Category Archives: Building

Moebius 1/144 Discovery Spacecraft: Part 6

Last time, I completed the wiring of individual sections of my Green Strawberry pod bay, and the neat little Falconware pods. This time, I’m assembling the bay and the extended pod platform, adding ceiling lights, and cramming everything into the Moebius command sphere.

First, though, I needed to do a little surgery on one of the Moebius kit parts. One of my few complaints about this kit is that Moebius have moulded the pod bay door and the door surround as a single part. Because I was modelling the Discovery with a pod bay door open, I needed to scribe, drill, file and sand one of the doors out of its frame.

Opening the central pod bay door on Moebius Discovery
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With the open door frame in place, I could then slot the assembled pod bay walls and floor into the lower half of the kit command sphere, for a dry fit.

Green Strawberry pod bay for Moebius Discovery overview 2
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It takes up a lot of space! One of the problems with modelling this spacecraft is that the movie interior sets weren’t a great match for the exterior model views—in particular, here, the interior wall of the pod bay film-set curved rather less than is evident in exterior views of the Discovery model. So there’s a bit of fudging evident in Green Strawberry’s side walls when compared to the “real thing”, and the assembled pod bay fills so much of the model interior that there would be no room for the centrifuge and airlock that featured in the film.

Here’s a rear view with the ceiling dry-fitted.

Green Strawberry pod bay roof in place in Moebius Discovery hull
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There’s very little clearance between this ceiling and the underside of the Paragrafix cockpit in the upper hemisphere. I wondered about replacing the thick Green Strawberry resin ceiling with the thin photoetch brass ceiling from Paragrafix, but decided against it because I preferred Green Strawberry’s detailing. In retrospect I might go with the Paragrafix part, because its thinness might have solved a problem that developed later in the build.

At this point I was finally able to judge the length of brass tubing I needed to use for the supports of my extended pod platform.

Green Strawberry pod bay for Moebius Discovery overview 3
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With the brass cut to length, I could slot it into place on the underside of my pod platform:

Connecting the Falconware pod lighting to Green Strawberry pod pad
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This involved a bit of high-stakes wiring. I had to trim the wires for my pod LED unforgivingly short, and then solder them to the interior of the brass tubing with my soldering iron very close to the resin part.

But the end result was a pod positioned exactly where I wanted it, and electrically connected to the rest of the command sphere.

Falconware pod in position in Green Strawberry pod bay and Moebius Discovery hull
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Falconware pod lit via Green Strawberry pod bay for Moebius Discovery
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The Green Strawberry platform includes a brass plate that seals over the end of the platform supports—I replaced this with styrene in order to avoid a short circuit.

Sealing the underside of the wired Green Strawberry pod pad
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Next I needed to complete my other two Falconware pods, but without the palaver of having to light them. (Because I was feeling lazy, I only detailed the side of each pod that would be visible in the assembled model.) I also put together the spacesuit rack. The Green Strawberry vertical supports are brass photoetch strips that locate in shallow indentations in the floor and ceiling. I couldn’t see a way to locate these easily and securely, so I replaced them with 0.5mm brass rod, on which I mounted the spacesuit and helmets as they were seen in the film during Bowman’s first EVA, and then I drilled holes in the floor and ceiling so that I could thread the brass through and epoxy it in position.

Here’s the pod bay with the pods and suit rack in position, and the lighting on:

Green Strawberry pod bay for Moebius Discovery lit 1
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Green Strawberry pod bay for Moebius Discovery lit 2
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Green Strawberry pod bay for Moebius Discovery lit 3
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Green Strawberry pod bay for Moebius Discovery lit 4
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Green Strawberry pod bay for Moebius Discovery lit 5
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And positioned inside the hull:

Green Strawberry pod bay for Moebius Discovery in place
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Then I wired up the ceiling lights—eight little low-profile light boxes that would just fit into the space between pod bay and cockpit, and an additional downlight to illuminate the ladder-well in the laboratory.

This was when the problem with the thick resin ceiling manifested itself. The light openings are small, and the thickness of the resin converted them into fairly constrained downlights, rather than general illuminants. With the extended pod removed, and peering in through the open doorway, the resulting illumination was pretty murky, particular at the rear wall, which was getting hardly any light at all.

Green Strawberry pod bay for Moebius Discovery with overhead illumination only
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So I decided I need to cheat, and mount some concealed lights either side of the door, to push light into the back of the pod bay:

Installing additional concealed lights for pod bay of Moebius Discovery
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On first testing, this produced a bit of a thermonuclear result:

Green Strawberry pod bay for Moebius Discovery, overlit
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The additional illuminants were producing noticeable bright spots and shadows, and overwhelming some of the detail lighting. With a couple of little baffles and some black paint, I then toned down my extra lights until I got the effect i wanted:

Green Strawberry pod bay for Moebius Discovery, revised lighting 1
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There are still a couple of anomalous shadows behind the suit rack, but they’re not overly eye-catching. And the additional light doesn’t drown out my feature lighting, like the octagonal corridor:

Green Strawberry pod bay for Moebius Discovery, revised lighting 2
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So then it was time to glue everything in place, and bundle up the wiring in the two halves of the command sphere:

Wiring of Moebius Discovery command sphere before assembly
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And then it all had to be stowed away neatly without nipping anything between the two halves as they were glued together:

Wiring of Moebius Discovery command sphere, assembled and stowed
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Finally, I did a check of the complete wiring run, from the batteries in the engine compartment, through the two steel spinal rods, to a connection block mounted in the rear of the command sphere.

Wiring of Moebius Discovery command sphere, test of full wiring run
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Improbably enough, it all worked!

To complete work on the command sphere, I masked off the cockpit windows and the pod bay door, and started airbrushing on layers of paint, from a dark grey base layer through progressively lighter coats, adding Aztek Dummy panel masks as I went along:

Aztek Dummy masks on Moebius Discovery panels
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The final result was a rather boldly variegated command sphere, which I’ll tone down when I apply my final blending coat to the whole model:

Preshaded command sphere parts for Moebius Discovery
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Next time: all the fiddly cargo pods for the long spine, final assembly, painting, and mounting on a display base.

Moebius 1/144 Discovery Spacecraft: Part 5

By the end of my previous post in this build log, I’d finished lighting the Paragrafix cockpit for my Moebius Discovery spacecraft. Now it was time for the pod bay. When I first bought the Discovery kit, I acquired the Paragrafix photoetch pod bay to go with it, but was a little disappointed with its general flatness. To be honest, that shouldn’t be a big issue in practice, because in the completed kit the view through the pod bay doors is pretty limited. But after a while, as the Discovery kit languished unbuilt in my stash, I became aware of the Green Strawberry pod bay, which is a mix of resin and photoetch that promised to give a much more three-dimensional result. So I acquired that, too.

Green Strawberry pod bay for Moebius Discovery

I hoped to build this model with one pod extended on its platform in front of the open central door, like the iconic scene in the film when Dave Bowman leaves the Discovery for the first time.

Reference image for pod on platform
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I’d set myself the task of having the pod lights illuminated, but also to be able to remove the pod and its platform to make it possible to inspect my (hopefully) gorgeously lit pod bay interior more easily.

