Airfix 1/72 Mosquito prototype


As a gift for a friend, I'm building the prototype Mosquito, as it appeared on its first flight. It then had the factory serial E0234 (later replaced by RAF serial W4050) and was RAF Trainer Yellow overall.



Mosquito kits in 1/72

The Airfix Mosquito is a rather dated model, but it was the best available at the time I started this project. I found a kit review in the March 1973 issue of Aircraft Illustrated. Overall the reviewer considered it a vast improvement over the previous Airfix Mosquito, and the best Mosquito yet. His criticism centered on the plan view of the fuselage, more specifically the tapering of the fuselage. This tapering should start at the rear spar, but on the model the tapering starts at the wing's trailing edge. This results in a slightly 'fat' fuselage, and the inboard side of the flaps don't have the required 1.5 degree angle. Also, the model has small fairings inboard of the flaps that shouldn't be present. Lastly, he judged the wheels and landing gear to be too wide and too small in diameter, giving a balloon appearance.

I built my model from the Airfix kit, using some components from a Matchbox Mosquito I got from fellow modeller Berry. The kit represents the fighter version and needs many modifications to bring it back to the original prototype bomber configuration. Apart from the bomber nose and canopy, the nacelles that are shorter at the rear are the most obvious modification. The Airfix model is quite old and rough, and needs quite some attention to make it look nice. I did all the conversion work myself; about halfway through, Paragon introduced a resin set, but I decided against buying it. It is a nice set though, see the end of the page.

Even worse (for me) was that both Hasegawa and Tamiya issued 1/72 Mosquitos some time later. Of course these models are much nicer and more detailed than the old Airfix kit, but I had progressed too far with my Airfix model to switch to these new models. The new models do have their problems however. Personally I would not build the Tamiya kit. Its detailing is really fantastic, but the overall shape is pretty bad. The rear fuselage is too much of a straight cone, the vertical tail is not correct, and worst, the radiator part of the wings is way too long, spoiling the fine lines of the Mosquito. I've also heard the comment that the forward fuselage is too thin (skinny). The Hasegawa Mosquito is much better shape-wise, but has little detailing. It seems it has a more correct fuselage shape than the Airfix kit. However, the cross-sectiom ahead of the canopy is way too square on the top side, the two fairly strong folds should not be present. The Hasegawa model would now be my clear choice when building a 1/72 Mosquito, but I would add some detailing sets.



Construction

  Here's an overall view of the model, halfway construction. It shows the Matchbox 'bomber' nose attached to the Airfix 'fighter' fuselage. The cockpit opening was reduced to the size of the Matchbox canopy (some 3 millimeters shorter at the rear side). Some Milliput was needed to make the different canopy fit properly to the fuselage.

It also shows some of the scratch built cockpit interior. I started with putting in a wing carry-through structure (the torsion box), made of a flat front spar and a curved upper skin. This can be seen painted interior green.

The horizontal tails were replaced by Matchbox ones, which had a much nicer fabric effect. I shortened the tails some 2 millimeters on the root side, since the prototype flew with smaller tailplanes for a while. The front of the nacelles is completely smooth, a small manifold exhaust still has to be added.
The left wing, showing the unique lay-out of the prototype's flaps and engine nacelle. The flap is a one-piece item, made possible by the short nacelle. The nacelle however created much turbulence that hit the tailplane, and was thus quickly lengthened (in two steps). Since I wanted to portray the prototype during the first flight, I built the short nacelle. The flaps (and the whole wing) were scribed, and all raised detail was removed. The wing tips were shortened and given a new 'square' contour. Wing tip lights (two each) have to be added.

This picture also vaguely shows some more the scratch built cockpit interior. After building the wing structure, I glued in the original Airfix floor. Next the front end of the bomb bay was built from plastic card. I removed the wing roots that intruded into the cockpit. The kit's instrument panel was cut back considerably and glued in. Just visible in the picture is the rectangular hole in the cockpit floor that leads to the cockpit hatch.
 
  Underside view, showing the shortened nacelle rear ends. These were made by cutting off the rear end of the kit nacelle, and gluing a small part of this back in place. The whole area was then filled with Milliput and sanded into shape. The rear of the nacelles show some sanding. Note that the upper rear part of the nacelle would move together with the flap, and slide into the lower rear part of the nacelle. The rear part of the wheel opening is covered by a curved piece of plastic sheet. Some 95% of this will be carved away, to leave a slightly rounded edge of the wheel well opening. The radiator flaps were thinned considerably.

