New Scientist Publish My Letter
Posted by apgaylard on October 10, 2008
Just a quick bit of boasting: New Scientist has published (an edited version) of a letter I sent in regarding claims made for a three-wheeled electric car, the Aptera (left), “Its radical design minimises air resistance, right down to little touches such as tucking the windscreen wipers below the airflow. As a result, the entire vehicle has a drag coefficient of just 0.15 – making its drag roughly the same as that caused by a single large wing mirror.” (emphasis mine)
As I pointed out in a previous post, this is falling into the trap of confusing drag force with the non-dimensionalised drag coefficient (CD). The comparison should have been made in terms of drag area (CD.A): it would have made sure that the relative sizes of the two objects figured in the comparison.
The upshot is that as the Aptera looks like it has – being generous – at least 25 times the frontal area (A) of a typical large European SUV mirror, this is going to more than outweigh the advantage it has in terms of drag coefficient when it comes to determining the force.
Anyway, I quite like the way my letter was edited. It was a shame that it lost a couple of equations and some assumed data values, but this sort of detail is likely to get cut given constraints on space. The only small downside is that without these details my assertions look a bit more arbitrary than they really are. Nevertheless, they have a lot of letters to fit into the print version and I’m really glad I made the cut.
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