A canna’ change the laws of physics

Scotty, The Naked Time, stardate 1704.3, Episode 7

Archive for the ‘Bad Aerodynamics’ Category

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) 

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Posted in Bad Aerodynamics | Tagged: , , | 2 Comments »

Sanity checking a striking claim

Posted by apgaylard on September 21, 2008

Interpreting technical data can be a tricky business, as demonstrated by an interesting article in last week’s New Scientist magazine.  In a fascinating review of the recent progress made by manufacturers of electric cars the journalist tripped up in his discussion of the aerodynamic drag figures claimed for the Aptera, a two-seat electric car (the word refers to wingless insects – appropriate enough as the car does look like someone has pulled its wings off!).

“…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.”

This is a very striking claim, however, we shall see that some simple maths and a few estimates are all that is needed to show that the journalist has made a mistake here.

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Posted in Bad Aerodynamics | Tagged: , , , , | 7 Comments »

What a plane fishy old bird

Posted by apgaylard on May 30, 2008

Viktor Schauberger - CrankViktor Schauberger had some peculiar ideas.  One of them was that aeronautical and marine engineers had got it all wrong with the propeller, or airscrew. 

“As best demonstrated by Nature in the case of the aerofoil maple-seed, today’s propeller is a pressure-screw and therefore a braking screw, whose purpose is to allow the heavy maple-seed to fall parachute-like slowly towards the ground and to be carried away sideways by the wind in the process. No bird has such a whirling thing on its head, nor a fish on its tail. Only man made use of this natural brake-screw for forward propulsion. As the propeller rotates, so does the resistance rise by the square of the rotational velocity. This is also a sign that this supposed propulsive device is unnaturally constructed and therefore out of place.”

 (Viktor Schauberger, Implosion Magazine, No. 112, p. 52) Read the rest of this entry »

Posted in Bad Aerodynamics, Fluid Mechanics, Pseudoscience | Tagged: , , | 2 Comments »