Also visible are the bomb bay doors, which were converted to single piece doors (Airfix has two piece doors). In front of the bomb doors a hole was drilled for the cockpit access hatch. Scribing of the hatch was done afterwards.
The next big task was the canopy. I needed a bomber canopy, but the Matchbox canopy (seen on the left) had a blister in the escape hatch, instead of in the side windows. I bought the Aeroclub vacform Mosquito bomber canopies, but these were of low quality and had very vaguely defined side blisters. The only solution I saw was vacforming one myself, something I hadn't tried before. Note that this all happened before Tamiya and Hasegawa decided to issue their 1/72 models.

I definitely wanted to do female vacforming. I had done some heatforming over positive moulds, but the results were not very convincing. Female vacforming requires a negative mould, so a lot of work would be in order. The amount of work was quite silly to be honest, but I had long wanted to try vacforming, so I went ahead. First thing to do was to make a master. The Matchbox canopy was incorrect for my purposes, due to the top blister. Also, I had found out that the Mosquito canopy features many internal frames, and the Matchbox canopy had too many frames on the outside. I made a silicone rubber mould of the Matchbox canopy, and cast an epoxy copy in it. This copy was sanded down to remove all frames, and then 0.1 mm thick aluminium foil strips were used to build fewer new frames. The black canopy in the middle was the test bed for this technique. The master was then painted, as seen on the right. The windscreens are probably not 100% correct, being too tapered.
 
  Having a master, I had to make one more step before making the glass fibre negative mould. The problem was that my master canopy had undercuts, which would prevent releasing it from the hard negative mould. Therefore I made a silicone rubber mould using the master. In this mould I cast a special thin-walled copy. The thin walls would allow me later to bend the master slightly to make it release from the glass fibre mould. The thin-walled copy was filled with clay, and put on a piece of sheet metal, all of it wiped with release agent. A blue gel coat epoxy was brushed over this, followed by small patches of glass fibre and epoxy to make a hard mould. After curing tiny 0.3 mm holes were drilled in it, for air evacuation. The result can be seen on the left.
I hadn't figured out completely how to actually do the vacforming itself, but I found a really simple solution. First the mould needed some sort of air box beneath it. I built this from a piece of aluminium square tube and a piece of sheet aluminium, stuck together with Terostat tape (aka Tacky Tape). A small hole was drilled and a nozzle added, and it could be connected to a vacuum pump.  
  The vacforming itself was very simple. I put Terostat tape around the edges of the mould, and stuck a piece of polycarbonate sheet on it. This was then heated with a heat gun (paint stripper) until soft, after which the vacuum pump was switched on. Voila, one canopy. It took a few canopies to find the right heating time. Unfortunately, the first products had lots of bubbles in them. This turned out to be absorbed water, boiling during the heating phase. Drying of the sheets at 100 degrees C solved it completely. From then on the canopies were close to perfect. Not quite the level of Falcon vacform canopies, but the canopies were of pretty good quality.
The canopy story isn't finished yet though. The side blisters are still lacking. I didn't dare to incorporate them in the canopy master, because both the master and the vacformed copies would have never released from the mould. So I decided to make the blisters separately, and add them later to the canopy (another challenge). Seen on the right is a epoxy copy of the blister master.  
  One last detail from the cockpit is the pilot seat. I built it from plastic card and some strip. Seat belts still have to be added. Under my new vacformed canopy it is very clearly visible!
Tyres! After studying photos of E0234 I decided that True Details' Mosquito tyres were the best choice. They are very nice detailed, but they were egg-shaped for some reason, and the bulges were horrible. I decided to modify one tyre to get rid of the egg-shape and the bulges. It wasn't easy at all to make the tyre round and unbulged, and it took me three rounds of modifications and spray-painting before it looked flawless. I made a mould of this modified tyre to cast two copies. The original TD set is shown on the right side of the photo, the improved version are on the left, in clear epoxy. I think it was worthwhile.

