Using SketchUp to Create a 1:72 Scale Model of an Iowa Class 16" Battleship Turret

I’m in the process of creating a detailed interior for the 16" gun turret that was on all the Iowa Class battleships. A plastic model of this turret has just come on the market in 1:72 scale, but has no interior detail at all. I’m going to create all of this on SketchUp and print the parts on my own 3D printer. The turret and two of the five levels in the barbette is a very complex thing and it will challenge my SU skills to their limit.

Here is the overall plan and elevation of the turret. I’m modeling down to the electric deck where all the electro-hydraulic machinery.

Here’s some of the work so far…

Getting the steps on the Step-thread breach was a challenge, but I was able to get it done. The curator of the USS New Jersey BB62 in Trenton, NJ sent me some critical dimensions needed to scale it all correctly.

Now my dilemma. I can’t figure out how to shape the flanks of the gun slide. The 16" gun moves back and forth in this component when it recoils 78". I’m getting it close, but there are intersecting angles and curves that always gets me into trouble.

Here’s a screen print showing the actual part of the drawing I need help on, and I’m including the actual SKP file.

Gun Slide.skp (472.2 KB)

Any help will be appreciated.


Looks like a perfect job for @TheOnlyAaron in a live modeling session.

Hard to tell exactly whats going on with that shape around the sides where it flows and tapers without more detailed drawings or a set of cross sections of the whole shape. Here is a method using components and the extension Curviloft to skin a perimeter.



I just noticed that the actual slide flows into a cross barrel cylinder toward the business end of the cannon, which looks like it is actually proud of the other surface. Skinning this area required the addition of some extra arcs on the perimeter to guide the skinning process. A bit fast and furious this gif, but you get the idea.


that’s very cool. I have curviloft! I guess I should use it. I did it using straight line segments and triangulation. It worked… sort of, but didn’t give me the smooth transition that you got. I may do it over to get it more like what you did. I found another picture of the gun and it showed that it wasn’t as smooth curved as what you and I have been striving for. I did the multiplication a little differently, using copy, paste-in-place and then the -1 scaling. This keeps the new object directly connected where I want it.

Here’s the one of the guns from the USS New Jersey BB62, during construction in 1944. It’s the best view of that geometry that I could find.

I do not have to model the gun barrels since the 1/72 scale kit has metal turned barrels included, but nothing behind the exposed portions of the turret. That’s the part I’m going to model.

And here’s the next challenge. This is the Welin Step-thread breech for this gun. There are 20 threads on each of the 15 segments, and I’m not sure the best way to draw them. That said, at 1:72, the entire part is just a 1/4" in diameter and the threads probably would be invisible, and that’s if my resin printer could even resolve them.

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I had to look that one up, wacky threading but makes sense once I read it through. Looks like a job for the thread-master @DaveR . But yes, the details are unlikely to read at 1/4” diameter. Would you model it with the breach open? Cool challenge project.

You know, you’re not that far from the North Carolina. Perhaps a visit with tape measure and camera would be possible. I read 90 to 95 percent of the ship is accessible. I took the public tour probably thirty years ago but don’t recall being in the turret. Very impressive though.
Good luck with your project.

Thanks @endlessfix. This isn’t the same as the one on the gun so I didn’t save it after making the screenshot but…


I’m developing a relationship with the curator of the USS New Jersey Museum Ship and with that am going to get a special tour to investigate all the nooks and crannies in the turret including the electric deck and the little side compartments where the manual aiming stations are. But any pictures you guys take are highly welcome as is all the great help you’re providing.

The curator has already agreed to display the model there. Now all I have to do is draw it, print it and finish building it. That’s all…

Jeez! Those breech threads are terrific! I’m going to find thread-master.

I’m going to model two guns with open breeches; one loading a projectile and the other powder (or not since the spanning tray hides the breech plug that’s open below. The other will be in firing position with the loading trays in the retracted position.

If I was modeling in 1/4" + 1’ the threads would definitely be visible. But I may draw it just for fun.

