Modeling a Forged Part

There are dozens forged or cast parts, like the one below, in an aircraft. Forming their shapes with polygon meshes and Bevel modifiers is difficult, because of their complex, rounded edges. Usually it takes many hours, in the worst cases – it is impossible. (For example: in 2018 I could not model in Blender this propeller governor in “one piece”).

Figure ‎128-1 An example of a forged part

In this post I am proposing a new workflow for recreating these machine parts in Blender. It is based on a custom modifier named Fuse with Collection. This modifier uses the new SDF Geometry Nodes, introduced in Blender 5.1. It converts a group of simple solids into voxel volumes, merges (“fuses”) them into a single volume, performs a Laplacian smoothing, then reconstructs the outer boundary of the result as a manifold mesh. Although it sounds like a complete abstraction, Fuse with Collection coupled with a Decimate and an eventual Boolean modifier creates an effective “stack” for modeling cast or forged machine parts.

Baking Reference Image for Textures

In the previous post we projected scale plans onto 3D model surface:

Figure ‎127-1 Reference drawing, mapped onto model surface

In this post we will use so-called “texture baking” method to unwrap this image into the UV space. This way we create an accurate reference image for various textures:

Figure ‎127-2 Reference drawing, unwrapped into the UV space

(This is the continuation of the tutorial from the previous post.)

Projecting Reference Images onto Model Surfaces

To work with textures, you need to unwrap your model surfaces in the UV space:

Figure ‎126-1 Model state after UV-unwrapping

However, when it is done, you face another problem: how to obtain an accurate reference drawing of the aircraft skin, mapped onto these unwrapped mesh surfaces? I mean an image like Figure ‎126‑2b):

Figure ‎126-2 How to transform scale plans into a texture reference image?

We need such a reference to draw the bump maps and reflectivity maps. It must be accurate, otherwise we would spoil the overall precision of our model. In this and the next post I propose a new method to do this in a (relatively) quick and easy way.

Curtiss Propellers of the Early P-40 Variants (2)

In the previous post in this blog I described the state of my P-40 model at the end of 2020. In that time, I was missing information about its propeller blades. Ultimately I identified the two propeller variants used in the early P-40 (up to the P-40C version): first batches used hollow steel blades, while in the later aircraft they were made from solid dural. I expected that sooner or later I will find new information about their geometry, so I left their meshes in the ready for further modifications (see Figure ‎124‑5 in the previous post).

Three years later I exchanged some materials about various aircraft with a modeler from Ukraine. Among them there were three inconspicuous images:

Figure ‎125-1 Geometry of the Curtiss “Tomahawk” blades according to a Soviet source

It looks like a scan of an unidentified printed material (a book?). I can read it, so I quickly learned that tables a) and b) describe blade geometry of the Curtiss “Tomahawk” propellers. Image a) describes its duraluminum variant, while image b) – the hollow steel version. Image c) depicts the measurement scheme and explains the meaning of the columns from these tables.

Curtiss Propellers of the Early P-40 Variants (1)

The classic metal propeller blade resembles a thin, twisted wing. Unfortunately, you can seldom find any detailed drawing of their geometry. Many scale plans, even those of high accuracy, often skip this detail. For example, there are accurate P-40 drawings made by Jumpei Temma. They are based on the available Curtiss blueprints and photos of restored P-40s. J. Temma drew the propellers in some of the side views, but not in the front view, so you cannot determine the blade shape.

Temma’s drawings of the “Tomahawk” propeller and spinner are based solely on the photos, because in the original P-40 documentation you can find only a few clues about this subassembly. Propellers were produced in specialized factories, usually run by another company. For aircraft designers, the propeller was just a “complete part” coming from outside. What is interesting, the key manufacturer of the aviation propellers – Hamilton Standard – still declines to reveal the geometry of their historical models (see this post).

The Curtiss company was less successful in their business: it disappeared in 1948, and the documentation of their propellers is lost. All what we have now are aircraft photos, but it is difficult to determine the accurate widths of the twisted shape blade using these pictures. The best source material that I found is an illustration from Curtiss advertising booklet from 40’s. It depicts the hollow steel propeller blade. It looks like the one used in the early, long-nose P-40s:

Figure ‎124-1 “Anatomy” of the Curtiss hollow steel blade

Writing Progress: Vol. III Published!

I am still working on the aircraft modeling guide. Since yesterday, its vol. 3 (of 4) is available in the web shops (645 pages, 1076 illustrations):

Figure ‎123-1 Cover of the new book (“Materials and Textures”) [fourth edition]

It teaches you how to “paint” a computer model. The course starts from the absolute basics, then in the subsequent sections we gradually enhance the initial visualization, until it resembles a real-life photo.

New Guide about Modeling Historical Aircraft

My new book on modeling historical aircraft is already available in the web shops. This is the second volume of the new (fourth) edition of the “Virtual Airplane” guide:

Figure ‎122-1 Cover of the new book (“Modeling”) [fourth edition]

Recreating the P-40B: 3D Reference of the Fuselage (2)

In this post I will complete the 3D reference that I started in the previous post. Here is a link to the Blender file that contains 3D reference skeleton of the “long nose” P-40, described in the text below. It was compiled from all available blueprints.

Studying the dimmed blueprint scans, I was not able to read some horizontal ordinates placed close to the top and bottom segments of this fuselage. This created gaps in my 3D grid (Figure 121‑1a):

Figure 121-1 Additional vertical planes

Fortunately, in the fuselage ordinates diagram (dwg 75-21-020) I was able to identify ordinates of two vertical planes, placed at +3” and +6” from the symmetry plane (Figure 121‑1b). This allowed me to interpolate these datapoints with curves.

Recreating the P-40B: 3D Reference of the Fuselage (1)

At this moment I am working on second volume of my book about 3D modeling.  It describes building a 3D model of a WW2 aircraft on the example of the P-40B. Preparing for this work, I discovered that the original documentation of this early P-40 variant (also known as “long nose Warhawks”) is missing. On the other hand – you can find plenty of the “short nose Warhawk” blueprints (related to the P-40D later variants), as well as some P-36 drawings. I started by picking over 1000 original Curtiss blueprints and sketches related to the P-40, XP-40, and the P-36 from the vast resources of the AirCorps Library. Then I analyzed their contents, comparing them to the available historical photos. I described this process in this and following posts, written in 2019. Ultimately I traced side view of the P-40B. I also concluded that a 3D visualization of the available ordinals will be a better reference. In the previous posts I built such a reference for the SBD Dauntless. In this and the next post will I describe similar work on the fuselage of the early P-40 variants (P-40-cu, P-40B, P-40C).

I prepared an empty Blender file. For the convenience, I placed there my side view (from this post, see Figure 102-15). As for the SBD model, I assumed that 1 Blender unit = 1 in. For the main part of this fuselage, spanning from the firewall to the rudder, I used two P-36 diagrams. First of them (dwg 75-21-140) provides locations of the fuselage stiffeners at each bulkhead. There is also its modified variant (dwg 75-21-836) for the XP-40:

Figure 120-1 XP-40 fuselage stiffener dimensions (dwg 75-21-836)

Original SBD Dauntless Blueprints: Ordinates

I decided to upload the Blender file in which I reproduced in the 3D space the original ordinates of the SBD fuselage and wing. (I described creation of this 3D reference in my previous posts). I think that in this form they can be useful for other modelers, who would like to recreate the geometry of this aircraft. Here is the link to the *.blend file (102MB) that contains the model presented below:

Figure 119-1 3D reference of the fuselage and wing ordinates