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

[Dr PR]

Here is another "sea tale" about the Cape - and minesweepers in general.

 

We went out once while I was aboard to sweep magnetic mines. Our forward engine room had two large generators to produce current for our "magtail." This was a two wire cable - the wires were 1 inch (25.4 mm) diameter copper cables (probably the most valuable part of the vessel) - that was strung out behind the ship. It had two electrodes that were spaced 50-100 feet apart. The current from the generators was fed to these electrodes and then flowed through sea water. The current through the water generated a large magnetic field several hundred yards behind the ship. This magnetic field simulated the change in the Earth's magnetic field that a large iron ship would create, and this would detonate mines that had magnetic sensors.

 

But the minesweeper itself should create no change in the Earth's magnetic field if it wasn't to be blown up. As I have explained earlier, our engines and other large metal objects were all made of non-magnetic materials. We had a few magnetic things aboard, like the magnetic compass, but these things had degaussing systems to cancel the magnetism.

 

While we were in port (most of the time for the Cape) we had all sorts of magnetic items on board. Metal office chairs, typewriters, some tools, personal belongings and such. When we went out to sweep magnetic mines all of these things had to be off loaded and stored in a locker on shore. It was a real pain in the posterior to get all of these things off the ship and in storage, and then to have to move them all back aboard after the sweeping exercise.

 

We went to San Diego for a yard period (when they screwed up one of our engines) and afterward passed through the Navy's degaussing station off Point Loma. This was a series of under water "metal detectors" off to the side of the channel into harbor. We made several passes through these and adjusted our degaussing system to cancel all magnetic fields from the ship. However, there was one magnetic field we couldn't cancel. As we passed through the array yet one more time the station ashore radioed us and said there was a metallic object in the bilges and gave us a frame number.

 

Our enginemen pulled up the deck plates and looked around in the bilges. Sure enough - we found a small crescent wrench one of the yard workers had dropped, right where the degaussing station operators said it would be!

 

That really impressed me! After losing the wrench over the side the ship had no magnetic signature.

Edited December 8 by Dr PR

[Ras Ambrioso]

Great stories Phil. I am learning a lot about minesweepers. Thanks.

[Dr PR]

Another of the hull details to be completed is the garboard strake. I have installed the first layer flush with the other hull planks. Now I need to add the second layer that is built up on top of the first layer.

 

The blueprints do not show the details of this strake clearly. However, thanks to photos from Austin Cox (the current owner of the Cape) of the vessel on blocks I can see what the strake looks like and where it ends.

 

 

 

 

 

 

As you can see in these pictures the strake tapers down to match the contour of the other hull plating just aft of where the stem starts to curve upward, This is about bulkhead 2 on my model. The taper at the aft end is a bit harder to see.

 

 

 

It is clear that the strake tapers down to the contour of the hull planking a bit forward of where the planks fair into the deadwood, forward of the stern frame and propeller. This is just aft of bulkhead 15 on the model.

 

To help visualize the shape of the strake I made a series of paper templates from the drawings of the bulkheads.

 

 

You can see the gaps in the templates where the keel and planking come together. These show the shape of the garboard strake. I think the strake can be carved from a 1/4 x 1/8 inch (6.35 x 3.175 mm) basswood stick. I will cut the angle at the corner between the keel and planking first. This will be on the "inside" with the glue where it won't be visible so the angle doesn't have to be precise. Then I will use heat to curve the plank to the shape of the hull. After that I will use the templates with files and sandpaper to shape the exterior surfaces.

 

At least that is the plan. We'll see what Murphy has to say about it!

 

Edited December 9 by Dr PR

[Dr PR]

The garboard strakes are finished - well, I may do a bit of retouching before I paint the hull.

 

 

 

I may taper the front and rear ends a bit more.

 

These "planks" had to be about 0.080 inch (2 mm) thick, so I couldn't use any of the 1/16 inch (1.59 mm) planks. I started with a 1/4 x 1/8 inch (6.35 x 3.175 mm) basswood stick and shaved it down to 0.080 inch with a plane. Then I used wet heat to bend it into the shape of the hull. I used a file and sanding blocks to make the angled edges and shape the piece to fit in the angle between the hull planking and the keel.

 

Next will be the bilge keels, and then the "guards" (rub rails) around the edge of the deck.

Edited December 11 by Dr PR

[Jim Lad]

Looks good, Phil. Now you need to tackle to bilge keels!

