Structural Materials
Sheet metal quoted form tsaka
"Remember that almost all automobiles are today constructed with a sheet metal body that has no solid frame or chassis underneath it. Automotive engineers gain the strength and rigidity they need from sheet metal by making careful use of the inherent strengths of this material and applying geometric principles to overcome the weaknesses. Done properly, sheet metal produces a very light, strong, and inexpensive frame.
The biggest difficulty that might face a team wanting to make full use of sheet metal in their design is the expense of tooling. Sheet metal can be easily and inexpensively bent and joined in simple shapes to improve strength and rigidity. However, the complex shapes used in automotive bodies required very expensive metal forming equipment. These complex shapes bring sheet metal construction to very high levels of strength and beauty. But as long as you do not want to push the construction technique to the extreme levels used in auto bodies, you can do a lot with this material quickly, and at a modest cost."
Tube
wall 1x1 inch aluminum box 50% weight reduction. Also good for ¼ pound/foot , tougher to build with than 80/20 but lighter and similar strength
80/20
quoted form EOC
http://www.chiefdelphi.com/forums/at...7&d=1352834904