The SLA was a fairing that contained the Lunar Module (LM), and supported the CSM. It was composed of two sections, the upper and lower SLA, which sat on top of a highly technical guidance/tracking/communication interstage called the Instrument Unit (1.1MB pdf), which in turn sat on top the third stage of the Saturn V, the S-IVB (1.9MB pdf). The Instrument Unit constituted the very top of the Saturn V launch vehicle, and was responsible for guiding it through the process of getting Apollo to orbit. Once the S-IVB had injected the spacecraft into a transfer orbit to the moon, the upper SLA was discarded as four separate panels, to reveal the LM sitting in the lower SLA, waiting to be picked up by the CSM.
As supplied, the Revell version of the SLA is a pretty disappointing object. The upper SLA comes as a single unit with a transparent panel, which allows the kit builder to admire the LM inside at the expense of any shred of realism. The lower SLA is moulded as a single piece along with the Instrument Unit (IU)—which actually isn’t a great problem, because the lower SLA and IU always remained firmly attached to the S-IVB, and never separated from each other.
There’s a little tab inside the upper SLA kit part which is supposed to help locate the kit CSM correctly—but it’s in the wrong place for the Block II, so it has to go.
Another problem is the lack of detail on the surface of the kit SLA and IU. This can be partially resolved using New Ware’s Saturn V detail kit, which provides a selection of additional photo-etched and resin parts, as well as some decals.
But first I had to get some primer on to the brass photo-etched parts. I didn’t want to clog any of the spaces in the fine detail, so I constructed a little corrugated cardboard frame that supported the photo-etched sheet vertically, allowing my primer spray to blow through the gaps, and then I misted the primer on in four or five delicate applications.
The transparent panel had to be fixed—I glued it in place with epoxy, sanded and filled around the edges, and painted the inside with primer, to stop a later internal coat of metallic paint showing through and darkening the external white. That left me with a clean, sanded external surface that would provide a firm bonding surface for the detailing.
There’s also a small umbilical port on the Launch Umbilical Tower side of the SLA that needed to be created. I found a suitably sized square in one of Verlinden’s scribing templates, taped it in place, and scribed my way through the kit plastic. Then I closed the hole with a piece of styrene sheet on the inside. (I’d embed a link to Verlinden Productions website, but it’s been flagged as containing malware for months now—you should be able to hunt down their products from your friendly modelling supply store, though.)
After that, the photo-etched panel margins from New Ware were put in place on the upper SLA, along with the fairings around the spring ejector hinges at the base of each panel. This gave me a bit of a problem, because I wanted the upper SLA to still be detachable from the lower SLA, so that I can eventually put the LM in place. So the hinges and panel margins are glued only to the upper SLA, and lift away with it—it’s not an entirely realistic result, but it’s the best I could come up with.
The detailing is panel-specific, and the kit has locator flanges that fix the orientation of the SLA relative to the whole Saturn V stack. So it can all go horribly wrong if you start the detailing without first checking the orientations. The LM faces towards the transparent panel in the kit SLA, which should have a personnel access port in the middle of it; the hatch of the command module faces in the opposite direction from the LM; and the umbilical port is on the launch tower side, which is the LM’s right. So I invested a bit of time with photos and diagrams before I took the major step of scribing out my umbilical port, and then used that as my anchor point for subsequent detailing.
The detailing was attached with a mixture of cyanoacrylate, five-minute epoxy and Microscale Kristal Klear. I used the Kristal Klear for the long, delicate brass strips of the photo-etch—it was forgiving for positioning and any residue could be rubbed off cleanly. Before the Kristal Klear dried, I tacked down one end of the strip with cyanoacrylate, let that set, pulled the strip tight and tacked the other end with more cyanoacrylate. The combination produced a nice flat, secure result.
Once the panel frames, hinges and hatches were in place, I moved on to adding detail of the structural framing with a variety of styrene strip from Evergreen. That structure then provides clear positional guidance for the remaining few pieces of detail from New Ware—a selection of covered elliptical ports that were, to judge from photographs of the real SLA panels, connected to various pieces of internal machinery of mysterious function.
Next, I had to paint it. A few coats of base white, and then I needed to mask it up for the black paint on the Instrument Unit. I’m vaguely phobic about painting black on white—masking leaks somehow seem so much more catastrophic when the contrast is so high. So I decided I’d experiment with Bare-Metal® Foil—the manufacturers recommend it for tricky paint masking. It certainly did the masking job very well, but I’m not sure I’ll use it again—it leaves a horrible dark residue behind that needs to be removed with white spirit; the paint doesn’t adhere to it, so it can leave a ragged edge if you don’t carefully cut along the foil edge before lifting; and it is very difficult to remove, coming off in little bits and pieces. That said, the final result was perfect, so I shouldn’t complain.
I finished off with four resin antenna fairings from New Ware, and then four decals, before a final layer of varnish.
You wouldn’t think four decals could take two hours, would you? Here’s the problem:
On the real Saturn V, there were four letters stencilled on the Instrument Unit, marking the positions of its reference coordinate axes: +Y, +Z, -Y, -Z. On a black Instrument Unit, they were stencilled in white. The exception occurred with the Saturn V stacks that launched Apollos 10 to 17, when the IU had a white panel on the side opposite the launch tower, requiring a black letter in that location. So New Ware, being thorough people, provide all four coordinate letter decals in white, and one alternative in black. So far so good. But they provide a black -Y.
Now, the coordinates systems used on the Saturn V and its Apollo stack are confusing. In the Apollo stack, Y was the pitch axis (aligned north-south at launch) and Z the yaw axis, and in that system +Y was directed towards the launch tower and -Y was opposite it, towards the white panel on the IU. And that’s the marking system that New Ware has provided. However, although the Saturn V launch vehicle also had a Y pitch axis and Z yaw axis, all its coordinates were rotated 180º relative to the Apollo stack, so that all the plus and minus locations were reversed. And, since the Instrument Unit belonged to the launch vehicle, it was in reality marked up with that coordinate system. To me, this mix of coordinates is so disorientating it’s a miracle they got to the moon at all. But anyway—what I actually needed was a black +Y.
Just for confirmation, here are details from photos of the Apollo 11 Saturn V that I’m modelling.
So I had to cut a tiny sliver of black decal from my spare stock, trim it to the correct length and width, float it into position as a vertical crossbar on the minus sign of the black -Y, and settle it securely in place with Micro Sol. That’s what took the two hours. Pleasingly, I obtained that little sliver of black from a swastika decal I had left over from a previous WWII Luftwaffe modelling phase—so a little nod to Wernher von Braun, there.
Here’s the final result, with and without the CSM in place.
As a final tweak, during all my obsessive checking of the orientation of the SLA, I noticed that the locating flanges between the bottom of the IU and the top of the S-IVB were 10º out of correct alignment—the systems tunnel of the S-IVB in the kit was lining up exactly with the -Y coordinate of the IU, whereas it needs to be rotated slightly to the right. So I sanded off the locating studs on the S-IVB and replaced them with some styrene in the correct position.
But that’s all for now on the Saturn V. I’m getting a little tired of detailing at 1/96 scale, so I’m going to take a break and start a 1/48 kit instead.