USS Indianapolis (SSN-697) Fast Attack Submarine in 1/72 Scale

The USS Indianapolis (SSN-697) was a U.S. Navy Los Angeles class fast attack submarine.  She was commissioned in 1980 and was assigned to the Pacific Fleet, homeported in Pearl Harbor.  She was decommissioned halfway through her service life in 1998, one of the many victims of the so-called “peace dividend”.

I have always been fascinated by submarines, particularly the U.S. Navy nuke boats.  It just so happens that the outer diameter of 5 inch PVC well casing is almost exactly the hull diameter of the LA class submarine in 1/72 scale.  The center 30 inches of the model is 5 inch PVC, the bow and stern sections are vacuformed over poplar masters.  The fins and sail were made from plastic sheet and copies cast in resin.

For anyone interested, there are work in progress construction posts here:















1/72 Scale Los Angeles Class Submarine Build, Part IX

The sails of the Los Angeles boats are covered in access panels.  The patterns changed as the design evolved, so check references for particular boats.  I decided to use paint to represent the panels, this is the masking job.
Two more variations of “scale black” were misted over the upper surfaces.  When the masks are removed the darker panels become visible.
An overall shot shows how the different tones of black add complexity.  If you look at any large monochrome object, the first impression is that it is all one color.  When you study it in detail, you find that the colors actually vary in tone and intensity across the surfaces.  If you use only one mix of color the model will appear unreal and toy-like, but if you vary the shades a bit it adds complexity and appears more realistic.
The only permanent markings carried by most U.S. submarines are draft markings.  Here dry transfer numbers from Model Graphics are being applied to the rudder, the style is called “45 degree”.  The strip of masking tape is marked to help with spacing and alignment.
There are another set of draft marks on the bow.  This set is a little trickier to apply as you have to account for the hull curvature which affects the spacing.  The numbers are a little further apart as you go up the hull.  After the numbers were applied the entire model was sealed with Testors Glosscoat, and after that dried the model got a coat of Future.
The gloss coats are important to prepare for what comes next – toning with oils.  This looks like a huge mistake when you’re doing it, but it adds some nice subtle complexity to the finish when you’re done.  The gloss coats are vital, particularly the acrylic coat, as otherwise the oils will strip through the underlying paint layers.  When using oils, think “wax on, wax off”.  Most of the oil will be removed, leaving only slight discoloration to the surfaces.
Here is the model after weathering with oils.  The overall impression is slightly darker and more uniform, but subtle color variation is visible up close.  The hull red on the underside got a similar treatment using reds, yellows, orange and browns.
Submarines in port build up a “slime line” of marine growth along the waterline.  To represent this I used a mix of Dark Ghost Gray and RLM 02, airbrushed in thin layers over a masked waterline.  After the masking tape was removed I went along the line with a stiff brush and thinner and roughed up the hard masked edge.  This broke up the hard edge and varied the density of the color at the transition for a more realistic effect.
The various masts and sensors changed over time.  The snorkel to the left was built up from Evergreen, but most of these are made from aluminum airfoil stock and 1/8″ tube from the hobby store.
Here the masts are painted and in place.  The tubes run through the airfoil sections and are pinned into the sail.  This gives the assemblies strength and makes them a bit easier to align.
The model was given a coat of Testors Dullcoat and mounted to an Oak base.  Four strips of Zinc blocks are used as sacrificial anodes on the real submarines, these were made from 0.015″ x 0.060″ strip and mounted at the stern.  This is the finished model posed with the Mobeus Skipjack.

