Category Archives: Building

The Coordinate Axes Of Apollo-Saturn: Part 1

As a matter arising from my long, slow build of a Saturn V model, I became absorbed in the confusing multiplicity of coordinate systems and axes applied to the Apollo launch vehicle and spacecraft. So I thought I’d provide a guide to what I’ve learned, before I forget it all again. (Note, I won’t be talking about all the other coordinate systems used by Apollo, relating to orbital planes, the Earth and the Moon—just the ones connected to the machinery itself. And I’m going to talk only about the Saturn V launch vehicle, though much of what I write can be transferred to the Saturn IB, which launch several uncrewed Apollo missions, as well as Apollo 7.)

First up, some terminology. The Saturn V that sent Apollo on its way to the Moon is called the launch vehicle, consisting of three booster stages, with an Instrument Unit on top, responsible for controlling what the rest of the launch vehicle does. Sitting on top of the launch vehicle, mated to the Instrument Unit, is the spacecraft—all the specifically Apollo-related hardware that the launch vehicle launches. This bit is sometimes also called the Apollo stack, since it will eventually split up into two independent spacecraft—the Lunar Module (LM) and the Command/Service Module (CSM). The combination of launch vehicle and spacecraft (that is, the whole caboodle as it sat on the launch pad) is called the space vehicle.

Components of Apollo-Saturn
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From NASA Technical Note D-5399

The easiest set of coordinate axes to see and understand were the position numbers and fin letters which were labelled in large characters on the base of the Saturn V’s first stage, the S-IC. You can see them here, in my own model of the S-IC:

Position and fin labels, Saturn V
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In this view you can see fins labelled C and D, and the marker for Position IIII, equidistant between them.

The numbering and lettering ran anticlockwise around the launch vehicle when looking down from above, creating an eight-point coordinate system of lettered quadrants (A to D) with numbered positions (I to IIII) between them, which applied to the whole launch vehicle. They marked out the distribution of black and white stripes—each stripe occupied the span between a letter and a number, with white stripes always to the left of the position numbers, and black stripes to the right. The five engines of the S-IC and S-II stages were each numbered according to the lettered quadrant in which they lay, with Engine 5 in the centre, Engine 1 in the A quadrant, Engine 2 in the B quadrant, and so on. The curious chequer pattern of the S-IVB aft interstage (the “shoulder” where the launch vehicle narrows down between the second and third stages) is distributed in the lettered quadrants, with A all black, B black high and white low, C white high and black low, and D all white.*

S-IVB Aft Interstage axes and paint
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Umbilicals & Hatches, Saturn V Pos. II
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Umbilical connections (red) and personnel hatches (blue), Apollo-Saturn Pos. II

Position II of the launch vehicle was the side facing the Launch Umbilical Tower (LUT), so that side of the Saturn V was dotted with umbilical connections and personnel access hatches, as well as a prominent vertical dashed line painted on the second stage, called the vertical motion target, which made it easy for cameras to detect the first upward movement as the space vehicle left the launch pad. You don’t often get a clear view of the real thing from the Position II side, so I’ve marked up the appropriate view of my model instead, at left.

The two Cape Kennedy launch pads used for Apollo (39A and 39B) were oriented on a north-south axis, with the LUT positioned on the north side of the Saturn V, so Position II faced north. Position IIII, on the opposite side, faced south, looking back down the crawler-way along which the Saturn V had been transported on its Mobile Launcher Platform. Position IIII was also the side that faced the Mobile Service Structure, which was rolled up to service the Saturn V in its launch position, and then rolled away again before launch. And so Position I faced east, which was the direction in which the space vehicle had to travel in order to push the Apollo stack into orbit.

These letters and numbers seem to have been largely a reference for the contractors and engineers responsible for assembling and mating the different launch vehicle stages. Superimposed on them were the reference axes used by the flight engineers, who used them to talk about the orientation and movements of the launch vehicle and the two Apollo spacecraft. These axes were labelled X, Y and Z.

For the launch vehicle, LM and CSM the positive X axis was defined as pointing in the direction of thrust of the rocket engines. So the end with the engines was always -X, and the other end was +X. The +Z direction was defined as “the preferred down range direction for each vehicle, when operating independently”. For the launch vehicle, that’s straightforward—downrange is to the east as it sits on the pad (the direction in which it will travel after launch), so +Z corresponds to Position I, and -Z to Position III. The Y axis was always chosen to make a “right-handed” coordinate system, so +Y points south through Position IIII.

In the image below, we’re looking north. Once the Saturn V has launched it will tip over and head eastwards (to the right) to inject the Apollo stack into orbit.

XYZ axes of Saturn V launch vehicle
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Apollo 8, S68-55416

These axes were actually labelled on the outside of the Instrument Unit (IU), at the very top of the launch vehicle. Here’s one in preparation, with the +Z label flanked by the casings of two chunky directional antennae—a useful landmark I’ll come back to later.

Saturn V instrument unit
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Source

So here’s a summary of all the axes of the Saturn V:

Saturn V principal axes
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Moving on to the Lunar Module, its downrange direction is the direction in which it travels during landing, when it is orientated with its two main windows facing forward—so +Z points in that direction, out the front. The right-hand coordinate system then puts +Y to the astronauts’ right as they stand looking out the windows.

XYZ axes of LM
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Apollo 9, AS09-21-3212

The landing legs were designated according to their coordinate axis locations. In the descent stage, between the legs, were storage areas called quads—they were numbered from 1 to 4 anticlockwise (looking down), starting with Quad 1 between the +Z and -Y leg. The ascent stage, sitting on top of the descent stage, had four clusters of Reaction Control System (RCS) thrusters, which were situated between the principal axes and numbered with the same scheme as the descent-stage quads.

Lunar Module principal axes
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But it’s not clear that there is a natural downrange direction for the CSM—the +Z direction is defined (fairly randomly, I think) as pointing towards the astronauts’ feet, with -Z therefore corresponding to the position of the Command Module hatch. That places +Y to the astronauts’ right side as they lie in their couches.

XYZ axes of CSM
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Apollo 15, AS15-88-11961

The Command Module was fairly symmetrical around its Z axis, and its RCS thrusters were neatly place on the Z and Y axes. Not so the Service Module, which was curiously skewed. Its RCS thrusters, arranged in groups of four called quads, were offset from the principal axes by 7º15′ in a clockwise direction when viewed from ahead (that is, looking towards the pointed end of the CSM). The RCS quad next to the -Z axis was designated Quad A; Quad B was near the +Y axis, and the lettering continued in an anticlockwise direction through C and D. I’ve yet to find out why the RCS system was offset in this way, since it would necessarily produce translations and rotations that were offset from the “natural” orientation of the crew compartment, and from the translations and rotations produced by the RCS system of the Command Module.

The Service Module also contained six internal compartments, called sectors, numbered from 1 to 6. These were symmetrically placed relative to the RCS system, rather than the spacecraft’s principal axes. Finally, the prominent external umbilical tunnel connecting the Service Module to the Command Module wasn’t quite on the +Z axis, but offset by 2º20′ in the same sense as the RCS offset.

Command/Service Module principal axes
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So those are the axes for the launch vehicle and spacecraft. But how did they line up when the Saturn V and Apollo stack were assembled? Badly, as it turns out.

First, the good news—all the X axes align, because the spacecraft and launch vehicle are all positioned engines-down for launch, for structural support reasons, if nothing else.

With regard to Y and Z, it’s easy to see the CSM’s orientation on the launch pad. Here’s a view from the Launch Escape Tower, which we’ve established (see above) is on the -Y side of the launch vehicle. The tunnel allowing access to the crew hatch of the Command Module (-Z) is on the left, and the umbilical tunnel connecting the Service Module to the Command Module is on the right (+Z), so the CSM +Y axis is pointing towards us.

YZ axes of CSM on launch pad
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Apollo 11, 69-HC-718

Oops. The CSM YZ axes are rotated 180º relative to those of the Saturn V launch vehicle.

It’s more difficult to find out the orientation of the Lunar Module within the Apollo stack, since it’s concealed inside the shroud of the Spacecraft/Lunar Module Adapter. Various diagrams depict it as facing in any number of directions relative to the CSM, but David Weeks’s authoritative drawings show it turned so that its +Z and +Y axes align with those of the CSM—facing to the right in the picture above, then, with its YZ axes rotated 180º relative to those of the Saturn V launch vehicle below. We can check that this is actually the case by looking at photographs of the LM when it’s exposed on top of the S-IVB and Instrument Unit, during the transposition and docking manoeuvre. The viewing angles are never very favourable, but the big pair of directional antennae flanking the +Z direction on the IU are useful landmarks (see above).

