In June 2019 I followed C. West suggestion and ordered a set of Douglas SBD original technical documentation from U.S. National Air and Space Museum. Technically these blueprints are stored on several microfilm rolls. In that time all what I knew about this package (NASM id: “Mcfilm-000000408”) was the information printed on the order form:
As you can see, this set has no index, which I could order earlier to examine its contents. When I finally received these microfilms in November 2019, I also discovered the meaning of enigmatic “(roll C” in the item description: it was truncated phrase “(roll C missing)”!
Well, this set was incomplete, but anyway I ordered its high-resolution scans from a local company that provides professional microfilm scanning services to museums. In January I received these data (4700 high-res, grayscale images in LZW-packed TIFF format – in total, about 300 GB). Finally I was able to scroll these blueprints. Frankly speaking, I was afraid that the most important drawings were lost with the missing roll C. Fortunately, during the initial review I noticed many detailed assembly blueprints among the scanned images. I even found a complete inboard profile of the SBD-5:
In the previous post I finally identified Curtiss layout sketch L-10202 as description of the XP-40 geometry, as it was in February 1940. In that time Curtiss was finishing preparations for serial production of the P-40. (The first P-40 from this batch was accepted by USAAC in April 1940). This final variant of the XP-40 resembled the serial P-40-cu, except the tail wheel cover and rear glass frames, “inherited” from the P-36. However, the archival photos revealed minor differences between engine cowlings of these aircraft: the serial P-40 had longer spinner and deeper radiator cover.
It seems that all the original drawings and sketches of the early P-40s that I collected from the AirCorps Library resources describe the XP-40. Thus, first I will prepare the XP-40 side view using this original documentation. Then I will draw a P-40B side contour, using these XP-40 lines and available P-40-cu/B/C photos.
As I showed in one of previous posts, the XP-40 sketches are not only rare, but also in poor shape:
Generally speaking, the early P-40s (-cu, B, C) were “P-36 airframes with inline engines”. Thus, the only unique first-order assembly in these P-40 variants was their engine compartment. So far it seemed that the documentation of this area was lost, and the restoration teams had to rely on archival photos and other restored P-40B/C. (A P-40B restoration teamfrom New Zealand mentioned this in their interview).
In my post from August 2019 (Fig. 98-13 and Fig. 98-14) I described a previously unnoticed layout sketch, that I found among the “uncategorized” P-36/P-40 drawings in the AirCorps “P-40” microfilm set:
It can describe the geometry of the “long nose Hawk” engine cowling. In the same AirCorps Library uncategorized “pile” I also found some regular XP-40 drawings (engine mount, radiator support) and other sketches. However, the lines in all these images are faded, making them nearly unreadable. The L-10202 sketch is the most promising blueprint that I have found. In this post I will try to match this layout to the P-40B fuselage that I prepared in my previous post. I will also use photos to evaluate the results (i.e. for checking if the sketched engine cowling layout matches the real aircraft).
As I wrote in the previous post, it is impossible to find a complete documentation of the early P-40 variants (so-called “long nose Hawks”: P-40cu, P-40B and P-40C). I collected all what is currently available from the Internet portals: blueprints of their direct predecessor (P-36) and drawings of the later variants (the “short nose” P-40D … P-40N). Using these scanned microfilm frames, archival photos and technical descriptions you can recreate the wings, empennage, tail and mid-fuselage of these aircraft.
I started with the most obvious part of the side view: the fuselage. Behind the firewall it was basically identical to the P-36, except the tail wheel cover:
Before you organize the original blueprints of an aircraft, collect as many reference photos as possible, and familiarize yourself with the aircraft shape, main assemblies and – especially – their joints. You will need all this knowledge to quickly recognize the drawings you need. About 60% of the original blueprints depict various small, internal details (tubes, brackets, plates, etc.) which are necessary only when you would like to build a real, flying airplane.
To select a useful subset of these blueprints, I had to review all the drawings in the microfilm set, and copy some of them into one of the target folders:
You can do such a “review” using two File Explorer windows: one for the source drawing list (of course with the preview pane), and the other for the target folder.
Recreating geometry of a historical aircraft is usually a painstaking, iterative process. You can see this in my work on the SBD Dauntless. During the long hours of studying the photos and trying to figure out the precise shape of this plane I often wished to have its source blueprints! For many years the access to the original documentation was “the Holy Grail” of the advanced modelers. (Everybody wished to have this ultimate resource, but only few saw it. And even those, who saw these drawings, often did not know what they are seeing).
When the production of an aircraft is definitely closed, and it quits the service, its blueprints are packed into manufacturer’s archives. After a few decades most of these companies are sold, while the less successful ones are out of the business. The original technical documentation of an aircraft usually becomes a bunch of useless, unreadable paper rolls that disappear in trash bins.