It therefore becomes essential that the ships
that are in service are fully operational, and on station for the maximum
possible time.
Various ways of getting equipment, etc. to a squadron operating off the
Coast were considered; these included fast motor boats, helicopters, and
hovercraft. Of these, the first is limited to the use of quay facilities while the
second have limited endurance and load capability. The hovercraft seemed a
cost-effective solution.

The requirement for pay load and range suggested a craft of about 100
tonnes, close to the size of the Vosper Thornycroft VT 2. The prototype of
this craft has gradually been developed over the years, and R.N. experience
when the VT 2 has been chartered for amphibious exercises proves it to be a
reliable and controllable craft. In April 1979, the VT 2 was therefore
purchased to develop the support role. Initially it was sent to the Baltic to
take part in a NATO exercise, and this was followed by a series of joint
evaluation trials with the German Navy.

F9124858

The VT 2 has now been modified with a derrick and hatch, etc. and is
currently being evaluated in the MCMV logistic support role.

The leading particulars of the craft are:

Overall length 30.1 metres
Overall beam 13.3 metres
Propulsion: 2 Rolls-Royce Proteus.
Propulsors: 2 variable-pitch ducted fans.
All-up weight 110 tonnes
Pay load 39 tonnes (45 in new craft)

Conclusion

A conventional hull vessel can be made suitable for MCM work but the
achievement of low signatures and shock resistance can prove expensive. A
hovercraft has inherent advantages over such vessels; these can be exploited
and optimized to cover this role and introduce a flexibility by virtue of a
capability to fulfil associated roles, previously unavailable.

Acknowledgements

The authors would like to thank British Hovercraft Corporation and
Vosper Thornycroft for their assistance with the preparation of this article.
The views expressed are those of the authors and are not necessarily those
of the Ministry of Defence.


References:

1. Russell, B. J., 'The Interservice Hovercraft Unit'. Available only from Hover Publications, Jellicoe Avenue. Gosport.

2. Wheeler, R.L., ‘An Appraisal of Present and Future Large Commercial Hovercraft’, Trans. R.I.N.A. 1976.

ivorthediver
26-11-2012, 09:51
Hello Andy,

My response to your question was unintentionally curt. I only added the bit about looking at my profile to help put my RN career in perspective in case you had not read it. I'm sure that Ivor, like me, meant no offence.


Rob I recently viewed a DVD on the Swedish Navy and their approach to mine detection and countermeasures which was very enlightening

Whats your view on the purpose made plastic boats they are now using and the foam core minesweepers they market now

whalecatcher
30-07-2013, 17:02
Lay of sweep wire.

Sweepers of WW II era fitted for Oropesa sweeping, carried right-hand laid sweepwire on the starboard drum of the minesweeping winch, with left-hand laid wire on the port side. I am pretty confident the practice carried on after the War. Can anyone give the reason for this?

Whalecatcher

ivorthediver
30-07-2013, 18:55
Thanks for posting that Whalecatcher, which answered another long standing question .

I built an RC model of HMS Manxman a while ago , and quite a while later I saw a conversation to her with two large drums stowed on her aft deck and often wondered why they were fitted .....now all becomes clear .......thank you .

whalecatcher
01-08-2013, 17:45
[QUOTE=ivorthediver;10084245]
Thanks for posting that Whalecatcher, which answered another long standing question .

I built an RC model of HMS Manxman a while ago , and quite a while later I saw a conversion with two large drums stowed on her aft deck and often wondered why they were fitted .....now all becomes clear .......thank you

I don't know the purpose of the large reels on MANXMAN's quarterdeck, but don't think they had any minesweeping connection. See photo.

I am fairly sure that the WWII practice of using RH laid wire on the starboard side of minesweeping winch, and LH laid to port would have persisted in the post war TON and maybe HAM minesweepers.

There must be folk on the List who served in these vessels, who might be able to comment. Private message me, if more convenient.

Whalecatcher

Rob Hoole
02-08-2013, 09:37
Rob I recently viewed a DVD on the Swedish Navy and their approach to mine detection and countermeasures which was very enlightening

Whats your view on the purpose made plastic boats they are now using and the foam core minesweepers they market now

Hello Ivor,

I lack sufficient knowledge or experience of these ships to offer an informed opinion. Being Swedish, they are doubtless fit for purpose although I don't think anything else in the world matches the RN's MCM capability. Our HUNTs and SANDOWNs also use a foam-filled GRP construction and are extremely tough as well as having a low magnetic signature.