I had an idea for this, but it needed a bit of proof-of-concept work. Key to the process was some square-section brass tubing from Albion Alloys. I got some lengths of their 1.6mm and 2.4mm tubes (codes SSB1M and SSB2M)—the smaller slides fairly neatly inside the latter, meaning I could (in theory) produce a conductive pathway from the pod bay to the pod platform, while being able to remove the pod platform and its supporting brass tubing as required.

So first I needed a bit of surgery on the underside of the Green Strawberry pod bay floor and pod platform, carving out channels for my brass tubing, soldering the wiring in place where it will be concealed under the pod bay floor, and drilling out a hole in the pod platform so that I could eventually run wiring to an LED inside my pod:

Green Strawberry resin pod-bay floor for Moebius Discovery, wiring pod platform 1
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Green Strawberry resin pod-bay floor for Moebius Discovery, wiring pod platform 2
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At this point, I merely pressed the brass tubing into place on the underside of the pod platform to check fit—I’ll need to get the pod bay to the point of fitting it inside the command sphere before I can decide on the right length for my sliding brass platform supports.

Another bit of wiring has to run through the pod bay floor, to light up the test bench, which is visible in my film still, above. Green Strawberry provides a resin bench, but I decided to use the hollow, folded photoetch version provided by Paragrafix. This is pierced in strategic locations, and HDA Modelworx provides a decal that covers the piercing and can be transilluminated by an LED concealed inside the bench—so the same effect as I’d previously exploited when illuminating the Paragrafix cockpit.

Here’s the bench, lit up:

Paragrafix photoetch pod-bay console for Moebius Discovery, lit
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Then I constructed the resin pod bay floor, painted it white, applied Green Strawberry’s black decals, and attached the test bench, running its wires through a hole in the floor and light-sealing the join between bench and floor with a dollop of plastic filler smeared around the bench’s interior edges.

Then I pushed a couple of balls of screwed-up kitchen foil into my under-floor brass tubes, to improve electrical contact, slide in some test lengths of the finer brass tube and an LED, and wired the whole thing up to a battery for a test:

Green Strawberry and Paragrafix parts for Moebius Discovery, wired for lights
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Yay, it works.

As you can see, Green Strawberry provides a trio of fiddly support structures to sit under each retracted pod platform. These don’t seem to be visible in the film, and for a long time I wondered what reference source Green Strawberry had used. I think they may come from pictures of the pod bay set taken during filming:

Pod bay set for 2001
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It makes a lot of sense that hidden support structures were required for the pods on the set, but they make much less sense in the “real” thing—the pod bay is supposed to be in zero gravity, after all. They’re a bugger to assemble and position, each consisting of one fragile resin part and five photoetch struts, and mine required to be slightly shortened so that the pod platforms could sit level with the pod bay floor. If I were building this again, I’d be strongly tempted to omit them.

For my illuminated pod, I used one of the excellent 3D-printed Falconware pods distributed by Shapeways. These come with premoulded channels for 0.75mm fibreoptics, so that the four headlights can be illuminated with one LED in the hollow interior. I drilled a fifth 0.25mm channel in the location of the red “HAL eye” on the front of the pod, so that I could light that up, too. The pods come with a selection of extremely delicate arms, which are initially protected inside the hollow pod, and need to be carefully extracted. The locating channels for the arms are the same diameter as those for the fibreoptic headlights, and also extend into the interior space, so there’s definite potential for absent-mindedly attaching an arm to a headlight channel, or vice versa.

The pods are moulded in translucent plastic, so I brush-painted the interior with four coats of white primer, then a couple of coats of black, then a couple of coats of white to provide a reflective surface for my LED. All this tended to clog up the fibreoptic channels, so I ran them through regularly with an interdental brush, and intermittently cleared my 0.25mm channel by poking it with my fine drill bit.

With that done, I painted up the exterior in white, and then applied fine detail with a mixture of hand-painting and some custom decals I printed to reproduce the larger detail visible in the film. Here’s the final version (still without arms and lights) poised on a UK penny for scale:

Falconware pod for Moebius Discovery, painted 2
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Falconware pod for Moebius Discovery, painted 3
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Falconware pod for Moebius Discovery, painted 1
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Falconware pod for Moebius Discovery, painted 4
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Here’s the decal sheet, for anyone who’s interested in using it—the resolution for printing is 600dpi:

Decals for Falconware Discovery pods, 600dpi
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With the pod painted, I cut some short lengths of 0.75mm optical fibre, and melted the ends by holding them close to a hot soldering iron. This makes the ends blob up into nice curved surfaces:

Fibreoptics prepared for Falconware pod for Moebius Discovery
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The fine “red eye” fibre got a blob of red paint over its interior end, once threaded. I placed my LED in the pod interior, and threaded its wires out through small hole in a piece of thin styrene sheet I’d cut to form a base for the pod. Adding this base made the job of eliminating light leaks between pod and platform easier. Here’s the final result, mounted and tested:

Falconware pod for Moebius Discovery, with lights
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(The red light has inevitably bleached in the photo—it’s redder than that in real life.)

On, then to prepare the various pod bay parts for lighting.

There’s a little lab area on the starboard side of the pod bay, accessed by a ladder, and rather dimly lit in the film—a few instrument screens, a downlight above the ladder, and light from the pod bay itself coming in through a large window:

Reference view of 2001 lab area, beside pod bay
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Here it is from outside, seen behind the astronauts;

Reference view of 2001 pod-bay interior, looking to starboard
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Green Strawberry provides some solid resin parts, with photoetch and decals for the instruments. I chiselled out a hole in the resin behind the photoetch computer screens, so I could mount a light box behind the wall to transilluminate the decal and simulate the screens, which will then shine visibly through the lab window. I also drilled a small hole through the lab wall so that I could illuminate the door-control panel, reproducing the prominent red light visible in the film still above.

Green Strawberry lab area for Moebius Discovery pod-bay, modified for lighting
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The main lighting challenge, however, is the iconic illuminated octagonal tunnel that enters the rear of the pod bay:

Reference view of 2001 pod-bay interior, rear and port

The Green Strawberry part is made of solid resin, with multiple little photoetch plates and black decals to simulate the appearance of the tunnel, but with no option to light it realistically. Here are the parts, with the photoetch already painted white and decalled:

Green Strawberry parts for pod bay "tunnel" for Moebius Discovery
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The photoetch has slots exactly where the tunnel lighting should be, so I decided to eliminate the resin walls and replace them with thin styrene sheet, which I could transilluminate. Here it is, measured, scored and folded, with the photoetch parts ready to be glued in place:

Replacing Green Strawberry pod bay tunnel with folded styrene 1
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And an exterior view of the final assembly:

Replacing Green Strawberry pod bay tunnel with folded styrene 2
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You’ll see I’ve retained a cuff of the original resin tunnel. This is because the last short segment of the tunnel lacks lighting in the film—and, as a bonus, the resin part helps shape the styrene. The blobs of black paint are blocking light-leaks at the corners of the octagon, where the photoetch panels don’t quite come together in the interior. I used an LED temporarily placed inside the tunnel to ensure I put my paint only where it was needed.

Then it was just a matter of building a lightbox around the tunnel, using the styrene-and-foil method I illustrated in previous posts when I was building the cockpit. I used warm white LEDs to try to simulate the difference between the tunnel and pod bay illuminants visible in my film still.