XY axes of LM and IU
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Apollo 9, AS09-19-2925

We can see that the front of the Lunar Module (+Z) is indeed pointing in the opposite direction to the directional antennae marking the +Z axis of the IU and the rest of the launch vehicle. Weeks’s drawing are correct.

So, sitting on the launch pad, the axes of the launch vehicle are pointing in the opposite direction to those of the spacecraft. NASA rationalized this situation by stating that:

A Structural Body Axes coordinate system can be defined for each multi-vehicle stack. The Standard Relationship defining this coordinate system requires that it be identical with the Structural Body Axes system of the primary or thrusting vehicle.

NASA, Project Apollo Coordinate System Standards (June 1965)

So the whole space vehicle used the coordinate system of the Saturn V launch vehicle, and the independent coordinates of the LM and CSM didn’t apply until they were manoeuvring under their own power.

So, beware—there’s real potential for confusion here, when modelling the Apollo-Saturn space vehicle, because different sources use different coordinates; and many diagrams, even those prepared by NASA, do not reflect the final reality.

Next time, I’m going to write a little about what happens to all those XYZ axes once the vehicles start moving around.


* I suspect I’m not the first person to notice that the S-IVB aft interstage chequer can be interpreted as sequential two-digit binary numbers, with black signifying zero and white representing one. Reading the least significant digit in the “low” positions, we have 00 in the A quadrant, 01 in the B quadrant, 10 in C and 11 in D—corresponding to 0, 1, 2, 3 in decimal. (I doubt if it actually means anything, but it’s a useful aide-memoire. Well, if you have a particular kind of memory, I suppose.)

Pegasus Hobbies 1/350 Von Braun Lunar Lander

Pegasus 1/350 Von Braun Moon Lander box art
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This is Pegasus Hobbies’ version of Wernher von Braun’s original conception of how we’d land on the moon—in a stonking great 4000-ton spacecraft with 30 engines and a crew capacity of 25. (Actually, three stonking great ships were planned—one carrying cargo and the others carrying crew.) The landing would be preceded by a lunar fly-by mission, in a spacecraft I’ve previously modelling by adapting Lindberg’s venerable old Moon Ship kit.

The design and mission plan for this spacecraft were outlined in three articles written for Collier’s magazine, published in the issues of 18 and 25 October 1952, and these were my guides when building the kit. They’re available on-line, republished in Horizons, the newsletter of the American Institute of Aeronautics and Astronautics, Houston Section. The first two articles, by Wernher von Braun and Willy Ley, were reproduced in the Horizons issue for September/October 2012 (47MB pdf); the third, by Fred Whipple and Wernher von Braun, appeared in November/December 2012 (49MB pdf). In fact, the Horizons issues from July/August 2012 to September/October 2013 all reproduce classic Collier’s articles on the theme “Man Will Conquer Space Soon!”

The first thing to say is that this is a lovely kit—the parts fit together like a dream. And it arrives beautifully packed, with delicate pieces wrapped in foam. It’s also complicated, with some parts actually threading through other parts, and a few opportunities to mis-assemble if you don’t pay careful attention to the instructions and examine the pieces carefully before you commit to gluing. Parts are supplied for the crewed version or the cargo version.

I added a few details from ParaGrafix’s photoetch detail set, and some decals left over from previous projects. I ignored Pegasus’s painting guide. This follows Chesley Bonestell’s illustrations for the Collier’s articles, with fuel and oxidizer tanks tinted in shades of red, yellow and blue—you can see the effect in the box art at the head of this post. The colours seem to be lifted from a colour-coded diagram in Collier’s, showing the function of each set of tanks, and I couldn’t see a reason for them to be colour-coded in “real life”, so I went for plain white tanks instead.

I also needed to do a little modification. The big, outer, spherical tanks, prominently visible in the box art, didn’t actually make it to the moon. They were used to accelerate the ship out of Earth orbit, where it had been assembled, and were then discarded during the trans-lunar coast. So the ship actually landed in a slightly stripped-down configuration, as illustrated by Bonestell’s cover illustration for Collier’s.

Cover of Collier's 18 October 1952
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Until the landing approach, the legs were stowed out of the way of the rocket blast—the outer legs folded upwards, and the telescopic central leg (which doubled as a landing sensor and shock absorber) drawn back between the rocket nozzles. The outer kit legs look as if they could be assembled in the folded-back position (though I didn’t try it), and it would require only minor surgery to model the central leg in the retracted position—so there’s the potential to configure this model into “Earth departure” mode with the large tanks in place. But I elected to reproduce the appearance shortly after landing, so I needed to remove the large tanks and then add a little scratch-built detail to the stumps of the support structure.

First up, I drilled out the portholes in the crew compartment, and added ParaGrafix detailing. Here’s a comparison of the upper half in its original state and the lower half with its modifications completed:

Pegasus 1/350 Von Braun Moon Lander detailing crew sphere
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Then there was a tedious and repetitive period spent assembling and painting the various subcomponents of the spacecraft:

Pegasus 1/350 Von Braun Moon Lander prepared parts
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To get the eighteen central engines aligned with each other, I used slow-drying epoxy glue, so that I could tweak them around once they were in place:

Pegasus 1/350 Von Braun Moon Lander engine placement
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Getting to the next stage of assembly requires the horizontal support structures to be slid on to eight vertical rods, while locating the various tanks between. There’s potential for confusion with the relative placement of long and short rods; and note that the shorter rods, which bear the small spherical helium tanks, have a definite right way and wrong way up.

Pegasus 1/350 Von Braun Moon Lander part assembled
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Since I was planning to omit the big departure tanks, I needed to modify the support structures, guided by a diagram from one of the Collier’s articles which shows the plane of separation when the tanks were discarded:

Diagram of departure tank detachment, from Collier'sFirst I needed to remove most of the external framework:

Pegasus 1/350 Von Braun Moon Lander modifying departure tank supports
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And then chop through the horizontal support frames and add a few bits of styrene to close off the open ends:

Pegasus 1/350 Von Braun Moon Lander modified support structures
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The upper end of the framework will support a couple of cranes which are included in the kit but are effectively undeployable until the departure tanks are discarded. The only way for the crew to reach the ground from their habitat sphere, 40-odd metres above the ground, is to descend using these cranes. The ParaGrafix detail set includes a couple of little elevator cages and some crane hooks.

To populate my elevator cage and add some indication of scale to the model overall, I wanted to add some astronaut figures. Tamiya produce a set of 1/350 crew figures for ship models, and I modified a few of these to look a bit more like astronauts by adding some strip styrene for backpacks and blobs of glue for helmets:

Tamiya 1/350 crew figures modified as astronauts
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Here’s the final product, with a pair of crew members descending to the ground while others look on from the airlock “balcony” of the crew sphere and from the engine platform.

Pegasus 1/350 Von Braun Moon Lander model 2
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Pegasus 1/350 Von Braun Moon Lander model 1
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Pegasus 1/350 Von Braun Moon Lander model 3
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Pegasus 1/350 Von Braun Moon Lander model 4
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Pegasus 1/350 Von Braun Moon Lander model 8
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Pegasus 1/350 Von Braun Moon Lander model 9
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Pegasus 1/350 Von Braun Moon Lander model 7
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Pegasus 1/350 Von Braun Moon Lander model 5
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Pegasus 1/350 Von Braun Moon Lander model 10
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Pegasus 1/350 Von Braun Moon Lander model 6
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The outer banks of engines can be vectored in a single plane on the model, as was intended for attitude control in the real thing:

Pegasus 1/350 Von Braun Moon Lander model 11
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Finally, I’ve put together a couple of size comparisons to show what a monstrous thing this spacecraft would have been. Firstly, compared to the real Lunar Module:

Von Braun lander and Lunar Module
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And with the Statue of Liberty:

Von Braun lander and Statue of Liberty
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Now that would really have kicked up some dust when it landed.

Revell 1/96 Saturn V: Fully Assembled

Revell 1/96 Saturn VThis is the final post of my three-year project to assemble Revell’s 1/96-scale Saturn V model kit. It’s intended to provide a few views of the completed model, and to act as a sort of index to the various sections of the stage-by-stage build log I wrote as I went along.

