APA project

[Fliger747]

Peeks at the "Paravane crane", ah for a high rez photo!

[Fliger747]

Working on a pre prototype crane unit. My dad's 1943 BJM has an interesting section on paravanes, PP 447-453. The cranes generally have a working load of 4 tons (8000 lbs) and a max reach over the side of 7 1/2 feet. This ship would use a type M paravane, for a max speed of 16 knots. The paravane has a (slight?) positive buoyancy but will run the paravane to about 5' deeper than the draft of the vessel when towed at greater than 2 knots. The cutter will sever a 1/2" mine cable with a pull of 700 lbs.

Here is the base of the pre prototype crane soldered from brass tube and wire.

[DrPR]

My first ship was an inshore minesweeper (USS Cape MSI-2). It was a 1950s vintage minesweeper, but the sweep gear was not much different from the WWII version.

Simple davits as shown in pictures below are all that was necessary to get the gear over the side and retrieve it.

Our sweep lines had cutters placed every so many feet along the wire. The cutters used a blank 30-06 cartridge. A trigger on the cutter tripped when the mine mooring line slid down the cable to the cutter. The explosive charge drove a blade that cut the cable.

We also had a "depressor" ("kite") that was attached to the cable close to the ship to pull the sweep wire down vertically to a predetermined depth. It was a frame with several vanes that pulled it down as it moved through the water. Then the cable led more or less horizontally to the paravane ("otter") at the same depth, The paravane towed a float ("pig") with a flag so we (and other ships in the sweep formation) could see the position of the end of our sweep line. This configuration was in use in WWII on mine sweepers and destroyers/destroyer escorts.

I don't know if a rig this elaborate was used on service ships like the troop transports and oilers.

The kite/depressor was essential to pull the cutting line down to a depth below the floating mine so the mine's mooring cable would be cut instead of fouling the mine and possibly detonating it. So if you see something in pictures that looks like a large white rectangular frame with several "wings" in it, it might be a kite.

However many WWII era ships of all types had paravane cables rigged at the bow through a doughnut-shaped fixture at the base of the stem. From there the cable ran more or less horizontally at the depth of the keel to the paravanes. With this rig the kite wouldn't be necessary. These ships had capstans or winches at the bow to feed out and retrieve the paravane cables.

Some of this gear can be seen in the movie "The Caine Mutiny."

Phil

[Fliger747]

Thanks Phil:

I have a copy of the "Caine Mutiny" and it has some excellent footage of DMS work! As far as I an tell the APA's streamed from the forefoot. My dad's BJM (1943) mentions the depressors to control depth for stern towed paravanes. According to the BJM the destroyers and DE's of the time were not paravane equipped. That the DMS towed from the stern was an example of the "They were expendable" philosophy.

Mine sweeping of course continued post war with the occupation of Japan. Interesting that the cables had the cartridges to cut the cables, one keeps learning more and more form the body of knowledge out there!

Cheers: Tom

[Fliger747]

As to the paravane cranes, I have built a better and hopefully more accurate pair, which are currently in primer. A small item, but as always building is a learning experience on their application.

[DrPR]

There was a lot of minesweeper activity in the Korean War too, especially before the Inchon landing.

Minesweepers normally worked in groups. The lead ship ran sweeps to both sides. The following ships streamed to one side only, following the "pig" of the lead ship. This way all but the lead ship moved in an area that was swept by the ship ahead of it.

The lead ship had to look after itself and steer to avoid any mines it saw ahead of it. If you look at the profile of WWII minesweepers you will see that the bridge of far forward and fairly high. They had lookouts up there and on the bow looking into the water for submerged mines. Everyone topside carried a gun of some sort and if a mine popped up we all blasted away. I was stationed on top of the pilot house and had a BAR (Browning Automatic Rifle). We had a 50 caliber machine gun on the bow. Larger ships had 20mm or 40mm guns.

Mine sweeping was a slow process. The ships had top speeds of 10-15 knots, and when streaming they moved very slowly, maybe 6-8 knots flat out. The sweep gear acted as a sea anchor. So they didn't go rushing into mine fields.

It was hard to steer with all the sweep gear out but they could turn enough to dodge a mine directly ahead - in most cases. We had a photo on our mess decks bulletin board of a minesweeper that hit a mine at Inchon. It was a column of water several hundred feet high with bits and pieces of minesweeper flying through the air around it. A mine designed to put a hole in a 45,000 ton battleship would vaporize an 850 ton minesweeper.

