Before you organize the original blueprints of an aircraft, collect as many reference photos as possible, and familiarize yourself with the aircraft shape, main assemblies and – especially – their joints. You will need all this knowledge to quickly recognize the drawings you need. About 60% of the original blueprints depict various small, internal details (tubes, brackets, plates, etc.) which are necessary only when you would like to build a real, flying airplane.
To select a useful subset of these blueprints, I had to review all the drawings in the microfilm set, and copy some of them into one of the target folders:
You can do such a “review” using two File Explorer windows: one for the source drawing list (of course with the preview pane), and the other for the target folder.
Recreating geometry of a historical aircraft is usually a painstaking, iterative process. You can see this in my work on the SBD Dauntless. During the long hours of studying the photos and trying to figure out the precise shape of this plane I often wished to have its source blueprints! For many years the access to the original documentation was “the Holy Grail” of the advanced modelers. (Everybody wished to have this ultimate resource, but only few saw it. And even those, who saw these drawings, often did not know what they are seeing).
When the production of an aircraft is definitely closed, and it quits the service, its blueprints are packed into manufacturer’s archives. After a few decades most of these companies are sold, while the less successful ones are out of the business. The original technical documentation of an aircraft usually becomes a bunch of useless, unreadable paper rolls that disappear in trash bins.
This winter I was busy with my daily business and took a break from the SBD model. However, in February and March I spent few Sundays helping in another project: the Fokker D.V biplane, used in 1917 as an “advanced trainer” by German Air Corps:
I was asked to take part in this project by C. West. He did all the research and provided all the materials: blueprints and photos. My part was recreating the geometry of this aircraft, especially its fuselage frame made of steel tubes. All what we had was a dozen of various archival photos, a poor general drawing, and the landing gear dimensions:
In this case I had to turn the available photos into the precise reference, as I did for the SBD, then use them to determine the required geometry details.
After “mounting” the R-1820 engines into my SBD models, I decided to recreate some details of the inner cowling (the cowling panels placed behind the cylinder row). In this post I will form the missing parts of the carburetor air ducts, hidden under the NACA ring. There are significant differences in this area between various SBD versions, which never appeared in any scale plans, or in any popular monograph of this aircraft. I think that the pictures presented below highlight these differences. They can be useful for all those scale modelers who are going to build the SBD “Dauntless” models with the engine cowlings opened. (Sometimes you can encounter such advanced pieces of work on the various scale model contests).
Let’s start with the SBD-5s (and -6s), which are better documented (because they were produced in much larger quantities). They had a dual intake system, of the filtered/non-filtered air, which I discussed it in the previous post. I already recreated the two intakes of the filtered air, placed between the engine cylinders. Now I have to create the central, direct air duct and its opening at the top of the internal cowling.
Figure 94‑1 shows the initial state of my SBD-5 model:
In my previous post I have finished the second variant of the R-1820-52 “Cyclone” engine, which was used in the SBD-3 and -4. (It looks like the earlier R-1820-32 model, mounted in the SBD-1 and -2). In the resulting Blender file linked at the end of that post you will find two “Cyclone” versions: the R-1820-52 (for the earlier SBD versions, up to SBD-4) and the R-1820-60 (for the SBD-5 and -6). Each of these engines has its own “scene”.
To “mount” these engines into my SBD models, I imported both scenes to the main Blender file. I defined each engine variant as a group, to facilitate placing them in the aircraft models as the group instances. I also added the firewall bulkhead and updated the shape of the cowling behind the cylinder row. (I will refer to this piece as the “inner cowling”). So far I did not especially care for the shape of its central part, hidden below the NACA ring. Now I updated it for the real size and shape of the engine mounting ring (Figure 93‑1a):
In this post I will finish my model of the R-1820-52 “Cyclone”. (This is the continuation of the subproject that I started reporting in the previous post). Figure 92‑1 shows the oil sump, used in this engine:
I decided to write a post about the first decade of the R-1820 “Cyclone” development (up to the R-1820-60 version, i.e. 1940). This engine was used in many designs from 1930s, and you can find the references to its various models in many technical specifications. However, sometimes it is difficult to determine how such a referenced version looked like! The early models of the “Cyclone” were produced in small batches, so there is less historical photos. Sometimes even the specialists from the museums are misguided: in one of them, you can find a SBD-3 fitted with the engine and the propeller from the SBD-5. My query, which resulted in this article, started with comparison of the R-1820-60 (used in the SBD-5) and the R-1820-52 (used in the SBD-3 and -4). I have found so many differences, that I started to wonder about the engine used in the pre-war SBD-1 and SBD-2. (They used the earlier “Cyclone” version: R-1820-32). The results presented below may be interesting to the modelers who recreate aircraft from this period (for example – the Curtiss “Hawk”, or the Grumman F3F-2 “Flying Barrel”).
