Chrysler Airflow and it's aerodynamics
 

This video covers this ground-breaking design. Cd 0.51, vs Cd 0.66 for the cars it replaced.
The DeSoto Airflow aerodynamic test mule, not shown, achieved Cd 0.244 as a 'long-tail.'
An SAE Paper was published finally, four months before the attack on Pearl Harbor. We've already discussed that elsewhere here at EcoModder.com.
https://www.curbside.tv/blog/2018/8/...rysler-airflow

I don't think the paper you mention cites the Airflow, does it?

(Edit: I am wrong, it does.)

paper
 

Zeder's paper, to my recollection, covered the R&D of the DeSoto Airflow sedan aerodynamic test mule, which pushed the boundaries of the Airflow's streamlining. A quarter-view is shown, plus a schematic representation.
In AUTOMOBILE QUARTERLY, a more proper side elevation view is presented, illustrating the stinger and belly pan.
The United States entered the war and folks had more on their minds than aerodynamics I suppose.
I didn't know anything about any of it until not so many years ago. Alex Tremulis was the first to write about it, that I was able to run across. At his home, his models, scattered about, reflected the elongation and boat-tailing reflected in his Tucker and Ford Advanced Styling, Gyronaut LSR motorcycle, and later Subaru projects. Nice guy. Miss him.

I went and looked again. The paper is: "Is It Practical to STREAMLINE
for FUEL ECONOMY?", SAE 410139.

Drag coefficients are shown as 'K', which is in lb sq feet (mph)^2 - eg a De Soto Airflow is listed at K = 0.00140. Does anyone know how that could be converted to Cd?

[This equation is wrongly cited by me. I correct it later in the thread.]

The shapes that are shown are very generic.

When I was working on the section on the Airflow in my upcoming book I glanced through the paper and then discarded it. A second look hasn't told me a whole lot more!

Reading the paper, and reflecting on the quotes attributed to Chrysler at the time, I think that they had no idea of what had been going on in car aero in Germany over the previous decade or so.

The racing aircraft people are always talking about flat plate square foot area, so my guess is that this is the square foot equivalent. I'm not sure if the advanced people go from there to drag as my eyes glaze over (squirrel!!) this point.

converted
 

Alex Tremulis did the conversions from aeronautical, to frontal area-based coefficients.

You don't know the maths?

maths
 

I did do the calcs. All flavors. I'm not comfortable otherwise. There hasn't been 100% consensus between aeronautical engineers on flat-plate coefficients, so that's been problematic.
Larry Mauro, one of three aeronautical engineers I know, uses 1.0/ sq-ft, designing airplanes. Glynn B. used 1.15 at NASA, as was used in Fluid Mechanics we took at Texas Tech. Chris is a supersonic aeronautical guy and doesn't use 'em at all. Some, at the time of Zeder's paper were using Cd 1.0. Some were using Cd 1.15. Since Alex lived in both worlds, I figured I'd just defer to him. Alex also helped with Alexander Gustave Eiffel's coefficients. I'm certain that his calculus was way better than mine.

I don't understand. The K value doesn't appear to have thing to do with Cd for flat plates.

"Drag coefficients are shown as 'K', which is in lb sq feet (mph)^2"

Why aren't they talking of the frontal area of the car? ie lbs drag per square foot of frontal area * (mph)^2.

I am no mathematician but I would have thought the conversion of that to Cd would be fairly straightforward.