Douglas DB-7 Boston

by J.D. King

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Here is a 1/48 scale Douglas DB-7 converted from 1/48 scale A-20C Boston. The kit is very similar to AMTs earlier releases of the G and J model A20’s. The fuselage, nose section and carburettor intake housing sprues are the most noticeable, and required, changes.

Similar standards to the later variant are maintained - finely engraved surface detail, basic internal fittings and good clear parts. It is of note though that problems in the earlier kits of difficult nose section and tail surface joins remain, along with the very weird main wheel tread pattern. Methods of remedying these problems will be discussed later in the article.

Primary areas of attention for the conversion revolve around the engine cowling and exhaust and the nose section. RAAF DB-7’s were delivered with clear glazed nose sections for the Navigator/Bomb aimer’s station, and the standard four gun (30 Cal) armament. Like many USAF aircraft these were converted in the field to eight gun noses and the third crewmember was removed. Additionally the DB-7B’s cowlings were fitted with fixed vents following the lower centre line and a single exhaust port on each nacelles outboard side. The remainder of the conversion is simply based around enhancing or correcting the kits detail.

Internal

Internally the most effort was expended in enhancing the kit detail. In the cockpit enhancement was provided by the addition of seatbelts made using masking tape and finished with some PE buckles. Wiring was added to the sidewalls and floor and the small panels mounting fire extinguisher controls to the lower instrument panel. A small hand held extinguisher was scratch built and added behind the pilots seat.

As I wanted to display the canopy open enhancement of the life raft bay was required. Sidewalls were drilled and fashioned from sheet styrene. The inside of the hatch was enhanced by drilling out the weight saving holes, adding a sun screen made out of fine wire and tin foil, and scratch building some internal details and latches. The bay was finished with the addition of a scratch built life raft, in hindsight the available resin accessory would have looked better.

The mid-upper crew position required a little more effort.

Internal ribbing was scratch built along with racks for ammunition boxes. Visible cabling was added, as was controls for the opening of lower hatches. Seatbelts for the crew station similar to the cockpit were added and the barrels for the twin 30 Cal guns were replaced with hypodermic tubing. Careful washing and dry brushing completed the respective cockpits.

Fuselage and Nose Section

The fuselage was joined without incident once some small guides were made for the bomb bay doors. At this point I added the horizontal tail surfaces, vertical surfaces would follow later. The hole at the rear of the fuselage was covered with styrene and the clear tail light cover added. These were then sanded and polished to an acceptable finish. Work now commenced on the nose section.

In this area lots of dry fitting saved my bacon. It was found that the two piece lower nose was smaller than the fuselage width, but the glazed section was the right size. My solution was to add a 2.5 mm spacer between the lower sections and join these to the clear before fitting to the fuselage.

No filler was required between nose and fuselage but some sanding of the clear parts was required. This sanding removed some of the raised detail on the clear parts, and as a result I removed it all. The conversion to an 8-gun nose replaced plexiglass panels with aluminium ones so preservation of a clear surface was not required. The raised detail previously removed was replaced with very fine masking tape and sealed with a clear varnish. Four holes were drilled into the forward flat surface of the section and all 8 MG barrels were replicated with hypodermic tubing.

Work now commenced upon the wings and tail.

Wings and Tail

To make the vertical tail surface accurate a little effort is required. Firstly the two kit rudder mounts were hollowed out with a scribe. Two small triangular pieces of styrene were then added to replicate the flat rudder mounts. A scratch built two piece housing for the rudder trim mechanism was then added to the lower right side of the fin. The assembly was then placed on the kit and substantial filing was completed to gain an acceptable join.

The wings were joined in the standard manner before fitting. In order to get the right dihedral the kit comes with a form of main spar, but a couple of mm need to be shaved off the botom at the ends in order to get the correct effect. This also helps in reducing the amount of filler and sanding required for the wing to fuselage joint.

Engine Nacelles

The kit engine nacelles require fair amount of work to firstly improve the accuracy and secondly, be converted to DB-7B standard.

Work commenced on the inboard side oil cooler intakes. The kit provides intakes and vents that open directly into the undercarriage bay. Using sheets of styrene cut and bent to shape along with some stretched sprue the required vertically divided intake was created. A similar method was used to represent the exit vent.

After significant dry fitting the outboard side was cut and a mount for the single exhaust was built. Care should be taken here that the mount does not protrude into the undercarriage bay so much that it interferes with the upper legs. The two halves of the nacelle were then joined.

There is a lot of scope here for further detailing as the internal bay is very sparse. However from experience with the G model any scratch built detail will not be easily seen, accordingly I added no further detailing. The nacelles were then joined to the wings, some small spacers in the locating recess helped to achieve a join that did not require filler. Both nacelles were placed over the already inserted upper undercarriage mounts, less the leg.

Undercarriage Accuracy

The kit undercarriage though basic is reasonably accurate in all areas except for its placement. The locating holes given mean that the legs are placed much to far to the rear. I alleviated this problem by creating new ones 4mm forward. This was not quite enough and if I were to build another, a 6 mm move would be used.

Engines and Cowlings

The kit engines are quite basic, but have scope for improvement. The only improvements I made was to add ignition leads. This was done by painstakingly drilling mounting holes for all leads and then threading monofilament through. Small clips to hold the leads together were made from styrene before careful painting, washing and drybrushing was completed to produce an acceptable finish.

The fixed vents were produced by marking the holes out with pencil, before drilling and squaring off with a fine hobby blade. The inside of the cowl was then thinned down with a motor tool. I had some designs to replace the scribed cowl flaps with some scratch built ones but baulked at the effort required to scratch build the visible detail at the rear of the engines. Accordingly the flaps remained in the closed position.

Finally the single exhaust was fashioned from brass tubing, with the opening suitably thinned to scale.

The remainder of the kit was built as per usual with the addition of replacing the nose gear doors with ones that were of scale thickness and opening the boarding ladder hatch. A scratch built ladder was also added in its deployed position.

The kit wheels were used albite with the weird fish scale tread removed, these remained attached without glue so true details resin ones can be added in the future. HF antennae and fixed forward sight were made from monofilament.

22 Sqn Bostons were finished in the standard RAF Dark Green Dark Earth and sky type S finish. This was replicated with Humbrol, Model Master and Aeromaster enamel paints. The kit was given a coat of Future before decaling and weathering. Decals are from the Aussie Decals range. The aircraft depicted is DB-7B/Boston III A28-9 DU-K as it was seen in early 1943.

Weathering was achieved by dry brushing Model Master Aluminium buffing Metalizer,  and adding washes of dark green, black, grey and raw umber. Finally a flat coat from the Floquil railway colors range was used.

• Wilson, S. 1992, Boston, Mitchell and Liberator in Australian Service, Aerospace publications Pty Ltd, Weston Creek ACT

• Flightpath Magazine Vol 10 No 1. pp. 66-75 article on the RAAF Museums Boston III restoration.

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Model, Images and Text Copyright © 2002 by J.D. King
Page Created 10 July, 2002
Last Updated 04 June, 2007

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