No 1A de Haviland: 1/32 stripdown Airco DH 1A

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2 weeks 15 hours ago #275 by Stevef
Evening All,

“It is a truth universally acknowledged, that every serious aircraft modeller makes pusher biplanes, either from kits, vacuforms, conversions or scratch builds: they are landplanes, floatplanes or flying boats, and can have a combination of tractor and pusher engines. Ideally they should be in God’s Own Scale, but other scales are permitted. When the modeller has built up a suitable collection in the Proper Scale, it is quite appropriate for them to turn to a larger scale and build them in strip-down form.”

Making Real Model Aeroplanes by Stevef, Idontgoto University Press, (in prep).

In keeping with the above, I will attempt to build another large scale (1/32) strip-down pusher, this time the Airco de Haviland D. H. 1A.



When I built the Vickers FB 5 Gunbus I wrote that this was an alternative possibility but because of a lack of information about some parts of the machine, especially the internals of the nacelle, I chose to attempt the Vickers. I am still lacking some information but have come to the conclusion that it probably does not exist. Consequently I intend to use modeller's license and the fact that G. de Haviland helped to design the Royal Aircraft Factory FE 2a: the two machines were remarkably similar in many ways. Given this I intend to construct what I think is a plausible representation - if anyone has contradictory evidence I would be very pleased to have it.

I have already converted one of these from the Airfix 1/72 D.H. 4,

It looks like this:



So I have put together my kit which consists of the usual plastic strip, card, rod, brass rod and bar, wood, thread, etc and some odds and ends from specialist suppliers:



As the engine in the above image is a bit small and the wrong type, I have selected this lovely specimen from WingnutWings:



I had toyed with the idea of making one of these from scratch but decided that I might want to build another model before senility prevents me from doing so. I also used these wheels on the Gunbus and recommend them to anyone building early aircraft in this scale:



I used these instrument bezels on the Gunbus and although they are barely visible on the model at least I know that they are there together with Airscale transfers for the instrument faces (not illustrated here):

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2 weeks 15 hours ago #276 by Stevef
Another small detail will be provided by resin representations of the pulsometers:



That is enough pre-manufactured material, now to start the real modelling. The Gunbus was a half-strip down model but that presented unforseen problems because the weight is concentrated on one side, making the model inherently unstable and in need of permanent support to stop it leaning. The undercarriage is also not as strong as I would like it to be, so I have decided to build this model as a complete strip down. This means that all of the interior detail in the fuselage nacelle and the engine will be fully exposed, together with the structure of the flying surfaces. I know that there are kits that represent different aircraft in varying degrees of strip down, but as far as I am aware, none of the Airco D.H. 1A.

I have been experimenting with some parts as I was finishing the FE 2d, the first being how to make the wing ribs. There are rather a lot of them and they have to be the same size in two patterns: some with holes and some with slots and holes. To ensure that they are all the same size I am using the following procedure:

a. cut a length of 60 x 180 thou Evergreen strip (top)

b. shape the strip to the shape of the rib. This will be the master strip for all subsequent ribs of this size. (second from top)

c. using the master as a template, cut and shape another piece of plastic strip and mark on with a sharp pencil where the spars pass through (4th from top)

d. drill holes between the lines which mark the spars (bottom)

e. cut out square holes for the brass bar spars (middle):



Complete the rib by drilling holes and cutting the slots as necessary. There are 40 full chord and 29 narrower chord ribs to make for both sets of wings, so I will make some and then work on another part of the model, go back and make some more, repeat etc until they are all made....

I also want to try out another idea which is to use wood laminate for the propellor. I have already commented elsewhere that British propellors were made from laminated mahogony or similar wood and so should be uniformly dark, as on my Gunbus, but I decided to be a little inaccurate on this model and have used two types of wood instead. Strips of laminate were cut to length:



These were glued with Evostick wood glue which dries clear, and the piece put under a press overnight:



Not much chance of that delaminating when it is shaped! First mark out the plan of the propellor and file the wood so that the basic outline of the propellor is made:



I marked on both surfaces where the bosses would be and the curved flat faces between the bosses and the edges of the blades. By carefully filing one face at a time the propellor can be shaped:



As stated this is not strictly accurate as the laminations should be much thinner and darker but most people who look at the model will not be aware of this and I want something a little different.

It may be a little while before the next post because although like others I am currently confined to my home, I have rather a lot of ribs to make and I need to work out the internal structure of the nacelle, and then how to start making that and the internal fittings.

If you have been, thanks for looking.

Stevef.

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6 days 6 hours ago #277 by Stevef
Evening All

I have been informed via another site that pulseometers (small pumps) were only used on rotary engines! So that bit of AM has been stored in the spares box, although I do not have any projects in mind at the moment which will need them.

I have been making ribs - I have to make rather lot - but constantly having to drill holes using a hand chuck has caused strain in my arm so I am having a break from that and have started work on the nacelle instead. I will continue making ribs, but rather than make them all in one go as originally intended, I will make two or three per evening, and hope that I do not lose track of what I have made and what I still need to make. Then I have the riblets to make for the wing leading edges.....