I used Curviloft and did get a pretty good rendition of the slide geometry.

And here’s the same part exported in 1:72 scale to my 3D printer’s slicer. You can see some slight angularity on the filling lines, but that would disappear with a stroke of some sand paper. 1/4" scale would be almost twice this big and wouldn’t fit on my machine.


I attempted to fit the entire slide/truniion/yoke assembly on my printer and it does just fit. The base raft sticks out of the edges, but that’s not a problem.

In this orientation, none of the supports foul the all-important back end. Given the close fit in the gun house and the bulkheads that are just inches away from the gun’s flanks, really the only thing you do see is the back end.

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Just for clarity, Thread Master isn’t an extension, @endlessfix was referring to @DaveR being a master of thread making.


Well that sure does clarify! I searched for it and didn’t find it since it didn’t exist. I did find EP thread extension, but it’s not working correctly. I’m getting a blank dialog box when I activate it. I’ve written to the author for advice.

My apologies for the confusion, I was giving DaveR the thread-master title as he has shown his amazing thread making techniques many times here on the forum. And he did not disappoint this time either. DaveR himself is not an extension.

If only there really was a DaveR extension that put a tiny Dave in your Computer to model threads and other challenges. That I would pay a subscription for. :rofl:


Oh wait, I guess we already have that, it’s called: the forum.

How can we be sure? :slight_smile:


The DaveR Turing test. Interesting.


An extension works in garbage in, garbage out mode. DaveR can turn garbage into gold.


I’m reviewing a bunch of thread making tutorials, and the EP Thread author got back to me with an updated version which I haven’t loaded yet. I’ll let y’all know how it works.

Have you ever been to that battle ship? They let you go into the turret - you can look through the gun sights. The USS Iowa is in Los Angeles as well. It’s interesting to tour them both. G

Myles, best of luck with this very cool modeling challenge you’ve undertaken. Battleships have always been high on my list of one of the coolest machines built by man ! Got to tour one decades ago when I was in grade school. They actually took us into a turret and let us look up the barrel of one of the guns. Impressive doesn’t describe it !

The very first model I built in 1954 on my birthday was Revell’s USS Missouri. With that I was hooked on Iowa Class battleships. Big guns fascinate me… not on their war making capacity, but their technical interest. And the Iowa guns are like the finest example of them. I visited the USS New Jersey 3 times (twice with the grandsons) once on the USS Alabama, and the USS Texas. The Alabama had the shorter barreled 16" guns that was shared with all the classes except the Iowas.

It took a lot of hours of work, but I have the actual gun fully detailed. I probably spent 4 hours just on the breech details and getting the hinging and counter-balance system arranged in correct engineering.

I created two versions: breech closed and breech open. The handles and cams are in the correct position for each mode. The first two images are screen prints from SketchUp and the second two are Podium Rendering Engine photo-realistic outputs. Notice that the areas that are black show up as polished chrome on the renderings.

While the drawing was challenging just in the details, what made it more so was ensuring that every part was a complete solid, all normal faces, and all parts fully attached to the model in enough places so the print would be stable in the 1:72 scale. I want to print the entire receiver is as few pieces as possible. I think I’ll print the breech assembly in the open position as a separate parts. All the rest will fit on my printer as I showed earlier in thread.

There are left- and right-hand guns since the powder hoists come up the central column of the turret. The port and center gun have their hoists back-to-back so they have their powder hoist doors on opposite walls meaning the guns are loaded from two different sides. The starboard gun loads on the right side with the powder door on its left.

I still don’t have my hands on the kit or the barrels. Without them I can’t get too far into the weeds of the internal structure. I know that the guns are right. I will start designing the hardware in the gun rooms themselves including the rammer (which extends into the officer compartment) and the projectile cradle and the spanning tray. Getting the guns right was the centerpiece of this whole undertaking. And in doing so gives me a boost in confidence to do the rest.

I will be putting this up on the Warehouse.