Initial Approximation of the Engine Cowling (2)

In this post I will continue my work on the engine cowling. I started it in the previous week by forming a “first approximation” of the forward part of the SBD Dauntless fuselage. Now I will create the last elements of this auxiliary object.

First of them are the covers around the M2 gun barrels. They were hinged around their inner edges, and their cross-section varies from a semi-circle at the NACA cowling to a flat line at the firewall (Figure 41‑1):

Figure 41-1 Geometry of the gun barrel cover

I started forming this cover from a conic cylinder, created around the gun barrel (Figure 41‑2):

Figure 41-2 Initial geometry of the gun covers

Then I cut out its bottom part and flattened its end section along the side “bulge” (Figure 41‑3):

Figure 41-3 Updated geometry of the gun covers

I formed it to resemble the gun barrel covers as they were in the SBD-1..-4s. Studying the photos I identified that this detail looks a little bit different in the SBD-5 and -6 (Figure 41‑4):

Figure 41-4 Minor differences in the gun barrel covers between the SBD-5 and earlier Dauntless versions

As the last element of this auxiliary object I will form the windscreen. I need it for determining the ultimate slope of the “bulges” around the breeches of the M2 guns, and for checking the shape of its intersection with the fuselage. (If I did it later, it could reveal some unexpected surprises about the fuselage geometry, resulting in additional work).

I used the reference photos to determine the basic radii of the canopy hood and the windscreen cross sections (Figure 41‑5):

Figure 41-5 Shaping initial contours of the cockpit canopy

(In this aircraft canopy hood slide under the windscreen, thus the radius of the windscreen cross-section was a little bit larger). As you can see in Figure 41‑5b), the obtained contours differs a little to my reference drawings. (It seems that on these drawings the top of the cockpit canopy is a little bit lower than I have ultimately found it now on the photos).

In the next step I determined the radii of the cylindrical fragment of the windscreen (Figure 41‑6):

Figure 41-6 Finding the radius of the windscreen glass

It seems that it was not a regular cylinder — its radius at the top of the windscreen seems to be larger than the radius at the bottom (Figure 41‑6a).

I created this cylinder as the first part of the windscreen surface (Figure 41‑7a). I verified its shape using another reference photo (Figure 41‑7b):

Figure 41-7 Forming the front ‘cylinder’ of the windscreen glass

In the next step I removed the rear part of this cylinder and formed the flat, triangular side plates of the windscreen. As you can see in Figure 41‑7b), they were hinged, providing the maintenance access to the M2 guns on the cockpit sides.

Then I extruded two additional rows of faces, forming the upper part of the windscreen (Figure 41‑8a):

Figure 41-8 Forming the remaining faces of the windscreen mesh

When the shape of the intersection between the windscreen and fuselage matched the reference photos, I also verified its side contour (Figure 41‑8b).

Figure 41‑9a) shows the complete object that approximates the shape of the SBD engine cowling. I set its color to red, as I do for all the reference objects in this model:

Figure 41-9 The reference object for shaping the engine cowling panels

In Figure 41‑9b) you can see that it fits pretty well the reference photos. This is a picture of the SBD-5 from Chino Air Museum. The SBD-5 and -6 had their engines and the NACA cowlings shifted forward by about 4”, so did I in this model (see in this post Figure 4-6 for details).

In this source *.blend file you can evaluate yourself the model from this post.


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