In previous post I discussed how the SBD landing gear retracts into its wing recess:
In principle, it is simple: the landing gear leg rotates by 90⁰. However, the parts responsible for shock strut shortening during this movement increase mechanical complexity of this assembly. The figure above does not even show the deformations of the brake cable, which follows the shock strut piston movements.
For some scenes I will need the landing gear extended, while for the others – retracted. In practice, moving/rotating each part individually to “pose” my model would be a quite time-consuming task. That’s why I created a kind of “virtual mechanism”, which allows me to retract/extend the landing gear with a single mouse movement. In the previous post I already presented its results in this short video sequence. In this post I will shortly describe how I did it.
The SBD shock absorbers had to disperse a lot of the kinetic energy of landing aircraft, minimizing the chance that the airplane accidentally “bounce” back into the air. (This is a key requirement for the carrier-based planes). For such a characteristics you need a relatively long working span between the free (i.e. unloaded) and the completely compressed (i.e. under max. load) strut piston positions. Indeed, you can observe that the Dauntless landing gear legs are much longer in the flight than in their static position on the ground (Figure 80‑1):
The working span of the SBD shock strut piston was about 10” long, while the difference between the static and the free (extended) piston positions was about 7.5”.
I published my previous post a month ago, but the current stage of this project – detailing – requires less frequent reports. (Otherwise the posts would become rather monotonous: week after week they would describe making similar things, using the same methods). I started this last phase of the Dauntless project by recreating its main landing gear. First, I had to finish it, then I am able to write about this process. Thus I will describe it in this and next two posts. (I will publish them in a short sequence, week after week).
The retractable main landing gear of the SBD was probably a direct descendant of an experimental solution used in the Northrop 3A fighter prototype. In general, it looks quite simple:
In my previous post I finished the case of so-called “two-color” U.S. Navy camouflage, which was used between September 1941 and January 1943. You can observe on the archival photos that its non-specular Sea Gray / Light Gray combination was especially prone to weathering, and accumulated every grain of the soot and drop of the oil stains. Simultaneously the weathered Sea Gray paint became more and more white.
The new, “tri-color” camouflage, introduced in January 1943, fixed these flaws, and provided better protection on the vast, dark waters of the Pacific. You can see an example of this pattern on an SBD-5 from VB-16 (Figure 78‑1):
However, this historical photo has a technical flaw: its colors are “shifted toward blue”. You can unmistakably see this “shift” in the color of the bottom surface (it was Intermediate White). I was not able to correct this deviation, finding acceptable. Below you can see another photo of a SBD-5 from VSMB-231, which colors are more balanced (Figure 78‑2):
The last texture for my model contains various elements that in the plastic kits are delivered as the decals: national insignia, radio-call numbers and various service labels. I prepared it as another vector drawing in Inkscape:
I exported this picture to a raster file named color-decals.png. It has transparent background, because I will combined this image with the other components of the color texture, prepared in previous posts.
It seems that Douglas used a high-quality paint for their SBDs, because I cannot find any trace of chips/flakes, even on such a worn-out aircraft as this from VSMB-241 (Figure 76‑1). However, you can see some scratches on the center wing, trodden by the crew:
In the photo above, the minor scratches are yellow, because Douglas used a yellow layer of Zinc Chromate primer below the camouflage paint. (The interiors were painted with another layer of the Zinc Chromate, mixed with Lamp Black to obtain a darker, greenish hue).
However, the larger area along the leading edge was often trodden to the bare metal, which you can see in the photo. This scratch has a typical, irregular band of the primer around its borders. In this post I will recreate these abrasions.
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).
The color (also known as “diffuse”) map is the most obvious texture, which you can find on every model for games. In my models it is composed of three separate images: the camouflage, the dirt (stains, soot, etc.), and the markings (national insignia, tactical numbers, warning labels, and all other similar stuff). In this post I will compose the basic camouflage texture.
Some time ago I unwrapped the left side of this model (see this post, Figure 62-3). Now I had to complete this work, creating remaining elements of the right side, and unwrapping them on the UVMap layout. The final result looks like the model in Figure 74‑1:
For the precise mapping, I used here the color grid image, which I already used in my previous posts. Note the different square colors on the left and right wing, as well as the different letters on the right and the left tailplane.
I already finished the bump map (in the second-last post), so it’s time to introduce another texture: the reflection (ref) map. It alters the basic reflectivity (gloss) assigned to the material. In addition, it also alters the material “roughness”. (In the typical CG materials the roughness and reflectivity are coupled in an inverse proportion). These two parameters are important, when you have to paint an oil streak or a soot streak. Both are black – the difference between them lies in their reflectivity.
The effects of the ref map are most visible inside these areas of the model that actually reflect the light:
Figure 73‑1 shows two renders of the same model: the upper one was created without any reflectivity map, the lower one uses a basic ref map. (I created this texture around the technical details of the aircraft skin).
This post is a small digression about a modeling technique that you may find useful.
There is a detail on the bottom surfaces of the SBD center wing: an opening, made partially in the cover of the fuselage belly (Figure 72‑1):
The difficult part of this detail is its flange, stamped in the fuselage cover. I just have two photos of this element, both of average resolution. On both of them you can see a typical circular recession, made around the opening in the belly cover. In fact, such a feature is quite common in the sheet metal design (you can see plenty of such stamped flanges in various places inside your car). This is a minor detail, too small for any serious modeling, but too large for recreating it with the textures.