1/72 Zeppelin-Lindau (Dornier) Rs II scratch build

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2 years 8 months ago #138 by Stevef
Evening All,

I have been working on the ailerons. I had cut out the sections from the wings where the ailerons will go, but I need to make new ones as the later versions had balance ears and the outboard trailing edge curved upwards in a similar way to those on the Ago C II. That meant that I had to cut new pieces from 60 thou card with a laminate of 60 thou card:





These look rough at the moment but that is normal for my scratch builds. Once again I decided to use my new tool to make life quicker and easier as there was a lot of plastic to remove:



By judicious use of the file I was able to remove the underside and introduce the curve on the outer part of the trailing edge. I also thinned the trailing edge and rounded the ear and leading edge. The junction of the two pieces of plastic also needed treatment with Mr Surfacer and the whole units were given a polish with fine worn glass paper. Now they are ready for the ribs to be added which is what the pencil lines are for.





Thanks for looking.

Stevef.

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2 years 7 months ago #139 by Stevef
Evening All,

I have been working on the part of scratch building WW1 aeroplanes that I enjoy the least - the wing and other flying surface ribs. They are not difficult to put on but shaping and scraping them can get a bit tedious, especially if there are lots of surfaces or if they cover a large area. In this case both apply!


The method is simple enough: transfer from the plans the positions of the ribs on to the flying surface with a pencil line. I use Evergreen strip and select a suitable size for respective surfaces. In this case I used 10 x 30 thou for the wing and 10 x 20 thou for the stub wings, and tail surfaces. If the wing ribs sound large just remember the size of the original aircraft - there were lightweight girders in there! The main ribs were added first by applying liquid cement to the wing surface and laying the strip on to it. Liquid cement was then run along the strip to ensure that it was properly held down - these are long strips and the cement dries quickly:



I added the small leading edge ribs in the same way:



In the case of these short ribs I had drawn a line span wise along the wing to make sure that they are all of the correct length, in addition to the chord wise lines for each rib. After what seemed like a long half of an evening I had this:



On to the other flying surfaces and the same procedure was followed. Everything was left to dry overnight. Then I could do what I like doing best with this task which is to trim off the leading and trailing edge pieces of strip. Before I sanded the ribs I added some filler to the edges to help smooth them into the general flying surface. After sanding they are ready for priming:



Any irregularities which show after priming will be filled with Mr Surfacer and sanded and primed again. These are the ailerons, elevators and horizontal stabilizer for the tail. From the top the ailerons and upper elevator are complete and primed, the lower elevator has still to be filled and sanded and the horizontal stabilizer awaits trimming:



Still a lot to do on these surfaces before they are ready, so I will plod on....

Thanks for looking.

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2 years 7 months ago #140 by Stevef
Evening All,

I have to write that I am currently very fed up with repeated sanding, filling and priming of ribs.... only to find still more holes!!! I gave up for a while this week and took a break to make something else, but still took a little time on them which I am pleased to report are now nearly ready....sigh.

I forgot to explain how I made the stub wings which are on the lower rear of the hull. They are made from 30 thou card and bent in a pipe of near-boiling water as described by Stevehed. The method is very good for making curved card for wings and other flying surfaces. (I just wish that I could have used the technique for the wings of this model but they were too thick). They were then filed and sanded to aerofoil section in the usual way:



The stub wings have been given the rib treatment too and are now primed and ready to have the ends drilled to take metal pins: these will be used to attach the stub wings to the hull later.

For a change I went back to the hull to drill out the cockpit area. I am not proposing to add internal detail for two good reasons. The first is that I have absolutely no idea of what the internal structure looked like other than the fact that it was built from girders like the wings, and secondly the hull is solid wood and trying to hollow out a section and fill it with detail which would never be seen anyway seems to be going too far, so I have settled for a minimal approach, rather like Airfix and Revell kits of the early 1960's where all you had was a pilot and seat if you were lucky. In my case there will be two seats as the pilots sat side by side. I will put control wheels in too and a generic instrument panel which I think was behind the windshield. Well that is where mine is going!