1/72 Scale Los Angeles Class Submarine Build, Part VIII

Part VIII?  Are you kidding me?  This build is soaking up the time, largely due to the distractions of the home remodel.  High time I got on with the painting!  The Los Angeles boats all have a non-skid coating applied along the centerline.  Being a cylinder, the hull curves more and more steeply the further you go abeam, so there is actually only a small area which can be safely walked on before footing becomes precarious.  Here I have stippled on Mr. Surfacer 1000 to simulate the rough non-skid finish.
The non-skid helps show off the added surface details.  These are made from raised panels or lines scribed into the hull or a combination of both.  I struggle with this as in 1/72 scale neither method is prototypical, actual indications of the details would be almost invisible.  The same can be said of panel lines on 1/72 scale aircraft, but the models just do not look quite right without them.
I primed the model with rattle can primer from the hardware store.  These primers are generally much less expensive than specialized modeling primers and work just as well, especially on large subjects such as this one.  This picture also shows the stands I’ll be using while painting, made from scrap plywood and bolted into the mounting holes under the hull.  They provide convenient handles for moving the model and can be turned to the sides when needed for painting.
The primer did its job and helped identify a slight dip in the hull contour here, which was filled with Bondo and smoothed out.  The other areas which show signs of sanding are corrections to flaws in my scribing, I’m still working to perfect that skill and have a long way to go.
With the corrections re-primed it was time to add color to the hull.  In service the red lead protective paint wears and takes on a distressed appearance which I wanted to duplicate.  I built up the red underside color with thin applications of Testors Insignia Red, altering the density to vary the color intensity.  Then the hull was stippled with Wood and Dark Tan to simulate wear.  These areas were then blended with thinner applied with a brush.
Next the hull was airbrushed with patches of Root Braun RAL 8012, and those areas were again blended.  It looks like a hot mess now but the finish coats will pull it all together.
The hull red areas were masked off using Saran Wrap stolen from the kitchen and the rest of the hull was given the first coat of “scale black”, which is just black toned down with grey.  Rarely should anything be painted truly black on a model, and this finish will receive some additional scale black paint layers with slightly varied tones to break up the finish.

1/72 Scale Los Angeles Class Submarine Build, Part VII

Time has been at a premium lately due to the home remodeling project but I have managed to sneak down to the workbench and make some progress on the submarine.  This is a section of the TASS hump being installed on the hull.  TASS stands for Towed Array Sonar System, which is basically a series of hydrophones in a rubber tube which is trailed behind the submarine.  The TASS was carried in the long hump when not deployed.  All the 688 boats carried TASS, but the first few boats were not commissioned with the system and had it added later.  It turns out that the outer diameter of 3/4″ PVC has the correct curvature for the TASS hump in 1/72 scale, so this was formed by shaving off an appropriate section with a band saw.
The sail is now permanently attached using superglue and bronze rod pins.  The seam is blended with Perfect Plastic Putty.  On the earlier boats the forward diving planes were mounted to the sail.  Later boats moved the planes to the forward hull and made them retractable to make it easier to punch through Arctic ice.
I have begun adding the various surface details to the upper hull, following the Greg Sharpe drawings.  The four “H” shaped fittings are retractable mooring cleats.  Some details are made from thin plastic sheet, others are scribed into the hull.
It’s getting closer.  I was hoping to have work completed in time for the Louisville show on the 18th but that’s going to be pushing it.

1/72 Scale Los Angeles Class Submarine Build, Part VI

While time has been at a premium the last few weeks, I did manage to sneak down into the Secret Underground Workshop and make some progress on the submarine.  These are the horizontal stern planes, assembled and with the TASS tubes and hinges added.  The tubes were blended in with plastic strip and superglue and sanded to shape.
This is the last of the castings for the model, one of the forward diving planes which is mounted to the sail.  These were replaced with retractable planes mounted forward on the hull in later boats to improve the ability to break through Arctic ice.  I pinned all the control surfaces in place with 0.040″ bronze rod and glued them with superglue.
Here are all four stern planes in place.  The gray areas on the hull are Mr. Surfacer 500 which I used to check seams.  The planes fit pretty well overall but there is still some blending needed at the joints.  Lots of sanding and still some more to go.
With the sail on she’s starting to look like a sub.  The sails on the Los Angeles boats are fairly small overall as is apparent in this view.

1/72 Scale Los Angeles Class Submarine Build, Part V

Measuring the length off of the drawings is easy but measuring the length of the three dimensional model is a little more challenging.  Here I have positioned rafter squares to confirm the lengths match.  The tail piece of the model is built up around a length of 1/2 inch PVC pipe fixed in place with casting resin.  This will allow the screw to be socketed into place on the finished model.
With the length and alignment checked the bow and stern pieces are glued into place.  Seams were filled with two layers of superglue and sanded back down with an 80 grit sanding block.  Next is two layers of Bondo and sanding with 320 grit which is shown here.  Seams were then checked by spraying Mr. Surfacer 500.
In between sanding sessions I worked on the screw.  The drawings show a long screw hub coming to a point like a pencil, but photographs show a shorter hub which is blunt like a bullet.  Both may actually be correct, submarine screws were updated as quieting technology improved.
Here are the screw hubs in rough form and shaped on the belt sander.  The beige tube is 1/2 inch PVC, the white shaft is Evergreen, the whole assembly is filled with casting resin.
Screw blades are made from 0.020″ Evergreen with the edges sanded smooth.  There are seven blades, they are curved and swept back.  The screw was prepped with Mr. Surfacer 1000, then primed with Alclad black primer.  The finish coat is Alclad Polished Brass.
I have also begun casting the control surfaces.  These are the stern planes.  I will have to add hinges and towed array tubes to the horizontal planes, there was no way to cast them in place and still get the pieces out of the molds.

