1/72 Grahame-White Type X Charabanc scratch build

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Stevef
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3 years 9 months ago #319 by Stevef

The above image shows the top wing sections (top), the lower wing with 10 x 20 thou Evergreen strip cemented on prior to sanding to represent ribs (centre), and the two tail surfaces, one with strip and one without (bottom).

I have also cut out plastic for the nacelle. I am using 30 thou card for the sides and 20 thou for the floor and nose, which is one piece.

The curves on the sides of the floor/nose are there because the nose tapered a little, the crosswise curve at the end is the pilot's position. I intend to make a simple box structure using card braces to make the nacelle and then remove the braces and replace them with wire rods when it is dry and firm. I have bought some wicker seats from Barracuda Studios which i will use for the pilot and passengers. It is my intention to scratch build all of the other parts.

More later when I have made the nacelle and finished the ribs on the flying surfaces.

Thanks for looking.

Stevef.

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3 years 9 months ago #320 by Stevef

The above shows (top) the wing with the strips glued in place, (middle) after application of Mr Surfacer filler, (bottom) the flying surfaces after the filler has been sanded and smoothed but not primed. Sanding off the 4 surfaces in the lower part of the image took nearly 2 hours.....

So in the meantime I have made some othe parts. Here is the nacelle structure completed - including having filled around the curved section of the nose because I just could not get the card to fit properly. Grrr.

Note in the top image tha I have added filler to the underside - joints are rarely perfect in scratch building. Also the rear has still to be fixed properly - the floor follows the sides completely. In the second image the bulkheads are there to hold the sides rigid and square while the cement dries- they were only tacked in and have since been removed.

I made a slatted floor for the cockpit - I am sure they must have had one for the passengers to stand on because that would have been lighter than a heavy gauge plywood alternative, but this is modellers licence as I know of no photos of the interior.

I have also painted the engine - acrylics for the aluminium and Humbrol metallic enamel for the cylinders. I have still got to dirty it a bit as it is much too shiny. I have also got to make and add some of the other details - they will come later.

Thanks for looking.

Stevef.

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3 years 9 months ago #321 by Stevef

Of course the above is just a small number of the pieces - there are very many more as will be shown on the model later.

I have also painted the engine and made the exhaust and carburettor parts.

The exhaust was very large: from photographs it seems to have been designed to quieten the engine so that when the aircraft was flown low over the crowds a Klaxon could be sounded! (The klaxon is very clear in some early photos; later it was removed and replaced by a long step on the port side of the nacelle). I will fix the exhaust and fuel pipes after I have fixed the engine mounting in the rear of the nacelle. The frame on which the engine was mounted was made from plastic strip and has been painted and rigged.

The seats I am using are from the Barracuda Studios 1/72 wicker seats in resin:

I had previously used one of their 1/32 scale seats and it was of the highest quality. These are no different - there are two seats per pack and they are easily removed from the casting blocks with a razor saw. The texture on them is beautifully represented. I made some simple cushions from one of the card headers and painted these to represent slightly worn covers:

They will be barely visiible and in this scale it is very difficult, (at least for me), to represent nice neat buttoned seat cushions! There are five of these - 4 for the passengers and one for the pilot.

Finally I have painted all of the wings, tail unit and fuselage with a mixture of white and Humbrol CDL (103), acrylics: - about 6 coats all of which had been thinned and applied with a hairy stick. Prior to fixing the engine in the rear of the nacelle I made and inserted a pertol and oil tank. I am not sure how accurate this is because I cannot see either of these in the photographs. On RFC aircraft the oil tank was mounted on the side of the engine beneath the exhaust pipe, but on this machine the exhaust was so large I cannot see where the tank could have been mounted, and on the only photo I have found of the starboard side of the aircraft showing the engine, there is no sign of an oil tank at all. Photos of the aircraft taken later in its career show that a gravity tank was mounted under the top wing, but this is absent in early photos and as I am trying to represent the machine in its early phase I have assumed that the tank was in front of the engine in the nacelle.

Finally I have rigged the interior of the nacelle with rolled copper wire before I add the seats:

There is till quite a lot to do before I can start mounting the top wing, but I have realised that this machine was a highly modified Maurice Farman MF 7 Longhorn, not an original design. That means that I can follow closely the build sequence for the Longhorn that I scratch built several years ago which will save me having to think too much about what to do and when!

Thanks for looking.

Stevef.