I drilled out the cavity for the cockpit and then lined it with 10 thou card so that it could be painted. I also tidied up around the hole with filler to smooth out the surface:



The next item was the windshield which sits in front of the pilots. I carved a male mould from balsa and push moulded one from 30 thou card.....and did not think that it looked right. I had been following the drawing but the result looked different from the photos, so I tried again...and again and finally got a shape which I think is close to what the original may have looked like:





It is not glued into place yet because I still have to make the instrument panel and fit that first. While I was moulding the windshield I decided that I would also make a mould for the propellor spinners. This was a piece of 1/4 inch (6mm) dowel with the end shaped to the correct curve. I made 6 spinners to make sure that if I make a mess of one or two (highly likely) I will have enough to complete the job without having to go through the moulding process again. Just to test things I also carved a propellor from some strip wood which I use for the purpose, (please do not ask what the wood is because I have no idea - it was given to me by my late father and he did not know what it is either). The result:



Only three more to make.

One thing that struck me when I was sanding the elevator surfaces was the size of them. On the aircraft they form a biplane structure which was at the extreme rear of the aircraft, and they hinged as a single unit. Just to give an idea of their size I got out my model of the Avro biplane of 1912 which is to the same scale: the span of the elevators is the same as the span of the wings of the biplane! (5 1/2 inches: 14 cm).



Thanks for looking.

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2 years 7 months ago #141 by Robbo
Outstanding work Steve

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2 years 7 months ago #142 by Stevef
Evening All,

Thanks Robbo for the kind remark.

I am posting two sets in one again so that I do not overload the system: once again I have a large number of photos to show how I have made the model so far. I have not reported anything recently as I have been away to visit my brother, but we have been busy together as he has helped me with some of the work where two sets of hands were necessary and with a process which I have not mastered - soldering.

Before I left to see him though I added two small pieces of 60 thou card to the middle of the hull sides. These represent where the rear cabane struts were fixed to the top of the hull: the hull tapers slightly in plan but the cabanes were parallel with the thrust line and set close to the hull edge at the front.. Consequently the rearmost attachment point was slightly outboard of the edge of the hull and some form of bracket was fixed and then concealed behind a cover. It is not entirely clear from the photos what this looked like so I have shaped the card to what I think is a fair representation:





All of those crosses on the top of the hull mark where I will have to drill locating holes for the cabane and engine support struts. The one in the centre is where the boom will be inserted into the top of the hull. First though the boom had to be made. For reasons of strength I decided to make this from brass rod, using 1/16 inch (1.6mm) for the arm which will be fixed into the hull and the 4 long arms, and 3/64 inch (1.19mm) for the cross pieces. I had intended to superglue these together but after a discussion with my brother he suggested that this would not be strong enough particularly given that the top side booms are attached to a single boom which enters the top of the hull via a triangular piece. This strange design came about as a consequence of the redesign of the engine installation: originally this machine was powered by three engines in the hull connected to the propellors via drive shafts. This arrangement was not very satisfactory for a number of reasons, among them being that one of the drive shafts broke causing the aircraft to make a forced landing. Then when the pilot tried to take off the central unit broke away and severely damaged the tail booms in the process. This caused a major redesign of the aircraft. The hull was reshaped, 4 engines were fitted instead of three, and these were placed in tandem in nacelles between the hull and the wing. This in turn meant that the upper boom attachment had to be reduced to a single central arm to clear the rear propellors.

My brother is very skilled with a soldering iron so he offered to make the upper part of the boom with the triangular joining piece and central arm for me. The triangular section was cut from a piece of brass sheet and after the boom parts had been cut form rod and the ends filed and cleaned, they were mounted on a jig of balsa wood to check size and alignment prior to soldering:



Both ends of the boom are too long. This was done deliberately so that they can be cut to the correct lengths later: in particular the forward end needs to be buried as deeply into the hull as possible to give maximum strength. The boom was soldered and the new piece had the very small amounts of excess solder removed with a file.

Then we set about drilling the holes for the booms in the hull. The hull was wrapped in cloth to protect it as it was held in a vice and G clamp to make sure that there was no movement when we started to drill the holes. The first one to be drilled was the most difficult: this was the central hole in the middle of the hull. This has to penetrate at a low angle which meant that a small vertical pilot hole was drilled to a depth of approximately 1/4 inch (0.5cm), and then a paper template which had been made from the plan was crudely taped to the hull just to one side of the it:



We checked the alignment by pushing the single arm of the boom into place:





No extra drilling needed there! Part 2 to follow.

