Originally Posted by
UniChris
Because stiffness, the subject of your erroneous claim to which I responded, is not the same thing as strength.
In this case however, it's likely that low carbon steel probably would work for many parts of the project.
Sorry I got a little overheated, but I do understand the difference; if you'll look back at my posts in this thread you'll see a mention of 'cross-sectional stiffness' and 'girder.' I thought to mention the lack of elasticity in the low-carbon steel the OP referred to, but didn't know if that would cause confusion.
I still wouldn't use the stuff for anything but maybe a decorative fence. Common square- or rectangular-section box channel would be far better; that stuff is used for a lot of trailer framing. Getting it rolled into a hoop still requires an industrial machine, though. Round-section tubing would be lighter for equivalent strength--excuse me, stiffness.
Aluminum box-channel has been used for some experimental HPVs:
Manual for xyz spaceframe vehicles
I'm not sure I'd count on those for longevity.
I still like the idea of plywood best for this project.