I don't know the purpose of the large reels on MANXMAN's quarterdeck, but don't think they had any minesweeping connection. See photo.

I am fairly sure that the WWII practice of using RH laid wire on the starboard side of minesweeping winch, and LH laid to port would have persisted in the post war TON and maybe HAM minesweepers.

There must be folk on the List who served in these vessels, who might be able to comment. Private message me, if more convenient.

Whalecatcher

Hello Whalecatcher,

HMS Manxman was converted to support minesweepers from 1963. The large reels probably held spare magnetic minesweeping loops which were quite bulky and often required replacement. The exercise minelayer HMS Abdiel, her successor, was used more often as an MCMV command & support ship and had the same arrangement.

As the indirect source of your attached diagram of mechanical sweep wires, I think we may have communicated by email fairly recently. The left and right hand lay of sweepwires is still used today and is intended to enhance their outward spread when towed through the water, thus increasing their swept path.

ivorthediver
02-08-2013, 11:18
Thanks for that Rob, I did not know if we had made the transition or not at the time of posting that question ,....but as I had no response thought perhaps we were still using traditional hull construction .....so again my thank's.

I have long held an interest in this subject and although I was never a "wreck'y" who's sole interest as a diver was exploring wrecks I have pottered about most of the more popular Red Sea hulks and unlike others was more interested in exploring the design of the craft rather than the "Pot of Gold" mentality that most seem to possess

It was not until I dived the" Thistlegorm "in the Red Sea that I had any appreciation of the destructive force of explosives on a ships hull whilst sat in the confining nature of the water envelope.
So it was about this time that I started to gain my initial interest and respect for the danger and fragility of the hull in these situations .
Had I my life to live over I would have made a more concerted effort to get involved .....but thats life as they say .:o

I have read some books on the topic of mine clearance and thoroughly enjoyed them and gained an appreciation of the development and the initial early days of mines and countermeasures all of which upheld the respect for mine clearance that I had developed .
Once qualified first as a diver then as an instructor realised our frailty in the environment but spurred on by the quest for knowledge.....and the honing of what little skills I had gained in the ten years I was involved in Diving before hanging up my fins at 65 .

Whilst I'm sure yours may have been a slightly different approach couched in a professional Military environment , I share your love of the water and all its facets ...both good and destructive ........

regg3y
13-04-2015, 11:44
Mine Sweeping and the Hunt Class MCMV's
I know that Mine Sweeping has been phased out in the RN, but do the Hunt Boats still carry a Loop/Tag/Tin gear etc?
I would have thought that they would need to for weight distribution and the like, but I'm no expert.

Also, I have seen a photo of one of the Hunts and they had no Short Scope Buoy floats. Have Short Scopes been phased out as well and if so how long ago?

Rob Hoole
14-04-2015, 08:31
Hello regg3y,

The RN's last conventional minesweeping operation took place off the Isle of Wight on 12 October 2005 (see 'To Sweep No More' in the MCDOA website's Dit Box (http://www.mcdoa.org.uk/Dit_Box_Frames.htm) and the entry for 29 Dec 05 in News Archive 12 (http://www.mcdoa.org.uk/News_Archives_Frames.htm) among others on the same page)

The only sweep gear left on the Hunts these days are the empty loop winch (for its weight), the empty mechanical winch (for its drum ends) and the cranes because they are still required for other purposes, e.g. berthing, lifting and lowering Gemini dinghies and ROVs (Remotely Operated Vehicles), recovering exercise mines, etc. I am attaching some photos I took last December (see entry for 11 Dec 14 in News Archive 48 (http://www.mcdoa.org.uk/News_Archives_Frames.htm) of the MCDOA website).

The job of shortscope buoys is now done by military standard GPS.