1/72 Scale Los Angeles Class Submarine Build, Part IV

The central core of the 688 SSN model is made from a 30 inch (76.2 cm) section of 5″ PVC well casing.  The outer diameter of this pipe is 5.563″ or 14.13 cm.  The stated hull diameter of the Los Angeles class is 33 feet (10.1 meters) so the pipe is oversized by 0.063″ or 1.6 mm, although this is mitigated by the addition of rubberized hull coatings designed to absorb sound so I am happy with it.  I also constructed a work stand from scrap lumber, necessary to prevent the hull from rolling around the work bench.
A lip was made from a 1 inch (25 mm) band of scrap plastic to increase the bonding area for the vacuform bow and stern sections.  This band was built up with additional strips of scrap until the outer surfaces of the finished pieces were level.  MEK from the hardware store was used to glue all these pieces, it reacts well to both the PVC in the pipe and in the sheet and ensures an outstanding bond.  It is the active component of most thin hobby glues, only much, much cheaper when bought in bulk.
The vacuforming process stretches and thins the sides of the formed plastic, so additional spacers were added to compensate on the hull sides.  The 0.060″ sheet had thinned to 0.040 – 0.045″ on the sides.  Easier to get things level now than to file and fill later, although that is inevitable in modeling.
The bow and stern sections were cut loose from the backing sheets and trimmed to fit as best as possible.  The seams were backed with more scrap strip.  Here is the stern section with the strip clamped in place while the MEK sets up.  I found that this did not take long, I was able to alternate between the bow and stern assemblies and keep working.  Note the screw head on the pipe in the picture.  This will be one of the anchoring points for the base.  Inside the pipe a nut and washer have been epoxied in place and the long screw is  tightened down while the epoxy sets.
Here the halves of the bow sections have been joined in place and are taped to the hull while the glue sets.  I kept the bow and stern sections removable at this point to allow me to fill the ends of the pieces with casting resin.  This helps solidify the assemblies at their weakest points and prevent any splitting while sanding.  If you use this method you must make certain that the pieces are completely sealed, as the resin will find even the slightest gap and leak out.
The completed sections are test fit and posed with the sail master.  Alongside is the Mobeus Skipjack for comparison.  The Los Angeles boats are longer and have a greater hull volume, but also have a much smaller sail structure.

1/72 Scale Los Angeles Class Submarine Build, Part III

One thing which is missing from most models of modern submarines is the flood vents on the bottom of the hull.  These are similar to the wheel wells on model aircraft in that they are difficult to see on the finished model.  Add to that the difficulties in referencing details on submarines and most kit manufacturers just skip them altogether.  Fortunately the prints we are using show the locations, here I have used masking tape to transfer the measurements to the vacuform hull components.
The corners were drilled out and then the centers were opened up with a Dremel.  From there the holes can be expanded with an Exacto blade.  The plastic sheet we used to make the vacuform piece had not stretched much on the bottom surface and was still close to the original thickness of the sheet.  I expect it will be thinner on the sides.
The holes are closed off with a sheet of plastic applied from the inside.  This prevents the see-through look and offers support for the 0.015″ strip louvers.  Any areas which need it can be built back up with superglue.
Progress has also been made on the various diving planes. These are the masters before priming, made from Evergreen stock and superglue.  Since we will be building both a Flight I and a Flight III boat there will be differences in the planes needed for each model.  The masters will be copied in resin to provide all the finished pieces required.