Let’s start from the beginning: below you can see the first model of the R-1820 family, designed in 1931 (Figure 90‑1):
Frankly speaking, there is only a general resemblance to the later “Cyclone” versions. Note the small crankcase front section and the “archaic” cylinder heads. (They have different shape, and their fins are much shorter and widely spaced: these are indicators of a simpler casting technology). Another strange feature is the exhaust, which could be also mounted in the reversed (i.e. forward) direction. (Some of the aircraft from this era used front exhaust collectors). This engine used large spark plugs, mounted horizontally (in parallel to the centerline). It was rated at 575hp on takeoff, and used in some contemporary designs, like the Curtiss “Hawk” biplane.
The engine is the heart of every powered aircraft. In the case of the SBD it was the Wright R-1820 “Cyclone 9” (the “G“ model). In fact, this engine was one of the “workhorses” of the 1930s: designed in 1931, it was used in many aircraft, especially in the legendary DC-3. “Cyclone” was a reliable, fuel-saving unit for the Navy basic scout type. (Remember that the “Dauntless” was not only the bomber: it was also a scout airplane). In general, the R-1820 is a classic nine-cylinder, single-row radial engine (Figure 83‑1):
The R-1820 G had been produced for over two decades, not only by the Curtiss-Wright, but also (under license) by Lycoming, Pratt & Whitney Canada, and Studebaker Corporation. Thus various less important details of this engine “evolved” during this period. In this post I would like to highlight some of these differences. I will focus on the forward part of this engine, because at this moment I am going to create a simpler model of the “Cyclone”, intended for the general, “outdoor” scenes. Inside the closed NACA cowling, you can see only its forward part. (Thanks to the air deflectors, placed between the cylinders – see Figure 83‑1). In such an arrangement, the visible elements are: the front section of the crankcase, cylinders, ignition harness, and the variable-pitch propeller governor. While the front section of the R-1820 crankcase remained practically unchanged in all versions, and the governor depends on the propeller model, I could focus on the cylinders and their ignition harness.
Identification of the version differences is the basic step, because otherwise you can build a model of non-existing object that incorporates features from different engine variants.
In this post I will work on the weathering effects of the color texture, while in the next one I will add scratches and some other remaining details.
The weathering effects that you can observe on the aircraft from WWII era are quite “dramatic”. The paints used in mid-20th century were not as chemically “stable” as the contemporary coats, thus they could change their hues in few months of intense service. The archival color photos below show an extreme case of this effect (Figure 75‑1):
These photos were taken by Frank Sherschel on 14th November 1942, for the “Life” magazine. The SBD-3s depicted on the pictures belonged to VMSB-241 squadron, stationed at Midway in that time. Marines received these aircraft in July 1942, but all of them were already used before – most probably on the U.S. Navy carriers. I think that in November 1942 these SBDs had accumulated about 10-11 months of the war service. I will use them as an extreme case of the weathering. (It is always good idea to recreate such an ultimate case in the texture, because you can always make your model “newer” by decreasing intensities of the weathering layers. On the other hand, you cannot use more than the 100% of their intensities, thus you cannot make your model “older” than you initially painted).
Because of the holiday break, during July and August I will report my progress every two weeks. I will return to weekly reporting in September.
I have just begun the third stage of this project: “painting” the model. At this moment I am unwrapping its meshes in the UV space . I will deliver you a full post about this process next Sunday. Today I will just signalize how it looks like.
So I started by creating a new reference picture. It had to have a rectangular shape. Inside I placed my drawings of the fuselage, wings, and the tailplane (Figure 60‑1):