 

John

[Dr PR]

After "completing" the garboard strake I was looking at the photos of the current day Cape and realized I did not carry the strake forward enough. I was going by the blueprints, and they don't show the strake extending forward of frame 7, just forward of my bulkhead 2. But the photo (below) clearly shows the strake running forward to where the planking is starting to turn up at the stem. I should have been paying more attention to the photos!

 

 

I cut off the most tapered part of the strake (left below) and added a new piece to extend the strake forward to just past my bulkhead 1 (right below).

 

 

This is closer to what is on the real vessel. Maybe not perfect, but good enough.

 

I have also started working on the bilge keels, but that is a story for another post.

Edited December 12 by Dr PR

[Jim Lad]

Nice recovery, Phil!
 

John

[Austin Cox]

Your attention to detail is fantastic, Phil. I can look at your hull and recognize it! We're enjoying following this build. Regarding the garboard strakes, they may have been closer to the blueprints originally. The garboard and worm shoe were replaced several years back - this is worrisome because so far most recent work seemed to have been fastened with stainless steel, which doesn't mix with the old growth doug fir! Luckily the keel bolts are still bronze. I can't really blame anyone, given the price of these fasteners, but it's still annoying. I've spend countless hours removing stainless fasteners and replacing them with silicone bronze.

 

I can't remember if I replied to your last email. We've been very preoccupied with holidays and a sick puppy dog. I apologize if your last email went unanswered. The blueprint displays well on my screen. We have most of not all of the original paper blueprints and ship documents. Although there's not much room aboard to roll them out for viewing. We still use the original Docking Plan blueprint when planning and implementing a stay in the shipyard. Cape is due to be hauled again this coming August in Port Townsend, WA.

 

[Dr PR]

Austin,

 

Thanks. I think we are up to date on emails. I sent some propeller information.

 

Your photos are invaluable! They have simplified some of the problems in deciphering the blueprints. For example, I am planning the bilge keels right now, and your photos show the shape of the ends. The blueprints aren't very clear about that, but they do give the cross-section dimensions.

 

Hope you have a good holiday and a healthy puppy!

[Dr PR]

I have bilge keels. It took a while to figure out how to make these. Part of the delay for a few days was an annoying head cold. I made some paper templates using the drawings for the bulkheads with the keel positions marked on them.

 

 

I placed each template over the keel at the corresponding bulkhead and marked the bilge keel positions on the hull. I used the Table of Offsets to get the positions of the bilge keels. Oddly, two of the dimensions (bulkheads 11 and 12) were inaccurate. But the remaining positions lined up perfectly. I have seen errors in the Table of Offsets for other ships so I wasn't too surprised.

 

The cross section of the bilge keels is a trapezoid (truncated isosceles triangle) with sides angled 15 degrees from the base and a height of 0.208 inches (5.28 mm). I cut them from a 1/4 x 1/4 inch (6.35 x 6.35 mm) dowel from a local hardware store. The wood has no grain and sanded/filed/carved easily. If I had a milling machine the setup would have been trivial - but I don't have one. I figured out how to hold the dowel with some alligator clips and set the table on my disk sander to 15 degrees. I used this for the rough cut and finished it with sandpaper lying flat on the table.

 

 

The pieces were temporarily fastened to the hull in approximately the right positions with large rubber bands. Then I used the wetting/heating process to bend the sticks. Even though I was bending across the wide dimension the wood bent to shape fairly quickly.

 

 

Next I shaped the ends of the keels, using the photo above provided by Austin Cox. The blueprints do not show the overall shape of the bilge keels in any detail.

 

 

I drilled 0.041 inch (1.04 mm) holes near the ends and at the center Then I held the keels to the hull in the correct position and used the holes as templates for drilling holes into the hull planking. I made six small pins by filing and sanding a bamboo skewer until it just fit into the holes in the keels. These "pins" assured that the keels would be properly aligned while I was gluing them onto the hull. It worked perfectly!

 

 

The keels matched the curvature of the hull almost perfectly after gluing. At the ends there were slight gaps of 0.010 to 0.015 inch (0.254 to 0.381 mm) between the hull planks and the ends of the keels. I filled the gaps with Squadron White Putty.

Edited December 18 by Dr PR

[Jim Lad]

Nicely done, Phil.

 

John

[TBlack]

Phil, How you figured out the cross sectional profile of the bilge keels is an art/science in itself. wonderful progress!

