USS Cape (MSI-2) by Dr PR - 1:48 - Inshore Minesweeper

[Jim Lad]

Great stories, Phil!

 

John

[Dr PR]

One of the challenges for this model will be the propeller. The MSIs had a five-bladed propeller and I will need one for the model.

 

I don't have a machine shop and the necessary tools to tackle this problem like Keith Aug is doing on his Cangarda build. I have designed three-blade props for my future 1:96 USS Oklahoma City CLG-5 build, and printed them with a 3D resin printer, so I guess this will be how I make the prop for the Cape.

 

The blueprint for the MSI propeller is marginally clear - not very good images on the microfilm. But it does have all the necessary information to allow an accurate 3D CAD model to be constructed. I don't look forward to this because stretching surfaces over the twisted outlines of the propeller blades is a tedious task. But I only have to make one and then copy it five times!

 

Here is the propeller blueprint with all the gruesome details.

 

 

This leads me into some details of the Cape's engineering plant - another reason the MSIs were "special." Hey, I was Engineering Officer and this was my "turf!" We had two engine rooms. The Forward Engine room contained two large minesweeping generators to produce power for the "magtail" magnetic mine sweep. It generated a large current through the salt water and this produced a large magnetic disturbance that triggered magnetic mines. Each generator was powered by two GMC 6-71 diesel engines.

 

 

The After Engine Room had four more 225 hp GMC 6-71 diesels ganged together with 900 hp driving a single transmission connecting to the propeller shaft to turn the propeller. The transmission had a clutch and gearing for forward and reverse. This was a very uncommon arrangement. Also in this space were two GMC 4-71 diesels driving two Ships Service Generators that provided electricity for the ship.

 

That is  a lot of diesels. The "-71" meant a 71 cubic inch (1.16 liter) cylinder, and there were either 4 or 6 cylinders depending on the engines. So many of the parts were interchangeable. These were similar to ordinary GMC truck engines, with one major exception. Everything was non-magnetic! Specially made of fantastically expensive alloys!

 

****

 

I have claimed the Cape was the smallest ship in the navy, but this might not have been totally true. Technically, the USS Cove MSI-1 was probably the shortest ship in the navy. The Cape and Cove were built from the same plans, but due to propulsion plant design shortcomings the Cove was perhaps a bit shorter.

 

This 900 hp quad 6-71 diesel power plant drove a 36 foot (11 m) long 4.5 inch (114 mm) diameter propeller shaft and a 5.83 foot (1.78 m) diameter propeller. The propeller and prop shaft weighed 1374 pounds (623 kg), several times the mass of the crankshaft and pistons in the engines. When the ship needed to stop we couldn't just shift into reverse. The propeller "windmilled" as the ship moved forward. If we shifted to reverse suddenly the propeller would just turn the engines over backwards, and they were quite happy to run that way!

 

So we first had to "stop shaft." To do this everyone in the engine room pulled on a lever that tightened a brake band around the prop shaft. This slowed the shaft and propeller and eventually brought them to a stop. Then we could shift into reverse and start slipping the clutch to turn the propeller in reverse.

 

This took several minutes, and meanwhile the ship's momentum kept it moving forward, so rapid maneuvering wasn't possible. Add to this that the ship lost steerageway (the rudder stopped working) below 6 knots (and the speed limit in harbors was 5 knots), and the MSI's were about as maneuverable at low speeds as the Rock of Gibraltar. With mine sweep gear in the water, running at full throttle, the ships went wherever the currents took them.

 

A consequence of all this was that early in the USS Cove's career it was maneuvering into a berth at the stern of a destroyer. The CO ordered all back (reverse) to check the ship's forward momentum and the engines stalled. The Cove continued forward and rammed into the stern of the destroyer, cutting a "V" shaped notch about a foot deep in the tin can's stern. In recognition of this event, the destroyer's officers presented the Cove with a plaque dedicated to the officers and men of the USS Canopener.

 

The Cove may have been a bit shorter than the Cape as a result of that collision, and, therefore, actually the smallest ship in the navy. But because this episode brought the Cove to momentary fame (or notoriety), I claim the Cape was the least notable ship of the two.

Edited August 31 by Dr PR

[TBlack]

This is all hilarious! Keep the stories coming!

[KeithAug]

5 hours ago, TBlack said:

This is all hilarious! Keep the stories coming!

Seconded.

[Jim Lad]

You were right first time - McHale's Navy for sure! 😀

 

John

[bdgiantman2]

Take at look at Blue Jacket, I saw a 5-blade prop on there you can buy. Not sure the scale. https://www.bluejacketinc.com/shop/fittings/under-water/propellers/5-blade/f0918-1-1-2-dia-rh/

[Dr PR]

bdg,

 

Thanks for the link. The 1:48 scale prop should be 1.4574 inch (37 mm). The Bluejacket 5 blade prop is 1.5 inch (38 mm) diameter. That is 0.0425 inch (about 3/64" or 1.08 mm) oversize. I could probably live with that. It looks like the part is cast metal, and it will need some cleanup. That would be an opportunity to reduce the blade length (prop radius) by 0.021 inch (0.5 mm).

 

But the Bluejacket prop blades are not shaped like the MSI propeller blades. That would be more noticeable, and to keep with the tradition of the original, there should be nothing noteworthy about it.

 

The Bluejacket part is only US$5.16. That is a LOT cheaper than all the hours and frustration needed to produce the STL file for the 3D printer.

 

I'll try to make a 3D print of the propeller, but if that fails the Bluejacket part is a backup.

 

****

 

Thanks to everyone for the likes. But believe it or not, I am not exaggerating!