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3 years 9 months ago #322 by Stevef

The paint pot helped to keep the horizontal position of the tail unit - the curvature of the tail surfaces is quite marked and this extra support was an unexpected requirement.

The upper wing had a slightly more complex jig:

After the epoxy had cured over 24 hours the two sub-assemblies could be compared for alignments:

The engine sub-assembly was fitted into the rear of the nacelle, after I had added a small fuel and oil tank. I have not found any photographs of this part of the machine so what I have done is pure guesswork: I am not even certain how the engine frame was attached to the airframe, but as it will all be under the wing nobody is going to be able to take a very close look. Anyway, sometimes one has to use modeller's license! Contemporary photographs of this part of the aeroplane showed that the rear of the engine frame really did stand clear of the trailing edge of the wing:

Now the real test awaits: mounting the top wing to the lower and putting in the struts and starting the rigging. I will photograph the different stages and post them next time.

Thanks for looking.

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3 years 8 months ago - 3 years 8 months ago #323 by Stevef

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Evening All,

Putting wings on biplanes is, I know, one of the features that deters many modellers from building them. Rigging is another deterrent for some, so in this post I will try to reveal some of the (dirty) secrets that I use to build multi-bay biplanes. (For those who do not know, a bay on a biplane wing is the area between two pairs of struts. In this model there are 3 pairs of struts on each side of the fuselage so this is a 3-bay biplane). On this aircraft the struts were at 90 degrees to the wings so mounting them is a straightforward process, provided that they are put in carefully using the following simple procedure:

1. I cemented the 4 centre struts to the lower wing - two in each side of the nacelle;
2. I cemented the two centre struts to the tail unit;
3. while these struts were still setting and therefore able to be moved I laid the upper wing sub-assembly on the bench and put small drops of cement into the locating holes in the underside of the wing and tail unit;
4. I gently lowered the lower wing sub-assembly on to the upper wing adjusting the struts as necessary to fit into the holes on the wing and tail unit;
5. I adjusted the assemblies so that the lower wing assembly was exactly over the top wing and then held the lot in position with a standard Mk 1 jig:

Provided that the wings and booms are correctly aligned this jig will work well because it keeps the leading edges of the wings parallel and square and supports the tail unit at the same time. I left this overnight to dry out thoroughly. In the morning I could carefully invert the assembly and handle it without fear that it would fall apart:

Clearly this is not the strongest of assemblies, so to help stabilize it I added the outer wing struts. I put drops of cement on to the ends of the struts and gently push them into place making sure that they are in line with the other struts and are vertical when viewed from the front. A little weight was put on top of the wing to ensure that the joints are held together while the cement sets:

With the wings secure I put the front struts into the tail unit because that helped to stabilize the rear of the assembly while I added the radiator. This was cut form 60 thou card and scoured to represent the grille. It was suspended on wires between the rear inner wing struts just in front of the engine - I used thin copper wire which I CA'd to the sides of the radiator and bent the wires so that I could CA the ends to the srtuts. I wanted as much space as I could have while doing this - hence the remaining wing struts were left off until this task was completed. The water pipes were made from rod with the outlet from the engine to radiator cemented to the top of the engine and the lower pipe extended to the water pump on the front end of the engine. Unfortunately I was unable to get good pictures of this assembly because I cannot get the camera into the tiny space and have enough light to see things properly:

Having put the radiator in place I rigged the centre struts and front bays of the tail as these will be difficult to reach later:

Rigging with rolled copper wire is easy. The length of wire needed is measured directly from the model by using a pair of dividers. The wire is measured with the dividers and a length cut from the spool. This is rolled between a piece of brass strip and a block of wood which had been sanded flat. The wire is held against the model to check it for length: I usually cut the wire a fraction too long before rolling it out so that I can trim it if necessary. If the wire is too long I use my Mk 1 eyeball and experience to judge how much needs to be removed. I place a small drop of CA on the model in the two places where the ends of the wire are to be attached and gently place the wire on to the model. With a little practice this can be a fairly quick and easy method.

Next I added all of the remaining struts on the wings and tail unit, and rigged fore-aft between the wing struts, the rear of the wing struts and the remainder of the tail.

There is still much rigging left to attach, but with these areas done I do not have to worry about access and knocking small pieces off later. Most of what has been attached is unlikely to be damaged when I add the remaining sub-assemblies and details.

Thanks for looking.

Stevef.

Last Edit: 3 years 8 months ago by Stevef.

