Using Panel Lines to Verify the Fuselage Shape

In every creative process, after each “big step forward” you have to stop and carefully examine the results. Usually you have to make various corrections (sometimes minor, sometimes major), before taking the next step. This post describes such minor corrections that I had to make after mapping the key texture of the panel lines.

In my first post published in October, I drew the panel lines on the model, then compared them with the photos. Sometimes a minor difference between their layouts can lead to a discovery of an error in the fuselage shape. I in that post already found and fixed an issue in the shape of the tailplane fillet.

I also mentioned (see Figure 65‑9 in previous post) that I can see a difference in the bottom part of the wing fillet. Now I would like to resume my analysis at this point (Figure 67‑1):

Figure 67-1 Difference in the shape of the wing fillet bottom seam

Continue reading Using Panel Lines to Verify the Fuselage Shape


Tracing Aircraft Skin Details: Panels on the Outer Wings

I always start drawing the image of the aircraft skin by tracing the lines of the main panel seams. They will form a kind of reference “grid”, which later I will fill with other details: rivet seams, inspection doors, etc.

I will draw all these technical details in Inkscape, because it is much easier to modify such shapes in this vector-based program than in GIMP, which is mainly intended for the raster images. What’s more, I can export this scalable vector graphic from Inkscape to a raster image of any resolution.

Initially I prepared in Inkscape an empty drawing, set up its layer structure, and placed the appropriate links to reference drawings on the UV and Reference layers (Figure 64‑1):

Figure 64-1 Preparing the “canvas” for the texture drawing (Inkscape)

I duplicated here the basic structure for the detailed bump map, which I worked out during my P-40B project. It is explained in all details in the “Virtual Airplane” guide (chapters 3 and 4 in Vol III, or chapters 6 and 7 in the complete edition). In this case I just used the hierarchical layers feature for grouping the related layers (in Panels, Fabric) together. (This feature was introduced in the latest Inkscape 0.9x, while the guide was written earlier, using older versions of this software).

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A New Book — and New Fixes in the Model

Last week I found a new edition of Bert Kinzey’s “SBD Dauntless” book (Figure 59‑1). After ten years break, Bert started to continue his “Detail & Scale” series, this time in a different form: digital editions. This e-book is the “updated and revised” version of an earlier publication (from 1995). For me, the most important part of Kinzey’s books are the “walk around” photos. They differ from all other “walk arounds” by careful selection of the pictures and comprehensive comments that explain many technical details depicted on these images. Usually these comments are as important as the photos.

Figure 59-1 Bert Kinzey’s book and one of the photos from inside

Continue reading A New Book — and New Fixes in the Model

Final Adjustments of the Model Shape

While working on the cowling details, I discovered that the SBD-5 from the Commemorative Air Force (“white 5”) uses a non-original Hamilton Standard propeller. It has larger hub and a pair of bolts in the middle of the hub barrel edges. (As I wrote in this post, the original Hamilton Standard hubs used in the SBDs were smaller, thus they had a single bolt in the middle of each barrel edge). What’s more, I also noticed that the centerline of my model does not precisely pass through the tip of the propeller dome visible in this photo. When I corrected this mistake, I also noticed that the edges of certain cowling panels in my model are minimally below their counterparts on the photo. I examined this difference and decided that I should fix it by rotating the camera of this projection around the fuselage centerline. It was really a “cosmetic” adjustment — the rotation angle was about 0.7⁰. However, suddenly everything in this model matched better the reference photo — except the horizontal tailplane (Figure 58‑1):

Figure 58-1 Improved matching of my model to the largest reference photo

Continue reading Final Adjustments of the Model Shape

Verification of the Model Geometry: the Wing

In this post I will continue verification of my model by matching it against the photos. This time I will check the wing geometry.

In the first photo from the Pacific Aviation Museum (in my model it is marked as PAM-1) I identified several differences (Figure 31‑1):

Figure 31-1 First differences that I found in the outer wing panel

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Matching the Model to the Photos

During the previous weeks I formed two main elements of my model: the wing and the main part of fuselage. As you saw, I could not resist myself for adding some details to the wing (like the ribs and spars of the flaps).

Now I think that this is a proper time to stop modeling for a moment and compare the shape of the newly modeled parts to the real airplane. If I find and fix an error in the fuselage shape now, it will save me from much more troubles in the future! If I find an error in the wing shape – well, I will have more work, because I already fit it with some details which will also require reworking… You will see.

The idea of using photos as a precise references emerged from the job that I did two years ago. One of my colleagues asked me if I can recreate the precise shape of the stencils painted on an airplane. He wanted to determine details of the numbers painted on the P-40s stationed in 1941 around Oahu. He sent me the photo. I started by fitting the 3D model to this historical picture, finding by trial-and-error the location and focus of the camera (as in Figure 29‑1):

Figure 29-1 Using an photo to precisely recreate stencils and roundels of an historical P-40B

Then I made the model surface completely transparent. I placed the opaque drawing (texture) of the large white tactical numbers on its fuselage, and the black, smaller, radio call numbers on the fin. I rendered the result over the underlying photo, finding all the differences. Then I adjusted the drawing and made another check. After several approximations I recreated precisely shapes and sizes of these “decals”.

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Finishing the Wing

In this post I will finish the “general modeling” phase of the wing, recreating the last missing elements. Of course, the result presented in this section is not the “final product”. It is just detailed enough for the next phase — applying textures and materials. (I will do it when I form the whole model). After applying the textures I will come back to this wing during the detailing phase, and recreate all its small details (like various small openings, aileron hinges, running lights, landing light, etc.).

Finishing the wheel bay, I decided to add the rounded flange around its edges (Figure 21‑1):

Figure 21-1 The flange around the wheel bay
Figure 21-1 The flange around the wheel bay

I just did it because I do not like to see a non-realistic, “suspended in the air” edge of an opening. A part of this flange has to fit into the bottom of the fuselage. At this moment I left on that flange an “informal”, elevated fragment. I will fit it to the fuselage when it will be ready.

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Modeling Wing Ribs and Spars

Inside the Dauntless landing gear bay (which I cut out in the previous post) you can see fragment of the wing internal structure. Because I plan to create this model with retractable landing gear, I have to recreate these details. During this “general modeling” phase I will create here just the few key ribs and spars. I will show it in this post. The remaining details have to wait for the detailing phase.

Examining the photos I identified two auxiliary spars and three ribs as the key elements of this structure (Figure 20‑1):

Figure 20-1 Key spars and ribs of the wheel bay
Figure 20-1 Key spars and ribs of the wheel bay

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Cutting Out the Landing Gear Bay

In this post I will cut out the opening of the landing gear bay in the wing. In the SBD Dauntless its shape consists a rectangle and a circle (Figure 19‑1):

Figure 19-1 Landing gear bay in the SBD Dauntless
Figure 19-1 Landing gear bay in the SBD Dauntless

However, when you look closer, you will notice that the contour of the main wheel bay is not perfectly circular. There is a small deformation of its shape on the leading edge (see Figure 19‑1). I think that it looks in this way because of the technological reasons. Another feature of this opening is the fragment “cut out” in the bottom part of the fuselage, below the wing. (We will make it when we will form the fuselage).

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Modeling the Center Wing

On the first glance the SBD center wing section seems to be a simple rectangular (i.e. constant chord) wing, with modified leading edge (Figure 18‑1):

Figure 18-1 Center wing section — the basic shape
Figure 18-1 Center wing section — the basic shape

However, the landing gear openings visible on the photo can be difficult to recreate in a mesh smoothed by the subdivision surface modifier.

Continue reading Modeling the Center Wing