The kit is fundamentally flawed because it was based on the original SA-500F Facilities Integration Vehicle, a test version of the Saturn V which never flew. (Any Apollo buff can tell that, immediately, from the paint pattern featured on the box art.) The sad thing is that Revell have never revised the kit, despite reissuing it a regular intervals, including this year’s 50th anniversary of the first moon landing. So the kit includes parts, decals and painting instructions that are inaccurate for any of the Apollo flights, because based on an early test article. It also includes things that are just plain inaccurate—wrongly placed and wrongly sized parts, and incorrect alignments of each stage with its neighbours.

To help me understand and try to fix these problems, I used David Weeks’s 1/48 Saturn V drawing sets, available from RealSpace Models. At exactly twice the scale of the kit, they were a real boon to confirm the location and orientation of various details.

To correct many of the kit’s errors and omissions, I used various after-market detail sets—batted F-1 engines and a Block II Command/Service Module from RealSpace, New Ware’s extensive resin, photo-etch and decal detail set, and a separate decal set for the CSM from Space Model Systems.

1/96 Saturn V aftermarket details
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First, here’s a four-quadrant view of the completed model, which depicts AS-506, the launch vehicle and spacecraft for the Apollo 11 mission:

Four quadrant view of complete Revell 1/96 Saturn V kit
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And the upper section, in isolation:

Revell 1/96 Saturn V with RealSpace & New Ware details (upper part)
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There now follows a stage-by-stage description, from the top down, with links to the relevant parts of the build log.


RealSpace 1/96 CSM (2)
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RealSpace 1/96 CSM (1)
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The kit provides an early Block I Command/Service Module, whereas all manned flights used Block II CSMs. This is the resin replacement Block II from RealSpace. Kit parts are used for the Service Module’s Reaction Control System thruster blocks and S-band antenna. Some additional details were added from the New Ware set. RealSpace’s scimitar antennae on the Service Module were poorly moulded, and were removed and replaced with New Ware’s photo-etch parts. Bare-Metal Foil for the finish on the Command Module and aft Service Module heatshield. Some detailing with styrene sheet on the SM aft bulkhead. Decals from Space Model Systems appropriate for CSM-107, the Apollo 11 spacecraft.


Revell 1/96 escape tower and RealSpace BPC
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The kit lacks a Boost Protective Cover for the Command Module—this is the vacu-formed part that comes with the RealSpace Block II Command/Service Module. I punched a couple of holes in it to represent the two windows over the central and commander’s (left) window of the Command Module. I added the kit Launch Escape System tower, detailed with some styrene rod to simulate structural ribbing and wiring harnesses.


Revell 1/96 Saturn V SLA & IU (2)
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Revell 1/96 Saturn V SLA & IU (1)
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This is the Spacecraft/Lunar Module Adapter (SLA) which housed the Lunar Module and supported the CSM. The kit provides an upper and lower section. The upper section contains an unrealistic window, to allow viewing of the Lunar Module in situ. The lower SLA is moulded in one piece with the Instrument Unit, in reality a separate section of the launch vehicle. I filled and painted over the SLA window, and detailed the structure with New Ware parts and styrene strips. I found it was possible to leave the upper part detachable from the lower section, so that the Lunar Module could be displayed in a realistic position on top of the Instrument Unit and S-IVB stage. I also scribed out an umbilical connection port, and corrected an error in New Ware’s decals—the black -Y axis marker provided for the Instrument Unit should be +Y. The moulded support for the kit CSM was removed, since it was positioned wrongly for the RealSpace CSM.


Revell 1/96 Saturn V S-IVB
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Revell 1/96 Saturn V S-IVB thrust structure
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With lower SLA attached:

Revell 1/96 Saturn V S-IVB with lower SLA
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The alignment between the kit SLA and S-IVB stage is wrong, and requires correction—see build log for details. The kit parts include a printed styrene sheet to be rolled to form the central tank structure. This is marked USA, which is inappropriate for manned missions—I turned it inside-out and painted it to match the rest of stage. The fore and aft skirts needed extensive detailing from New  Ware, and the service tunnel was replaced.


Revell 1/96 Saturn V S-IVB aft interstage 1
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Revell 1/96 Saturn V S-IVB aft interstage 2
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Revell 1/96 Saturn V with New Ware details (upper interstage)
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The kit provides a single part for the S-IVB aft interstage. The alignment between this part and the S-IVB stage is wrong, and needs to be corrected—see the build log for details. Instead of using New Ware’s replacement retro rocket fairings, I added simulated fairing covers to the kit part using epoxy. I also scribed a personnel access hatch, using David Weeks’s drawings for guidance. The chequered sway targets I painted are too large, but this is deliberate—when sized correctly they could not be made to look square, because of the oversize stringers of the kit parts.


Revell 1/96 Saturn V S-II (2)
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Revell 1/96 Saturn V S-II (1)
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Revell 1/96 Saturn V S-II forward skirt and tank
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Revell 1/96 Saturn V S-II thrust structure (2)
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Revell 1/96 Saturn V S-II thrust structure (1)
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Revell 1/96 S-II stage + interstage
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The S-II stage is wrongly aligned with the S-IVB aft interstage—see build log for details of the correction required.

This stage is very poorly depicted by the kit parts. Fairings are missing or wrongly positioned, and need to be replaced with New Ware parts. Attachment points for the kit parts need to be removed and the stringers restored. Stringers extend too far on both the fore and aft skirts, and need to be trimmed back. I added an additional insulation layer to the fore skirt using styrene sheet. Several other areas need to be cleared of stringers to allow the addition of New Ware umbilical connectors and hatches.

The liquid oxygen vent pipes are wrongly positioned, and need to be moved. I also corrected the number and position of the gores on the forward tank dome so that the vent pipes could be properly placed in the correct position. New Ware provides a resin aft heatshield—the support structure was scratch-built using 0.5mm brass rod. The kit’s aft thrust structure is extremely inaccurate, and required considerable modification and detailing with styrene rod before adding resin instrument packages from New Ware. Again, I turned the kit’s printed styrene sheet inside out so that I could produce a uniform paint job, and then mark up with decals from New Ware.


Revell 1/96 Saturn V S-II aft interstage
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Revell 1/96 Saturn V with New Ware details (lower interstage)
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Revell 1/96 S-II + aft interstage + New Ware details 1
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The kit S-II aft interstage comes with eight ullage motors. These were reduced to four on the Apollo 11 launch vehicle, and were later omitted entirely. The attachment points for the kit parts therefore need to be removed and the stringers restored. The kit motor fairings are too small and need to be replaced with New Ware parts. The S-II fairings extended on to the aft interstage—all the New Ware resin fairings need to be divided at an appropriate level, with their trailing parts added to the interstage and aligned. New Ware provides a photo-etch personnel access hatch.

The white flight-separation junctions, above and below the interstage, were added using 0.5mm x 1.5mm styrene strip, wrapped around the locating flanges at the base of the S-II stage and the interstage.


Revell 1/96 Saturn V S-IC Pos II
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Revell 1/96 Saturn V S-IC Pos IIII
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Revell 1/96 Saturn V S-IC forward skirt and tank
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Revell 1/96 Saturn V with batted RealSpace engines
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Revell 1/96 Saturn V S-IC aft skirt
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The S-IC stage is wrongly orientated relative to the S-II. I corrected this at the junction between the S-II aft interstage and the S-IC—see build log for details.

The entire aft end of the S-IC stage needs to be remodelled, because of inaccuracies in the heatshield and engines. The F-1 engines were covered with batted insulation, but the kit parts are bare. I used RealSpace’s resin replacements, with Bare-Metal Foil detailing and some scratch-building to reproduce the appearance of the real engines. The kit heatshield is surround by air scoops, most of which were removed in S-IC stages that actually flew—New Ware provides resin replacement for the heatshield, engine fairings and fins, and photo-etch parts for the remaining air scoops on either side of the engine fairings. The New Ware heatshield is poorly detailed—I printed a custom decal sheet to depict rivets and other details in this area. I also scratch-built lunate heatshields for the engine fairings—neither Revell nor New Ware provide appropriately shaped parts.

Slots must be cut in the kit’s aft skirt to accommodate resin hold-down posts from New Ware. The kit service tunnels are the wrong shape and size, and New Ware provides photo-etch parts that can be applied to 7mm half-round rod to produce a more realistic result. Again, I turned the kit’s printed styrene sheets inside out, so that I could achieve a uniform paint job, and then apply New Ware’s decals. And again, stringers need to be removed in several areas to allow the addition of multiple umbilical connections and access hatches from New Ware.

