Jet-powered quad.
https://s3-us-west-1.amazonaws.com/h...ered_quad1.jpg
https://s3-us-west-1.amazonaws.com/h...ered_quad2.jpg
Previously:
https://www.homemadetools.net/forum/...3600#post78372
https://www.homemadetools.net/forum/...6521#post83830
https://www.homemadetools.net/forum/...423#post104253