[Dr PR]

Tom,

 

This was the first time I have put bilge keels on a model. I have seen drawings like the Booklet of General Plans for many vessels and wondered how to translate the 2D hull profile drawing into 3D positions on a hull. Likewise, the fore/aft drawings often show the bilge keels as more or less straight lines around the curvature of the hull (like great circles), but I couldn't decide how to turn this 2D information into 3D curves. It was a puzzle!

 

So I would like to weave another long-winded tale (this is getting long) about the trials and tribulations of bilge keel design, but that would be BS!

 

 

This is from the MSI Lines and Offsets blueprint. All I had to do is scale it to 1:48. And the 3D curvature on the hull? Just follow the instructions in the Table of Offsets - go to the frame number and get the height from the baseline and distance outboard from the center line and you have an offset point on the hull for the centerline of the bilge keel. That is what the paper bulkhead cutouts were for.

 

Or, if you want, it was an arduous process full of missteps and endless rambling ...

Edited December 18 by Dr PR

[Dr PR]

The ship had a "guard" or rub rail around the edge of the hull at the main deck level. This was even more complex in cross section than the garboard strake. The sections of the blueprints on the left below give an idea how the shape changed along the length of then hull. The drawing on the right below shows how I plan to create the guard.

 

 

The red lines in the right hand drawing show the guard at several bulkhead positions. The top of the guard is flush with the sub deck, continuing the camber of the deck. The outboard side of the guard is vertical, and about 0.1 inch (2.54 mm) high along most of the length. The inboard side follows the line of the hull planking for a distance of 0.15 inches (3.8 mm).The bottom of the guard angles up from the hull planking to the bottom of the outboard edge.

 

I gave some thought to trying to pre-shape a 0.25 x 0.25 inch (6.35 x 6.35 mm) strip before gluing it to the hull, but that would be pretty tricky with all the changing angles. Then I thought about trying to bend and twist a 0.25 x 0.25 inch (6.35 x 6.35 mm) strip around the hull edge but I wasn't confident about trying to bend a piece that thick without breaking it.

 

I decided to build up the guard with two or three 1/16 inch (1.59 mm) thick strips. These could be shaped to fit the curvature of the hull easily using wet heat. In the image above right the outlines of these strips are shown in green. Where the hull angles outward near the bow I needed a 1/4 inch (6.35 mm) wide strip against the hull planking. Farther aft where the hull side is nearly vertical a 0.18 inch (4.6 mm) wide strip would do - this is the same as the hull planking strips. Near the bow and stern I may need three layers of strips to have enough wood for the guards.

 

 

I used large rubber bands to hold the strips against the hull while gluing them. Metal pins were placed along a line 0.15 inch below the subdeck edge to fix the position of the strips vertically.

 

The first layer of the strips rose above the edge of the subdeck, and the rubber bands tended to pull the top of the strips over and cause them to pull away from the hull at the bottom. I put some wood blocks on the subdeck under the rubber bands to change the pull angle on the guard strips. I put another set of short wood strips between the rubber bands and the guard strip along the lower edge of the guard strip to force it back against the hull planking. This worked nicely to hold the guard strip against the hull while the glue set.

 

 

The first layer of the guard strips was the most challenging. After the glue had set the raised edge of the first layer gave a place for clamps to hold the second layer in place. The second layer was easier, but where the hull angled outward it was still necessary to use the short wood pieces between the rubber bands and the lower edge of the strips to hold the guard strip tight against the first layer.

 

 

Here is the hull with two layers of strips in place for the guard.

 

 

I am going to recalculate the dimensions again to see if the third layer is necessary. It will be needed for only a very thin extra width to the outboard edges in some places, and I may just build this up with wood shavings.

 

The guard will be shaped in three steps. First the top edges will be planed, filed and sanded to continue the camber of the subdeck. Then the width outboard will be marked and trimmed to the correct thickness, with the outboard edge shaped vertical. The final step will be to mark the lower corner of the outboard edge and cut away wood on the lower side to create the angle down to the bottom of the guard at the hull planking. That will be the tricky and time consuming part of the job.

Edited December 22 by Dr PR

[Jim Lad]

A interesting problem in model construction.

 

John

[TBlack]

A creative use of elastic bands!

[Dr PR]

 

The guards are now shaped to the proper angles.

 

I am researching sea chests and a few other small details for the hull before going on to the last major piece - the stern frame that holds the propeller and rudder. I haven't decided what material to make if from. I could carve it out of Castello boxwood. That would be easier than cutting if from a brass or aluminum bar.

