Last month I was busy with my daily business, so in this post I would like to share just single detail, which I encountered in the P-36/YP-37/P-40 documentation.
This finding is related to the “long tail” P-40 variants. In August 1942 Curtiss decided to definitely resolve the directional problems of the “short-nose” P-40s. They extended their tail, adding an additional segment after station 16. It shifted the original “P-36 – like” fin and rudder back by about 20 inches. This modification was introduced to the Allison-powered P-40K-10, and to the Merlin-powered P-40F-20. (These two versions were produced in parallel).
Below you can see how these two tail variants are depicted in typical scale plans:
In the picture above I placed drawing of the P-40F-1 (“short tail”, in black) over the P-40F-20 (“long tail”, in red). As you can see, the tail is the only difference between these aircraft. Note the shape of the fuselage in the bottom view. In all scale plans of the long-tail variant that I saw, the width of the fuselage was wider than in the “short tail” version. These differences usually begin at station 12 and continue to the rudder.
However, the original Curtiss assembly blueprints reveal a more prosaic truth:
The fuselage up to station 16 in “short” and “long” tail variants was identical! The only difference between these two tails was made by the additional segment. Note also the sharp edge (a “corner”) formed in the top view along Sta. 16:
The P-40 blueprints are available online in AirCorps Library, so you can check details of this drawing (87-21-451) yourself. You can also find there several similar blueprints for the P-40L, M and N variants.
This finding should not be any surprise: in the mass production, you always try to minimize the influence of a modification on the existing tooling. You can observe similar sharp edges along the additional tail segment in the Focke-Wulf 190D. However, while these edges are properly depicted in the scale plans of that German fighter, this detail of the later P-40s remained obscured under the tailplane. For example – it is practically invisible in such a side-view picture as in the picture below:
However, you can (hardly) notice it in the pictures of the flying aircraft:
So – does your “long tail” P-40 model (for example: the P-40L, P-40M, or P-40N) have this feature?
I did not mention that the rear part of the fuselage in the Curtiss blueprints seems to be generally wider than in Kagero scale plans. However, this is another issue, for another post.
2 thoughts on “A New Finding about the “Long Tail” P-40s”
Did it really affect the stability?
Yes, NACA conducted special tests to find a remedy.
These troubles are described in many sources, see for example: Franics H. Dean “America’s Hunderd-Thousand: U.S. Production Fighters of World War Two” (ISBN 0-7643-0072-5), page 252.