Initial Approximation of the Engine Cowling (1)

SBD Dauntless had a radial engine hidden under typical NACA cowling. The Douglas designers placed its carburetor air intake on the top of this cowling, and the two Browning M2 guns behind it. In the result, the upper part of the SBD fuselage, up to the pilot’s windscreen, had a quite complex shape (Figure 40‑1):

Figure 40-1 Complex shape of the upper cowlings

I am sure that I will tweak this shape multiple times before I reach the most probable compromise between all the reference photos I have. It will be much easier to do it by modifying a simple mesh instead of the complex topologies of the final cowling. Thus I decided to create first a simpler version of this fuselage section and adjust it to the all of the available photos. I will describe this process in this and the next post. Once this shape “stabilizes”, I will use it as the 3D reference in forming the ultimate cowling. Because I am going to recreate all the internal details of the engine compartment, I will create each cowling panel as a separate object.

Adjusting the Tail Tip Shape

In the previous post I formed the shape of the SBD Dauntless tail tip. In this post I will finish its “closing strip” that contains the running light frame. I will also verify the overall shape of the tail tip using the available photos.

There is one thing I didn’t mention in the previous post, just to keep the narration focused on the pure modeling. Before the modeling I carefully studied the reference photos. In the result I found differences in the shape of the curved trailing edges of the fairing behind the elevator. On the photos you can see a straight fragment of this edge (Figure 39‑1a). Its presence means that the curve of the trailing edge was smaller, and the fuselage was somewhat thinner here. You can see the differences between the real shape and my reference drawing in Figure 39‑1b):

Figure 39-1 Another mistake that I found on my scale plans

I did not notice these detail before. As you can see, I applied this modification when I started to model this part.

Modeling the Tip of the Tail

The tip of the SBD tail was a light fairing, attached to the last bulkhead (at station 271 — see Figure 38‑1b). That’s why you can see “NO PUSH” label on the photo in Figure 38‑1a). The tail wheel was attached to the bulkhead 271, which transferred the resulting loads forward, via the tail structure. The tail tip fairing was always free of any significant loads. However, the shape of this part is a combination of the empennage fairing and the last fuselage segment. What’s worse, there is a large opening at the bottom — for the eventual tail wheel deflection (Figure 38‑1b):

Figure 38-1 The tip of the tail — from the top and bottom

Modeling Empennage Details

After the previous post I decided to simplify the empennage fairing. Originally I created it from two separate objects: the fin fairing and the tailplane fairing, split across their fillet. Now I decided to eliminate this troublesome seam by joining these two meshes into single object (Figure 37‑1):

Figure 37-1 Initial merge of the two fairings

I will split it later, along the bottom rib of the fin (there was another panel seam in the real airplane). To simplify creation of the original overlapped panels, I simultaneously split the fin into the forward and the rear part, along one of the original seams.