>Al,
>
>I can't wait for the fires! And don't drive in the rain.
>
>Quoting VW
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>The carbon-fibre-reinforced outer skin is tensioned over a spaceframe that is not made of aluminium, but rather of magnesium, which is even lighter.
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>And a couple of sections from http://en.wikipedia.org/wiki/Magnesium
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>Like its lower periodic table group neighbor calcium, magnesium reacts with water at room temperature, though it reacts much more slowly than calcium. When it is submerged in water, hydrogen bubbles will almost unnoticeably begin to form on the surface of the metal, though if powdered it will react much more rapidly. The reaction will occur faster with higher temperatures (see precautions).
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>Magnesium is a highly flammable metal, but while it is easy to ignite when powdered or shaved into thin strips, it is difficult to ignite in mass or bulk. Once ignited, it is difficult to extinguish, being able to burn in both nitrogen (forming magnesium nitride), and carbon dioxide (forming magnesium oxide and carbon). On burning in air, magnesium produces a brilliant white light. Thus magnesium powder (flash powder) was used as a source of illumination in the early days of photography. Later, magnesium ribbon was used in electrically ignited flash bulbs. Magnesium powder is used in the manufacture of fireworks and marine flares where a brilliant white light is required. A full blown magnesium fire can burn over 5,400 °F (2,980 °C).
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>>Here's the most future-looking, yet practical modern small car I've seen recently: http://www.seriouswheels.com/cars/top-vw-1-liter-car.htm

The full evolution of that concept would be to have a carbon-fiber space frame, rather than magnesium. For an analogy you can look to bicycle frames, where carbon fiber is the current material of choice. Literally no-one makes bike frames from magnesium.

Partly due to its flammability, magnesium is usually only worked in bulk-forming operations such as casting and forging. Any high speed machining, or forming of thin sections such as tube walls could be hazardous. It wouldn't surprise me if the magnesium spaceframe was forged beams and channels rather than more conventional tubes. The lugs would be cast, and possibly forged afterwards to improve strength.

One area where carbon fiber is at a disadvantage is recyclability. This is getting to be quite important in Europe, especially Germany.