"Airfix" 1/72 Vickers FB.5 Gunbus

   The Vickers FB 5 was dubbed unofficially the "Gun Bus" because it was the first RFC machine to be armed with a machine gun. It was a two seater powered by a 100 h.p. Monosoupape or 110 h.p. Le Rhone rotary engine, but because there was no interrupter gear available to stop bullets from striking the propellor blades, the engine had to be mounted at the rear of the fuselage nacelle in what is called a pusher configuration: the tail unit was carried on booms attached to the wings. This gave the observer/gunner an enormous field of fire in the unlikely event that the aircraft should meet an enemy. It was designed to an Admiralty specification for a fighting aeroplane and the first prototype was produced in 1913 as an armed photographic reconnaissance machine. The first FB5 was accepted by the RFC in October 1914, with machines being taken to France in February 1915 by No. 2 Squadron. These were some of the few aircraft to be armed at this time, so they quickly gained a reputation for being dangerous: the characteristic pusher layout and impact that these aircraft had because they were armed meant that the Germans henceforth called all British pusher types "Vickers," irrespective of the manufacturer or design. In July 1915 the first fighter or pursuit squadron in any air service to be formed and equipped with a single aircraft type with the specific purpose of fighting and destroying enemy machines was No 11 Squadron RFC which used the FB 5. However F B 5 Gun Buses quickly became obsolete as they were too slow and were therefore outclassed by the Fokker and Pfalz Eindekkers (monoplanes), so they were withdrawn from front line service in the spring of 1916.

    The Danish Arsenal Workshops bought a licence to build 12 machines which entered service in 1917 but they were not used for very long because the Monosoupape engines were so unreliable. Indeed the poor serviceability of the engines plagued the machine in RFC service, with many sorties having to be aborted because of engine failure. One pilot reported having to return to his airfield on over 20 occasions out of 40 because of engine problems. Nonetheless the pilots and observers had some success with these aircraft, with Lt. A. J. Insall being awarded a VC in 1915 and several pilots managed to "make ace" (force down more than 5 machines) with this type, no mean feat in a slow and not very manoeuvrable aircraft.  

   When I started this project over 30 years ago there was no kit of the FB 5, nor indeed any prospect of one, although Pegasus/Merlin have produced one since, and these can be obtained on e-bay or other sources, although the author considers them to be rather expensive and they have been described as an aid to scratch building. That said this is a conversion project based on the Airfix DH 4 (kit no.01079) and the Avro 504 (kit no. 01048). It is worthy of note that the Airfix DH 4 and Avro 504 kits were two of the most useful in the WW1 range as they provide parts for so many conversion possibilities, so if you are interested in building less well known aircraft that are avoided by the manufacturers then I advise that you buy in a stock of these items when they become available. This project requires experience of converting/scratch-building, including some experience with biplanes and is not recommended for those who have little or no experience with WWI subjects. Pusher aircraft do not seem to be popular with either kit manufacturers or many modellers, yet as they formed an important part of the RFC equipment during the early and middle years of WWI, modellers have no choice but to build their own, especially in 1/72 scale. With a little experience they are no more difficult then many other conversion projects.

    I started with the fuselage which has to be moulded using balsa wood and plywood. From a plan of the fuselage nacelle, trace the side profile and transfer this to a block of balsa wood 7/16 inch thick. If the block is a little thicker it does not matter as it can be sanded down. Now cut a former from card to the exact shape of the cross section of the fuselage between the cockpits, using the DataFile 56 FB 5 as a guide. Carefully carve the balsa block to the correct shape of the fuselage nacelle: this requires patience and should not be rushed - continually refer to the plans and former to make sure that you do not take off too much wood. The finished mould should be smoothed with fine grade glass paper and when finished should be very slightly smaller than the drawing to allow for the thickness of plastic to be moulded. When you are happy with your nacelle draw another side profile on to a piece of three or five layer plywood, leaving a margin of two to three inches of wood around the outline. Cut out a hole the shape of the fuselage profile and sand this smooth, making sure that this exactly fits the plan. Check that the balsa mould will pass through the cut-out leaving enough room for the plastic i.e. about 10 thou all round. Now take a piece of 30 thou plastic card and pin it over the hole in the plywood, allowing at least one inch of surround. Hold the wood with a heatproof glove and put the plastic and wood under a grill with the plastic side facing the heat source and heat it gently. Make sure that the grill and the wood are hot. When the plastic starts to wrinkle and curl a little at the edges take it away from the heat and push the balsa mould gently but firmly into the plastic through the hole in the plywood. Stop pushing when the balsa mould is just over half-way through. Wait for about 15 seconds for the plastic to cool and remove it from the plywood. Then carefully ease the balsa mould out of the plastic taking care not to damage the male (balsa) mould. This will give you one half of your fuselage nacelle. Repeat the above operation, but this time put the plastic sheet on the other side of the plywood mould and push the balsa mould through the heated plastic card from the other side: this will give you the second half of the nacelle. Carefully cut out the two new parts using a very sharp scalpel knife and gently sand the edges until they are flat. Put the two halves together and check for size against the plan. Sand down the edges of both halves until the width of the new nacelle is correct and you have a good join. Finally cut out the two apertures for the cockpits making sure that they also match exactly.

