It’s strange how some things begin. Davy, my very good friend, told me about an event he had bumped into at the weekend. He had taken his boys to see the Shell Eco Marathon run at the Alford Motor Museum. Small racing cars drive round a track and the team using the least amount of fuel wins, easy. Or so it appeared until I put in a little research. It turned out this was the tip of an iceberg involving 128 competing teams from schools, universities and individuals spread right across Europe, Scandanavia, USA, Japan and Australia. Shell had started the challenge and had sponsored the event for more than 30 years. The main attraction for me was there are very few rules. The vehicle has to have more than 2 wheels, it has to have a human driver in control and it has to move under it’s own power. There are safety and construction rules to specify mirrors, seatbelts, rollbars, fire extinguishers that sort of thing. If you think you can win by using an engine from a double decker bus, try it, find out.
I researched the most successful teams and the cars they had built. They were all very small and very light with small and light drivers. Aerodynamics seemed to play a major role which is surprising for vehicles which move so slowly. The engines were comparatively small, but there was very little information available. I have always enjoyed building light weight structures and using light weight materials. I knew I could not compete building an engine but I could by designing the chassis, body
and geometry. Most of the cars were Tadpole tricycles with the 2 front wheels steering and the single rear driving. The driver lies prone with their head tilted just enough to see over their feet, this gives a very low frontal area. Mostly the front wheels were encased in faring front wings. Rightly or wrongly I figured this would lead to the air travelling into the tunnel between the farings would increase in pressure leading to turbulence and drag. I would attempt to divert the airflow as much as possible to avoid barriers.
I drew up a series of layouts gradually narrowing down compromises until I was happy with the overall scheme. After a short period I returned to the design and it struck me what do these lines, these curves, actually represent?, and can i do better. I started to delve into aerodynamics, especially concerning Human powered vehicles (HPV’s) and World Solar Challenge cars. Both have very limited power available and both have made incredible advances in performance.
At the heart of the aerodynamic work are databses containing NACA airfoil profiles. These profiles are calculated, not drawn and have been used in mostly aircraft applications for wings, struts, propellers but have also been used for designing boats, rudders and keels.
I downloaded a profile (NACA 0010) ready to copy the curve and away we go……. NACA 0010.dat
What I found was two lists of numbers, six digit decimals. I was not expecting this, I was expecting an image. The numbers are X and Y co-ordinates. This was the begining of a line of research and work that would last for years, until the present day.