****

I doubt if other types of ships worked together in this coordinated pattern. They were usually in different formations to defend from submarine or aircraft attack, or for underway replenishment. So while in that formation they could stream paravanes to provide some protection for the group. But even with sweep gear out to the side from the bow the ships were vulnerable to mines dead ahead, just like the lead ship in a minesweeping formation.

Phil

[Fliger747]

Phil:

Thank you for the interesting recounting of minesweeping experience. Was your ship one of the wooden ones? Those ships always reminded me of fishing trawlers. I have a friend who has a BAR, interesting weapon, but I suppose the weight was needed to absorb the recoil of a full 30.06 cartridge if fired full auto. What sort of hits on a mine were needed to detonate it? I would suppose a .50 cal or 20 mm would shock the mine enough to detonate without a hit on the horns?

Cheers: Tom

[Fliger747]

Sometimes as the project evolves items are re worked. Still working towards a satisfactory prop. One of the issues in soldering was the mass of the prop hub compared to the relatively thin blades. So this attempt I bored out the center of the hub and will later turn a spindle for it to rest on. The idea being make the heat required for a good solder joint less.

Here it is with test blades of heavy paper (Strathmore) as a proof of concept and to test the size and fit.

[DrPR]

Tom,

The Cape was wooden. And the old minesweepers did look a lot like fishing boats. In fact we sometimes used the sweep winches and cranes to pull a fishing line trolling for sharks! It was McHale's Navy.

I really don't know what it took to sink a mine. We practiced on 50 gallon drums. The MSIs were pretty much worthless and the Navy got rid of them while I was aboard. After a brief stint as Officer in Charge (an Ensign with six months active duty and I was O in C!) for decommissioning an old MSCO coastal minesweeper I went to the USS Oklahoma City CLG-5.

Phil

[Fliger747]

Ah, it was "Captain Phil"! Good sea stories!

[Fliger747]

Ex minesweeper USS Cape, Captain Phil's first command. Built in Bellingham Washington, after decommissioning owned by an Indian Tribe and later by and individual in Olympia Washington. Here in it's post Navy livery!

[Fliger747]

New iteration of the four bladed prop. I learn something with each one! I'll pitch and polish this one and see how it "feels"

[Fliger747]

Latest prop iteration installed after pitching. My greatest respect to the experts at constructing these!

Cheers: Tom

[Iceman 29]

Great job, Tom! Not easy to manufacture.. The rendering is magnificent.

[Fliger747]

Thank you Pascal. This is my fourth try at this! I might or might not try for a fifth as I have learned a lot! The stern post is currently pinned in place allowing prop swap.

Tom

[Fliger747]

Mostly I have been busy working with a 3D design program called Design Sparks Mechanical and learning how to do some basic 3D evolutions.

However here is the installed Paravane Cranes on the boat deck.

[Iceman 29]

Very successful, not much space to put the paravane in the water. These decks were really very congested...

[Fliger747]

Yes I am amazed by how closely packed these ships were and how complex all the evolutions were for hoisting away all the boats. Required a very highly drilled crew! Sometimes there was so little deck space available that a change of command ceremony was conducted in the small space between the two fan units on the boat deck, right in front of the bridge. Sometimes the clearances wore down to inches rather than feet. So far if there is a square cm open on the deck of the model, I've forgotten something! Certainly not the wast open spaces of a battleship's holystoned teak deck!

I have been experimenting with 3D design and I think I can have some minor success with this, but this ship will be 100% scratchbuilt using the "old ways". Currently I am working on a 20 mm (single) Orlikon and have it up to the top of the pedestal so far. I think (hope) that this will print ok in 1:120.

Cheers: Tom

[BB62vet]

Tom,

Paravane crane looks good! Your deck space is getting sparse - I wouldn't have wanted to stand a mid-watch out there!

Hank

[Fliger747]

Hank:

Perhaps it will be done when I run out of deck and bulkhead space. In the book "Away All Boats", an officer or two took a tumble at night over a cable or cleat. Organizing the disembark met of troops had to be carefully orchestrated. I imagine they were brought up to stations after the boats were lowered or slung overboard.

Cheers: Tom