Tom wrote:The point I'm trying to make is that although supercars and sports cars look sleek and streamlined they really aren't, you cannot see drag so no one knows what will be aerodynamic without a windtunnel or computer sofware. Sure you can make an educated guess if you've been to university and studied the stuff but a layman would not know.
Car designers rarely take into acount aero but go on what looks best. The Austin Allegro was famouse for being more streamlined in reverse (as well as for having a square steering wheel) but in reallity most cars are because aerodynamics doesn't sell cars, the people who buy them would not understand, so they are sold on looks.
All IIRC
:
The evolution of road car aerodynamics had 3 distinct phases.
The first was "if it looks right", so cars had big smooth fairings etc [1930s or so], unfortunately this didn't work, as the rear of the car tended to slope down at around 30 degrees, which is near the worst angle (approx 32 is worst IIRC) for formation of 2 longitudinal vortices which have high drag). This phase of mainstream car design tried to incorporate fashion and design, but the design knowledge wasn't up to it.
Some aircraft manufactuers, notably rumpler made cars with real low Cd figures, but they weren't fashionable:
The next phase was detail design [1980s or so], getting things such as windows flush with the frames, doors sealing better, closer fits between panels etc. This went along way to reducing drag figures.
The final (and current) phase is incorporating detail design with careful windtunnel tests to subtly adapt fashion driven [although with most of todays cars you could argue over the fashion bit!] designs to improve their aerodynamics. By adding flatter floors, packing exhausts, suspensions better, the underfloor drag is reduced, leading to better Cd figures.
