27 Feb 2009

The gas tank is tentatively done, in CAD at least. By moving one side a little, capacity is now 16 gallons! This is enough for just about any drivetrain builders might want to use and gives the option of cutting it down if not as much capacity is needed. Still waiting for the fuel level sensor, and have to place the various external hose fittings, but it’s getting there.

I had a discussion with a race car designer who feels that the flat diffuser is better. The Katz book (figure 6-39 if you have it) shows that downforce increases with a diffuser angle of up to 12 degrees, while drag actually drops at angles up to about 4 degrees, then increases up to 12, but remains lower than if there was no diffuser. McBeath, in, Competition Car Downforce, discusses curved diffuser design but doesn’t provide data (which is understandable since aero design doesn’t transfer easily between vastly differing cars.) I don’t have a big-ass wing helping to suck air out through the diffuser, though the Katz data does not either which is good for my application. So, since Katz has actual quantifiable data, and because Kimini felt very stable at high speed, I’m going back to the flat design.