3D Printing Helps USS Cod Submarine Recreate Its Old Glory

The USS Cod was built during WWII and served for decades afterward. Over that time parts were swapped, worn, or simply removed and never put back. A GATO-class boat has thousands of small fittings, brackets, covers, and internals that no catalog lists anymore. When a curator wants the boat to read as it did in 1945, the missing pieces matter as much as the hull.

Original spares do not exist. Wartime production lines shut down long ago, and the subcontractors who made torpedo components, battery jars, and instrument housings are gone. Salvage from other museums is rarely an option, since every boat is short of the same parts and swapping originals between hulls damages both collections.

So restoration teams face a choice. Leave the gap, machine a new part from drawings that may not survive, or reproduce the geometry from the object itself. That third path is where scanning and additive manufacturing earn their place in a museum budget.

A volunteer starts by documenting what is left. If a matching part survives elsewhere on the boat, a handheld scanner or photogrammetry set captures it. Where nothing survives, they work from archival photos, maintenance manuals, and the mounting features still present on the hull. The point is to recover mating geometry, not to guess at surface finish.

The captured mesh is rebuilt into a solid model. Holes, threads, and locating shoulders get measured by hand and typed in, because scan data is noisy at small features. This is the step that decides whether the final part drops in or needs filing. A thread that is 0.3 mm off will not start.

Printing comes next. FDM suits brackets, covers, and display internals. Resin printing suits small detailed pieces such as knobs and nameplates. For anything that will be handled by visitors or used as a working substitute, the print is often a pattern for casting rather than the final part.

The last step is fitting on the boat, dry, with no glue and no drilling. A reproduction that requires modifying the original artifact has failed, no matter how accurate it looks.

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  Scan what existsCapture mating surfaces first; cosmetics come later.
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  Rebuild small features by handThreads, dowel holes, and shoulders rarely survive scanning intact.
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  Print as pattern or as partDepends on whether it will be touched or load-bearing.
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  Dry-fit before anything elseNo adhesive, no drilling into original steel.

One well-known job on the Cod was a replacement propeller for a Mark 27 torpedo. The original was missing. Volunteers measured the opening in the torpedo head and printed a replica that seated in the nose without glue and without any modification to the artifact. That is the ideal outcome for a display part: it reads correctly to a visitor and leaves the original untouched.

The larger project was the battery compartment. A WWII submarine battery is a bank of heavy cells, and the originals were removed decades ago. Fabricating full-size mock cells in metal would be slow and costly, so the team printed imitation cells that fill the space and restore the visual read of the compartment.

Both jobs share a trait. The parts are seen, not stressed. A visitor looks at the torpedo nose and the battery room. Nobody hangs load from them. That is exactly the envelope where polymer printing is the right process.

Printed polymer creeps under sustained load. A bracket that holds a hatch open, a cleat that takes a line, or any part that carries vibration will deform over months. Those parts belong on a mill, in aluminum or stainless, even for a museum.

Heat is the other limit. A part sitting in a sunlit deck area or near machinery can see temperatures that soften PLA and warp ABS. If the location gets hot, either print in a high-temperature material such as PEEK or move to metal.

Accuracy is often oversold. A desktop printer holds roughly ±0.2 mm on a good day and less on tall thin walls. If a reproduction needs to slide into a machined groove with 0.1 mm clearance, print it oversize and finish the mating face on a machine, or machine the whole part.

Finally, layer lines show. For a display piece behind glass this rarely matters. For a part that sits next to original wartime hardware, sanding and a coat of primer bring the surface closer to cast metal.

Museums rarely need one part. A boat has rows of identical fittings, and a memorial project may need the same replica for several display stations or for a traveling exhibit. Once the CAD is clean, moving from one printed piece to fifty cast urethane parts is a short step.

The usual route is a printed master, a silicone mold, and urethane casts. That gives consistent color, a tougher surface than a raw print, and a per-part cost that falls with quantity. For metal versions, the printed master becomes a pattern for investment casting.

If the part must be metal and the quantity is small, CNC is often cheaper than tooling. A five-axis setup cuts a complex bracket in one fixturing, and the same program runs again in five years when the next boat needs the part. Nothing about the process depends on a mold surviving in storage.

GreatLight runs both sides of this. Custom 3D printing covers the replica and pattern work. When a restoration part has to be metal, the machine shop covers one-offs up to 10,000+ piece runs, with no minimum order quantity and tolerances held to ±0.005 mm on critical features.