For a glimpse of the future, see:

UK Government website dated 27 Mar 2015: UK works with France to defeat threat of underwater mines (https://www.gov.uk/government/news/uk-works-with-france-to-defeat-threat-of-underwater-mines)

IHS Jane's 360 dated 6 Apr 2015: UK selects Atlas Elektronik UK for MHC sweep (http://www.janes.com/article/50440/uk-selects-atlas-elektronik-uk-for-mhc-sweep)

mstary1
14-04-2015, 08:56
Well Australia still does Oropesa sweeping, though on a limited scale.
Whilst our minehunters don't carry the gear, it can be delivered by container
at short notice. Just yesterday I walked past past a group of trainees practicing deploying and recovering the sweep on a mockup deck.

regg3y
15-04-2015, 08:50
Many thanks for the replies.
I guessed they would have kept some stuff simply because of the hassle of removing things. The loop winch for one.
What do they keep in the Sweepstores these days? With no float wires, SSB weights, umpteen shackles, swivels and slips etc. it must be a nearly empty compartment.
With the Navy being the way it can be, I would have thought they would have kept one SSB just in case the GPS broke down.

regg3y
15-04-2015, 08:55
Any ideas what the green string is on the big reel by the Ensign Staff? Is it a new fangled Tow Rope?

mstary1
15-04-2015, 21:18
Any ideas what the green string is on the big reel by the Ensign Staff? Is it a new fangled Tow Rope?

Mine Disposal Vehicle tether line?
In the same postion as Australian minehunter tether line, but ours is orange.

regg3y
16-04-2015, 10:27
I know nothing about this. I only used the PAP's which could be pain in the backside.
The problem I found with the Pap's is that on recovery they often bent the Recovery Hooks. It dawned on me one day that the Pap's weight was something like 750kg and the SWL of the recovery Hooks was only 500kg. On wonder they got bent out of shape, bouncing around in slightly rough seas.

Rob Hoole
19-04-2015, 10:46
For those living in or near 'The Smoke' who haven't yet seen around a 'modern' MCMV (Mine Countermeasures Vessel), HMS Middleton (http://www.royalnavy.mod.uk/our-organisation/the-fighting-arms/surface-fleet/minehunters/hunt-class/hms-middleton) (Hunt class, not a Ton) will participate in the Royal Naval Reserve Live Event alongside at HMS President (http://www.royalnavy.mod.uk/president) on the Thames in London next Saturday (25 April) and will be open to visitors from 1000 to 1600. Tickets are free but going fast. See here on the Eventbrite website for booking details:

HMS MIDDLETON Ship Tour & HMS PRESIDENT Royal Naval Reserve Live Event Saturday 25 April 2015 (http://www.eventbrite.co.uk/e/hms-middleton-ship-tour-hms-president-royal-naval-reserve-live-event-saturday-25-april-2015-tickets-16550727672)

Perhaps someone can report back about the 'yellow string'. :)

regg3y
19-04-2015, 11:33
For those living in or near 'The Smoke' who haven't yet seen around a 'modern' MCMV (Mine Countermeasures Vessel), HMS Middleton (http://www.royalnavy.mod.uk/our-organisation/the-fighting-arms/surface-fleet/minehunters/hunt-class/hms-middleton) (Hunt class, not a Ton) will participate in the Royal Naval Reserve Live Event alongside at HMS President (http://www.royalnavy.mod.uk/president) on the Thames in London next Saturday (25 April) and will be open to visitors from 1000 to 1600. Tickets are free but going fast. See here on the Eventbrite website for booking details:

HMS MIDDLETON Ship Tour & HMS PRESIDENT Royal Naval Reserve Live Event Saturday 25 April 2015 (http://www.eventbrite.co.uk/e/hms-middleton-ship-tour-hms-president-royal-naval-reserve-live-event-saturday-25-april-2015-tickets-16550727672)

Perhaps someone can report back about the 'yellow string'. :)

I was trying to be as technical as possible.:D

Rob Hoole
21-04-2015, 07:05
Are you or do you know someone who served in the 11th MCM Squadron, i.e. the five Hull trawlers converted for minesweeping and sent south for the Falklands conflict? Without the ships of this squadron, the reinforcement of 3 Commando Brigade in East Falkland in 1982 would have been delayed unacceptably. They cross-decked the 5,000 men of 5 Brigade and 1,200 tons of stores at South Georgia in 36 hours. In the Falklands, they inserted and re-supplied Special Foces patrols, carried out a potentially dangerous 'guinea pig' influence task and, finally, cleared the sea minefields off Port Stanley.

