At first look, aluminum looks no better than steel for lightweight construction, for although aluminum is 1/3 the weight of steel, it also has only 1/3 of steel’s stiffness. This changes when we make tubing of the two materials. Aircraft fuselages are large thin-walled tubes. They are not made of steel, even though steel could be rolled to a thickness 1/3 that of existing aluminum fuselage material. But steel that thin would be foil, lacking adequate buckling resistance (it is for this reason that traditional steel motorcycle frame tubes are typically made no thinner than 16-gage, or .0625” wall thickness). This is the basis of the aluminum chassis revolution in motorcycling – that for a given weight of tube per foot, a bigger aluminum tube can be made with adequate buckling resistance than can be made from steel. The larger the tube’s diameter, the greater its stiffness – even though its wall thickness must decrease to keep to the given weight per foot of tube.