Here’s the result:

Replacing Green Strawberry pod bay tunnel with folded styrene 3
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And the illuminated screens and door light for the lab:

Lab area of Green Strawberry pod bay for Moebius Discovery, lit
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(Looking a bit grubby in that photograph—I’d slightly overdone the dark wash to bring out surface detail. I’ve since fixed that.)

So all the pod bay components are ready to be glued together and installed in the command sphere:

Green Strawberry pod bay for Moebius Discovery overview 1
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That’s all for now. Next time—the pod bay and command sphere final assembly, and even more lights.

Moebius 1/144 Discovery Spacecraft: Part 4

Last time, I reached the point at which I needed to start lighting my Paragrafix cockpit.

I wanted to provide a source of illumination at the front of the cockpit, which will probably be invisible from outside but will provide a little front-lighting for the couches and pilot, as if coming from the large panel of instruments and screens in the “real” thing:

Discovery cockpit reference 2

My light source was necessarily going to be a much humbler affair, crammed into the limited space available—just a white light and a few spots of coloured light. I built a little box around an SMD LED, and pierced it with a lot of little holes and one big rectangular slot. Then I laid on a couple of spare instrument-panel decals from the HDA Modelworx sheet, which helpfully provides duplicates of pretty much everything.

Cockpit instrument lightbox for Moebius Discovery
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Lighting box in place in Paragrafix cockpit for Moebius Discovery
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The box stows neatly under the window to which the cockpit will eventually be attached, and there’s room for my wiring to escape through a gap between the Paragrafix photoetch and the kit part. I belatedly had to provide the central light (intended to simulate screen lighting) with a little tilted shade, because I found it was illuminating the window frame above in a decidedly unrealistic manner.

For the rear corridor, I erected a large light-box on its roof, in order to try to get a fairly uniform light coming through the styrene-sheet diffuser in the ceiling.

Preparing Paragrafix cockpit corridor for lighting
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Above, you can see the LED clamped to some black styrene sheet while the 5-minute epoxy dries. Then I’ll position it at the front of the light-box, illuminating the tilted foil reflector you can see above, which will deflect light down on to the white styrene diffuser already fitting to the roof of the corridor.

At the back of the corridor part, I covered the windows in the door with a bit more styrene diffuser, and then added a small light box. At the sides, a pair of light boxes illuminated a red “HAL eye” on the left, and a little computer display on the right.

Here’s the final assembly:

Paragrafix corridor for Moebius Discovery, rigged for lighting
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And the view of the inside:

Paragrafix cockpit corridor for Moebius Discovery, lit (2)
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Paragrafix cockpit corridor for Moebius Discovery, lit (1)
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Moving back to the cockpit, with my little light box in place I eventually folded up the Paragrafix photoetch into its final configuration:

Paragrafix cockpit for Moebius Discovery, prepared for lighting
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The kit part for the windows needed a little surgery to accommodate the corners of the Paragrafix cockpit, as you can see above. I’ve also placed my styrene-sheet diffusers over the various lighting panels, and started work on a slim little light box to illuminate the forward instrument panel in the cockpit ceiling—there’s very little room between the cockpit roof and the dome of the command sphere, here, so I’ll borrow light from the LED above the ceiling light panel, which I’ll set high enough to throw light into a flat reflective tunnel over the forward instrument panel.

With the cockpit assembled on to the windows, I did a test fitting into the command sphere to confirm that everything still came together okay, and that I was producing the desired glimmer of light on the pilot’s face from my little indirect light box immediately under the windows.

Paragrafix cockpit in position in Moebius Discovery kit
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You can also see, above, how I’ve added some styrene strip to produce a bit of depth in the window frames, as an approximation to the appearance in the film.

The overhead light box went on easily, and then I needed to build a complicated pair of boxes to illuminate the side lighting panels and instruments. Here’s an early stage in construction, showing the array of right-angle styrene strips I used as a support structure for black styrene panelling covered in reflective foil:

Building lightboxes for Paragrafix Discovery cockpit 1
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You’ll see I also used a bit of the same styrene strip to add a little step to the back of the cockpit, where it opens into the rear corridor, and added padding detail from a spare bit of HDA Modelworx decal.

Here are the side light boxes at a later stage of construction, with LEDs in position and the reflective side walls in place.

Building lightboxes for Paragrafix Discovery cockpit 2
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All of this has to fit inside the low dome of the command sphere, so a lot of dry fitting and readjustment was required.

Once everything was in place, I was able to check the result by peering in the “rear door” of the cockpit, before attaching the corridor. Here’s my overhead panel:

Paragrafix discovery cockpit lit 1
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And the two side walls:

Paragrafix discovery cockpit lit 3
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Paragrafix discovery cockpit lit 2
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All of this detail, of course, will be fairly minimally visible through the front windows unless you go looking for it.

After checking that the cockpit lights were working properly, I attached the rear corridor, and then soldered the cat’s cradle of wiring to the two master wires for this assembly.

Completed Paragrafix Discovery cockpit lighting
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I find it difficult to do the final assembly justice with photographs—the combination of “cool” lighting in the corridor and “warm” in the cockpit tends to make either the corridor look blue or the cockpit yellow, or both; and the coloured lights tend to blow towards uninteresting pastel shades. But it here it is, anyway:

Paragrafix Discovery cockpit and corridor fully lit 3
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Paragrafix Discovery cockpit and corridor fully lit 1
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Paragrafix Discovery cockpit and corridor fully lit 2
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For reference, the Tamiya paint pot on which the cockpit is perched is three centimetres in diameter.

Next time, I’ll move on to start work on the pod bay. There will be a lot more lights and wires.

(Be the first)

Moebius 1/144 Discovery Spacecraft: Part 3

Last time, I finished lighting and preliminary painting on the engine compartment of my Discovery spacecraft from the film 2001: A Space Odyssey. This time, I’m working on the cockpit. I’m using the Paragrafix photoetch set for this, combined with the HDA Modelworx decal set.

HDA Modelworx decals for Paragrafix cockpit (Moebius Discovery)
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There are two areas to light—a rear corridor and the cockpit itself. There’s a degree of inconsistency in how these two areas are lit, especially when comparing the two films, 2001 and 2010.

Discovery cockpit reference 1
Discovery cockpit, 2010

But in exterior views the cockpit looks fairly warm and dim, so I’m going to light it that way using an array of little SMD LEDs, while making the corridor brighter and colder.

Discovery cockpit reference 4

Here are the photoetch parts primed and glossed, ready for the decals:

Paragrafix photoetch & HDA Modelworx decals for Discovery cockpit
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The two objects in the middle are the acceleration couches, which are provided as plain bits of brass to be folded into shape. In the film, they’re covered in the white padding that appears on many interior surfaces of the Discovery.

Discovery cockpit reference 2

I printed up some coverings for the photoetch, intending to make decals, but then decided that just wrapping the parts in printed paper would work fine:

Seat padding for Discovery cockpit (600 dpi)
Paragrafix photoetch seats detailed with padding
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Notice the big expanse of empty floor in front of the couches in the model, compared to the area of controls and screens visible in my film still of the cockpit interior, above. It’s actually impossible to reproduce the film’s appearance using the Paragrafix kit—there’s just not enough room below the windows. But, to be fair, that’s largely because the Discovery film sets notoriously wouldn’t have fitted inside the command sphere as depicted by the models used in the film. And, in any case, the sight-lines through the narrow windows of the cockpit probably don’t allow much of a view of the area in front of the couches, anyway. But I do want to put some sort of light source there, tucked out of sight, so that the couches and pilot get some front illumination, as if from that bank of television screens.