There will be a special reunion of 11th MCM Squadron personnel and their supporters in Kingston-upon-Hull during the weekend of 13/14 June (14 June is 'Falklands Liberation Day'). See the entry for 21 Apr 15 on the Latest Page (http://www.mcdoa.org.uk/News_Frames.htm) of the MCDOA website for further details.

Scatari
07-06-2015, 12:54
Still a threat after 75 years!

(From BBC News)

Unexploded WWII mines disrupt Dover to Calais ferries

"Two unexploded World War II mines discovered near the port of Calais have led to the cancellation of a number of cross-Channel ferries."

Complete article here:

http://www.bbc.com/news/uk-england-kent-33039719

ivorthediver
30-10-2016, 14:01
Not sure who to ask about this ....I suspect Rob is my best bet ....... What can you tell me about the use of :-

1/ Bow waves to set off pressure sensitive mines

2/ "Egg Boxes" which were apparently towed over areas thought to have a heavy mine presence

Any comments please lads :confused:

nigelweysom
30-10-2016, 23:12
a very interesting thread one that i have a real interest in, my God Father
George collas Hocart LT RNR (Rtd), was awarded the DSC during ww2 for mine-sweeping in North Russian Waters aboard HMS Boscawen can i assume that they were sweeping German magnetic mines using the methods already described
Nigel

ivorthediver
31-10-2016, 09:36
I have scant information that has been proffered :-

Destroyer captains would go full ahead then full astern to create such a bow wave to create a change in pressure necessary to trigger the mines

the "egg Box" was a sacrificial device towed over areas thought to contain pressure mines .

One was in fact beached on Swansea beach for demolition after the war .

So I can only assume they were in fact German Mines .

Like wise my uncle was a stoker on HMS Puffin on the convoys ....

EwenS
31-10-2016, 13:42
As far as I can recall the Germans were the first to use pressure mines in WW2 following the Normandy landings in 1944. The Allies were expecting them and had various schemes to defeat them. The Egg Boxes / crates were one. Another was HMS Cybele & Cyrus constructed at the beginning of 1944.
https://en.wikipedia.org/wiki/Cybele-class_mine_destructor_vessel

These devices had to be towed around to be effective and several Bangor class minesweepers were converted to do the job.
Basically the bigger the ship the bigger the pressure wave at a given speed and depth of water. So the best solution was the shallower the water the slower you had to go. Tidal movements could sometimes be enough to trigger them. Usually a pressure circuit in the mine would be coupled with an acoustic or magnetic circuit just to make more life difficult for the sweepers.
The Americans sowed a lot of these around Japan in 1945 in an attempt to cut it off from resources on mainland Asia.
If you want to learn more about the mechanics of minesweeping at that time you could try to track down a copy of Peter Elliot's Allied Minesweeping of WW2. It was published away back in 1979.
Alternatively you could try to locate a copy of Out sweeps! The story of allied minesweeping in WW2 by Paul Lund.

ivorthediver
31-10-2016, 14:11
Thanks for that , I will dig around and see if I can find those books , thanks for the reply .
Must admit I had not heard of the Egg Boxes but assured they existed and were used .

Yes I had heard of the Korea mine laying but again scant detail

jbryce1437
01-11-2016, 16:28
There is a thread for HMS Cybele here (http://www.worldnavalships.com/forums/showthread.php?p=10046991&highlight=Cybele#post10046991)

Jim

ivorthediver
01-11-2016, 17:05
Thanks Jim ,

I have seen a very poor photo of them very recently and I am trying to get a decent copy , so fingers crossed eh

ivorthediver
01-11-2016, 19:01
Ok this is the best I have been able to find from a document sent to me by my sister in Swindon source not known but believed to be from a contact on one of the chat lines she visits

I understand that these were scrapped and cut up on Swansea Beach in or around 1946/7 .....sorry for the vague nature of this info but best I can do on this subject

Unable to credit the source or origins of these sadly

Rob Hoole
05-12-2016, 00:37
Not sure who to ask about this ....I suspect Rob is my best bet ....... What can you tell me about the use of :-

1/ Bow waves to set off pressure sensitive mines

2/ "Egg Boxes" which were apparently towed over areas thought to have a heavy mine presence

Any comments please lads :confused:

Hello Ivor,

Please see the linked pdf file of notes from my archives. I apologise for the poor quality but the originals are not very good either. I have been unable to attach the file to my post and upload it direct to the forum.

