Boeing Engineering

[Tulio]

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[bdk]

Get out your calculator Tulio!

https://amesweb.info/Materials/Density_of_Aluminum.aspx

[bdk]

Bdthe B-17 and B-29 used 24ST,the B-50 switched to 75ST, it's one of the major engineering differences between it and the '29.

Are you talking the skins, the extrusions, forgings, or what? I'm not sure your blanket statement is accurate, especially considering production changes.

From Wikipedia, "The first 7075 was developed in secret by a Japanese company, Sumitomo Metal, in 1935, but introduced by Alcoa in 1943 and was standardized for aerospace use in 1945. 7075 was eventually used for airframe production in the Imperial Japanese Navy." https://en.wikipedia.org/wiki/7075_aluminium_alloy

[JohnB]

Bdk...
I'm just quoting Boeing engineer/historian Peter M. Bowers in Boeing Aircraft since 1916, page 345 of the second edition.
He made quite a point about it with its weight savings, yet being substantially stronger. He was not specific which parts were involved. I assume the primary structure itself, not the skins.