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2 years 7 months ago #143 by Stevef
With the arm of the boom inserted into the top of the hull, this now formed a convenient alignment jig for the two holes which had to be drilled in the lower rear of the hull where the lower boom arms will be fixed:



When both holes had been drilled we were able to use the boom to make sure the gap and angle was right:





Now I have to cut the remaining the parts of the boom assembly from brass rod and fit it to the hull with epoxy and superglue. However I will drill all of the remaining holes in the hull and wing first, as the hull will be easier to handle without a large lump of brass sticking out of the rear!

Thanks for looking.

Stevef.

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2 years 6 months ago #144 by Stevef
Evening All,

Once again I am posting several sections in one go because I have so many pictures. I will try to make each post a separate sub- section so that it is easy and logical to follow.

The first step was to attach the top boom arms to the hull. I laid the boom on to a set of plans and cut off the excess rod at both ends, leaving enough at the front end to be pushed about 2.5 cm into the hull. This will ensure that it does not move or fall out later.. The boom was supported by three upright posts at the very rear of the hull - these were made from brass rod and expoxied into holes drilled into the hull. These holes were drilled at the same time as others which will be used later for among other things, engine support struts, stub wings, and cabane struts. In all 41 holes of different sizes, and all had to be in the correct places - not 3mm or 5mm too much to one side or the other. I too can get cross-eyed when measuring so I made a tracing from the plans to show where all the holes on the top of the hull needed to go and transferred this to the model. I could then check each location and correct if necessary without finding later that I had mis-drilled one or two! The holes in the sides of the hull for the stub wings were easier as I will explain later.

Back to the boom: with the vertical posts in place I epoxied the front post and pushed this into the hole in the centre of the hull until the triangular section at the front of the boom sat directly over the posts. A quick dab of CA on the tops of the posts and put the boom on to the posts: the CA made sure that the boom did not move while the epoxy cured overnight. In the morning I added the centre strip in the triangle at the front end of the boom - this was from 15 tou plastic card held also held in place with CA.











The last photo shows the holes where the lower boom arms will be inserted into the hull.

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2 years 6 months ago #145 by Stevef
Before I put the lower boom arms into the rear of the hull I cut the fins from 30 thou card and rouned the leading and trailing edges: these were fabric wrapped around the boom struts so did not need to be either aerofiol section of very thin. These two pieces of card were CA'd to the underside of the upper boom arms:





Now the lower boom arms could be epoxied into the rear of the hull and CA'd to the card fins. This method of using epoxy and CA means that the arms are securely fixed to the wood and plastic: I have some wriggle time to get the boom in the correct place with the epoxy, and when it is where I want it the CA holds it in place while the epoxy cures.



When the above was set and rigid I could add the remainder of the boom struts - vertical and horizontal. I started with the horizontal strut at the rear: I measured the gap with a pair of dividers, cut the rod and filed the ends with a round file to fit into the circular boom arm and CA'd it into place:







Having checked that all was square and true I was able to cut the remaining pieces of brass rod as per the above and glue into place.

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2 years 6 months ago #146 by Stevef
I finished the boom structure by cutting the vertical centre posts from 20 thou plastic rod and CA'd them into place too:









At last I have a structure which is beginning to look like a flying boat! There are alternative ways to do this but experience has taught me that making the parts as I go along is better in the end because I can measure everything to fit together exactly rather than finding that something is not quite square, the wrong length, too short, etc when the completed sub-assembly is tested against the other part of the model. I also used CA for the brass attachments because it was easier and safer than solder and a hot iron: imagine trying to hold the rod with one hand and solder and iron in another......and then get it all square and true!!!

The front arm of the boom was braced on each side by small struts which I represented with 15 thou rod. Of course holes had been drilled in the top of the hull to receive these.... Finally I added the stub wings at the rear of the hull. I had drilled two holes in the edges of each wing and inserted a piece of stiff wire which was held in place with CA. The wire ends were held against the hull to mark where the holes should be drilled. (This was actually done before I fixed the boom into place - I am describing it here to make it easier to follow). Add a drop of CA to the ends of the wires and insert into the holes in the hull. A little filler as necessary was run along the joint and the whole rubbed down and primed.









Thanks for looking. I am hoping that this next post will allow the reader to begin to see the shape of an aeroplane beginning to appear, but it wiil be a long time before the wing is put into place because of the structure of this particular machine - the wing was a parasol on cabane and large V struts mounted on the hull sides.

Thanks for looking.

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2 years 6 months ago #147 by Robbo
Amazing work

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