 

I am continuing to apply thin layers of acrylic sealer and then sand the hull smooth with fine grit sandpaper. I don't plan to apply paint until after the stern frame is installed and all the other hull details are finished.

 

There will be a pause in construction while I spend some time with kids, grandkids and great grandkids and enjoy Christmas.

 

 

 

 

 

Edited Tuesday at 07:30 AM by Dr PR

[Rick310]

Beautiful work and Merry Christmas!

Rick

[Austin Cox]

Looks great! 👍 Happy Christmas and Holidays!

[Dr PR]

Happy holidays to you all!

[Richard Dunn]

Nice build, and an interestng subject with lots of lovely drawings, the spirketting board being wider forward threw me  on the deck plankng drawing.

[Dr PR]

Richard,

 

I too was surprised to find the planksheer boards wider forward of frame 51 than they were aft. I am guessing that the wider planksheer forward was to accommodate the bulwark supports and fastener hardware up forward. There is no bulwark back aft.

 

Another surprise was the nibbing strake inboard of the planksheer that is the same width from bow to stern. The deck planks are not nibbed into the wider planksheer but into this separate nibbing strake.

 

And to add to the fun the forward and aft planksheers are scarfed together along with the nibbing strakes to create a pretty gentle transition at frame 51. I still haven't figured out exactly how this will work.

[KeithAug]

Excellent work on the hull Phil. You have been busy. The stories keep me well entertained.

[TBlack]

12 hours ago, Dr PR said:

And to add to the fun the forward and aft planksheers are scarfed together along with the nibbing strakes to create a pretty gentle transition at frame 51. I still haven't figured out exactly how this will work.

Can’t wait to see how you do that, also.

Great grandkids! You must have started early?

Tom

[Dr PR]

Tom,

 

My wife started early (18) in a previous marriage. And our oldest son married a slightly older woman with two young kids. All together that makes for several generations of rug rats.

 

I have been making bits and pieces as I go along, ahead of when they will be installed. The plankshears and nibbing strakes are some of these pieces. Here is a photo.

 

 

The plankshears are the wider outboard pieces and the nibbing strakes are the inner parts. The straight piece in the center is the stern plankshear. I didn't want to try to bend a 0.31 inch (7.9 mm) wide wood strip across the wide dimension so these pieces were all cut from a large 1/16 inch (1.59 mm) thick sheet of basswood.

 

And that brings us to the latest work. I needed the stern plankshear piece to finish the transom.

 

 

Mr. Cox sent the photo (left above) that shows the transom of the current Cape. The top of the vertical "guard" pieces end below deck level, and the bottoms merge into a horizontal member at the bottom of the transom. But the original blueprints (right above) are quite different. Most of the guard pieces extend up to the stern planksheer piece, and all but the outermost two on each side extend down to the bottom of the hull. So there have been a few changes to the vessel since it was originally constructed. I want to model the ship as it originally was - as a minesweeper - so I will follow the blueprints.

 

 

I originally thought I would make the stern like the current vessel so I extended the planks and built up the piece all around the edges of the transom (left above). However, when I finally figured out how the blueprints showed it I trimmed back the edge part to extend only to the second vertical piece from the outer edge of the transom (right above). The other vertical pieces were glued in place (below) as shown on the blueprints.

 

 

The vertical guard pieces protected the transom when we were streaming minesweeping gear and hauling it back in. The heavy pigs (floats), otters (pull the sweep cable down below the pigs) and kites (pull the cable down at the ship's stern) were suspended from derricks while rigging the gear and could swing around wildly in heavy seas, banging against the hull. I will describe this gear in detail when I get to that part of the build.

 

And this brings us to another episode of

 

DrPR's Story Time

 

Once upon a time on a slow day when nothing much was happening the Cape's Captain, Executive Officer and I (Ensign Fuzz) went over to the Long Beach Naval Station's Officer's Club for lunch. Afterward the CO and XO went to the Base Exchange while I wandered back to the Cape. When I got to Pier 9 I saw a large crane on the pier beside the ship. It was lifting the stern minesweeping roller chocks from the ship. Our Chief Bosun's Mate (senior enlisted on board) was on the pier.

 

"What's going on?" I asked.

 

He handed me a piece of paper with orders to get underway IMMEDIATELY as soon as the sonar was ready! Sonar? The Cape didn't have a sonar - well, normally, that is. But the Bosun explained that occasionally we would take aboard an experimental mine hunting sonar for testing. That was news to me!