  You can now put in the cockpit details, including bracing with thin rod or stretched sprue and a cockpit floor from card. You need seats for the pilot and observer plus a control column and rudder bar. Instruments were basic - there was not a panel as such. Seat belts can be added from thin paper, but often were not fitted. Paint the interior of the cockpits clear doped linen on the sides, metal for the front and upper curved sections and wood for the floor. Assemble the fuselage and make a fuel tank from round sprue and glue it to the rear fuselage, smooth with filler and rub down. Add a tiny piece of very thin stretched sprue to the top of the tank to represent a filler cap, and two bands around the body of the tank. Cockpit coamings are from stretched sprue or thin rod. A rectangle of 5 thou card represents the step on the port side of the front cockpit. Mark on to the fuselage the positions for the struts for the top wing and cut out small holes, and drill a hole in the rear of the nacelle for the engine locating pin.

    I used the engine from the Avro 504 and cemented thin lengths of stretched sprue to the front of the cylinders to represent the push rods. Shorten and reshape the propellor of the Avro, cut off the locating pin, drill a small hole in the front of the propellor and re-insert the pin. Cut a disc of 5 thou card for the boss on the front of the propellor and represent the bolts by pushing a sharp pin from behind. When the engine and propellor have been painted cement them together: the engine was black or gunmetal with silver push rods and the propellor natural wood. Set this assembly on one side.

   Take the bottom wing from a DH 4 and cut out the central section. Trace the shape of the tips from the plan and mark the new shape on to the wings before cutting and shaping them. Place one wing half on the plan and lay the fuselage nacelle on top so that you can accurately measure how much of the inner part of the wing needs to be removed. Cut this off and file to the exact size. Repeat for the other wing half. Take the top wing of the DH 4 and again reduce the span and reshape the tips according to the plan. Fill all of the strut locating holes, the aileron grooves, and any ejector marks with filler, and the slots for the struts in the upper wing with strips of card. Straighten the upper wing so that it has no dihedral. Fill the cut-outs on the trailing edges of the wing sections with 40 thou card and sand to the correct shape. Rub down all of the moulded ribs on the wings and score shallow grooves on the line of the ribs of the FB5, using the plan as a guide. Use liquid cement to stick thin rod or stretched sprue into the grooves and when this is dry rub down gently until they are just prominent on the surface. Score grooves for the new ailerons on the wings, and drill new holes for the struts, again using the plans to get the correct locations. Mark where the booms will need to be attached to the wings by laying the wings and a length of brass, steel or plastic rod on the plan, and score shallow grooves into the top surfaces of the wings, making sure that the groove gets deeper as it goes forward of the trailing edge.

  The horizontal and vertical tail surfaces were cut from 20 thou plastic card which was sanded to an aerofoil section and the elevators and rudder were scribed on to the surfaces. Add ribs to the top surface of the horizontal unit and the fin/rudder. Cut two short lengths of stretched sprue and glue these to the top and bottom of the fin where it joins the rudder: these will be used to attach the rudder to the booms. A small piece of sprue needs to be glued on the port (left) side of the leading edge of the fin: this will take bracing wires to the booms and the tail skid later. Cut lengths of brass, steel or plastic rod for the booms using the plan as a guide - be sure to allow for the booms to be glued to the tops of the wings. The lower booms formed a V under the rudder but the top ones attached to the leading edge of the horizontal tail surface. Carefully lay the top wing on the plan and glue the upper boom rods on to the top of the wing and allow to dry. Cut two small slots and glue the rods directly into the horizontal tail unit, again using the plan to ensure that alignments are accurate. Cement the lower wing halves to the nacelle making sure that they are perpendicular to the fuselage sides, fill any gaps and sand down. Glue the booms to the lower wings, again making sure that you get the correct angle by lifting the trailing edges of the wings while the booms dry out. Add the horizontal strut between the lower booms from rod - the location can be taken from the plan.  Now do most of the painting.