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3 years 8 months ago #324 by Stevef

Next up was the undercarriage. The layout of the main undercarriage was very similar to the Maurice Farman Longhorn, so I used a similar method of construction. The skids were pieces of 30 x 40 strip which were bent at the ends by holding the end in a pair of tweezers and twisting the plastic steadily until the desired shape was achieved. Holes were drilled to take the struts and the three uprights cemented into place. While the cement was still soft I placed the strut ends into the underside of the model and adjusted the struts to the correct angle. The bracing struts at the side were added quickly to keep the whole sub-assembly square and upright. When this had dried thoroughly I repeated the construction on the other side:

Axles were CA'd to the skids: these were cut from a paper clip:

The wheels, (not illustrated here), have tyres made from 60 thou rod which has been wound around a paintbrush handle and held in boiling water for about 10 seconds. The diameter of the brush handle is smaller than the finished tyre so that I can open the coil of plastic and hold it around a disc of card. I cement the ends of the rod making sure that not too much cement gets to the disc. When the joint has set I carefully release the tyre from the disc with a sharp scalpel blade The spoked wheels will be made from an Eduard PE set but I am having problems making these up at the moment - hence the lack of a picture.

The tail skids were a rather complex structure. There is a drawing in Flight magazine which shows them in detail, but I have had to simplify things a little in order to be able to make a viable structure which will be sufficiently robust. Basically it consists of the skid (filed and bent plastic strip), struts (rod), and side brackets (thin strip). The skid has been CA'd to the lower boom but in reality it should be free: practical considerations necessitated my field modification. I had drilled holes in the ends of the skids so that I could thread some wire through them - this makes the spring and wire attachment to the top of the tail unit. The remainder of the support was straightforward - put in the vertical strut between the skid and boom, side strut next and finally the two strips on each side of the skid. I had to work quickly to make sure all lined up properly before the cement set on the styrene. Finally the spring/wire was CA'd to the tail unit.

With the bulk of the construction now complete I am working out a rigging plan. There are rather a lot of wires left to add to this model, and I want to try to ensure that I do not knock any existing ones and have to replace them, so the order of addition matters a bit. They are also going to take a little time to fix into place.....

Thanks for looking.

Stevef.

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3 years 8 months ago #325 by Stevef

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Evening All,

After a bit of a struggle (time, not complexity of task), I have finally finished the charabanc. From a construction perspective this meant that I needed to add the bungee cords to the axles and skids - they were made from dark grey thread which I would around a couple of times and secured with CA. Then I could add the wheels which are wire wheels from Eduard with 40 thou rod for tyres. The propellor was carved from hardwood strip which I inherited from my father many years ago, the control horns, pulleys and a klaxon, (motor horn), which was mounted on the port side of the fuselage! Then it was time to complete the rigging, using rolled copper wire.

I will describe my method for rigging pushers in full here in case some of you think that it is more difficult than it is in reality. If a systematic method is used it is straightforward, if time consuming.

On this model I rigged the tail unit and the fore-aft gap between the cabane struts first, because later these are not very accessible. I also rigged the rear bays of the inner struts for the same reason. Then I rigged the fore-aft gap between the wing struts, followed by the rest of the rear of the wing bays. Next were the boom bracing, followed by the undercarriage and underside control wires including the aileron and elevator wires. I also rigged the upper wing overhang supports and the lower boom anti-drift wires. These latter make a cross between the rear of the booms and then run to the rear struts of the lower wings. Next were the rudder control wires from the horns to the pulleys on the wing struts, followed by the elevator wires to the rear struts. The remaining anti-drift wires for the upper part of the booms followed. With the rear of the model rigged I turned to the front. First were aileron wires on the upper wing, followed by the control wires for the rudder and elevators: these crossed from the rear struts to the front cabanes and then to the control horns and rudder bar at the front of the nacelle. Now I could complete the front strut bracing followed by the aileron control wires from the nacelle to the lower and upper wings were next and last were the front anti-drag wires. If that reads like a large number of wires then you will have read correctly! There are a lot of them, even for a pusher. I did not count them all but I think that it must be in the order of 150 - 170 in total (There were 190 on the Maurice Farman Longhorn which had slightly more than this one).

The windscreen was made from 10 thou acetate which I CA'd to the top of the nacelle. However it went a bit foggy when I bent it so I will have to replace it later - I left it in place to take the photos.

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Thanks for looking.

Stevef.

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