Unfortunately, I later found out the wheels were still not completely correct. True Details modelled spokes on both sides of the wheel, forgetting that at least one side should show drum brakes. The spoke detail on one side was drilled out, and a discs cut from plastic card were glued in their place. I also cut openings the wheel bottoms to install small nuts. This will ease mounting the model on a base later.
 
  One more detail of E0234 that required scratch building and casting are the exhausts. E0234 had smooth nacelles, with internal manifolds, exiting in small single exhausts on each side. I made a master from a piece of tube and card, followed by lots of Milliput and spray painting. The master was glued on a strip of plastic card, and another silicone rubber mould was cast. The master and four copies can be seen in the photo.
And then it turned grey again. I decided to paint the model grey, because it is much better suited for finding small building defects. And I found plenty of building defects, that I did not see well with the yellow paint applied. That also means that my model will look very well-built once painted yellow again! :-) The photo also shows the exhausts fitted to the model.  
  Some examples of building defects are visible here. My scratch-built nacelle rear end wasn't smooth at all, and required more sanding. The inboard end of the flap needed some Milliput, and the scribing of the rear hatch wasn't very tidy.
More sanding. Here the wing tip, that showed a small step. The outboard side of the aileron had a very wide panel line, that was filled with Milliput and rescribed. The scribed slat can be seen here too. After this round of improvements, the model was given another coat of grey paint to check progress. It took a few more rounds of touch-ups and repainting before the model started to look really smooth, and all panel lines were up to standards. It was fun seeing the model getting better and better.  
  The most difficult aspect of this model are the plans I had with the canopy. Most Mosquito model canopies are wrong in a sense that they have panel lines in places where there are only internal frames. On my master canopy, I had left off these panel lines, and I planned to build an accurate internal frame inside the vacform canopy. I feared that this would be difficult, and difficult it was indeed! It cost me many, many hours to fit the three transverse frames seen in the photo. The canopy is a very tight fit around them. Using these three frames as a basis, I will now add the longitudinal frame parts. One is already fitted between the middle and rear frames. The model was painted one more time meanwhile, in a medium grey this time.

At this advanced point I had to make a tough decision: I decided to scrap the vacformed canopy. The reason is that I made the master's windscreen windows too small (take a look at the tan master), and this has too big impact on the appearance of the model. It's like a portrait painting where the painter got the nose wrong. I long had my doubts about my windows, and I don't want to find out after painting that they are indeed wrong. A Tamiya canopy was ordered from Japan. It was quite a job to make the somewhat smaller Tamiya canopy fit on the Airfix/Matchbox fuselage, but after many hours it finally fitted like a glove. I decided to use a Hasegawa bombardier's window, if only to make this officially a four kit kit-bash :-) The small side windows were taken from the Tamiya sprue, and I was very pleasantly surprised to find that their contour matched my fuselage well.
A long time afterwards I found another possible solution. Rob Taurus from the Czech Republic produces aan amazingly sharp and clear vacformed Mosquito canopy. It even has integral side blisters.  
The landing gear was another difficult item. The landing gear legs are too long, and I modified the parts so they would sit 2 mm deeper in the wells. They are pretty wobbly if you can't glue them together for fitting, and making them fit was a frustrating experience. In the end I put brass pins in the legs, that fit in corresponding holes in the wheel wells. I can now try to align everything. The photo shows a test fit of the legs and the modified True Details wheels. It may look a bit strange because the doors are missing.


Markings

For a long time I searched for decals for the serial number, but I never found any. But then I found a solution in Alps decals. I learned how to prepare decal artwork with vector graphics: starting with an RAF font found on the internet, I reworked every letter and number to make them identical to what I saw in the photos. And here they are: my own 'E0234' serial numbers, Alps printed by Luca Beato! Also visible on the sheet are decals for some other modeling projects (BD-5J, X-1 and RF-84F).

A set went to Scott Bregi, who was building the prototype too. His Tamiya-based model can be viewed on Hyperscale. After a lot of puzzling I also found the sizes of the roundels:

The lower wing Type A roundels are not available in 54" so I will have to use 50" roundels instead. The 1.4 mm difference is acceptable I think.



Resin conversion parts

Paragon Designs from the UK once produced a resin conversion set for the Mosquito prototype (catalog number P72028). It is long out of production. The two photos below were borrowed from the Luchtvaart Hobby Shop / Aviation Megastore.





Modeling links

I found a few other models of the Mosquito prototype:





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