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):

0038-01
Figure 38-1 The tip of the tail — from the top and bottom

I had no initial idea about the mesh topology that I should use for such a part. Thus I started by copying all of its external edges from the adjacent objects (Figure 38‑2a):

0038-02
Figure 38-2 Preparations before the modeling

Then I worked out an idea of its topology by sketching possible mesh edges on a scrap of paper. (I often do that before I start modeling a complex mesh). You can see the scan of my sketch of this tip in Figure 38‑2b). I “think by drawing”, so this method helps me to better realize the shape that I have to create. These working sketches object do not have to perfect. The more important thing is the order of the individual edges and vertices (identified by the numerical IDs).

When the mesh topology on the sketch looked simple enough, I started building this mesh by extruding the trailing edges of the elevator fairing (Figure 38‑3a):

0038-03
Figure 38-3 First steps in shaping the mesh

Then I extruded the upper edge of the elevator fairing into another rectangular “patch” (Figure 38‑3b). In the next step I extruded similar “patch” from the rudder contour (Figure 38‑4a):

0038-04
Figure 38-4 Forming the upper part of the fairing

Finally I filled the gaps between these three mesh “patches” by creating two rows of new faces (Figure 38‑4b).

0038-05
Figure 38-5 Further adjustments of the mesh shape

While sketching this tip, I decided that it will be better to close it with a separate object — the “closing strip”. Such a strip reproduces the original piece of the sheet metal that contained the frame of the running light. (I thought that the side-view contour of this tail tip might require different edge distribution than the mesh of its sides). At this moment I created the initial segment of the “closing strip”: the part around the running light frame. Then I used it as the reference object for shaping the mesh of the tip sides (Figure 38‑5b).

I split the model surface into separate objects when I expect significant differences in their mesh topology. I “mask” outer edges of such objects by placing them along the original panel seams.

When the upper part of the tip was ready, I started forming its bottom part. As you can see in Figure 38‑6, I did it in the same way as the upper fairing. First I extruded a part of the bulkhead contour (Figure 38‑6a), then I created new faces to incorporate this patch into the main mesh (Figure 38‑6b):

0038-06
Figure 38-6 Beginning of the bottom part

I extruded the side faces of this tip from the bulkhead edge (Figure 38‑7a), then filled the gap in the resulting mesh by creating a row of new faces (Figure 38‑7b):

0038-07
Figure 38-7 Forming of the bottom part

(Note that I had to create more “bulkhead” edges in this mesh than I originally sketched in Figure 38‑2b). Some of these edges came from the original vertices of the elevator edge, while the other were required by the shape of the bottom edge (around the tailwheel opening).

The ultimate number of edges in a mesh is often the sum of the vertices required to obtain appropriate shape on its opposite border edges.

Finally I extruded (Figure 38‑8a) and merged (Figure 38‑8b) the last part of this tip:

0038-08
Figure 38-8 Forming of the last fragment of the bottom part

As you can see in Figure 38‑8b), I added an additional, diagonal edge below the trailing edge. I did it to obtain a better shape of the elevator fairing.

Figure 38‑9 shows the smooth resulting shape:

0038-09
Figure 38-9 Resulting shape

I had no photo taken from the top or the bottom that would precisely reveal the vertical contours of this part. Thus I assumed that this tip is a smooth continuation of the tail cone (as I marked with the dashed line in Figure 38‑9). In the next post I will verify this assumption using available photos.

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

Advertisements

One thought on “Modeling the Tip of the Tail

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s