1/72 Scale Los Angeles Class Submarine Build, Part II

The center section of the submarines will be made from 5″ PVC pipe, but the bow and stern will be vacuformed.  Greg Prater is an old hand at this and agreed to show us how it’s done.  The first step is to laminate poplar blocks.  The center sections are glued together over a sheet of paper.  The paper allows the blocks to be split down the middle into perfect halves after they’ve been turned.
Here is the master for the stern section on the lathe.  The masters were turned to a slightly smaller diameter to allow for the thickness of the plastic sheet which will make up the finished pieces.  The flared portion on the thick (forward) end of the piece is there to help prevent the plastic sheet from wrinkling or tearing as it draws down over the master.
After the masters were split along the paper seam, the halves were placed on cardboard supports.  A strip was removed from the underside to allow the vacuum to draw the plastic tight against the lower edge of the masters through the horizontal channels in the cardboard.  This helps reduce the tendency of the plastic to drape at the bottom and keeps the plastic tight against the form.
All the masters with their cardboard spacers underneath are positioned on the vacuform table.  The suction from below draws the hot plastic sheet down over the forms, transferring their shapes to the plastic.  At least that’s the plan, we’ll see how it works!
This is the large vacuform machine we will be using.  Neither Michael nor myself have ever done this before, so Terry Hreno gave us a quick tutorial and a lot of good advice.  Terry had used this machine to pull slot car bodies before the machine was donated to the AMA.  It uses plastic sheets measuring 32 x 26 inches (81.3 x 66.0 cm).
Here Michael is positioning the plastic sheet in the frame.  We used 0.060 inch (1.5 mm) thickness for this project.  The heating element is lowered to a position just above the plastic, then the softened plastic is lowered over the forms where the vacuum draws it tight.
From below you can see the plastic as it is heated.  The sheet contorts and softens, eventually it begins to sag.  After about ninety seconds the sag is uniform and the plastic is ready.
This is the moment of forming.  The soft plastic is quickly lowered to the waiting masters and the vacuum from below draws it tight.  This is fun to watch – the shapes magically appear through the material in just a second.
There are some areas at the bottom edge of the forms where the plastic cools before it draws completely snug to the masters.  Here Michael is using a heat gun to soften any remaining areas while the vacuum is running to ensure a tight fit.
The finished product!  With the bow and stern sections formed we now have all the major hull components ready to go.

1/72 Scale Los Angeles Class SSN Build, Part I

The list of interesting modeling subjects is long.  Somewhere near the top of that list for me have always been modern submarines, particularly US Navy nuclear subs.  My friend Michael Smith also shares this interest, but in his case he prefers his models to not only look nice but to operate as well.  By good fortune I happened to have a set of Greg Sharpe’s excellent 688 class plans drawn to 1/72 scale.  We decided to pool our resources and build two models, a static one for me and an RC version for Michael.


Work started with the sail.  The plan view was traced onto paper and transferred to 0.060″ sheet.  Four of these “airfoil” shapes were cut out, one for the base, and three laminated together to allow for shaping the contours of the top.  Internal bracing is in place to define the sides for the 0.040″ sheet.  A section of tube is used for the round leading edge.
Here is the sail completely skinned and filed to shape.  I used superglue to blend the pieces together and to fill any gaps.  This works well, as any area which is not level still appears shiny after sanding.  These areas are hit again with superglue and sanded down, this is repeated as many times as is necessary.  The snorkel exhaust grill work at the top of the trailing edge was cut out before the side pieces were glued in place.  The slats were made from 0.015″ strip.
We will need enough copies of the sail and control planes to equip both models.  This is the first step in the casting process.  The sail master is being enclosed in an open rectangle made from Lego bricks.  The bricks define the shape of the Room Temperature Vulcanizing (RTV) rubber mold.
This is the bottom of the mold.  Masking tape seals the mold to prevent leakage and also serves to anchor the master in place to prevent it shifting or floating while the liquid RTV is being poured around it.
I use RTV and resin materials from Micro Mark for casting.  The RTV is mixed and poured in over the top of the master.  It is important to mix the RTV components thoroughly but gently to avoid entraining air bubbles.  This is the cured mold in blue with the Lego bricks and masking tape removed and the original master in front of it.  The mold is inverted, ready for the casting resin to be poured inside.
Here is the first completed casting.  The resin only has about five working minutes before it starts to set up, so with this large of a piece I had to work quickly.  Usually any small air bubbles can be whisked away with a wire or rod, but this time I was worried about the resin setting up before the pour was finished so the snorkel exhaust will require some clean up.  This piece took about 150ml of resin, easily the largest piece I have ever cast.