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

[Javelin]

That is looking marvellous Phil. Very realistic in any case. 

 

Were there really ropes wound around those rings on 4 places? Just wondering since I'm from the reflective SOLAS tape era and don't know about Navy habits on this... 

[Dr PR]

Roel,

 

I don't know if any Navy manuals said to wrap ropes like shown here, but we had it on both the Cape and Oklahoma City. I suspect it was a bosun's thing - they killed time by applying small stuff around life rails, stanchions, ladder rails and just about everything else that didn't move. Fancy knots, braiding and such were normal. 

 

For example, here sailors are removing horizontal threads from a sheet of canvas. The vertical threads will be bunched together and braided to make "McNamara's Lace." It was a decoration that was hung around the quarter deck in port and on other things to make them look fancy.

 

The braiding around hand rails and stanchions actually served a purpose. It made it easier to grip, especially if things were wet.

Edited Wednesday at 07:34 PM by Dr PR

[Dr PR]

Roel,

 

Your question made me do a double check on the life rings, and that brought a surprise!

 

As you can see in this photo life rings were sometimes made up as I have modeled them. But if you look closely you will see this ring is labeled "USS COVE MSI ONE." This was the Cape's sister ship (possibly the actual smallest ship in the Navy).

 

I have been using photos of both ships for determining how to build the Cape model. And I remember that I found the life rings were made up this way on the USS Oklahoma City CLG-5 when I made the CAD model of that ship.

 

However, when I looked at the photo in post #420 above I realized that the life rings on the Cape were painted differently. The turns around the life ring were painted orange!

 

 

 

I'll have to correct that! Although the Cove and Cape were very much alike, there were many small differences like this between the two. This was especially true in the way the crews painted the details like this. But there were also some structural differences, such as the Cove having 12 inch (305 mm) searchlights on the O1 level open bridge and the Cape having them above on the O2 level. The ladder on the port side of the O1 superstructure was a bit farther aft on the Cape. And the O2 level life rails and lines were a bit different.

 

Thanks for keeping me on track!

 

And I hope everyone had a happy day. It was Thanksgiving in the US and I am stuffed more than the turkey!

Edited Friday at 06:40 AM by Dr PR

[Dr PR]

Venturis

 

 

The Cape had venturis around the edges of the bulwarks on the open bridge. The supports are shown in the photo (left) while the venturis were being repaired. On the right you can see the venturi at the top outboard edge of the bridge bulwarks. The ship's name board is mounted on the venturi.

 

What is a ship's venturi? It is a channel for air flow between two converging surfaces (marked in red). Air blowing against the sides of the ship's superstructure flows outward and upward along the deckhouse sides. It enters the bottom of the venturi at relatively slow speed (short and wide green arrow), and is compressed as the channel narrows.

 

If you remember Boyle's Law (you did take physics, didn't you?) the initial pressure and volume equal the final pressure and volume

 

P₁V₁ = P₂V₂

 

As the air flows through the venturi the volume decreases by about half, therefore the pressure doubles. This causes the air to flow faster to escape the top of the venturi. It comes out as a jet of air deflected upward around the sides of the bulwarks (long and narrow green arrow).

 

Now you may be asking yourself "Who cares?" Well, that up flowing air collides with the wind coming from ahead and deflects it upward and over the bulwark. This actually does work, and has a significant effect. I have stood watch on the Cape's open bridge in a downpour. Standing back a few feet from the bulwark I was pelted by raindrops. But standing close up to the bulwark the jet from the venturi deflected oncoming wind and rain up over my head! Behind this invisible windshield the air was fairly calm. These things made standing watch on the open bridge a bit more pleasant.

 

I have put off adding the venturis to the model for two reasons. First, they are on the outside of the wide bridge structure and subject to damage from handling while all the other work was being done. And second, I really had no idea how I was going to make them!

 

The blueprint above shows that there is a "choke" piece attached to the bridge bulwark that forms the inner surface of the venturi channel. It was made from an assortment of wooden and metal pieces, but I decided to simplify it for the model. I shaped a strip of wood with a triangular cross section for this inner part. I tried to cut a concave surface into the face of it. First I made a scraper with the cross section pattern and tried to use it to remove wood. That was a failure - the basswood strip didn't cooperate with the scraper.

 

Then I found a small bottle with a 1 inch diameter (25.4 mm) and wrapped it with sandpaper. This did work better than the scraper but the results weren't very consistent over the length of the strip. And after I was finished the curvature was so slight it really isn't noticeable! But the shape of the strip was good enough since it will be hidden inside the venturi anyway!

 

To make the spacers that support the outer surface of the venturi (to be made of 0.005 inch/0.13 mm brass sheet) I cut some strips (left side of the photo) of 0.010 inch (0.25 mm) brass to a width slightly larger than the vertical dimension of the parts (0.271 inch/6.9 mm). These were sliced into short pieces 0.33 inch (8.4 mm) long, longer than the 0.259 inch (6.6 mm) length of the supports.

 

Fifteen of these pieces were clamped together and soldered to make a single solid piece to work with. A paper template was glued to the side of the work piece and the block was filed to the correct shape. Then the spacers were sawed off the end of the soldered block. The remainder of the block can be seen on the left side of the photo - the multiple layers are readily visible.

 

The block of spacers was reheated to melt the solder and free the individual parts.

 

The wooden choke strip was cut into sections to fit between the individual spacers. These wooden pieces were glued to the bulwarks with Titebond Original cement. As each section was placed a brass spacer was glued to the end with Locktite Super Glue Gel. This allowed enough time to position the spacer correctly, and produced a very strong attachment.

 

I have been dreading this assembly because it just looked like it would be so easy to break off one part while placing another. But it has been very sturdy and I have had no problems so far.

 

 

I still have a bit of sanding, filing and filling on the wooden choke pieces to prepare for sealing and painting.

 

And notice that I did repaint the life rings in proper Cape fashion!

 

 

Edited 10 hours ago by Dr PR

[wefalck]

I noticed this feature on the bridges of 'modern' (from my point of view) ships, but never thought about their purpose and function. Thanks for the explanation, makes perfect sense to use the Venturi-effect for deflecting the air-stream.