 

After six months of McHale's Navy I went to the flagship of the Seventh Fleet - the largest fleet in the world at that time. There were nearly 200 officers in the wardroom and a disconcertingly large number of flag officers (Admirals, Captains and Colonels) roaming about. The other JOs (junior officers) were curious about my background,  and I told them that I was glad to be in the real navy. One of them, Ensign Clancy Omberg, rolled his eyes and said "This is the real navy?"

Edited September 1 by Dr PR

[TBlack]

But now you have to pay attention to your uniform and proper protocol. Not as relaxed as the previous 6 months.

[mtaylor]

I'm catching up and really loving the background stories that hit home for many reasons even though I was USMC and not USN. Thanks for this log..

[Dr PR]

Mark,

 

I am glad you enjoy the tales.

 

I have been collecting materials for the build. Here is a photo of wood for a do-it-yourself MSI kit.

 

 

I will be using 1/8 inch (3.18 mm), 1/16 inch (1.59 mm), 1/32 inch (0.79 mm) and 1/64 inch (0.40 mm) plywood for the hull bulkheads, center frame (keel), and the superstructure bulkheads. Much of the original superstructure was constructed of 3/4 inch (19 mm) marine plywood. There are 60 1/16 x 1/6 inch (1.59 x 1.59 mm) basswood sticks for the deck planking and 80 1/16 x 3/16 inch (1.59 x 4.76 mm) basswood sticks for the hull planking. A 4 inch x 1/16 inch (101.6 x 1.59 mm) basswood sheet will provide the planksheers, nibbing/margin boards, equipment foundations and other irregular pieces. I have some 1/8 x 1/8 inch (3.18 x 3.18 mm) basswood sticks to serve as internal support for the deckhouse bulkheads. There are a few sticks of various sizes for the bilge keels and rub rails around the deck edge.

 

The winches and minesweeping machinery will be made of brass mostly. I have a stock on hand, but will also try to acquire more as I go along. The "pigs" (minesweeping floats), acoustic sounder and details like bitts and chocks may be 3D printed. However, I am not enamored with 3D printing, so I may decide to make these things out of more traditional materials.

 

****

 

Here is a little more about the Cape and minesweeping.

 

Here is a very young Ensign Hays fresh out of Officer Candidate School leaning on the Cape's main armament - a M2 Browning .50 caliber machine gun - attempting to look like a fierce warrior. The machine gun wasn't provided to repel boarders or attack other vessels, although it could be used for that if war ever came to Long Beach.

 

Minesweepers operated in formations. I included a photo in post #28 above of minesweepers in formation. The first ship (the Cape in this picture) spread sweep gear to both sides. A cable rigged between the ship and the pigs (floats) was fitted with cable cutters to slice the mooring cables for moored mines. The following vessels lined up to one side or the other, with their bows following the pig of the ship ahead, and streamed sweeps to that side only. This produced a wide sweep pattern with each run through a mine field.

 

Each ship was protected by the sweeps of the ships ahead - except the lead ship.

 

 

If a ship did cut free a mine it popped to the surface ahead of the following ship. It was a threat to all the other minesweepers following in the formation. This is where the machine gun came in. It was mounted on the bulwark near the bow. When a mine popped up ahead we opened fire with the machine gun to try to detonate it. Minesweepers typically had a relatively high superstructure forward. Lookouts were posted on top of the pilot house to search for any mines visible in the water or those that were cut free by leading ships. A couple of fellows had M1 Garand rifles and I was stationed there with a BAR (Browning Automatic Rifle). If we saw a mine we opened fire primarily to mark the position for the machine gun crew, and maybe blow up the mine before the machine gun got it. This was a "high pucker factor" operation. Mines were designed to sink large ships like battleships and aircraft carriers. Minesweepers were tiny by comparison, and if they hit a mine they could be blown to splinters in an instant.

 

We occasionally practiced target shooting using 50 gallon barrels as target "mines." The machine gun had a semi-automatic mode where you could fire one shot at a time. This let you see where the bullets hit after you took aim. In fully automatic mode these guns just sprayed a bunch of bullets in an elliptical path all around the target and you really couldn't get a good idea how to aim the gun.

 

I also had my own Colt M1911 .45 caliber pistol. I am not really sure why and I never fired it while on the Cape. However, I had to qualify with the .45 when I went aboard the Oklahoma City because I was a nuclear weapons courier, classified document courier and payroll courier.

 

And I had my trusty sword that officers were required to buy. I did use it occasionally in fancy full dress uniform for change of command ceremonies and such. But we were never boarded by pirates or pleasure boaters.

 

 

Edited September 21 by Dr PR

[Dr PR]

Mark,

 

I worked pretty closely with the MARDET on the Okie Boat. They guarded the nuclear weapons spaces. I also have a few tales about those guys, but this isn't the place to tell them.

[Dr PR]

I have decided to make a small change of plans. I originally intended to lay the decking directly on the bulkheads, and the tops of the bulkheads were dimensioned for this. The decking is 1/16 x 1/16 inch (1.6 x 1.6 mm) basswood sticks. These will not be very strong and might break easily.

Looking at other builds I see that a subdeck of thin plywood is common, with the deck planking laid on this. I decided to use some of the extra 1/64 inch (0.4 mm) plywood for the base deck material and plank on top of this. I reduced the height of the bulkheads by 1/64 inch to allow for the thickness of the plywood.

 

I plan to try the technique mentioned in recent posts of using Titebond Original glue and heating it to fasten the planks in place. First the subdeck will be coated with a thin layer of the glue. Each plank will also have one side coated with glue. After the glue dries the planks will be put in place and then I will use my spiffy new small quilting iron/plank bending tool to heat the planks, melting the glue.
 

[TBlack]

Good idea on the sub decking. Your idea of heating the glue is new to me. Good luck.

Tom