NB: I failed to notice, until it was too late, that this stage is almost an inch too long for its scale size, with most of the extra length being in the forward tank and intertank skirt. This means New Ware’s service tunnels appear too short on the completed model.


Revell 1/96 Saturn V LM (2)
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Revell 1/96 Saturn V LM (1)
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Revell 1/96 Saturn V LM ascent stage
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Positioned in SLA:

Revell 1/96 Saturn V S-IVB with SLA & LM (1)
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Revell 1/96 Saturn V S-IVB with SLA & LM (2)
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The Lunar Module provided with the kit is wrongly shaped in several respects. I added some scratch-built detailing, painted the thermal panels and adding foil in appropriate shades for Apollo 11’s LM-5, and blocked off the hole in the access tunnel with styrene sheet. I also revised the tank support strut on the left front of the ascent stage—this is modelled as a flange in the kit part, which was removed and replaced with styrene rod. A lot more detail (plume deflectors, aerials and a docking target) could easily be added but I decided against it on the grounds that the LM would be invisible in the assembled model, and would be easily damaged on disassembly.


And that’s it. Something of an epic build, involving equal parts frustration and satisfaction. I’m glad to have done it, but I wouldn’t care to undertake such a large-scale revision project again.

Well … not for a while, anyway.

Revell 1/96 Saturn V: Lunar Module

After completing the entire Saturn V stack, top to bottom, I had one small additional component to complete—the Lunar Module. This sat invisibly inside the Spacecraft/Lunar Module Adapter during launch and translunar injection, and was revealed only when the SLA panels were discarded during the lunar coast phase.

Apollo Spacecraft/Lunar Module Adapter
Source

The LM that comes with the kit is incorrect in many details, and would need a complete rebuild or a resin replacement to fix. I contented myself with a few tweaks—adding some detail using pieces of styrene, filling the gaping hole of the docking port, and revising the depiction of the external strut that helped support the Aerozine-50 fuel tank on the left side of the ascent stage. The kit represents this last structure as a flange, which I removed and replaced with an appropriate section of rod. (The striking asymmetry of the LM in front elevation, including the presence of a support strut on the left but not on the right, is due to the different densities of the Aerozine-50 fuel and the nitrogen tetroxide oxidizer—to balance the structure around the thrust axis of the ascent engine, the heavier nitrogen tetroxide tank had to be kept close inboard on the right, while the lighter Aerozine tank was in an extended position on the left.)

After a lot of filling and sanding to patch together the two parts of the ascent stage, I painted the various panels with the peculiarly complicated pattern of different insulation colours specific to the LM5 of Apollo 11. The dark gold Kapton film on the underside of the ascent module was simulated with gold Bare-Metal Foil. I mixed up Tamiya’s Flat Aluminium, Yellow-Green and Buff to produce an approximation to the strange beige shade used for some of the LM’s panelling—it looks a bit too green in direct sunlight, unfortunately. And I used Tamiya’s Metallic Grey with a hint of Gold Leaf for the thruster quadrants.

Revell 1/96 Saturn V LM ascent stage primed
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Base-coated ascent stage
Revell 1/96 Saturn V LM ascent stage
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Completed ascent stage

The descent stage was painted black, and then patterned with silver foil and two shades of gold—Bare-Metal for the silver and dark gold Kapton, and some pale gold foil from a chocolate bar wrapper, stockpiled years ago when chocolate bars still came wrapped in foil. And although they don’t seem to be mentioned in the kit instructions, Revell does provide decals for the descent stages markings—an American flag and a UNITED STATES label, the second of which is distinctly oversized.

Revell 1/96 Saturn V LM descent stage with foil
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Revell 1/96 Saturn V LM descent stage with foil & decals
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I should note at this point that the supporting struts for the lander’s legs are in the wrong position in these photographs—the locating lugs on the top of the lower (gold) V-struts needs to be positioned inside the apex of the upper (black) V-struts. This isn’t remotely obvious from the kit assembly instructions, and the kit parts themselves are reluctant to assume this position, but the LM will not fit into its correct location in the lower SLA unless the struts are assembled in this way.

Here’s what it looks like, properly stowed on top of the S-IVB stage—this is the view the astronauts would have had as they manoeuvred the Apollo CSM to dock with and extract the LM, during the lunar transfer coast.

Revell 1/96 Saturn V S-IVB with SLA & LM (1)
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Revell 1/96 Saturn V S-IVB with SLA & LM (2)
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And here it is with its legs folded for SLA stowage. (I tried to cover the foot-pads with appropriate dark gold foil, but couldn’t get a good result, so eventually used gold paint instead.)

And that was the final part of my long Saturn V project—three years from start to finish. Although I’m posting this after the 50th anniversary of the Apollo 11 landing has come and gone, I actually finished work just after midnight on 1st July 2019, a couple of weeks before the Apollo 11 anniversary—closer to the wire than I imagined I would be, three years ago, but still on time.

In my next (and last) post on this topic, I’ll show you what the whole thing looks like, with all the stages stacked.

Revell 1/96 Saturn V: S-IC Stage – Part 2

Last time, I described how I needed to extensively modify the front and back ends of the Revell S-IC stage, using resin parts from RealSpace and New Ware, combined with some custom decals and a little scratch building.

Next, I needed to assemble the component parts of the stage—the fore and aft skirts, the intertank ring, and two styrene sheets that needed to wrapped into cylinders to represent the fuel and oxygen tanks.

Revell 1/96 Saturn V S-IC stage
Click to enlarge

As usual, I turned the styrene sheets inside out, so I could prime and paint the stage in a uniform pattern of black and white. (New Ware provides decals for the USA markings and the American flags.) Also visible in the picture above are the parts for the two long service tunnels that carried wiring up the outside of the tanks. The kit parts are undetailed and oversized, and New Ware’s solution to this is to provide a set of photoetch parts, ribbed to reflect the real surface of the service tunnels. These are supposed to be wrapped around the kit parts, and excess plastic pared away. The kit parts don’t really produce the right shape, unfortunately—the original tunnels were pretty close to being hemicylindrical. So I wrapped New Ware’s photoetch around lengths of 7mm half-round rod from Maquett instead, which produced a fairly nice result.

At this point, I noticed that New Ware’s tunnels were a little shorter than the kit parts. I checked against David Weeks’s Saturn V scale drawings and found that New Ware was pretty close to the correct length, and thought no more about it. (In retrospect, I should have thought more about it.)

So I wrapped the styrene, assembled the stage … and discovered that the service tunnels didn’t span as far as they should. I could have one end of the tunnel correctly located, but the other end wouldn’t reach far enough on to the skirt at the opposite end of the stage. More measuring ensued, and it turned out that Revell’s S-IC stage is almost an inch too long for the correct scale, with most of the excess length in the forward tank and the intertank. Well, sigh—they finally caught me out. I couldn’t see a good way to disassemble the pieces and trim them, so I accepted the inevitable and positioned the tunnels so that they leave a larger chunk of forward skirt exposed than they should do.

The engine fairings I kept separate, and painted in their final pattern of white, black and metallic. They were going to have to go on after I’d added the engine and firewall assembly I completed last time—the structural braces inside the engine fairings meant that each fairing assembly would need to be slid on sideways once its corresponding fairing firewall was in place.

So I primed and painted the cylindrical stage, leaving the final demarcation line between black and white on the aft tank to be completed once the fairings were in place. Then the firewall and engines were put in place, double-checking the correct orientation of the central engine. Then the fairings, then the finalization of the black stripes on the aft structure.

By this time, the whole thing was beginning to take up a lot of room on the workbench. Here it is, waiting for a coat of gloss and the New Ware decal set:

Revell 1/96 Saturn V S-IC on workbench
Click to enlarge

Positioning the American flags on the overlong forward tank needed a bit of calculation to make sure they were positioned in the correct proportion between the top and bottom margins, rather than working from the original measurements.

Finally, before the last coat of varnish, I added the delicate telemetry antennae to the forward skirt. (I knew that, if I added them any earlier, I would knock them off while preoccupied with decal positioning.)