I do not have any detailed information about the nacelle - I have been able to work out some of the framework, where there were engine bearers, fuel tank, some stringers on the sides, the pilot had a seat but the observer probably had a simpler flat folding(?) board, and I know that the nose was metal. Apart from that It is pretty much guesswork. I am using the wonderful drawings of the interior and structure of the FE 2B from the DatatFile No 147 because G de Haviland helped to design that machine and I am sure that he took ideas and incorporated them in the DH 1/1A. So I have made some scale drawings of what I think the design may have looked like but if anyone knows better please tell me soon because I have started to make the nacelle. Deciding what to use took almost as much time as working out what the nacelle may have looked like: I mocked up a side using plastic strip, and guidance for size of material from the FE 2b drawings:



The bottom longeron was deeper than the upper parts and I have decided that the spacing of the verticals is wrong. It has also confirmed to me that it is not practical to join the wing spars to an all plastic structure: the spars will be made from brass bar, and I am not happy about using CA or epoxy to join the spars to a plastic strip. I do not want this to fall apart just when I am at the rigging stage for example. So after yet another morning of working in a crabwise manner towards a solution I decided to make the upper part of the structure from brass bar and just the lower longeron from plastic. My reasoning is that on the FE 2 the lower longeron was wider than the upper parts of the nacelle frame because it was carrying extra weight and therefore was more heavily stressed, so G. de Haviland probably used the same idea in his second pusher. I decided to use 1/16 square brass bar for the upper part of the nacelle and 60 x 80 strip for the lower longerons. The lower longerons will not be carrying much weight so they can be epoxied to the uprights of the nacelle frame. Brass bar was cut and soldered in the usual fashion to make up two sides:



then the top frames were joined to one of the sides followed by the other. In doing this I discovered how easy it is to cause solder to melt when trying to join a new piece which is at 90 degrees to one already soldered. This is a good test of patience I decided, but I did get there in the end:



The observant reader will have noticed that the uprights at the rear of the nacelle were angled forwards to meet the rear spar, and that the front spar was probably bolted to the lower longeron beneath another upright. I intend to use these two uprights as points to solder the model spars: these will make much stronger unions than trying to use epoxy or CA with brass and plastic. Therefore it was imperative that the ends of the two rear uprights were in precisely the right place. This was easy to do - mount two ribs on to two pieces of brass bar which will be used for spars on the model and use them as a guide for spacing the ends of the uprights:



The nacelle frame now looks like this from the front,:



and like this from the side:



Now I can start to make parts for the interior - these will be from plastic for the most part. I will also continue to make more ribs and riblets for the wings....

Thanks for looking.

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3 days 18 hours ago #278 by Stevef
Evening All,

I have already described how G. de Haviland had been heavily involved in the design of the RAF FE 2a and later 2b before he left the Royal Aircraft Factory to join the Aircraft Manufacturing Company as the chief designer. I have also stated that I do not have drawings of the interior of the DH 1/1A, but both the FE 2a and the DH 1 were powered by 100hp Renault engines, and the FE 2b and DH 1A were powered by 120 hp Beardmore engines. I spent a morning and more earlier this week trying to make plausible drawings for the interior of the DH 1A based loosely on the FE 2b and thought that the engine installation should be similar on both the 2b and 1A. One of the key differences between the RAF and DH machines was that the former had a bulbous forward nacelle which tapered rearwards whereas the DH nacelle had parallel sides. The engines in both machines were mounted on frames inside the rear nacelle. It was only today when I closely compared the drawings of the two nacelles that I realised just how similar they were - even down to the length! Then the penny dropped! The DH 1A was almost a copy of the FE 2b although de Haviland made some modifications based on what he must have learned from the test flights of the prototype FE 2b. Now I have worked out without much difficulty the probable construction of the engine mounts and fuel tank, radiator installation, etc in the rear of the DH 1A and it must have been very similar to the FE. I suspect that the same applied to the cockpits - after all why try to reinvent the wheel?

This means that I have had to modify the fuselage frame somewhat: I have taken out the rear upper cross member and installed two extra vertical supports at the rear. These vertical supports would have been anchor points for cross members which were below the engine, which in turn would have carried two longerons on which the sides of the engine rested - just like the FE 2b! Doh!! The horizontal pieces and engine bearer longerons will be added from plastic strip later - they can be held with CA as they will only be supporting a plastic engine, so the main fuselage frame now looks like this:





Now I can fit the engine and I know roughly where the fuel tank will go, so I think that I have worked out the key elements of the interior and can now make the different parts. Sometimes it is only by doing something that the blindingly obvious becomes visible!

I have been fiddling with the engine in order to work out the precise dimensions and location of the bearers, and discovered that the parts tree for the Wingnutwings engine does not have an oil tank or exhaust pipe. I made up an oil tank from a piece of thick sprue and have found another piece of the correct diameter for the exhaust pipe, which I will make later. I have also made the blanks for the radiator from a sandwich of 2 x 80 thou card. I am trying to think about what to use to represent the mesh on the front and rear of the radiator - if anyone has any ideas I would be pleased to read about them. In the meantime here are the radiator blank, oil tank, lower part of the engine and frame:





The second picture shows that the parts will fit as they should when the various sticking out bits on the rear, (forward end in the photo - because the engine was mounted as a pusher the front end of the engine is at the rear of the aircraft), are put into place later.

More to come if you have not lost interest already.

Stevef.

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