Modeling the Aileron

In the previous post I have modeled the aileron bay in the SBD Dauntless wing. However, it was one of the cases when I followed my intuition and the mathematical precision of the computer models instead checking how this detail looks in the real airplane. So let’s do it now. I have reviewed many photos, Figure 14‑1 shows the one which is the most useful (made by my friend in 2014 in one of the air museums):

Figure 14-1 Internal details of the aileron and flaps walls
Figure 14-1 Internal details of the aileron and flaps walls

We can see here that the flaps are attached (via a very long hinge) to a reinforced structure which resembles a spar. It ends at the first aileron hinge. On the other hand, the aileron is mounted on three “point” hinges which protrude from the ribs. Thus the curved sheet metal that closes the aileron bay has much lighter structure, because it is merely a cover. It is riveted to the ribs and other wing skin panels. The “sharp corner” at the upper edge of the aileron bay is obtained by a fragment of the upper wing skin that overlaps (by about half of inch) the bent, rounded edge of the internal wall.

I recreated in my mesh the auxiliary spar along the flaps and the fragment of the wing skin that overlaps the upper edge of the aileron bay (Figure 14‑2):

Figure 14-2 Modified wing details
Figure 14-2 Modified wing details

I will model the bent upper edge of the internal wall later, during the detailing phase. The lightening holes in the spar will not be modeled. For such less important openings I will use transparency textures.

At the beginning of the previous post I cut off the wing trailing edge. Now I split it into two objects: the aileron and the flaps. Then I started to work on adapting the aileron mesh. First I simplified its topology: I slid its upper longitudinal edge forward, where the curved leading edge begins (Figure 14‑3a). I do not need its bottom counterpart, so it will disappear. In the effect the aileron cross section resembles a triangle, as in the real airplane. (Such simplifications of the theoretical trailing edge geometry were common in this aircraft generation).

Figure 14-3 Creation of the aileron leading edge
Figure 14-3 Creation of the aileron leading edge

To form the curved shape of the aileron leading edge I extruded vertically from its bottom edge two face rows (Figure 14‑3b). Then I closed the remaining gap with another row of faces.

After small adjustments of their vertices at the wing tip I obtained the rounded shape of the aileron leading edge (Figure 14‑4):

Figure 14-4 Updated aileron mesh
Figure 14-4 Updated aileron mesh

Then I did some further adjustments, checking if the gap between the aileron and the wing is wide enough (0.2”) for the whole aileron rotation range (from -10⁰ to +17⁰). Figure 14‑5 shows the result:

Figure 14-5 The first attempt to fit the aileron to its bay
Figure 14-5 The first attempt to fit the aileron to its bay

However, comparing this result with the photos, I discovered that I fitted it too tightly! What’s more, I also noticed differences in the shapes of the aileron tip and its bay between various restored aircraft (Figure 14‑6):

Figure 14-6 Differences in the restored airplanes
Figure 14-6 Differences in the restored airplanes

The outer wing panels were the same in all the SBD versions (at least their external details — see this post) — so I cannot explain these differences as the differences between various aircraft versions. Well, it seems that one of these restored aircraft was modified afterward. But which one?

Restored aircrafts are great resource of information for all modelers. However, some of them contain various modifications. Most of such differences you can find in the airplanes restored before 1990. Since that time the average level of restorations has significantly improved.

To determine which case is wrong, you have to look at the archival photos (Figure 14‑7):

Figure 14-7 Archival photo of the factory-fresh SBD-1
Figure 14-7 Archival photo of the factory-fresh SBD-1

In the picture of a factory-fresh SBD-1 you can see that the tip of the aileron was curved. Nevertheless, I had to widen the gap between the aileron and the wing tip (Figure 14‑8), reproducing the case I can see on the archival photo:

Figure 14-8 Updated shapes of the aileron and its bay
Figure 14-8 Updated shapes of the aileron and its bay

In this source *.blend file you can check all details of the model presented in this post. In the next post I will describe creation of the wing flaps.

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