And that was that. The literal final stage of this project:

Revell 1/96 Saturn V S-IC Pos IIII
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Revell 1/96 Saturn V S-IC Pos II
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Revell 1/96 Saturn V S-IC forward skirt and tank
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Revell 1/96 Saturn V S-IC aft skirt
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Revell 1/96 Saturn V with batted RealSpace engines
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Revell 1/96 Saturn V with New Ware details (lower interstage)
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Except … there’s one more small component to build before the project is complete. That’s what I’ll post about next time.

Addendum: I recently had an enquiry about my placement of the yellow drain labels at the top end of the aft tank. There are eight of these, placed just below the intertank section, at the top of each black and white stripe. They’re often depicted as being centred on the stripes (for instance, in the New Ware decal guide), but that doesn’t actually seem to be the case, at least in the S-IC-6 of Apollo 11. Looking at footage of the real launch vehicle from Apollo 11: Men On The Moon, by Spacecraft Films, I noticed that the labels were a little displaced from the centre line. Here’s a screen-grab to show the real positions, which I reproduced on the model:

Position of drain labels on S-IC-6
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Revell 1/96 Saturn V: S-IC Stage – Part 1

Having completed the S-II Aft Interstage for my previous post on this build log, I’ve now progressed to the Big Beast of the S-IC.

This stage is composed of Revell’s usual combination of moulded cylinders for the skirts and intertank, and printed styrene sheets to be rolled into cylinders for the tank sections. The stage also has two service tunnels running along its length, each one provided in two sections in the kit:

Revell 1/96 Saturn V S-IC stage
Click to enlarge

As with previous stages, my plan was to turn the printed sheets inside-out, paint them white to match the other structures, and then detail them using the decals provided in the detail set by New Ware. The kit service tunnels are both too long and too large, so need to be replaced—I’ll come to that in my next post.

For this post, I’m going to describe a small modification to the forward skirt, a rebuild to the aft skirt, and a wide-ranging replacement of the kit’s engines, fairings and heatshield.

As usual for this kit, the S-IC needs to be rotated to bring it into correct alignment with the rest of the stack. So the locating lugs on the forward skirt need to be moved. This is complicated by the fact that I have previously rotated the aft part of the S-II stage through ninety degrees so as to be able to conceal an unrealistic kit feature. Not having undone that rotation when I modified the S-II Aft Interstage (because that kit part is rotationally symmetrical), I need to reverse that rotation now. A corrective quarter turn would amount to moving the locating lugs 3⅜″ clockwise around the rim, looking down. Instead, judging from the position of the S-IC service tunnels, I found I need only three-and-a-sixteenth. (So it seems to me that, if you build this kit without rotating the aft part of the S-II, you’ll need to move the S-IC locating lugs five-sixteenths of an inch anticlockwise to fix the stage alignment. But please check my working.)

Shift locating lugs Revell 1/96 S-IC
Click to enlarge

As usual, the colours of the skirt interior and LOX dome are hard to ascertain. I used zinc chromate yellow-green for the tank on this stage, which matches the colour photos I’ve seen of the stage being assembled, as well as the apparent colour visible in the familiar footage of Apollo 4 staging.

At the other end of the stage, the big problem with the fairings and heatshield provided in the model kit is that they are rimmed with multiple air scoops, designed to drive cooling air across the heatshield between the engines and the fuel tank. These featured in early designs (on which the kit was based), but on operational Saturn V launch vehicles the scoops had largely been removed, leaving only a pair at either side of each engine fairing. So both need to be replaced with much plainer resin versions from New Ware.

Revell 1/96 Saturn V S-IC stage, NewWare replacements
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The kit engines also need to be replaced. Revell provides bare F-1 engine bells of the kind seen on the small number of Saturn V vehicles that are on display. But in reality, the F-1 engines on operational launch vehicles were swathed in external insulation called “batting”, to protect the engine bells from hot gases billowing back from the rocket exhaust. It looked like this view of a test item:

Batted F-1

(This photo rattles around the Internet uncredited, and I’ve so far been unable to find its source. If anyone knows, I’d be glad to give credit appropriately, or to remove a copyrighted item.)

Resin versions of the batted F-1 engines are available from RealSpace Models. Here’s a comparison of the kit version and the resin replacement.

Revell 1/96 Saturn V, F-1 engine and RealSpace replacement
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The batting consisted of both generic pads applied to the bell, and shaped sections which surrounded more complex structures. As the photograph of the real thing shows, there was a slight difference in the reflective properties of these two kinds of batting. I aimed to reproduce this by applying chrome-finish paint to the resin, and then adding bright chrome Bare-Metal Foil detail.

RealSpace’s resin engines are adequately shaped to locate them accurately on the kit heatshield. And New Ware’s resin heatshield is adequately shaped to locate the kit engines correctly. But the two detail kits don’t have enough locating studs to align them precisely with each other. So I sawed the locating studs off the kit engines, and cemented them to the resin parts, ready to engage with the holes in New Ware’s heatshield; and I drilled out the gimbal mounts on the resin heatshield, and added short sections of brass rod to engage with the sockets on RealSpace’s engines.

Then I needed to attach the gimbal actuators to the engines. In reality, these “fueldraulic” pistons steered the outer engines, and were supported on structures concealed inside the engine fairings. Each outer engine had two gimbal actuators, attached to its base by an open pyramidal outrigger. The kit provides each actuator and its engine outrigger as a single, poorly detailed part.

Revell 1/96 Saturn V gimbal actuators
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I used the kit heatshield as a gig to get the correct relative positions of each resin engine and its pair of actuators. Then I filled the open pyramid of each outrigger with clear glue, allowing the glue’s surface tension to gather it into a pyramidal tent-like structure—that was my way of reproducing the appearance of the real engine outriggers, which were wrapped in foil batting along with the rest of the engine.

After painting and the application of foil detail, here’s what the engines looked like:

RealSpace batted F-1 engines
Click to enlarge

You can see that the centre engine sports a couple of vertical rods in place of gimbal actuators. This engine was not steerable, but still had outriggers attached, which were supported by rods attached to the heatshield. I scratch-built outriggers and rods for this engine, since the kit neglects that detail.

The New Ware heatshield is light on detail, providing only the outlines of the various tiles. In reality, the heatshield was dotted with rivets and other details, which you can see in this view of the Apollo 11 S-IC:

Apollo 11 S-IC 69-H-365
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NASA image 69-H-365

Guided by this photo, and John Duncan’s excellent reference photos of the heatshield of the S-IC displayed at the Kennedy Space Center, I drew up and printed a set of custom decals, which I applied, tile by tile, to New Ware’s resin part.

NewWare S-IC heatshield, custom decals
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The next problem was the subsidiary heatshields positioned within each engine fairing. Both Revell and New Ware provide simple rectangles, supported at their outer corners by the base of the gimbal actuators. These certainly match the appearance in the Apollo 11 photo, above. But notice how many panels have been removed in the Apollo 11 view—engineers were gaining access to the interior of the Saturn V until late in the pre-launch period. So in fact, the whole interior of each engine fairing was eventually blocked off by a lunate heatshield built up of several panels—the rectangle in the Apollo 11 view is only the central part of a larger structure, as shown here:

S-IC Heatshield
Click to enlarge
From NASA-CR-153761 (1.6MB pdf)

The complete structure is visible in the S-IC at Johnson Space Center—see, for instance, this photograph by Kevin A. Boudreaux.

So I scratch-built replacement fairing heatshields using styrene sheet.

NewWare S-IC heatshield and fairing, scratch built additions
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A little experimentation with paper revealed that these needed to be cut from discs 22mm in radius, if they were to fit New Ware’s replacement fairings at heatshield level. (In fact, they should have been slightly elliptical, since the fairing heatshields were tilted a little from the horizontal.) These little lunes then got their own custom decals, reproducing what I could see of the panelling in various views of the JSC Saturn V.

Finally, the whole lot could be assembled:

RealSpace batted F-1 and customized NewWare S-IC heatshield
Click to enlarge

The Revell aft skirt also needed to be seriously modified, since it lacks hold-down posts. These were important components of the real launch vehicle, since they supported the entire weight of the Saturn V on the launch-pad, and at launch engaged with hold-down arms which prevented the Saturn V taking off until full engine thrust was achieved.

New Ware provides four resin parts, each of which requires a large, shaped slot to be fashioned to accommodate it. Starting with a series of hand-drilled holes, I expanded and shaped each slot before fitting the hold-down and epoxying it in place, only moving on to the next slot once the glue was dry.