 

 

Here is a photo of the SQS-16 sonar installed on the Cape's stern, along with the control shack just forward of it. The sonar is the spherical thing with something sticking out of the bottom.

 

Unlike most sonars up to that time, the SQS-16 didn't just send out a "ping" and measure the time for the return echo to determine distance. This thing used a very high frequency acoustic scanning "beam" to create a picture on a video screen.

 

The resolution was good enough to see nuts, bolts and other small features on the objects being viewed. It was bleeding edge stuff, and that is why it was classified SECRET.

 

 

You can also see that the vertical guard pieces on the transom were actually installed as the blueprint shows, and details of the stern ends of the horizontal guard rails. The white things on either side at the stern are the ordinary minesweeping otters and kites, and you can see one of the pigs on the starboard side aft. If you look closely you can also see some of the additional horizontal "lining" planks added to the exterior of the hull planking to protect the hull while the pigs were being lowered and hoisted over the side.

 

Well, we weren't going anywhere - orders or not - until the Captain returned. Fred would have been really POd if I left without him! After a while he and the XO came walking up the pier. Imagine his surprise to find the lines all singled up, the engines running and the gang plank ready to be hauled in! So off we went!

 

But where were we going?

 

This reminds me of a scene from the movie Le Roi de Coeur (The King of Hearts) where the WWI Scottish Colonel asked for three volunteers. When they arrived he said "Men, I want you to leave immediately!"

 

"Sir!" they replied, saluting. And then they all ran away.

 

"Stop!" the Colonel shouted. "Where the devil do you think you are going?"

 

"No idea, sir!" came the reply.

 

The CO made a call to the Squadron headquarters and learned we were supposed to motor down the coast to San Diego and hunt for something in the waters off Point Loma. The Captain said it was a downed helicopter, and there was something aboard they wanted to recover. Then after a quick call to his wife to say he wouldn't be home for dinner we cruised out of Los Angeles harbor and headed south. It was about 1600 (4 PM) before we actually got under way and well after dark when we got to San Diego.

 

We received the coordinates of two rectangular areas we were supposed to search where the "helo" might have gone down. The first was just a mile or two off the beach at La Jolla, just north of Point Loma. Our search pattern was just a series of parallel courses a few miles long. At the end of each leg we did a 180 degree turn and proceeded back parallel to the previous leg.

 

Simple, right? So simple that after a while the CO took to his bunk leaving Ensign Fuzz to complete the search area. I had only conned (driven) the ship a few times, and that was just around Catalina Island or such while the crew fished. This was different, because we had to proceed in straight lines proscribed distances off shore. Every couple of minutes I used the ships' surface search radar to get distances to shore, and visual triangulations to points ashore to locate our position. The positions were plotted on a chart so I could estimate the timing of our next turn.

 

But the fact that we had to conduct the search at night complicated the visual sightings - I had to locate certain reference lights that I was not familiar with against the background lights of a large city! But I figured this out and we were going along smoothly, except for two major problems.

 

First, the sonar sphere was dangling directly off the stern in the propeller wash. If we went too fast the sonar cable would twist and turn, making it impossible to get a picture and determine the bearing to anything spotted on the sea floor. And remember, the USS Cape was about as maneuverable as the Rock of Gibraltar at low speeds. We barely had steerageway (fast enough for the rudder to work).

 

The second problem was the Black Current (Kuroshiro or Japan Current) that flows from north to south down the Pacific Coast of North America. It streams close to shore at Point Loma, right where our search area was. Even with our bow turned into the current we moved backwards! Add to this that there were kelp beds inshore that would tangle and foul the sonar that I had to avoid. It was nearly impossible to steer a straight course (especially for a novice like me)! Instead of a set of nice parallel course lines on the chart there was a scribble of zig zag lines, but I did cover that search area thoroughly! There was no helicopter (or anything else of interest) there!! I was proud of myself for having accomplished the assigned task.

 

The CO came back to the bridge about dawn and asked if we had finished the search areas. Areas? All I knew about was the one. But apparently he had expected me to search both areas before dawn. He was upset! When I asked what the problem was - we could still search the other area - It seems we weren't supposed to be seen searching the areas in daylight. Why? Your guess is as good as mine!

 

It was another McHales Navy moment.

 

Happy New Year!

Edited 3 hours ago by Dr PR

[TBlack]

Great story but did you ever locate the helicopter?

[Dr PR]

What helicopter?