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The year 1924 marks the first circumnavigation of the globe by aircraft. In a recent podcast, a former employee of the National Archives remarked that the Army aviators planned to use an oak propeller when the aircraft was configured for water landing (on pontoons) and a walnut propeller when the aircraft was configured for terrestrial operations (wheels). (The comment occurs at elapsed time 01:14:58 in Episode 197, "World Flight Centennial, 1 of 3 - Build Up", September 16; accessed 20241001).

  1. Why was the propeller changed?
  2. Why was a different wood used?
  3. Why were these woods (oak, walnut) chosen for these kinds of operations?
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    $\begingroup$ Related, not a duplicate: What types of wood can be used for making propellers?. See also Basic Propeller Construction - Materials, ca. 1920. $\endgroup$
    – mins
    Commented Oct 1 at 13:34
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    $\begingroup$ Like most of tools: you choose the right wood for the right job (and often several wood on same tool). No material is perfect. I assume one is lighter, but the other is more water / salty resistant (aka: expand less when wet). And you need wood well known for tools (and construction), with people that can work it correctly, they can get it easily $\endgroup$
    – Giacomo Catenazzi
    Commented Oct 1 at 14:02

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This has to do with the properties of the wood: oak and walnut are both strong, non shrinking and resistant to warping.

Oak is a heavier and very water resistant. Walnut on the other hand, while lighter, cannot handle moisture very well.

Ever since the very beginning aviation has been "weight sensitive", hence the optimization.

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    $\begingroup$ This answer would be stronger with a reference that shows early aviators understood your comments about the quality of the wood. Scientific American suggests that walnut was used because it was common, and oak was simply a more economical replacement. The same article suggests that the glue holding the layers together was "not water proof." scientificamerican.com/article/… $\endgroup$
    – Mark Jones Jr.
    Commented Oct 2 at 9:28
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    $\begingroup$ I can try to dig something up, but I'm certain beyond a shadow of doubt that the professionals of early 1900's were well versed in properties of types of wood. Carpenter is one of the oldest trades with thousands of years of tradition. $\endgroup$
    – Jpe61
    Commented Oct 2 at 10:28
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    $\begingroup$ @Jpe61: Besides that, early water-landing aircraft drew heavily on boatbuilding techniques, which were certainly very well aware of how different woods would interact with water. $\endgroup$
    – Peter LeFanu Lumsdaine
    Commented Oct 2 at 15:22
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    $\begingroup$ Just to elaborate. White Oak is water-resistant. The more common (?) red oak, often used in furniture and interior flooring, is not. $\endgroup$
    – jimc
    Commented Oct 2 at 17:50

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