Revell 1/96 Saturn V, preparing aft skirt 1
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Revell 1/96 Saturn V, preparing aft skirt 2
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Revell 1/96 Saturn V, hold down post in place
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Finally, a dry assembly to ensure that everything fitted together. Notice the internal fairing support struts, which are photo-etched parts from New Ware.

RealSpace batted F-1 and customized NewWare S-IC heatshield, dry fit
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Next time, I’ll complete my build of this stage.

Revell 1/96 Saturn V: S-II Aft Interstage

Having completed the S-II stage, I’ve worked my way down the stack as far as the S-II aft interstage—a ring structure interposed between the first and second stages to provide clearance between the S-II’s rocket engines above and the dome of the S-IC’s liquid oxygen tank below. We can see it being dropped astern in this video taken from the second stage of Apollo 4:
Also briefly visible in that video are the ullage rockets on the aft interstage, which were fired to shove the S-II forward just before its own engines fired. The whole stack was in free-fall between the shutdown of the first stage motors and the firing of the second stage engines, and there was concern that liquid hydrogen and oxygen would float around in the S-II’s tanks during this time, allowing gas bubbles to get into the mixture when the S-II engines fired. So the ullage rockets gave a little shove to the S-II, settling its fuel and oxidizer to the bottom of their tanks, next to the drainage piping, before the S-II engines were fired up. (Ullage is a nice old word originally referring to the air-space within a cask or bottle of wine. By extension, the unfilled volume in a rocket’s tanks is called ullage, and ullage rockets are used to make sure the ullage moves to the top, and the contents to the bottom.)

It turned out the S-II didn’t really need this precaution, and the number of ullage rockets on its aft interstage was reduced over time—from the eight visible on the Apollo 4 video, to four by the time of the Apollo 11 launch, and the last few Saturn V launches had no ullage motors at all on this stage.

So that’s the first problem with the Revell kit representation of this interstage—it has eight attachment points for ullage motors, and I only need four for my Apollo 11 launch vehicle. The second problem is that the kit parts for the ullage motors are the wrong size and shape—but I have New Ware resin replacements to deal with that. And the third problem is (predictably enough) that the attachment points are in the wrong places—Revell sites the eight ullage motors exactly on the principal axes of the Saturn V, whereas they were all displaced about 16 inches anticlockwise from those axes (looking down).

So all these mounting points have to go:

Revell 1/96 S-II aft interstage
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It’s a slightly harder job than disposing of the similarly misplaced mounting points on the aft skirt of the S-II, because these are big moulded structures that partially overlap the stringers on either side. So I first had to trim them level with the stringers, and then apply Dymo Tape to guide my razor saw and preserve the remaining stringer structure.

Revell 1/96 S-II aft interstage - removing ullage rocket locating tabs
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Then I used a 2mm chisel to remove all the excess plastic.

The other thing I needed to do was to mount the lower ends of the various fairings that I’d applied to the S-II. Many of these fairings extended across the flight separation line between the S-II and the aft interstage, and their lower ends were discarded along with the aft interstage (you can glimpse them in the Apollo 4 video, above). So I’d had to chop the ends off the New Ware resin parts when I mounted the fairings on the S-II stage. All these ends went into a pot, individually labelled, and now I was able to fit the interstage to the S-II and reunite all the severed parts (after chiseling away small parts of the stringers to make room for their attachment). There was also a personnel access hatch to be added, provided as a photoetch part by New Ware.

After priming, the final result looked like this:

Revell 1/96 S-II aft interstage - resin ullage rockets and fairings in place
Click to enlarge

I attached the interstage to the rear of the S-II again at this point, so that I could ensure continuity of the black stripes which begin on the S-II and extend across the interstage to the forward skirt of the S-IC stage. I got all the masking in the correct place, and then separated the interstage again for painting.

The interior colour of the Apollo 11 interstage is another source of doubt. The only colour images I can find come from early Apollo missions. Although the interior looks yellow (or even pink) in the interstage jettison videos of Apollo 4 and Apollo 6, it’s being subjected to the rocket blast of the S-II’s engines in these images. But there’s a clear view of Apollo 6’s aft interstage during the stacking process on the ground, which shows its interior with a metallic finish.

Apollo 6 aft interstage during stacking
Source: Image Ap6-MSFC-6758331

So that’s what I went with.

Revell 1/96 S-II aft interstage + New Ware details 1
Click to enlarge

I also added a flight-separation junction to the bottom edge of the interstage, using 0.5mm x 1.5mm styrene strip, which you can see in this view.

Revell 1/96 S-II aft interstage + New Ware details 2
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The lines along which the interstage separated from the S-IC stage below, and the S-II above, were slightly raised ridges, painted white, which provided clear visual lines of demarcation traversing the black stripes, even when the rocket was viewed from a distance:

Apollo 11 interstage
Source: Image Ap11-69-HC-622HR

My original plan had been to add styrene to the top and bottom of the interstage, but it became evident it would be easier and more secure to attach the upper flight separation line to the flanges on the base of the S-II. Here’s the result when the two are stacked together, which I think simulates the appearance of the real thing fairly well:

Revell 1/96 S-II + aft interstage + New Ware details 1
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Revell 1/96 S-II + aft interstage + New Ware details 2
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So now it’s on to the first (and for me, final) stage.

Revell 1/96 Saturn V: S-II Stage – Part 2

In my previous post of this build log, I eventually got the heavily modified parts of the Revell S-II stage assembled, and had replaced all the kit fairings with more correct versions from New Ware. A good coat of white paint brought all the disparate parts to the same shade, and then I added the black chequer pattern to the aft skirt, using the same masking techniques I used for the S-IVB aft interstage. Then it was time to add the five J-2 engines (which I prepared when working on the S-IVB stage) and the aft heat shield, supplied as a resin part by New Ware.

New Ware resin Saturn V S-II stage heat shield
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This heat shield was suspended about halfway down the J-2 engine nozzles, completely surrounding the central engine and housing the outer engines within cut-outs around its edges. Its job was to protect the underside of the liquid oxygen tank from the heat of the engines immediately below. Each engine was attached to the heat shield by a flexible skirt, to accommodate vibration and to allow for the steering of the outer engines. The New Ware resin part imitates these flexible skirts with rigid collars.

As I’d previously discovered when trying to fix up and paint the S-II thrust structure, the heat shield of the S-II is poorly recorded photographically. It seems to have been added in sections after the engines were installed—it’s certainly absent from delivery photographs of the S-II. And it’s omitted from the three surviving S-II stages that are on display.

One of the best photographs we have comes from the stacking of the Apollo 6 launch vehicle, though the flexible curtains are not yet installed:

Apollo 6 S-II heat shield
Click to enlarge
Source: Image Ap6-MSFC-6758331

Here we get a good view of the intricate support lattice that suspended the heat shield below the thrust structure. (You can also see a slab of something dangling off the underside of the heat shield—we can only hope it was a protective cover of some sort, rather than a structural component.)

In terms of colour, we have the interstage separation video from Apollo 4, which shows the upper surface to be brick red:
And for the underside there’s an image from the stacking of the Apollo 13 launch vehicle, slightly obscured by the presence of a work platform around the engines:

Apollo 13 S-II heat shield
Image archived at Ninfinger Productions as S-II_heatshield1_MOD.jpg.
(A screen capture of the Apollo 13 S-II heat shield from Spacecraft Films, originally posted by lindensims and processed to bring out detail by scottbro41.)

So it looks like the aft surface was very dark, if not black, and the flexible curtains were very pale, if not white.

That’s the colour-scheme I used, anyway.

The next problem was figuring out how to get the position of the heat shield correct, while still being able to insert all those support members. The solution I came up with was to epoxy the heat shield to the central engine, at the correct height (taken from David Weeks’s invaluable drawings). I built a little cardboard jig to keep things level while the glue set.

Assembling New Ware S-II heatshield
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A millimetre or so needs to be shaved off the protruding elbow of the engine’s fuel line to allow it to sit centred in the heat shield. I also used the fuel line as my landmark to get the heat shield correctly rotated, so that it would align with the other engines once assembled in place—careful dry fitting and a pencil mark was the low-tech solution to that problem.

After that, I installed the central engine and levelled the heat shield.

Revell 1/96 Saturn V S-II heat shield installation 1
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Revell 1/96 Saturn V S-II heat shield installation 2
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This gave me a nice space into which I could insert the support structure, a strut at a time, modelled in 0.5mm brass rod.

