What is this on this ship?

I was referring to the countermeasures vs mine fuse race.

When the German introduced the crude magnetic needle ground mine (LMA; British code name GA), the Royal Navy developed the LL- sweep. Although the Royal Navy had deployed the first magnetic mine (the M-sinker) late in WWI, they were a little slow in developing countermeasures.

When the Germans introduced the acoustic sensor, the Royal Navy developed the SA sweep (based on the Kango brand pneumatic hammer).

The "concrete barge" and "Loch Ness Monster" pressure sweep were not successful, (well, there were difficulties keeping the minesweeper safe - any sweep towed by a minesweeper could sweep at least ONE mine ). However, it was soon learned that the German pressure sensor would not be actuated if ship speeds were kept low (safe speeds were calculated for different displacements). The crude sensors back then only detected a sudden change in water pressure as the hull of a passing ship displaced water and generated a pressure wave. There were arrangements in place to avoid the mine going off with the change in tides. Moving slowly mimicked the gradual pressure change caused by tides to avoid setting off the mine.

In contrast, the Japanese never really developed successful counters to the USN mines used in the blockade of the home islands. They starved while the British broke the blockade ...

Re: book on KM Minenschiffe book, sorry I have not come across it. Re: auxillary cruiser, surface commerce raiders in Asia - I have read about them. Came across them mostly due to other things - ULTRA assisted intercept and sinking of the Michel ... explosion of the Uckermark at Yokohoma destroying the Thor ...

 

Paravanes were developed in WWI to, oddly enough, try and snag submarines. For that role, the tow body carried explosives. I guess when you didn't have anything else, "trawling" for the sub was as good a method as any.

Later it was found to be better suited for dealing with moored mines. Mechanical cutters were fitted along the wire to cut the mine cables. Once the mooring cable parted, the buoyant mine body would float to the surface where it can be sunk by gun fire. Large warships also used paravanes for self protection - streaming one on each side of the bow to deflect mines in the ship's path.

Re: speed of 4-6 kt ... "slow" is a relative term ... Remember, the minesweeper has to sail deliberately into the minefield. You probably wouldn't want to blunder in any faster than necessary to operate the sweep gear.

Modern mine countermeasures craft use high definition sonar to help it avoid mines as they enter the field. Even Korean War sweepers had no such luxury (and paid for it - the sneaky Soviet advisors sowed magnetic mines amongst the rows of moored mines in Wonsan Harbor - and sank the YMS 516).

Yes, the sweep deck of a WWII minesweeper is a cluttered and potentially hazardous place. In the process of deploying the sweeps with wires paying out etc., there is a real danger of getting snagged and going over the side with whatever is being streamed. If something snaps, then the hazards are multiplied ...

 

Yah, I even saw pictures (while cruising websites) of the Bismarck with 4-6 paravanes. Hardly a minesweeper, but it might clear a path for followers.
In the pictures I came across the paravane had a cutter (similar to those of "Jeeps" for piano wire) which looked like a chains hook with a sharpened middle just below the float.
Other sites said the paravane/float would detonate the mine ( after snagging it)(and pulling it to it), and they'd just reel it in and attach another.
Hey, whatever works.
I did see a movie once to where there was a ghost ship (Hospital ship) sunk by mistake, which came back (la de da) for revenge against that "killer" sub.
Anyway, it had an excerp about dragging chains with assorted cutters/grapples along the bottom to snag hiding submarines. I guess they made hideous noises even if they didn't rip you open. They were all pretty terrified anyway.
That's the first time I even heard of that, but again....whatever works.

 

Here's a good on-line reference, got some nice drawings of kites, otters and cutters:

http://www.globalsecurity.org/military/library/policy/navy/nrtc/14160_ch8.pdf

Where you have "countermeasures", the other side would deploy counter to the countermeasures. The Italians were particularly fond of devices that obstruct or even destroy the wire sweeps. These included explosive cutters to try and cut the sweep wire.

During the Cold War, the French developed the PAP 104 minehunting ROV which became standard equipment on minehunters of many NATO navies. It wasn't long before there was talk of special mines that would activate themselves when they detect the minehunting sonars and try to destroy the ROV when it came near ...

Couldn't resist it ... had to suggest a nickname for such a mine ...

the ...

"PAP Smear" mine ...

 

I thought it was better than the "Hellenic Navy TACAN"

...

Grecian URN ..


The Norwegians preserved one of their coastal minesweepers, the KMN Alta (M314), in Oslo next to the Akerhus Fortress museum. The Alta has a complete set of sweep gear. Very well informed volunteers were available to do a "show-and-tell" ... They were delighted to be asked to bring out and describe the Mk 12 explosive cutters.

Oh yeah, the Akerhus Fortress Museum was also fascinating. It had a huge collection of historical arms and a diorama of the sinking of the Blücher at the Drøbak Narrows in the Oslofjord.

 

Just a comment: Since the ship in question is a US Coast Guard cutter and not a minesweeper, nor is it normally used in locations where mines would be present, why would it be carrying specialist minesweeping gear? It seems far more likely that the boxes are stowage for life rafts which fits the mission of the ship far better (convoy escort and rescue of merchant crews who have been torpedoed etc.).
Also note, that this ship is in the Atlantic, not the Pacific. Note the camoflauge. This is measure 23 "Thayer" scheme used exclusively in the Atlantic on ASW / Convoy escort ships.

 

Right you are, here's a bigger resolution shot and the objects are clearly not kites and otters. Other views of the stern showed no sweep gear. Small resolution shots can be deceiving ...


http://www.jacksjoint.com/cutter1.jpg

 

So either Carley floats or float nets they are. I see a Carley float in the second picture.
The launching of "whatever" they are is gravity easy, but wiring them up to function (as sweeping tools), or recovery/replacement to that "launcher" (with no crane)(no wench) would be labor intensive if even possible.
A busy "Poop" deck on that boat.
They do look like (otters/kites) but the placement for those is odd (per your second website).
The misery is back, I still don't know what they are.
Good call T.A. (as usual)