Witold Jaworski Posted February 13, 2016 Author Share Posted February 13, 2016 The tip of the SBD tail was a light fairing, attached to the last bulkhead (at station 271 — see figure "b" below). That’s why you can see “NO PUSH” label on the photo in figure "a". 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: 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 (see figure "a" below): 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 "b", above. 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 (see figure "a" below): Then I extruded the upper edge of the elevator fairing into another rectangular “patch” (see figure "b", above). In the next step I extruded similar “patch” from the rudder contour (see figure "a", below): Finally I filled the gaps between these three mesh “patches” by creating two rows of new faces (as in figure "b", above). The resulting subdivision surface required some minor adjustments of the control mesh vertices. They formed the proper shape of the mesh behind the elevator trailing edge (figure "a", below): 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 (see figure "b", above) 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 below, I did it in the same way as the upper fairing. First I extruded a part of the bulkhead contour (figure "a"), then I created new faces to incorporate this patch into the main mesh (figure "b"): I extruded the side faces of this tip from the bulkhead edge (figure "a", below), then filled the gap in the resulting mesh by creating a row of new faces (figure "b", below): (Note that I had to create more “bulkhead” edges in this mesh than I originally sketched (see the second figure in this post). 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 and merged the last part of this tip: As you can see in figure "b" above, I added an additional, diagonal edge below the trailing edge. I did it to obtain a better shape of the elevator fairing Figure below shows the smooth 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. Quote Link to post Share on other sites
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