    Most aircraft were clear doped linen overall with natural metal on the nose. I painted mine in an early camouflage scheme as used by aircraft of No 5 Squadron: the pattern is representative - there are photos of camouflaged machines in the  DataFile but the exact pattern is not clear. I used light grey but it could have been dark earth according to some sources. I think that it could also have been PC 8 a kaki colour used on the upper surfaces of aircraft before PC 10. I did not put camouflage on the fuselage sides, but I have no direct evidence that it was not applied. The fuel tank is copper, the booms are light grey and the struts light brown. I hand painted the rudder stripes and cockades on the wings, tail surface and the fin: you could use the under wing cockades from the DH 4 or use another suitable source if you have them. The fin roundels are very small and the one on the tail is an awkward size too and as I do not know of any source for these I hand painted them. I think that the underwing roundels should probably be inboard of the ailerons, as photos of aircraft from 5 Squadron show them there, but I mistakenly painted mine towards the tips. Oh well! The serial on the rudder came from dry rub down transfers: I painted the white outlines.

   Now complete the assembly of the model. I used the wing struts from the DH 4. Start by cementing the four outer struts in the holes on the underside of the upper wing, then place small blobs of glue into the outer holes on the lower wing and carefully lower the top wing and struts into the holes on the lower wing, and fit the rudder by putting the rudder posts into the V of the lower boom and the V of the horizontal tail unit. Secure the rudder posts with glue. Align the wings and struts so that all is square, and support the wings and booms while this dries out. When it is dry you can carefully handle the structure to be able to measure the lengths of the inner wing and fuselage struts with a pair of dividers. If necessary cut the struts to the correct length and measure them again to make sure that you have done this accurately. Glue the wing and fuselage struts into place. You will need to support the top wing and booms again while these dry. When they are set you can measure the lengths of the boom struts with a pair of dividers and cut them from card or use struts from the Avro 504 before glueing into position. Be careful with this assembly as it is a bit fragile while under construction, but when it is completed and has dried out properly it is fairly rigid. The undercarriage was made from 20 thou plastic card shaped to aerofoil section. The skids were also made from card. Drill small holes into the tops of the skids and then glue the axle to the skids and set aside to dry thoroughly. When it is ready glue the legs into the holes in the top of the skids, and cement the tops of the legs into small holes drilled in the bottom of the nacelle. This will also need to be supported while it dries out. Now paint the struts and skids a light wood, wheel tyres dark grey and wheel discs clear doped linen. Glue on the wheels. Cut and fit control horns on the fuselage, and horns for the elevators, ailerons and rudder, and paint light brown. Wing skids were from 5 amp fuse wire bent to the correct shape. Finish any other painting or touching in.

Rigging.

   I recommend either stretched sprue or very thin wire for the rigging. Measure each length of wire or sprue on the model using a pair of dividers and glue into place with either superglue (wire) or liquid cement (sprue). This model has well over 100 individual strands so it will take a long time and you need to be patient. So as not to leave any wires out (easily done), start with the wires between the fuselage struts, then the rear wires of the wings, and the fore-aft wires between the wing struts. Now glue on the engine and propellor. Run control wires from the control horns on the fuselage to the rear of the fuselage, and finish the wings. Then rig the booms starting from the front, and then the tail. Add the short wires from the control horns to the trailing edges of the ailerons, elevators and rudder, and from the tail unit control surfaces to the rear of the wings. Finally put on the anti-drag wires from the booms to the rear outer struts and from the front of the nacelle to the front struts. This sequence will hopefully reduce your chances of damaging work already done and the risk of missing out any wires. Add a tail skid, cut and shaped from card and painted light brown, with a small hole drilled in the top surface to glue to the bottom of the rudder post which should extend beneath the lower boom, and add the small spring to the post on the leading edge of the fin from stretched sprue. Glue a small length of stretched sprue to the front inner strut on the port (left) side to represent the pitot tube and add a Lewis machine gun from the DH 4 to a post in the front cockpit.

 I had not made a model in three decades, so I made a couple first before I attempted to finish this, including the Airfix 0/400 so that I had some recent experience to draw on. Much of the work had been done when I found this in the roof after 30+ years: I had to paint it and finish the assembly. I do not recommend it for a first attempt at a biplane conversion, but if you have already done some conversions or scratch building of WW1 aircraft this should not prove to be too difficult. Moulding your own parts is easier than it sounds - I had to mould a wing section for the 0/400, and I have posted a full article on this on the Airfix Tribute Forum. The most difficult sections on this model were getting the booms at the right angle, and the rigging, but I managed it even though my patience was tested, sometimes nearly to destruction! This is quite a long build but the result is worth it because you will have an under-represented aircraft in your model collection. People even ask me if this was from a kit: it is nice to be able to say no.

The best source is the Windsock DataFile No 56 by Albatross Publications: there are good plans in there. Warplanes of the First world War: Fighters Vol. 3 by J. M.Bruce was also used, as was The British Fighter Since 1912 by P. Lewis and Fighters 1914 -1919 by K. Munson. 

There is an article on making parts using the moulding technique described here in www.airfixtributeforum/top-tips-and-techniques .

May 2013

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