I also needed to revise the appearance of the rear wall of the cockpit—the photoetch and decals make this look like it’s striped with white padding but, as my film stills show, this wall was a pretty dark grey (with a few white panel lines evident in 2001, but not in 2010).

So I printed up replacement detailing for that wall, and again just glued the printed paper in place.

Revised back wall panels for Discovery cockpit (600dpi)

Here’s the rear corridor, partially folded with its decal in place.

Paragrafix cockpit tunnel detailed with HDA Modelworx decals
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The decal covers holes in the photoetch brass, which I’m demonstrating above with a bit of backlighting—I’ll build light-boxes behind all these holes to illuminate the various windows, buttons and screens.

And here’s the little corridor box assembled:

Paragrafix cockpit corridor with HDA Modelworx detail
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Those big gaps in the ceiling will be covered with a styrene-sheet diffuser and another light-box, to simulate the overhead strip lighting of the real thing.

And here’s the partially folded cockpit, test-fitted into the kit part that forms the spacecraft windows:

Paragrafix cockpit parts partially assembled
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All those multicoloured details represent illuminated control panels, which I’m planning to light with wrap-round light boxes, along with the main overhead lighting panel and the six side panels.

The Moebius kit provides a transparent window, but I’ve decided to dispense with it, since it’ll obscure some of the interior detail. I’ve replaced it with photoetch window-frames from Paragrafix:

Paragrafix cockpit window frame and revised Moebius Discovery kit part
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These are unrealistic compared to film images—I’ll deepen them with some styrene strip in due course.

I’ve also added a photoetch pilot figure, representing the character Frank Poole, as seen in my film still above. I’ve had to amputate his feet to get him to fit into the correct position, because of the rather high floor of the Paragrafix part, but this intervention will either be invisible through the windows, or obscured by the little light-box I’m planning on adding.

Paragrafix figure and HDA Modelworx decal for seated astronaut, Moebius Discovery
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Next time, I’ll get some lights into all this.

Moebius 1/144 Discovery Spacecraft: Part 2

Last time, I got all my wiring runs in place to illuminate this model. Now it’s time to add some lights, starting with the engine bells.

There’s room for a couple of large LEDs inside the flare of the engine bells, which means I can get a light behind both engine nozzles on each of the three engine bells. Here’s one LED in one half of an engine bell, showing how I plan to position my lights:

Positioning LED inside Moebius Discovery engine bell
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With that decided, I wired up and tested my three pairs of lights:

LEDs wired for Moebius Discovery engines
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Then there was a decision to make about what to do with the engine nozzles. The kit parts are solid, with a moulded grill. Yay! Monsters make a replacement part moulded of translucent plastic, so there’s the option to paint everything on these parts except where I want light to leak through, between the grill bars. But the Paragrafix photoetch parts I’ll be using for the cockpit interior include a set of nice engine grills, too—so I could drill out the kit parts and insert the metal replacement grills. Here are all the relevant parts, next to the Paragrafix photoetch—Yay! Monsters nozzles at left, kit part at right, engine bell below.

Moebius Discovery engine parts, Yay Monsters transparent part, Paragrafix fret
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My concern with the Yay! Monsters part was that the back isn’t finished. Here’s a comparison with the kit part (on left):

Back of Moebius Discovery kit part and Yay Monsters replacement
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You can see that the Yay! Monsters part would need a lot of work to get it to locate properly within the hexagonal engine bell. I also wasn’t sure how neat a final effect I could produce, applying paint on to the translucent grill. So I drilled out the nozzles and used the Paragrafix grills:

Moebius Discovery engine nozzles with Paragrafix grills
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There’s quite a lot of light inside the engine bells, and I didn’t want it to leak out anywhere except through the grills. So I lined the bells with metal foil on top of a layer of flat black paint, and then painted the exterior black, too, before finally placing the external layer of kit parts that add detail all around the bell.

Lighting test for Moebius Discovery engines
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When I checked for light leaks in a darkened room, I picked up a couple of seams that needed just a little filler and more paint, and one bright spot in the middle of an exterior part, where its locating tab had pushed through the interior foil and was acting as a light duct—a little more foil cured that.

But the hexagons containing the paired engine nozzles presented a problem, with the potential for unsightly light leaks around their edges. The position of the nozzles, very close to the edge of the part, meant that it was going to be difficult to fill any leaks around those edges. After a bit of contemplation, I came up with a solution that involved the diffuser I was going to place inside the grills. I wanted the nozzles to look uniformly dark when not illuminated—no glimpses of the interior foil and LEDs. And I wanted a diffuse illuminant when my engine lights were switched on. Eventually I settled on using a piece of the plastic packaging my LEDs had been delivered in. Here’s a demo—dark side of the plastic at left; plastic stretched and glued over the back of the engine hexagon at centre; final product at right:

Plastic diffuser for Moebius Discovery engines
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I dealt with the filler problem by “pre-filling” the edges of the hexagon—leaving a little edge of my plastic diffuser all around the part, and anointing it with fine filler before gluing it into the engine bell:

Light sealing Moebius Discovery engine nozzles
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This auto-filled the gap around the edges as I pushed it into place, and the small amount of excess that squeezed out was easily removed with the edge of a damp tissue. Then it was just a matter of checking the final effect:

Engine nozzle light test Moebius Discovery
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And the dark-room test:

Light-leak test for Moebius Discovery engines
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Now it was time to add some detail paint to the engine compartment and nozzles. My idea is to produce a quite strongly variegated effect, which I’ll eventually moderate with a uniform blending coat across the whole model.

For the engine compartment itself, I used a set of paint masks from Aztec Dummy.

Aztek Dummy paintmask for Moebius Discovery engine compartment
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The idea here is to layer on several shades of grey, with the paint mask orientation shifted and rotated between layers, to produce an overall mottle suggesting fine detail.

For the smoothly panelled front end of the compartment, I started with a dark shade, masked a few panels, added a paler shade, and so on. Here’s the final result:

Moebius Discovery engine compartment preshaded with Aztek Dummy masks
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I painted the engines bells mid-grey and then brought up detail with a dark wash:

Moebius Discovery engine compartment preshaded
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At present the engine bells are just tacked in place with some clear glue. There’s a slight problem with the bells, which is that in the “real” thing, the three hexagons containing the engine nozzles align edge to edge. But the kit parts want to sit very slightly apart. The solution is either to slip in a little sliver of plastic to fill the gap, or to tilt the outer engines very slightly to bring the hexagons together, and I wanted to take a look at my options at this stage.

Here are the hexagons aligned edge to edge:

Moebius Discovery engines preshaded
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And, actually, the slight tilt turns out to be no big deal, discernible only if you press the hexagons against something flat. So that’s what I’ll go with when I assemble this section permanently.

I was also able to check my wiring runs and light up the engines:

Moebius Discovery engines wired
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Moebius Discovery engines lit
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So that’s all good. Next time, I’ll move to the other end of the kit and start wiring up and illuminating the Paragrafix photoetch cockpit.

