I suspect the reference was to "double bubble" fuselage section, i.e. not a simple "hoop", but two joined, partial hoop sections of different diameter, designed to achieve more section height than width. A circular hoop section is in (essentially) pure tension when pressurized. A double-bubble is in tension, and also in bending at the join. - Bob Mann -- - R.W. Mann & Company, Inc. >> Airline Industry Analysis Port Washington, NY 11050 >> tel 516-944-0900, fax -7280 mailto:RWM@RWMann.com >> URL http://www.RWMann.com/ WaterskiPilot@aol.com wrote: > > In a message dated 12/29/01 3:36:24 PM Central Standard Time, wlw-jr@att.net > writes: > > > Isn't it all 2032 aluminum? > > > > Walter > > > > I mean the double hull, single hull thing, I don't understand, I haven't seen > an airplane with a "double hull" design. > > Jim > > Proud to be an American, > Jim Hann > Waterski J-41 Captain > STL