This is a "girdle" that fits around the vertical ballistic missile tubes in the HobbyBoss 1:350 scale Typhoon-class submarine model kit (83532). This is a great kit and one of the only ones that correctly models the submarine's rear below the waterline, but there's a glaring omission: the kit includes the missile tubes and missiles, and can be built with the missile doors open, but nothing supports the tubes.

As can be seen in the photos for this project, this is incorrect: there is in fact support structure for the tubes that appears to be a flat piece (well, many welded pieces) of steel or titanium that attaches to the two pressure hulls on either side.

Issues of correctness aside, this also causes modeling issues. The tubes are fairly tall and are secured by molded protrusions that don't provide any help supporting or aligning them. This results in a tendency for them to splay both side-to-side and bow-to-stern, and it may not be noticeable until you fit the upper hull and can see that they're obviously off-center. Captain Ramius deserves better.

This girdle corrects both problems by holding the tubes upright and providing the correct visible support structure for observers.

Scale model parts are usually best printed in resin but this is simple enough that it shouldn't matter - any decent primer will hide the evidence if you use FDM. The one in my sample photos was made on a Prusa using cheap PLA. It's a tight fit so make sure your printer is calibrated well.

Modeling Details Color photographic evidence is hard to come by but from what I can tell this should be painted the same chromate green as the missile tubes.

The tubes were not inside a pressure vessel and as a result were exposed to seawater when the submarine was submerged, so rust and salt staining is definitely appropriate if you weather the model.

The distance between the support structure and tops of the missile tubes appears to be about half a Russian sailor, so a 2mm or 3mm piece of masking tape is the perfect guide for aligning it vertically on the tubes.

I don't model the pressure hulls since it adds complexity to both the model and the print and there's poor visibility to the front, back, or sides even with the doors open. That said, someone might be able to see the inside of the model's shell from the right angle, so consider either painting the interior black or using a "lip" of black PlastiCard around the girdle to hide the interior completely if you're a stickler for detail.