Moebius 1/144 Discovery Spacecraft: Part 1

Box art from Moebius 1/44 scale Discovery kit

This is the large styrene model of the iconic Discovery spacecraft from the film 2001: A Space Odyssey. And when I say large, I mean large—assembled, it’s going to be 42 inches long, which will necessitate the hanging of a whole new shelf chez Oikofuge. To get a sense of its weird proportions, take a look at the “real” thing in profile, in a still from the film:

Discovery spacecraft from 2001: A Space Odyssey

To keep the kit rigid, Moebius have provided it with a steel spine, which runs from the centre engine bell at rear to the back of the command sphere at front. It consists of two hollow steel tubes, connected by a steel sleeve concealed inside the antenna module, halfway along the length of the spacecraft. That narrow tube running the whole length of the model is going to be important for what I’m planning for this kit, because I want to add some aftermarket detail (cockpit and pod bay) to the front of the model, and also want to add (quite a lot of) lighting.

So I need a place to put the batteries. The command sphere is going to be pretty full of aftermarket detail and wires by the time I’ve finished with it, but the rear propulsion unit contains a lot of empty space. Here it is, partly assembled, showing the run of the rear steel rod.

Moebius Discovery engine compartment rod
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To turn this into a battery compartment I need a removable lid, so I modified the upper kit part so that I can pop it on and off.

Moebius Discovery engine compartment mods to make battery bay lid
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I’ve extended the locating holes in the concealed side and rear flanges into slots, so that my lid can slide in and out, and I’ve removed a front flange which would otherwise foul the tapered front section of the propulsion unit. Here’s the assembled unit:

Moebius Discovery engine compartment battery lid in place
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Before going any further with modifications, I needed to convince myself I actually could run a pair of wires along the hollow steel spine of the kit, from back to front. And, with a bit of effort and some mineral oil, I managed to screw a twisted pair all the way through both metal tubes. Here they are with a battery pack and test light connected:

Successful test of wiring run through Moebius Discovery spinal rod 1
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And here are the steel tubes assembled end-to-end, demonstrating the length of the kit:

Successful test of wiring run through Moebius Discovery spinal rod 2
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With that option confirmed, I next planned to reduce the length of the rear steel tube so that it terminated inside my battery bay, rather than traversing it. It would, however, need some sort of support structure within the bay, to replace its original anchorage at the back. Here’s my solution to that problem, knocked together from brass rod and styrene. It’s being held in place by the steel tube while the glue dries.

Moebius Discovery engine compartment rod support structure
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Then I needed to measure off how much tubing to remove. I dry assembled the rear engine bell on to the steel tube, and marked off the length at the rear of my support structure:

Marking up cut point for Moebius Discovery spinal rod
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On the principle of measuring twice and cutting once, I also assembled the central cores of the four rear cargo pods, and threaded them on to the rear steel tube, ensuring that enough tube protruded to engage with the central sleeve. Then I pulled my wires back far enough to be out of harm’s way, and Dremelled 1¾ inches off my steel tube. Here’s the post-trimming tubing in position, showing that it both engages with the steel sleeve at the front, and allows my wires to enter the battery bay at rear:

Test of length of Moebius Discovery spinal rod, once trimmed
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There’s room inside for two AA 3V switched boxes, one to supply light to the engines, and one for the command sphere. In due course I’ll glue down a couple of electrical connector blocks in the rear space.

Moebius Discovery engine compartment converted to battery bay
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To get power into the command sphere itself requires only one hole to be drilled, in the kit part that forms the rear of the sphere. I made the hole just large enough to admit the wires, while still leaving enough plastic to form a stop for the steel tube.

Moebius Discovery command sphere drilled for wiring
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At the rear, the original hole for the steel tube gives access to the central engine bell. For the two side units, I drilled holes through the original supporting stubs.

Rear of Moebius Discovery engine bay drilled for wiring
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And in each engine bell, a few seconds with a rat-tail file was required to create a hole that would allow wires to run all the way to the back of the structure.

Moebius Discovery engine parts opened for wiring
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So far so good. Next time, I’ll start installing lights, and do a bit of painting.

Hobby Boss 1/48 Bv 141B: Part 3

At the end of my previous post, I’d finally managed to assemble the complicated crew gondola of my aircraft. After that, I finished off masking its many, many windows, and then set about airbrushing the underside in RLM 65 pale blue enamel, and the topside in a splinter pattern of RLM 70/71 greens, all from Sovereign Hobbies.

Hobby Boss 1/48 Bv 141, basic painting 2
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Hobby Boss 1/48 Bv 141, basic painting 1
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Hobby Boss 1/48 Bv 141, basic painting 3
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All surfaces were sealed with a layer of Plastikote gloss, ready for the kit’s relatively small supply of decals.

Hobby Boss 1/48 Bv 141, underside decals
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Hobby Boss 1/48 Bv 141, topside decals
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Then I belatedly turned my attention to the propeller and engine. The Bv 141B’s 14-cylinder BMW 801A engine proved to be its downfall, because these engines were scarce and going to other aircraft The kit’s representation of the engine is half-hearted—just the front seven cylinders, and those undersized. But the engine will be largely concealed by the fan mounted behind the propeller (which, mercifully, the kit has rotating in the correct direction, unlike its rendering of the propeller, which I had to replace).

Hobby Boss 1/48 Bv 141, propeller and engine parts
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The fan of exhaust stubs, to be mounted behind the engine cowling, provides sixteen rather randomly positioned exhausts. It’s difficult to be sure from photographs of the real thing, but I believe I count twelve outlets, arrayed in a 2:1:3 pattern on each side, with the 3-cluster set a little higher on the starboard side.

Bv 141B exhaust reference
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Here’s the kit part, before and after corrective surgery:

Hobby Boss 1/48 Bv 141, exhaust revision, before & after
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After a little painting of the engine parts, it was time to glue all the big bits together and strip off the canopy masks, producing something that (almost) looked like an aeroplane. Here’s the result after a little weathering (dry-brushed silver enamel, LifeColor Liquid Pigment, and some Tamiya powders) sealed with Plastikote matt:

Hobby Boss 1/48 Bv 141, matt finish 1
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Hobby Boss 1/48 Bv 141, matt finish 2
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Hobby Boss 1/48 Bv 141, matt finish 3
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Only a little tidying up was required when I popped off the hatches and upper turret:

Hobby Boss 1/48 Bv 141, fore gondola
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(There’s a little flake of paint sitting on the main spar in the photograph above, but I fished it out with a cocktail stick.)

