Modeling a C-47 Propeller Blade

This post is a small digression from the main thread – I will write here about a new method for recreating geometry of historical airplanes.

In one of my previous posts I complained that it is hard to find any reliable drawings of the historical propeller blades from the middle of 20^th century. In particular, the geometry of various popular Hamilton Standard propellers from WWII era is unavailable. I have found in a discussion on one of the aviation forums that Hamilton Standard Company still keeps this data as their “business secret” – even their design from 1936!

So far, all we had were the photos ­– but it is really difficult to precisely recreate from a few pictures such a twisted, complex shape as the propeller blade. However, it seems that there is a new hope! Two years ago I encountered on Blender Artists forum an interesting project. The Author of this thread (nick: NRK) used one of the general photo-based 3D scanning methods to obtain a spatial reference of a C-47 aircraft. Although this is not the SBD Dauntless, it seems that its Hamilton Standard propeller blades are similar to the blades used in the earlier Dauntless versions (SBD-1 .. SBD-3). Thus I asked NRK for the part of his 3D scan that contains the propeller. He sent me it within a few weeks (thank you very much, Nick!). Below you can see the picture of this blade and the contents of the 3D scan (Figure 66‑1):

Figure 66-1 The 3D scan of the C-47 propeller (courtesy Nick Keeline)

Tracing Aircraft Skin Details: Center Wing and the Fuselage

This week I continue mapping the SBD-5 Dauntless skin panels onto my model. After tracing the outer wing sections, described in the previous post, I traced the center wing section (Figure 65‑1):

Figure 65-1 Traced panels on the center wing

As you can see in the picture, I also traced the contours of the wheel bay on the wing surfaces. (These openings disappear, when you enter mesh edit mode, because they are dynamically created by Boolean modifiers. Thus such contours will be useful during further work, because in this way you can see these edges while editing the mesh).

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).