WWII Pressure Mine Countermeasures (http://www.mcdoa.org.uk/WW%20II%20Pressure%20mine%20countermeasures.pdf)

jbryce1437
05-12-2016, 09:22
Many thanks for the attachment Rob all very interesting, brought back memories with Bernoulli's Theorum - a regular question in fire brigade exams ;)

Jim

ivorthediver
05-12-2016, 20:09
Hello Ivor,

Please see the linked pdf file of notes from my archives. I apologise for the poor quality but the originals are not very good either. I have been unable to attach the file to my post and upload it direct to the forum.

WWII Pressure Mine Countermeasures (http://www.mcdoa.org.uk/WW%20II%20Pressure%20mine%20countermeasures.pdf)

I was right , thank god , as I knew that if anyone knew you would , so thanks very much .

A fascinating subject Rob that I knew little about , so Thanks for the fascinating insight your post exhibits , and I will offer the Spec to my sister who originally asked her Brother thinking he might know [ such faith :rolleyes:]

Again my thanks and deep respect for your knowledge

Rob Hoole
08-03-2017, 01:28
Not sure who to ask about this ....I suspect Rob is my best bet ....... What can you tell me about the use of :-

1/ Bow waves to set off pressure sensitive mines

2/ "Egg Boxes" which were apparently towed over areas thought to have a heavy mine presence

Any comments please lads :confused:
Hello again, Ivor (and anyone else interested).

While looking for some other information for someone leading a visit to Malta in September, I stumbled upon these pages (http://www.mcdoa.org.uk/Pressure%20mine%20sweeps%20reduced.pdf) in Allied Minesweeping in World War 2 (https://www.amazon.co.uk/Allied-Minesweeping-World-War-II/dp/0850593506) by Peter Elliott. The information is clearer and more comprehensive than my previous submission.

ivorthediver
09-03-2017, 14:27
Thank you Rob for posting that information , very kind of you .

I will pass this information on to the originator of the question who will I'm sure be very grateful for your help here

Kind Regards Ivor

greendragon
14-03-2017, 06:50
I went through the IWM collections and have found the following photos. Made by an official Royal Navy photographer in November 1941 shows the HMN mine disposal team in action supported by the Polish driver and a Bren carrier (note the PL markings on the vehicle and rude treatment to this sea mine).

Regards,

GD

ivorthediver
15-03-2017, 10:23
Was that [last picture] taken at saltfleet .....or did the driver lose the keys ?

As there are no Horns visible I'm asumming its been deactivated :confused:

Rob Hoole
15-03-2017, 13:39
Was that [last picture] taken at saltfleet .....or did the driver lose the keys ?

As there are no Horns visible I'm asumming its been deactivated :confused:

Ivor - The mine would have been rendered safe beforehand by removal of the detonator and explosive booster via the top cover plate but UK 'M' Mk1 moored mines like this were magnetically actuated. They lacked horns and had a wider belly band than contact mines to accommodate the central vertical coiled rod unit (basically a long metal bar with wire wound round it) that detected changes in the earth's magnetic field caused by the proximity of a ferrous surface ship or submarine.

ivorthediver
16-03-2017, 17:06
Thank you Rob , and sorry for showing my ignorance of mine's ....I'm afraid I rely on experts like you....... as this post illustrates only to well

Rob Hoole
17-03-2017, 13:08
Thank you Rob , and sorry for showing my ignorance of mine's ....I'm afraid I rely on experts like you....... as this post illustrates only to well

No problem, Ivor.

Incidentally, there is more than one way to skin a cat as the accompanying photos show. See entry for 4 Nov 16 in News Archive 56 (http://www.mcdoa.org.uk/News_Archives_Frames.htm) of the MCDOA website.

ivorthediver
19-03-2017, 11:57
Thank you Rob , that's an interesting site , thank you for allowing me in there , I can see you lead a busy life ........