The way the kit parts are configured forces the upper gun to point directly backwards, but that would foul the open hatch, so I did a little surgery and swung the gun around to a half-left position:

Hobby Boss 1/48 Bv 141, rear gondola
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I added the Eduard photoetch gun mount to the underside of the turret, with a little bit of styrene strip added to provide the mounting cross-bar, and then slid the final assembly over the gun barrel and into position. Then I sealed the hole in the dome with a little blob of Kristal Klear:

Hobby Boss 1/48 Bv 141, upper turret
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Hobby Boss 1/48 Bv 141, top turret 1
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Which I then painted red-brown to emulate the leather weather-seal around the real thing:

Bv 141 upper turret
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Hobby Boss 1/48 Bv 141, top turret 2
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The undercarriage went on:

Hobby Boss 1/48 Bv 141, gear 1
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Hobby Boss 1/48 Bv 141, gear 2
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Then I flipped it the right way up to add a final few details, including my little punch-out panel frame, and the open hatches:

Hobby Boss 1/48 Bv 141, canopy panel
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Finally, I applied a bit more weathering with Tamiya powders. These aircraft seem to have faded and chipped fairly readily:

Bv 141 weathering 1
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But I wanted to emulate the more subtle pattern of fading visible in some photographs:

Bv 141 weathering 2
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Here’s the final result:

Hobby Boss 1/48 Bv 141 completed 1
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Hobby Boss 1/48 Bv 141 completed 2
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Hobby Boss 1/48 Bv 141 completed 3
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Hobby Boss 1/48 Bv 141 completed 4
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Hobby Boss 1/48 Bv 141 completed 5
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Hobby Boss 1/48 Bv 141 completed 6
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Hobby Boss 1/48 Bv 141 completed 7
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Hobby Boss 1/48 Bv 141 completed 8
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Hobby Boss 1/48 Bv 141 completed 9
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Hobby Boss 1/48 Bv 141 completed 10
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Hobby Boss 1/48 Bv 141 completed 11
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Hobby Boss 1/48 Bv 141 completed 13
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Hobby Boss 1/48 Bv 141 completed 14
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Hobby Boss 1/48 Bv 141 completed 15
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Hobby Boss 1/48 Bv 141 completed 16
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Hobby Boss 1/48 Bv 141 completed 17
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Hobby Boss 1/48 Bv 141 completed 18
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Hobby Boss 1/48 Bv 141 completed 19
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Hobby Boss 1/48 Bv 141B: Part 2

In my last post, I finished detailing the interior of the crew compartment. This time, I’m moving on to some of the other details.

I bought a white-metal undercarriage set from Scale Aircraft Conversions for this model, but I’m not sure if there was any point—the metal parts don’t really improve on the kit parts:

Hobby Boss 1/48 Bv 141, comparison of kit and white metal parts
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Both the kit and the metal parts show the brake lines running tightly over the compressed oleos, which would be a bit of a disaster when the undercarriage was unweighted. So I carved off the sections crossing the oleos and used some stretched sprue to add a loop of flexible slack instead:

Hobby Boss 1/48 Bv 141, gear painted
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From my reference diagram, it seems there was a length of flexible brake line running down the inside of the wheel cover, which I made a mental note to add once I got to the stage of adding the gear covers.

Bv 141 brake line reference

Before I got to that stage, however, I had a bit of a puzzle to solve. Reference photographs of these aircraft usually show that each wheel cover was painted with a section of the large Balkan cross that marked the underside of each wing. For this aircraft, I have one photograph that seems to show this marking, and one that doesn’t:

Bv141 V10 reference photos
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After a bit of deliberation, I decided to add it, despite the fact the kit doesn’t provide the necessary decal, just the two crosses with circular holes for the wheel wells:

Bv141 Balkan crosses cutout for landing gear

So in my ancient graphics program, I used each cross as a mask for its opposite number, like this:

Bv141 Balkan crosses masked for landing gear

And ended up with the pattern for a couple of decals I could print on white Experts-Choice decal film:

Bv141 Balkan crosses for wheel covers

I found that I couldn’t reproduce the appearance of the real aircraft using Eduard’s photoetch gear covers unless I slightly trimmed the lower cover for the oleo scissor links. Here’s the final result, with the decals in place and a little light weathering applied:

Hobby Boss 1/48 Bv 141, landing gear
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I also started detailing up the bomb racks, using Eduard’s parts:

Hobby Boss 1/48 Bv 141, bomb racks with Eduard detail
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But I belatedly realized that the appearance isn’t a good match for the real thing:

I was going to have to snip off and rotate the eight little brackets moulded into the kit parts into the “stowed” position of the empty rack; and then I was going to need to reverse the orientation of the kit parts, front for back, to produce the correct final appearance. Sigh.

I attended to some other details at this point. The rear gun was mounted in a swivelling frame in the real aircraft, like this:

Fw 189 rear gunner

Eduard provide photoetch gunsights for the rear and upper gun, but they’re in a single, short part, like the sight on the upper gun pictured here:

Bv 141 upper turret

So I’ll use the Eduard part as provided for the upper gun, but did some surgery on it to reproduce the photographic appearance of the lower gun:

Hobby Boss 1/48 Bv 141, rear gun and mount
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Another small detail I wanted to add was the frame of a punch-out panel in front of the pilot, which you can see in this photograph:

BV141 port canopy
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I was a little puzzled as to how I might reproduce the smooth shape of the original, but eventually came up with this:

Hobby Boss 1/48 Bv 141, making punchout frame
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I’ve knotted and glued a length of fine wire around a couple of pieces of styrene rod of appropriate diameters. Here’s the result, held in its approximate final position on the canopy frame:

Hobby Boss 1/48 Bv 141, demonstrating punchout frame
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The upper and lower wing halves were such a snug fit, I decided I’d paint them separately before assembly, thus avoiding one stage of masking. At this stage I also dealt with a moulded bulge on the underside of the crew compartment, which represents the aircraft’s Direction Finding gear—actually a clear dome lined with metal strips, but I contented myself with painting it gloss black and adding narrow strips of Bare-Metal Foil:

Hobby Boss 1/48 Bv 141, D/F loop
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I started masking the exterior of the crew gondola, with the upper hatches held temporarily in place with Micro Kristal Klear, but I didn’t mask much of the upper transparency at this point, because I wanted to be able to see what was going on inside as I settled it into place:

Hobby Boss 1/48 Bv 141, preliminary external masking
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The underside transparency got a coat of light grey undercoat, to prevent the interior paint from darkening the pale blue underside.

You may also be able to pick out a small hole drilled in the underside canopy frame. This is my revised approach to the vexatious pilot’s gunsight mentioned in the previous post—a vertical rod that runs from the floor between the pilot’s feet to the roof over his head. Eduard provide a photoetch part for this, but it wasn’t clear to me how I was going to ensure it was correctly positioned after I’d closed the top and bottom halves of the canopy. So I’ve now come up with a revised plan, involving a length of fine wire running through holes in the upper and lower canopy, which can be snugged into place and fixed with CA glue after the canopy is closed. A few blobs of CA provide an imperfect appearance of the short crossbars in the real thing, but I figured it would look good enough when seen vaguely through the closed canopy:

Scratchbuilt wire bombsight for Hobby Boss 1/48 Bv 141
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With the lower canopy in position, I dropped the detailed crew compartment into place:

Hobby Boss 1/48 Bv 141, gondola assembly 1
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Hobby Boss 1/48 Bv 141, gondola assembly 2
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Then I threaded through my gunsight wire, and closed the upper canopy:

Hobby Boss 1/48 Bv 141, pilot's bombsight installation
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There’s a little bit of filling and tidying to do at the wing root, you’ll see, but otherwise it came together nicely.

Next time, camouflage and decals.

Hobby Boss 1/48 Bv 141B: Part 1

Hobby Boss Bv 141 box art

This is the classic asymmetrical aircraft designed by Richard Vogt for the Blohm & Voss company. It was intended for short-range reconnaissance and ground support. Eight version “A” aircraft were built, followed by a run of the “B” version, probably around twenty in number, though records are hazy and the final disposition of many aircraft unknown. Production was cancelled before it entered active service—not because it was particularly unairworthy, but because of competition for the scarce BMW 801A engine. It ultimately lost out to the twin-engined Fw 189.

