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Qantas 747-238B

This is a 3D printed 1/100 scale model of the first Qantas 747-238B, VH-EBA, City of Canberra, which Qantas took delivery of at the Boeing factory on the 8th July, 1971. It was the 35th aircraft delivered to Qantas by Boeing, and Qantas’ first 747.

Qantas originally ordered four 747-100 aircraft in October 1967, but cancelled the order and replaced it with an order for four 747-200 planes in june 1969. As Qantas was Boeing customer 38, this model of 747 was designated 747-238B. The ‘B’ designated the passenger version; F was the Freighter model; C was the Convertible passenger/freight model; M was a Combi model operated by KLM and UTA French Airlines.

VH-EBA operated its first revenue service on 17th September, 1971, on the Sydney – Perth – Singapore route. It’s last revenue flight with Qantas was on 23rd February 1984 from Sydney to Christchurch and back.

Source Files

The 3D .stl file was obtained from the Printables website, from a designer named Clerx. The files were for a 747-100, at 1/144 scale. The main and obvious difference between the 100 and 200 models, is the number of windows on the upstairs cabin in ‘the hump’. The 747-100 has only three windows per side, whilst the 747-200 has ten windows per side. Boeing later undertook some ten-window 747-100 retrofit conversions for some operators. 

Not so obvious to the casual obrsever, was the difference in engines. The 100 was equipped with a choice of four Pratt & Whitney JT9D-3A or 3AW engines, or Rolls Royce RB211-524C2 engines, but this Qantas 200 was delivered with four P&W JT9D-7A engines. Additional Qantas deliveries were supplied with either four P&W JT9D7 or four Rolls Royce RB211-524B2 or D4 engines.

Clerx made a ‘747-200 upgrade’ .stl file kit available, featuring a replacement front fuselage section and a choice of replacement P&W JT9D, RR RB211-524 or General Electric CF6 engines.

Printing

All prints were made on a Snapmaker A350, unsing PLA+ filament. Original .stl files were 1/144 scale, but I scaled the parts up to 1/100 in Snapmaker’s slicing program Luban. The result is a completed model of 706mm in length.

Final 1/100 model is 706mm long – bike helmet for scale!

Primer Paint

In the interests of time, I chose to print the model using ‘Fast’ settings (and it still took over 50 hours!). The trade off for speed is surfce quality, resulting in visible print layer lines and other surface anomalies which all needed to be smoothed and filled with a number of coats of automotive primer, with wet-sanding between coats. Dry sanding clogs the sandpaper and produces a lot of plastic dust.

 

All coats were applied with the wings, horizontal stabilisers and tail in place, but not glued. This was done to keep paint off the joiining parts, where plastic to plastic contact was required for gluing. I decided not to glue the wings in permanently, in order to make storage and transport easier if needed.

Different coloured primer was used in between coats to make identification of areas needing more attention during the sanding and priming process easier. Gently rubbing over the model with finger tips was also useful fo gauging smoothness.

Top Coats

At least three coats (I lost count!) of top coats were applied.

In order to make a line along the fuselage to act as a masking border between the white upper and silver belly, the most effective technique was to place the fuselage on a table and to use a pencil supported at the right height on a pile of Post-It Notes, and then move the fuselage around. Having the pencil stationary produced a neat consistent height line that wasn’t possible by doing it the othe way around i.e. by moving the pencil around the stationary fuselage.

Masking along the pencil line, using Yellow Frogtape, which is specially made for delicate surfaces and won’t pull the underlying paint off when removed. The purple tape is regular masking tape,  to keep paint out of the wing sockets and to affix a paper mask to the top.

Masking the belly for painting grey, shown with a full-size paper print of the starboard wing (more about that later).

Control Surface Details

With the wing, tail and horizontal stabiliser surface painted with many coats, all control surfsce detail was obscures and had to be replaced. Full size paper prints of the shape were made showing all the lines that needed to be created on their relevant surfaces.

The initial transfer idea was to backline the paper print with a 7B pencil, effectively making the paper into carbon-backed paper, which could be drawn over to transfer the image of the linework. Unfortunately this didn’t work very well as the resultiing carbon image wasn’t very visible against the silver paint.

A more effective technique was to use a spiked wheel to transfer a series of small guide holes to the plastic surface, which could then be drawn along with a sharp metal spike to inscribe the lines.

The resulting hole line-guides

Scribing linework using a sharp tool that was part of a jeweller’s scewdriver set

The inscribed lines were deep enough to survive more sanding and paint touch-ups, and it was easy to scribe off any excess paint.

A wing after masking and spraying with grey, leaving the silver spar. Scribed control surface lines are still visible.

Ready for decals. The tail still to be painted red, but the leading edge will remain silver.

Masking and painting the tail. 

Decals

Usiing a great number of photos as reference, I drew the decals in Adobe Illustrator and initially printed the sheets on paper using a colour laserprinter. The shape of the windscreen and the ochre stripe where it wraps at the rear, required much trial and error and re-drawing. I was resigned to the fact that the stripe decal would not bend around the nose, so decided to terminate it a couple of cm behind the nose and paint the remainder with a bruh.

The paper sheets were cut up for test fitting,as shown below with an original 1971 Qantas postcard.

Once happy with the fit of the decals, they were printed onto water transfer paper. Shown below, is a print onto a laser transfer sheet, and below it, an inkjet transfer sheet. Printed from the same file, the colour differences are striking. I decided to use the laser printed water transfer sheets as the ochre colour seemed to be a closer match to most reference photos I have seen.

As I don’t have a printer capable of printing white, I sent the kangaroo tail decal artwork to an online service as an A4 size PDF. They were able to print a page of kangaroo decals onto a water transfer sheet using a special laserprinter with white toner.

Applying the decals was delicate work, requiring a steady hand aided by tweesers and a small water-soaked paint brush.

The Stand

The provided stand .stl file may have been OK for the original 1/144 scale it was designed for, but didn’t look like it would support the extra weight of the 1/100 scale model. I adapted a stand I had previously designed for my 707, 727 and 787 models, adding a vertical support and a horizontal plate at the top to bear the extra weight and to allow for the hole in the fuselage not being at the model’s centre of gravity.

Adapting my existing stand design in Lightwave 3D

Printing the stand base and vertical support. The horizontal plate was printed separately and Superglued into place at the top of the stand, allowing the mounting tab to protrude through the top. Upending the stand and mounting plate into a bucket of baking powder set any excess glue and powder like rock, strengthening the bond. The mesh visible in the base is support material, yet to be removed, left over from the printing process. I decided to leave it in place as a bit more weight in the base is probably a good thing.

The Finished Model

Before and after hand painting the stripw around the nose. The base colour was Humbrol Matt 82 Orange, with a bit of Matt 15 Yellow and white mixed in to get a close match to the laser printed ochre decal stripes.

Comparative side of the 747-200 with my 787 Dreamliner; both 1/100 scale.