Revell 1/96 Saturn V S-II heat shield support installation
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Finally, the outer engines were set in place, and I added the various control packages provided by New Ware to the outside of the thrust structure. (In themselves, these are problematic, since there seems to be little consistency between the early Apollo 4 and Apollo 6 photographs and the three surviving S-II stages on display. I went with what New Ware provided, which was consistent with David Weeks’s drawings.)

Revell 1/96 Saturn V S-II aft assembly 1
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Revell 1/96 Saturn V S-II aft assembly 2
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The New Ware decals consisted of the vertical motion target (a black dashed line on the S-II which faced the launch tower) and four vertically printed “UNITED STATES” labels. All of these, being long and narrow, were excruciatingly difficult to get sitting perfectly straight and vertical. Eventually I hung a plumb bob from my modelling light, and used that to give me a vertical alignment against which I could gently nudge the decals into position.

Revell 1/96 Saturn V S-II 1
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Revell 1/96 Saturn V S-II 2
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Finally, I added the LH2 vent lines to the tank dome, so that they aligned correctly with LH2 vent valves on the forward skirt. (I also scratch-built a little rectangular telemetry package to sit on the tank dome.)

Revell 1/96 Saturn V S-II fore end
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And here’s the Position II view with the S-IVB aft interstage on top, just to check alignments.

Revell 1/96 S-II stage + interstage
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And that’s it for the S-II. Next up, the S-II aft interstage—which (you guessed it) needs considerable modification.

Revell 1/96 Saturn V: S-II Stage – Part 1

In histories of the Apollo programme, the S-II stage of the Saturn V is often referred to as “troubled”. There were difficulties with weight reduction that led to a delay in delivery of the first functioning S-IIs. That may be why Revell’s rendering of the S-II is so poor—it’s clear, from the paint scheme and other aspects of the model, that they were working from very early iterations of the Saturn V stack, and perhaps they didn’t get very long to look at the production S-II.

The main body of the Revell S-II comes in three parts—one piece for the forward skirt and the dome of the LH2 tank; one piece for the aft skirt, thrust structure and rear dome of the LOX tank; and a printed styrene sheet to be rolled into a cylinder to form the outer wall of the combined tanks.

The first problem with the forward part is a familiar one, if you’ve been following this build log—the locating strips inside the skirt, which engage with a gap in the flanges of the S-IVB interstage above, are misaligned, and need to be shifted so that the S-II is correctly aligned within the Saturn V stack. Unfortunately, the two features of the forward part that allow its orientation to be checked are in disagreement with each other, too—the notch that marks the location of the service tunnel is in the wrong position relative to the vent tubing on top of the LH2 tank. As described in my previous post in this build log, I chose to move the locating strips 11/16″ (17 mm)  to the right so as to get the service tunnel in the right place, and then went on to fill and smooth the circular depression that is the locating point for the vent tubing, which I’ll position correctly later.

Revell 1/96 S-II locating strips
Click to enlarge

I also removed the raised edges of the fifteen gores into which the kit divides the tank dome, and replaced them with the correct number—twelve.

Next, there’s the problem of the appearance of the tank dome. The Revell kit has an odd annular structure surrounding the dome, which doesn’t appear in David Weeks’s excellent Saturn V drawings set. It turns out to be difficult to check against reality, because finding an image of the front end of a complete S-II ready for launch is remarkably difficult. They were generally moved around with something called the Forward Hoisting Frame Assembly attached to the top end (there are some nice images of that in action over at Heroic Relics), which completely obscured the LH2 tank dome. And when the Saturn V was being stacked, the photographic views show the underside of the S-IVB being lowered into position, rather than a top view of the S-II. Two of the three surviving S-IIs on display have the Forward Hoisting Frame still attached, leaving the one at the Kennedy Space Center providing the only clear view. It’s a late model, from the cancelled Apollo 18 mission, by which time the method of insulating the LH2 tank had changed, but it’s the best I can find. There’s no structural ring around the tank dome. (That said, displayed Saturn V stages often omit components, like the S-II heat shield, which were added only late in the stacking process.) I suspect Revell have mistakenly moulded in a removable work platform or handling ring, but unfortunately it’s impossible to remove without having to scratch-build a new tank dome.

New Ware Saturn V Detail KitOne thing I could fix is the fact that the stringers on the kit’s front skirt extend too far back. On the real thing, they disappeared into an odd raised external cuff of insulation surrounding the top of the LH2 tank. So I took my measurements off David Weeks’s plans, created a demarcation line around the forward skirt using Dymo Tape, chiselled and sanded to remove the offending parts of the moulded stringers, and then created the appearance of the insulation by wrapping with a couple of strips of styrene sheet. While I was at it, I removed stringers from a few more areas, so that I could later add New Ware’s photoetched details (a personnel hatch, LH2 vent valves, and telemetry antennae). Here’s what I ended up with:

Revell S-II fore 2
Click to enlarge

Finally, a puzzle—the right colour for the tank insulation. Again the lack of contemporary colour photographs makes it difficult to know. The material covering the Kennedy Space Center S-II tank has aged to a shade of brown, but the fresh finish is generally described as having been yellow. Many modellers use a zinc chromate yellow-green finish, which was widely applied as an initial coat to protect the metalwork of Saturn V components, and which was certainly applied to the bare external metal of the fuel tanks. However, David Weeks’s drawings contain this piece of information:

Exterior of LH2 tank dome is covered with insulation and is painted FS 33558 Orange-yellow.

That’d be handy, except for the fact that there is no Federal Standard 33558 colour. There is, however, an FS 33538 orange-yellow, and I assume that’s what was meant. I used the Luftwaffe’s RLM 04 Gelb, which appears to be a close match.

If the front assembly is merely inaccurate, the rear assembly is a disaster. Really, Revell should have moulded this in at least two parts—the aft skirt and tank dome; the hollow conical thrust structure and cruciform engine support. Again, there’s nothing short of massive scratch building that can fix the unrealistic wall within the thrust structure, or the fact the cruciform is plastered on to the tank dome, rather than standing free.

The stringers on the aft skirt extend too far forward, so again there was a need for Dymo Tape, chisel and sandpaper to trim them back to their correct extent.

And the aft skirt should also bear a number of fairings protecting various bits of prominent piping—Revell manage to place a few of these, but of the wrong size, shape and position. I can replace the kit parts with more realistic resin parts from New Ware, but first I needed to get rid of the attachment points for Revell’s aberrant LH2 feed line fairings (only one of which aligns with the pipe on the thrust structure it’s supposed to be supplying), and fill the gap left by Revell’s LOX vent fairing.

For reference, here’s the offending item in its raw state:

Revell S-II aft 1
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Having first trimmed off the forward part of the stringers, I then applied myself to getting rid of the raised fairing attachment points. I protected the stringers on either side with Dymo Tape, then used a razor saw and a 2mm chisel to remove the offending part and restore the gap between the stringers.

Revell S-II aft 2
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Revell S-II aft 3
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Revell S-II aft 4
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The vent fairing gap was repaired with white filler, and the missing stringers rebuilt with 1mm styrene strip.

The thrust structure in the real world bore a number of control packages, which are supplied in resin by New Ware. Unfortunately, the Revell thrust structure has one little moulded package in place (at the left side of the image above, in partial shadow), which bears scant resemblance to anything in the real world. It’s also impossible to fully remove without leaving a hole in the thrust structure.

Saturn V axesAfter a bit of pondering, I decided to rotate the entire kit part through 90 degrees anti-clockwise (when looking down from above the Saturn V). This moved the remnant of the unrealistic package from a location next to the A-quadrant engine to the same position in the B quadrant, where it can be almost completely concealed under an engine actuator assembly and an electrical system assembly from the New Ware detail set.

All that was required to achieve this rotation was to fill and sand the locating slot for the service tunnel, and to remove the (in any case unrealistic) attachment points for the central engine, which needed to be counter-rotated through 90 degrees to restore its correct alignment with the rest of the stage. After all I’d already done to this kit part, that was a completely trivial task.

Then I used a grinder to remove the spurious moulded pipework that bedecks Revell’s version of the rear tank dome (just achievable, with care—the plastic was so thin in places that it was translucent by the time I’d finished). I added my own pipework using styrene rod—the LOX fill line, and the LH2 feed for the centre engine, both of which had been omitted by Revell. Then, with the orientation of the aft skirt pinned down, I was able to do a final bit of chiseling to make space for the fairings, umbilical connections and the new position for the service tunnel.