The kit provides parts for the “B” version, and decals and painting instructions for two airframes—call-sign NC+RA (pictured on the box art above) which was one of the test aircraft for the “B” series; and GK+GH, a wrecked late model photographed by Allied troops at Blohm & Voss’s Wenzendorf factory. I’m building NC+RA, using the kit decals but ignoring the painting instructions. Hobby Boss call for a dark grey interior, which would be odd for a Luftwaffe aircraft that first flew in the middle of 1941, so I’ve opted for RLM 02 Grau (a sort of greeny-grey shade), which would be typical for this period of the war. The dark grey RLM 66 Schwarzgrau corresponding to the Hobby Boss instructions wasn’t generally introduced until November 1941. The instructions also call for an upper splinter camouflage pattern of RLM 02 and RLM 71 Dunkelgrün, which would show a fairly high contrast between the pale and dark colours. But I don’t see that in the black-and-white photographs of the real aircraft, on which the upper camouflage colours are almost indistinguishable. So I’m going with the more standard mix of RLM 70/71, which are a dark green and an even darker green.

There’s one big problem with the kit, which is that its propeller is mirror-reversed—that is, it’s designed to rotate in the wrong direction. That’s a fairly significant error in any aircraft model, but for one that is grossly asymmetrical in order to counteract the torque from the engine and propeller, it’s a disaster. Fortunately, True Details make a replacement propeller, which is an essential after-market replacement for this kit. Here’s the True Details prop (left) compared to the kit prop.

Hobby Boss 1/48 Bv 141 True Detail replacement prop
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Although Hobby Boss provide a good level of detail, I’m also using Eduard’s photoetch detail set, which has unfortunately been discontinued since I obtained mine. Another prerequisite for this kit, if you want to retain your sanity, is a paint-mask set for that huge glasshouse of a crew compartment. Montex produce a set of masks for the interior and exterior. Eduard make a set of exterior masks. I hate working with Montex masks, which I find too thick and intolerant of repositioning, but I really wanted to paint this canopy inside and out, so I ended up springing for both Montex (as the only interior option) and Eduard (as my preferred option, for the exterior).

Here are the transparent crew-compartment parts with their Montex masks in position:

Hobby Boss 1/48 Bv 141 Montex interior masks
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I partially assembled some of the interior parts, including a fair number of Eduard’s PE details, before applying primer:

Hobby Boss 1/48 Bv 141 Eduard interior detailing
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Eduard provides a bomb-sight which attaches to the right side of the central tunnel at the front of the aircraft (covering one of the paired cannons), but there’s no way in which it can placed so that it’s actually centred on one of the floor windows, so I had to carve it up a little.

After priming, I blocked out some initial colours, and added some more of Eduard’s details:

Hobby Boss 1/48 Bv 141, initial detailing 3
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Although Eduard provides a lot of nice instrument panelling, for some reason they omit detail for the unit in the mid-compartment, for which I used the kit’s decal.

The three objects at right, above, are dispensers for the drum-magazines used by the aircraft’s rear and upper MG-51 machine guns. The kit parts depict a stack of five magazines that go all the way to the floor, but the real thing had a gap at the bottom, with the lowest magazine dispensing above this.

Bv 141, magazine dispenser

I’ve contented myself with blanking out the lowest moulded magazine in the kit part. (Eduard provides some nice PE dispensers, which have a more realistic wall thickness, but the kit parts would need to have their moulded walls carved off and replaced.)

The Eduard set includes a pilot’s harness and two lap-belts, but the instructions only mention the lap-belt for the rear gunner. The crew positions for take-off looked like this:

BV141 crew stations
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The observer, in the mid-compartment, sat on a little wheeled chair that ran on rails between the upper gun position, above the main spar, and the forward bomb-aiming station. So I added Eduard’s second set of lap belts to the observer’s seat. The kit provides no seating location for the rear gunner, and Eduard’s instructions just have the belts attached to a corner of the floor. But the pilot and observer sat on their parachutes in bucket seats, and I presume the gunner did the same. I built a little seat for him so that he could perch on his parachute, as in the diagram above. It’s all a bit cramped, however. Beside the gunner’s take-off station, there was a box for spent cartridges positioned against the back of the main spar (they tumbled down a canvas tube connected to the upper machine gun). The kit places this in the mid-line, whereas in fact it should be off to one side. Here’s a photograph of the real layout, looking back from the rear gun mount, with the cartridge box at the left of the picture, and the gunner’s station at right.

BV141 rear compartment looking forward
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Moving the kit’s cartridge box would also require moving one of the magazine dispensers, which is positioned too far back, which in turn would require surgery to the floor … Sigh. Having already partially assembled and primed the parts, I contented myself with squeezing in a slightly undersized gunner’s seat fashioned from styrene strip.

Hobby Boss 1/48 Bv 141, initial detailing 1
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Hobby Boss 1/48 Bv 141, initial detailing 2
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I painted up the canopy interior, and removed the masks:

Hobby Boss 1/48 Bv 141, canopy hatches
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The three roof hatches will eventually be modelled open, but I’ll fix them in the closed position with clear glue when I come to paint the external surfaces, and then pop them off later.

Lots of detail needs to go into the interior, including an overhead panel, various instruments, and a gunsight:

Hobby Boss 1/48 Bv 141, interior eduard canopy detail
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The object sticking out of the floor transparency at right is a primitive bomb-sight for the pilot, presumably only used if the observer was manning the upper gun position. It’s no more than a vertical rod, coming up from between the pilot’s feet and attaching to the cockpit ceiling. You can get a nice view of it in the Alamy photograph here. Eduard provide a nice PE part, but the problem is how to position this thing properly, since it attaches to the upper and lower canopy parts, which must be close around it. My present solution is to glue the sight in position on the floor, and to attach a thread of monofilament (visible in the photo) to its upper end, which I can then pull through a tiny hole drilled in the roof of the upper canopy as I close the two parts together. I’m slightly nervous that I’ll only succeed in pulling the lower end of the sight off the floor, however, at a mission-critical stage in the assembly process.

The final stage before closing the canopy around the crew compartment was to give the whole thing a bit of weathering—I dry-brushed with flat aluminium and buff enamel, applied a wash of Payne Grey watercolour, and then assembled all the bits and pieces. Here’s the result, just before I added the side walls on the starboard side:

Hobby Boss 1/48 Bv 141, interior 4
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Hobby Boss 1/48 Bv 141, interior 2
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Hobby Boss 1/48 Bv 141, interior 1
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Hobby Boss 1/48 Bv 141, interior 3
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Next time: closing the canopy and doing something with all the other bits of the aircraft!

How To Model Rotating Propeller Discs

A shorter version of this post was published on 11 October 2017.

There are some things I hate about “in-flight” models of piston-engine aircraft. One is when the aircraft appear to be flying without a pilot; the other is a stationary propeller.

Modellers have a couple of ways of dealing with this second problem. One is to simply remove the propeller blades, leaving only the filled and smoothed spinner visible—it’s a well-recognized technique which many feel produces the most realistic appearance. But it always makes me think, Where’s the propeller? I find the complete absence of anything in the space where the propeller should be is a little distracting. I’m also not very keen on the photo-etched “prop-blur” option, which aims to produce a blurred sector for each prop blade, reproducing what we see in photos and movies, but not what we see with the naked eye.

