Form drag (bumpers, lips, wings) and Surface friction are different things.. For example Airplanes are not waxed to look "tight" they are waxed to reduce surface friction.

Here is an example based on the flight of a baseball:
The drag force Fd = CdpAv2
Where

* Fd is the drag force
* Cd is the drag coefficient
* p is the density of the air
* A is the surface area of the object or in our case pi r2
* v is the velocity of the object

What does this equation tell us? It tells us many useful facts:

* The faster the ball is traveling the larger the drag force will be
* The drag force may change significantly between different stadiums due to change in p, density of the air. This equation might explain why more home runs are hit inside the Colorado Rockies' stadium.

http://library.thinkquest.org/11902/physics/air.html