Can We Rely on Scale Plans?

To build the model from scratch you need a good reference. Initially I decided to use for this purpose detailed scale plans from the monograph published by KAGERO in 2007 (Authors: Krzysztof Janowicz, Andre Zbiegniewski, ISBN: 978-83-60445-25-9 – see Figure 1-1):

Figure 1-1: The source

It contains SBD Dauntless plans in scale 1:48, traced by Krzysztof Lukasik. They are quite detailed (up to the rivets on the aircraft skin). I scanned them (at 300 dpi). Below you can see a fragment of their side view (Figure 1-2):

Figure 1-2: A fragment of Mariusz Łukasik’s scale plans

Apparently these drawings were made using Corel Draw or similar software. During the initial verification I did not find any flaws (Figure 1-3):

Figure 1-3: Basic verification of the scale plans (SBD-3)

All the key locations of the fuselage are in the same place in the side view and the top view. The proportions of the length and the span of the top view is correct: 0.787. (This ratio comes from 996/1266. According the dimensions specified in this monograph, the length of the SBD-3 fuselage was 996 cm (32’ 8”), while the wing span of all the Dauntless versions was 1266 cm (41’ 6”)).

This good impression disappeared, when I compared side views of two different Dauntless versions: SBD-3 and SBD-5 (Figure 1-4):

Figure 1-4: Comparing SBD-3 and SBD-5 fuselages

According the monograph data, SBD-5 fuselage was 4 inches (about 10.1 cm) longer than SBD-3. (The SBD-5 and SBD-6 fuselage was 33’ long. Most probably it has slightly different engine cowling and the propeller. The airframe after the firewall was the same in all Dauntless versions). However, in this monograph they have the same length!

Figure 1-5: Archival Dauntless drawing (BuAer, 1944)

Maybe the textual data contains an error? In such a situation I try to find an “official”, archival drawing of the aircraft. They do not show many details, but contain the key dimensions. I have found on the Internet a BuAer Navy drawing of the SBD-5, from 1944 (Figure 1-5):

It seems to be traced in ink, so it follows the basic rules of the technical drawings:

1. The outer contour is marked by a thicker line;
2. The “real” contour lies on the outer edge of this thick line;
3. When there is a difference between the explicit specified dimension and the size measured on the drawing, the explicit dimension prevails;

From the front view you can read the precise wing span: 41’ and 6 5/16“. From the side view you can read the exact length: 33’ and 1/8“.

This BuAer drawing isn’t an ideal source: it does not contain such details as panel seams. You can also find here some manual errors, made by its draftsman. While the aspect ratio of the top view matches the span and length specified in the dimensions, the actual fuselage length on the side view is somewhat shorter (see Figure 1-7). (The positions of the wing and horizontal tailplane match in the side and top view match each other. It seems that the part of the vertical tail contour was shifted). On the other hand, the BuAer top view is a little bit asymmetric, and the firewall line is moved forward a little (see Figure 1-6).

The good news is that the wing and the tailplane arrangement on the KAGERO plans and the BuAer drawing match each other (Figure 1-6):

Figure 1-6: Comparing KAGERO and BuAer top views

Then I compared the side views of these drawings (I marked the correct fuselage length measured on the BuAer top view in red):

Figure 1-7: Comparing KAGERO and BuAer side views

The differences of the side views are overwhelming: this is not only the engine cowling but also the cockpit canopy, the fin, and the tailwheel. (In general: none of these drawings shows the correct tail).

Thus, answering the title of this post, I can conclude: never rely on the scale plans as the only reference about the aircraft you are modeling! For example – in this case I need another source, to fix these drawings.

In the next post I will show you how to verify these drawings using photos.

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Note: I compared these plans using two free, Open Source programs: GIMP (it is similar to Adobe Photoshop) and Inkscape (it is similar to Corel Draw or Adobe Illustrator). You can find more about them in this e-book.