So what I want to see is a transparent disc of the correct propeller colour(s), with the colour density at each radius matching the relative amount of prop blade and empty space at that radius.  Like this:

Revell 1/72 Junkers F13 LN-ABH completed 4
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Years ago, I posted a short tutorial about this on; and shortly after I started this blog, I put up a slightly revised version. But it was light on detail—so now this is the extensively revised, expanded and updated version.

I appreciate that some people can’t be bothered doing all the measuring and editing I’ll describe below, which is intended to produce a prop disc that matches the specific measurements of the propeller. If you’re such a person, I encourage you to skip past the measurement and mathematics and read the start of the section about creating a GIMP gradient. Once you’ve seen how I create a gradient of the correct colour, skip ahead to the section on using that gradient to draw the prop disc, and follow on from there. (To skip the first dose of maths, follow this link.)

The first thing I do is to measure the radius of my kit propeller, and then divide it into eight equal sections, from boss to tip, marking off the divisions with a felt-tip pen. Here, I’m marking up two different kinds of propeller for a Blohm & Voss 138 seaplane:

Supermodel 1/72 BV 138 MS, measuring for propeller discs
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Then I measure the propeller blade width at each of my marked locations. To calculate what proportion of the prop disc is occupied by prop blades at each of my eight points along the radius of the propeller, I first work out the radius at each marked distance, which is just the radius of the propeller multiplied by the number of eighths—the first mark on my 24mm propeller is at 3mm, the next at 6mm, and so on. Then I multiply each of those distances by 2π to derive the local circumference. To find out how much of that circumference is occupied by propeller blades, I take the measured width of a propeller blade at that distance, and multiply by the number of blades. Dividing this length by the total circumference tells me what proportion of the prop disc is occupied by propeller blades.

I use a little Excel spreadsheet to do the calculations for me:

Spreadsheet for prop disc calculations

The first column is the number of eighths, measured from the hub of the propeller. The second column converts this to a radial distance. In the third column I’ve entered my measured blade widths, and the fourth column does the maths—multiplying the local blade width by the number of blades, and dividing by 2π times the local radius. You’ll see these numbers turn out to be relatively small, and I find that discs printed with opacities to match are fairly unimpressive, visually—primarily because you can see through even a “zero transparency” layer of ink. So in the fifth column I take the highest number in the fourth column, and express all my numbers as a proportion of that. These are the numbers I’m going to feed to my printer, with 100% representing maximum opacity printing, and 0% full transparency.

I also need to specify a colour for my prop disc. The BV 138 aircraft I’m modelling would have had propellers painted in Luftwaffe Schwarzgrün, which was coded RLM70. I can use the handy digital colour charts created by William Marshall, available here, to discover that RLM70 translates into RGB values of 56/62/50.

So now I’m ready to create my prop disc in a graphics program. I’m going to use GIMP, which has all the tools I need. You can download it here, for Linux, Apple or Windows. (My screenshots and menu sequences below are from version 2.10.)

After opening GIMP, I go through Windows/Dockable Dialogs/Gradients, which brings up a list of GIMP’s built-in colour gradients. I right-click on the list, and choose New Gradient. This gives me a simple colour gradient, from black to white, ready to be edited. Here, I’ve renamed it “BV 138 three-blade prop”, and I’m ready to edit:

New GIMP gradient

First, I tell GIMP my chosen colour, by right-clicking on the gradient and selecting Left Endpoint’s Color…, which brings up a colour dialogue box. All I’m interested in setting are the R, G and B values, for my colour, and the A value (for opacity). But first I need to ensure I’m using the right scale—the figures given by Marshall are based on a range of zero to 255, so I need to click on the 0..255 button before I start entering numbers. Then I set R equal to 56, G to 62 and B to 50, leaving A with its default value of 255 (that is, completely opaque). Here’s what that looks like:

Setting endpoint colour in GIMP

Then I go through the same process with Right Endpoint’s Color…, except setting A to zero, for full transparency. So now I have a colour gradient that is RLM70 throughout, fading from complete opacity to complete transparency. That would actually produce a pretty convincing prop disc, just as it stands, but I can make it more physical accurate by adding the opacity profile I derived from my little spreadsheet. (To skip that detail and go straight to instructions on how to draw the prop disc using a gradient, follow this link.)

To give the gradient a more realistic opacity profile, I need to split my colour gradient into eight equal parts, to match the eight measurements I made above. That’s easy to do. I right-click on the gradient again, and click Split Segment at Midpoint—now I have three little black triangles at the base of my gradient, splitting it into two segments, and two white triangles marking the midpoints of these segments. (These triangles can be dragged around to modify the gradient, but they can stay right where they are at present.) Right-clicking again produces Split Segments at Midpoints, and creates four segments; and again, and I have the eight segments I need. Clicking between two black triangles in the bar at the bottom of the gradient selects one segment to be edited—it appears bright while the others go dark. Like this:

RLM70 GIMP gradient

Now I can edit the colour and opacity within that segment. The RLM70 colour I set at the start has been inherited by all the segments I’ve created, so all I need to do is tweak the opacity. For the first (leftmost) segment, I leave the left endpoint unedited, but bring up Right Endpoint’s Color…. Now, because my calculated opacities from the spreadsheet run from 0 to 100, I click on the 0..100 button, and then set A to 80, the figure for the first eighth of my 3-blade prop.

RLM70 Eight-way split GIMP gradient

(Notice how the RGB numbers seem to have changed from the original 56/62/50—that’s just the effect of changing the scale from 0..255 to 0..100, and the underlying colour has stayed the same.)

Then it’s just a matter of selecting each segment in turn, and editing the opacity. For the other segments, I need to make sure the left end of the segment inherits its opacity from the right end of the previous segment—I do that by using the sequence Load Left Color From…/Left Neighbor’s Right Endpoint from the right-click menu. Then I repeat the process above to set the opacity for the right endpoint. And so on. Here’s the final result, with a distinctive dark band a quarter of the way out, created by the broad bases of the paddle blades on this propeller.

There’s one last thing to do, which will come in handy later. I select the leftmost segment, and then right-click to Split Segment at Midpoint. I select the leftmost of these new segments, and set its left and right endpoints to black (RGB 0/0/0) with maximum opacity. Then I select the new segment immediately to its right, and set the opacity of its left endpoint to maximum. That ends up looking like this:

RLM70 gradient with black segment

The narrow black segment at left is going to end up as a black dot marking the centre of the propeller disc. But it’s a little too broad at present. I can fix that by dragging the leftmost white triangle all the way to the left, and then dragging the neighbouring black triangle so as to close up the black segment while expanding the segment to its right.

RLM70 gradient with reduced black segment

Now I’m ready to use my gradient to create a prop disc.

I start with a new blank image using File/New… from the menu bar. Since I measured my propeller radius at 24mm, I make my blank 60mm across, to give plenty of space. And I note that the default resolution is 300 pixels per inch, which matches my printer settings.

Setting up new image in GIMP

Then I go through Tools/Paint Tools/Gradient to bring up the gradient tool at the left of the work area. I set Shape to “Radial”, and check that the Gradient is “BV 138 3-blade prop”. (If it isn’t, clicking on the little square to the left of Gradient brings up a list of available gradients.) I’ve captured all that in the screen-shot below: