Type of airfoil used by Briggs, Hull, and Dryden

Question

What airfoil do Briggs, Hull, and Dryden use in NACA Report No. 207: https://ntrs.nasa.gov/api/citations/19930091273/downloads/19930091273.pdf

They mention it a few times:

"The airfoils tested were members of a series of propeller sections of the form adopted by the engineering division of the Air Service as standard for propeller design. Six airfoils were used, the camber ratios, or ratios of maximum thickness to chord, being 0.10, 0.12, '0.14, 0.16, 0.18, and 0.20, respectively. The chord length was 3 inches and the span 17.2 inches so that the airfoils extended entirely across the jet, and there were no ends exposed to the stream as in ordinary wind-tunnel practice. The dimensions of the airfoils as measured by the gauge section of the Bureau of Standards are given in Table 1." They have a table of the dimensions of the airfoil as well.

I wasn't able to find the exact model of airfoils that they used. Here is the study: https://ntrs.nasa.gov/api/citations/19930091273/downloads/19930091273.pdf

Thanks in advance.

Answer 1

Although there is no specific reference given to the propeller sections used in this report, by cross-referencing and checking several reports on propeller performance being completed at this period of time, one propeller appears in common. The propeller section used in these reports was the RAF no. 6, modified. The studies examining propellers using this section were all by Fred E. Weick, initially at the Bureau of Aeronatics, U.S. Navy, and later at the NACA Langley Memorial Aeronautical Laboratory.

The reports by Weick briefly examined were the following -

1. NACA Technical Note no. 212, Simplified Propeller Design for Low-Powered Airplanes, January 1925.

2. NACA Technical Note no 238, A Simplified Method for Determining the Strength of Propellers, January 1926. $^1$

3. NACA Technical Note no 244, Navy Propeller Section Characteristics as Used in Propeller Design, August 1926.

4. NACA Report no. 302, Full Scale Tests on a Thin Metal Propeller at Various Tip Speeds, January 1929. $^2$

5. NACA Report no. 340, Full Scale Wind Tunnel Tests on Several Metal Propellers having Different Blade Forms, January 1931. $^3$

$^1$ This report mentions the RAF 6 section, with tell-tale table of coordinates.

$^2$ This report specifically references NACA Report no. 207, the study by Briggs, Hull, and Dryden.

$^3$ This is a definitive study mentioning the RAF 6 section.

The study referenced in your question was evidently completed by the National Bureau of Standards. A common practice in executing such studies was to use materials and methods already available that were used elsewhere. In this particular case, the study may have been contracted to the National Bureau of Standards by the National Advisory Committee for Aeronautics.

And, as a further note regarding these types of propellers, making them was not easy. The above referenced studies primarily concern tests of aluminum propellers. Such propellers were made of a material called duralumin. Propeller blades were forged first as a duralumin blank having the desired dimensions from which the propeller blade could be acquired. This blank was then precision machined to the correct dimensions. Because the cross-section of the propeller blade varied along the length of the blade, specific design of the cross section was not a primary consideration. However, reproducibility was primary. Consequently, a desired blade cross section would be of an airfoil that was easily manufactured, adequate for producing desired lift, and reproducible with precision. The RAF 6 section apparently meets these needs, exactly.

This was an interesting question. Thanks for asking.

Answer 2

The paper is almost one hundred years old (it's dated March 1925). According to Wikipedia the NACA airfoil system was introduced later: "By 1929, Langley had developed this system to the point where the numbering system was complemented by an airfoil cross-section, and the complete catalog of 78 airfoils appeared in the NACA's annual report for 1933."

Table I in the paper contains anyway the coordinates of the airfoils used in the test. Plus, the same airfoils had been used in the NACA "Report No 83" which also gives some information about the airfoils.

Hope this helps