Now it is clear, that this difference was caused by the wrong choice of the reference plane.
(In picture above I marked it at station 66). I found nothing wrong, thus all what I could do was just to compensate this difference by additional 0.86” offset to each wing. I checked again station locations, to make sure that I did not made an error. For such an angle, I obtained wing span of 496.4”, which is 1.73” short of the documented value.
Sbd dauntless manual#
To obtain the dihedral angle specified in the SBD Maintenance Manual (in the front view: 7.5° along the wing upper contour) in my model I had to raise the outer wing section by 10.2°. However, I knew that there is something wrong with the geometry of my wing. There was no chance to discover such a thing without this master diagram blueprint! However, in this wing Douglas engineers chose a strange reference plane, which fits to nothing! Look at the fragment of Douglas master diagram above: every spanwise line of the wing is oblique: trailing edge, leading edge, upper wing contour (1° downward), lower wing contour… It does not even fit any spanwise contours of its webs (all of them are trapezoids). In the case of the aircraft wing the most obvious candidate for such a base is the trailing edge. ultimate product cost), because these reference bases are reflected in the tooling geometry. Their choice is extremely important for the technology used in the manufacturing (i.e. Usually designers choose reference planes along an easily distinguishable element, which you can use as the base for physical measurements. In principle I was right, but I assumed wrong reference plane for the outboard wing! Below you can see the plane that I assumed for my model, and the real reference plane from the Douglas master diagram: Figure 109-4 Reference planes in the spanwise direction (outboard wing section) I also correctly assumed that the station distances are measured along the corresponding reference planes of the center and outboard wing sections.
From that diagram I knew that the wing tip station was at 251.06”. It seems that it was a standard approach in that era: I have found similar solution in the original Curtiss P-40 blueprints.īuilding my model, I used simplified stations diagram from the SBD Maintenance Manual. In this way their reference plane crosses the wing trailing edge and remains parallel to the fuselage centerline and perpendicular to the web planes. In the original Douglas diagram shown above you can see that its engineers took different approach: they used re-calculated airfoil ordinals for given inclination angle. (If they were also inclined at 2.5°, connecting webs to the fuselage bulkheads would be much more complex, i.e. However, from the photos I learned that SBD webs (spar) planes were vertical, so I adjusted their directions in my model. The SBD wing was inclined at 2.5°, thus I rotated my wing object by the corresponding angle. (Airfoil coordinates are specified in such a reference system). The first thing that I noticed comparing these blueprints to my model, are the different reference planes: Figure 109-3 Different orientation of chordwise reference planesįor my model I chosen the airfoil chord as the reference plane, with the origin point at the tip of the airfoil nose. This distance – 251.06” – is measured spanwise, along the reference planes of the outboard and center wing sections. Wing station names of the outboard section starts with “STA 66” and continue to the tip, which is named “STA 251.06”.
Sbd dauntless download#
Here you can download its high-resolution version (7MB). Their names correspond to spanwise distance in inches from the aircraft centerline: “STA 10” is 10” from the centerline, while “STA 66” is 66” from the centerline.Īnother part of this diagram contains a sketch of the larger, outboard wing section: Figure 109-2 Master diagram of the wing geometry (sheet 1/2) In the picture above I marked in red its key wing stations. In the sketch on its right side Douglas engineers depicted various other dimensions of the wing center section. As you can see, it contains the ordinal tables of the wing bulkheads (ribs) and webs (spars).
Here you can download its high-resolution version (5MB). Below you can see the first sheet of this diagram (dwg no 5090185): Figure 109-1 Master diagram of the wing geometry (sheet 2/2) This is a well-documented assembly, because I found a master diagram in the NASM microfilm that describes SBD wing geometry (ordinals).
I am preparing data from the original Douglas blueprints to verify my model.
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