Tracing Aircraft Skin Details: Center Wing and the Fuselage

This week I continue mapping the SBD-5 Dauntless skin panels onto my model. After tracing the outer wing sections, described in the previous post, I traced the center wing section (Figure 65‑1):

Figure 65-1 Traced panels on the center wing

As you can see in the picture, I also traced the contours of the wheel bay on the wing surfaces. (These openings disappear, when you enter mesh edit mode, because they are dynamically created by Boolean modifiers. Thus such contours will be useful during further work, because in this way you can see these edges while editing the mesh).

I also outlined contours of the bomb bay panels, which are modeled separately “in the mesh” (every panel is a separate Blender object). I did it, because the panel lines that I draw on this image will be used as the input for various final textures. In some case I will use them as the source of “dirt” that occurs around every cleft in the aircraft skin. These thick lines will provide a decent effect on the textures.

Of course, I also used the reference photos to verify panel locations (Figure 65‑2):

Figure 65-2 Checking the traces on the archival photo

When I compared panel lines in the photo and my scale plans, I discovered that I have to make some corrections. There was a significant difference in the size of the fuel line covers (Figure 65‑2). In the real aircraft they were somewhat larger than on my drawings.

In similar way I mapped the empennage panels. The growing number of identified differences between the reference drawings and real airplane forced me to use these panel lines as a kind of additional reference picture. That’s why I also decided to trace the ribs on all of the aircraft control surfaces.

Once I mapped these details, I started tracing fuselage panels. First I drew their “horizontal” lines that run along the longerons (Figure 65‑3):

Figure 65-3 Tracing the fuselage and tailplane panels

Fortunately, it was quite easy, because during the modeling phase I intentionally placed some edges of the fuselage mesh along rivet seams. Now this effort pays off.

Then I verified these new lines on the reference photo. I discovered that while the aileron and elevator ribs on the photo match my scale plans, the rudder ribs have different locations (Figure 65‑4):

Figure 65-4 Checking the traces on the side photo

I also noticed another difference in the upper part of the tailplane fairing. Its outer edge runs along one of the fuselage longerons. In my model it is placed somewhat higher than in the photo (Figure 65‑5):

Figure 65-5 Checking the tailplane fairing details

When the other fuselage lines match their counterparts on the reference photo, this difference means an error in the shape of my model. I analyzed this area, and I started to suspect that the gap between the real line and line on my model is caused by the difference in the fairing shape. However, to be sure, I needed more evidence to proof this hypothesis. I carefully checked all available photos of this area (Figure 65‑6):

Figure 65-6 Further differences in the fairing details

Ultimately, I had found that the upper edge of the tailplane fairing is too high. In my model it overlaps the longeron line, while it should be adjacent to this panel seam. Lowering this edge will decrease the fillet radius in the upper area of the horizontal stabilizer fairing.

Well, it means that I have to revert to the modeling, and adjust the shape of this part (Figure 65‑7):

Figure 65-7 Adjusting the tailplane fillet shape

I did most of the modifications shown in Figure 65‑7 by shifting mesh vertices along their edges. Fortunately, this command has an “update UVs” option, which automatically updates the mesh UV layout. Thus when I updated the fairing mesh and I looked on its UV map, the mesh was already updated there. I just had to export it to the reference image, and shift few lines into new location (Figure 65‑8a):

Figure 65-8 Adjusting texture image

After these modifications, fuselage panel lines match the photo (Figure 65‑8b).

I had another kind of troubles with the lower part of the fuselage, behind the wing trailing edge. The UV layout of this mesh fragment has a significant distortion. A straight line on the model maps to a curve in this area. What’s more, I had to split this area (using seams) into two separate parts, which also creates some continuity issues (Figure 65‑9):

Figure 65-9 Details of the bottom fuselage surfaces

It was quite difficult to find a proper curve on the UV plane that transforms into a straight line on the model. This process required several iterations. After I managed to keep shapes of these lines within acceptable tolerance, I identified another difference between my model and the photos: a short seam below wing fairing trailing edge (Figure 65‑9). While in the real airplane it was a nearly straight line, in my model its rear part reproduces the conical shape of the trailing edge cross section. I suppose that this fuselage area had a visible deviation from the “ideal” conical shape, caused by the technological constrains. (It is difficult to apply such a more pronounced curvature, as you can see in my model, to the aircraft skin stringer). I will deal with this issue in the next post.

Figure 65‑10 shows the complete set of the panel lines, mapped on the SBD-5 surface:

Figure 65-10 Panel seams mapped on the SBD-5 model

I still have to map the differences that occur in the other Dauntless versions (SBD-1, SBD-3). Frankly speaking, I started to note some variations in the layout of the fuselage panels between various restored SBDs. Sometimes it is difficult to distinguish the real, historical differences between various versions from the side-effects of a particular restoration.

In this source *.blend file you can evaluate yourself the current version of the model, and here is the Inkscape file.