Here’s the final item, still some way from being entirely accurate, but a great deal better than I started with:

Revell S-II aft 5
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The correct colour for the thrust structure was another problem. Again, photographs of the final assembly are rare, and apparently restricted to the S-II stages of Apollo 4 and Apollo 6. The Apollo 6 S-II thrust structure looks sort of white-ish in the NASA image. A good quality photo at Drew Ex Machina (scroll to about halfway down the post) shows the S-II of Apollo 4 with a metallic yellow-green thrust structure. The thrust structure of the very early S-II displayed at Huntsville is flat green, while the late models at Johnson and Kennedy are white.

Essentially, then, I’ve scant idea what colour I should use to realistically depict the SA-506 launch vehicle of Apollo 11. In the end, I mixed up a pleasing yellow-green shade using Tamiya Cockpit Green and Titanium Gold, which ended up about halfway between Apollo 4 and Huntsville*.

The pre-printed styrene sheet that connects the fore and aft skirts was only a little problematic. As with the S-IVB stage, I turned it inside-out so that I could paint it uniformly white and then apply New Ware’s decals. It’s supposed to be held in shape by pins on the service tunnel assembly, but that would leave an exposed edge visible. So (again, as with S-IVB) I glued it together and filled the locating holes, so that I could completely cover the edge with the service tunnel part. At this point, I discovered that aligning the locating holes properly resulted in a part that was very slightly too small to fit on to either the fore or aft skirt. So I pried it gently apart, and reassembled with holes misaligned by a half millimetre or so.

Revell S-II styrene
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Finally, the whole thing fitted together, and I was able to start placing New Ware’s resin and photoetch details.

Revell S-II assembly 1
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Revell S-II assembly 2
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Revell S-II assembly 3
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I’ll pick up the story from there, next time.


* While I was at it, I revisited the thrust structure of the S-IVB stage, which I’d previously left with a greenish metallic tint that looked right in some lights and very wrong in others. The real colour for this structure seems to have been about as variable as that for the S-II. I’m slightly more satisfied with the Tamiya recoat.

Revised S-IVB thrust structure colour
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Tamiya 1/48 P-47D Thunderbolt “Razorback”: Part 3

At the end of my previous post in this build log, I’d got the main body of the aircraft ready for final weathering and the placement of details like the propeller, external fuel tanks, undercarriage and guns.

The propeller is the Hamilton propeller (and associated decals) that comes with the kit, despite the fact it’s not required for either of the aircraft the kit instructions depict. (Thanks for that, Tamiya.) It has a red hub, because the aircraft belonged to ‘A’ Flight of 135 Sq. RAF, who gave their ‘A’ Flight aircraft red hubs, and their ‘B’ Flight aircraft blue hubs.

The external fuel tanks were filched from another kit, Tamiya’s P-47M—I wanted the big 150-gallon (US), rather than the smaller options available with the P-47D kit. The undercarriage was detailed with more Eduard photoetch parts and placards, and a set of resin wheels from Squadron.

They ended up looking like this:

Tamiya P-47D accessories
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I went on to weather the propeller slightly, with gentle metallic dry-brushing along the leading edges to simulate paint wear, and some pale LifeColor Liquid Pigment to the rear surfaces. (Real propellers are counter-intuitively dirtier on the back than on the front—the low pressure airflow across the front surface keeps dirt away from the propeller blade, while the high pressure behind concentrates the airflow and grime.)

I used the Tamiya decals for the fuel cap and label on the external tanks, and immediately regretted the label—it’s quite clearly marked as being for a 75-gallon tank. I went on to dull down the bright metal of the tanks a little—the real items were stored in heaps, sometimes outdoors, so they wouldn’t retain that factory-fresh look for long. And, during the weathering process, I decided I rather not have the labels than have the wrong labels, so they ended up in the bin.

With the tanks fitted to the wing pylons, I had one last detail to add to them. Because of worries about a dropped tank flipping in the airflow and striking the rear edge of the wing, the wing pylons were equipped with spring-loaded fork arms. These were deployed to pressed down on the rear of the tanks, and then they snapped up to a stowed position along the back of the pylon after the tank was released. The Tamiya kit provides these in the stowed position, as part of the pylon moulding. I’d previously removed these, and now I was able to add an Eduard photoetch part to depict the fork arms in their deployed positions. (I’m not convinced the Eduard arms are the right length, when compared to photographs of the real thing, but they were acceptable.)

Tamiya P-47D drop tank with Eduard spring fork arm
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The guns mounted in the wings fired through metal blast tubes. While a photo of 135 Squadron Thunderbolts exists showing the blast tubes painted white to match the SEAC white stripe on the wing, this seems to have been taken very soon after the SEAC markings were first applied.

135 Squadron Thunderbolts
Click to enlarge (You can just make out the spring-loaded fork arm on the drop tank, too)
© Imperial War Museum (CF 201)

I have photographs from later in the war, like the one below from my father’s photo album, which show bare metal tubes—I suspect the paint flaked off the stainless steel tubes fairly quickly.

135 Squadron RAF, 1945
Click to enlarge (Note the casually placed bomb)

Once the blast tubes were in place, I added a little smoke staining to the white SEAC stripe. I concentrated this on the underside, streaming back from the cartridge ejection chutes, and around the muzzles of the two outermost guns, which open almost flush with the wing edge. Some modellers depict four matched, parallel streams of smoke-staining on the upper wing, behind the guns, but this makes little sense when the gun muzzles protrude beyond the wing leading edge. The air stream crossing the upper wing is ascending as it crosses the gun muzzles, and will carry smoke in an arc above the wing, rather than across its surface. Photographs of the real thing generally show minimal staining of the upper wing, for the same reason the front of the propeller tends to stay clean.

Then a little weathering to the wing roots and the fuselage on either side of the cockpit, again with some metallic dry brushing to simulate paint damage. A few flecks of silver around the edges of panels that would be frequently removed (engine cowling, guns) and along the wing leading edges behind the propeller. And then some pale grubbiness at the wing roots and behind the gun panels, where the ground crew would have walked most frequently.

The last touch was to add a strand of stretched sprue to simulate the radio antenna.


The final model is as close as I can get to the appearance of HB981 on the morning of 2nd May 1945, when she took off from Akyab Main to perform “cab rank” duties for the Operation Dracula landings at Rangoon. (That is, the aircraft would loiter above the landing zone, using fuel from their external tanks, so that they could be called in at short notice to strafe any Japanese positions resisting the landing.) But instead of carrying on south with the rest of the 135 Squadron aircraft deployed that morning, HB981 lost power on take-off and ground-looped off the end of the runway, tearing off both wings in the process. The pilot (my father) hopped out of the cockpit unscathed, and then hopped back in again to retrieve his parachute (it was a chargeable offence to lose a parachute), before walking back to the end of the runway and having a seat (on the parachute) while he waited for a vehicle to come and get him.

Soon afterwards, he was photographed standing on the wreckage. The photograph then had a hectic life of its own, sustaining a lot of surface damage before being accidentally torn in half. My father then seems to have rephotographed the torn halves, before adding the picture to his wartime photo album, marked “My Crash”.

Crash of HB981, May 1945
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His crash even made it into the textbooks. In Thunderbolt: A Documentary History Of The Republic P-47, Roger Freeman narrates the story with some amusement (p.77):

Roger Freeman, Thunderbolt: A Documentary History Of The Republic P-47, p77
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The squadron number is wrong (135 didn’t renumber to 615 until later in the war), my father’s name is spelt wrongly (a common error) and the story has grown a little in the telling.

But here’s what HB981 would have looked like, I think, before it got so dramatically bent.

Tamiya 1/48 P-47D "Razorback" (5)
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Tamiya 1/48 P-47D "Razorback" (3)
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Tamiya 1/48 P-47D "Razorback" (1)
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Tamiya 1/48 P-47D "Razorback" (4)
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Tamiya 1/48 P-47D "Razorback" (2)
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Tamiya 1/48 P-47D "Razorback" (7)
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Tamiya 1/48 P-47D "Razorback" (6)
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Tamiya 1/48 P-47D "Razorback" (8)
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And finally, a comparison with the Hurricane IIC I built earlier, showing what a brute the Thunderbolt was in comparison, and why RAF pilots, used to Hurricanes and Spitfires, claimed that the easiest way to avoid enemy fire in a Thunderbolt was to get out of your harness and run around the cockpit:

Comparison of Thunderbolt & Hurricane
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