Firestone XR-9B experimental helicopter developed for the United States Army Air Forces in the 1940s.
https://diqn32j8nouaz.cloudfront.net...b_fullsize.jpg
https://diqn32j8nouaz.cloudfront.net...1_fullsize.jpg
Previously:
https://www.homemadetools.net/forum/...512#post215671
https://www.homemadetools.net/forum/...413#post173498
https://www.homemadetools.net/forum/...901#post160165
https://www.homemadetools.net/forum/...157#post214478
https://www.homemadetools.net/forum/...690#post159457
