This post was originally written by Phil Knox (aerohead), and it first appeared on the MaxMPG group. Phil has done a lot of work educating the masses about the critical role aerodynamics play in efficiency, and has spurred many in the DIY crowd to take matters into their own hands.
This is the fifth in a series which I'm reproducing here with permission.
Go to: Aerodynamics Seminar Index
Aerodynamics Seminar # 5
- by Phil Knox
Hellow all! As I mentioned last time,I wanted to mention some of the pioneers who's work affects today.
Daniel Bernoulli was a Swiss mathematician who discovered the relationship between velocity and pressure. Perfume sprayers work on his principles, and Gottlieb Daimler would use the same principles to create the carburetor which launched the Otto Cycle internal combustion engine we use today.
This same relationship is what our boattails and streamlining are working towards. As the air out front of our cars is at atmospheric pressure before we collide with it at hurricane force ( see John Gilkison's Guest Blog at EVWORLD
on this ), anything we do to get it back like it was is essentially what road vehicle aerodynamics is all about.
Leonardo da Vinci was the first scientist to study birdflight. His work from the 1480s may have been the starting point for Lilianthal in the 1870s. Our friend Sir Issac Newton was first to observe and document the relativity of fluid flow, which makes the use of windtunnels and watertunnels understandable. The wright Bros.' windtunnel produced the wing dynamics which allowed their powered flight. The same dynamics we must respect if we are to safely travel at high speed.
Newton's 3rd law of motion explains how military aircraft can fly in spite of the fact that thir wings have no curvature (no camber).It was Klemperer of the Zeppelin Werks who discovered the low drag 6 to 1 length to width ratio which gave the airships a drag coefficient of Cd0.04 in 1932. Klemperer would also, by 1922, shave a brick down to Zeppelinesque form to create a low drag automobile form which remains today a good starting point for low drag forms. Later with Paul Jayay, Klemperer would windtunnel test Jaray's designs which were reflected in the North American Solar Challenge afew weeks ago.
The Spirit of St.Louis flew at an airspeed slower than I routinely drive in my pickup on windy days. Ryan Aeronautical went to the trouble of covering the spoked wheels which they calculated to give the aircraft 7-miles additional range, which could have meant life or death over the English Channel.
The DYMAXION CAR of 1934 would accidentally brake racecourse speed records with its creator, R.Buckminster Fuller at the contols. This truly visionary vehicle can be seen at Harrah's in Reno,Nevada, Fuller's aerodynamic showpiece of remarkable performance.
As we look to the past we can gain a glimpse of the future. Should we fully exploit the aerodynamic technology which has been collecting dust for up to 70 years now,it may be amazing at what can be achieved.
Next time we'll get into a little numbers- crunching.If you've been following Gilkison's pieces, you've seen a taste of the numbers. I'll try and explain where they come from,and how to predict with them.
Low drag to all, see ya, Phil.