Seeing the record in the APSBF 1000cc class go from 219 to 252 mph, it became painfully apparent that major changes had to be made to the aerodynamics to allow the possibility of reaching a competitive speed. As the bike sat, it felt capable of 221 to 226mph, but the new 2009 rules allowed a considerable cleanup of the aerodynamics behind the rider.
Not having a lot of experience in aerodynamics on motorcycles over 200mph we are taking a conservative approach, using a bit of theory, a couple of photos of the Scott Guthrie bike ridden by Joe Amo that set the record, a bit of funnycar, and F1 aero. Improving upon the opening created by the bike and the closing up of the envelope behind will yield the lowest coefficient of drag (cd). While bikes have a relatively small frontal area, their cd is disproportionately high. Cleaning up all the surfaces allowed by rules and rounding edges, both trailing and leading is the initial area of change we are pursuing.
The 1999-2007 Suzuki Hayabusa has a proven speed stability shape that is an excellent starting point. We are not looking to reinvent the wheel here; that is the reason why we have used that model for the basis of our shapes.
Initially we removed the radiator ducts and closed in the holes for the alternator. This was followed by sectioning (see old-time hot rod vernacular for this) the profile three inches to reduce the frontal area.
The 2010 front end update involves closing in the sides, and a full bellypan (see photos below). The underside of the bike is often overlooked and subtle changes here can yield substantial results. Look at the bottom of the MotoGP bikes and F1 cars and you will see as smooth a surface as possible. Maintaining a slight negative pressure is a desirable effect to minimize the possibility of “flying” with the attending embarrassing results.
The remaining challenge on the front fairing is the generation of the rolled edges at the trailing areas of the profile. It’s off to the glass shop for this.