Aero Science

This is what it’s all about. From the very start of this project, more than two years ago, Jim Felt and the team of Felt engineers faced one daunting challenge. Create a bike that’s faster and more aerodynamic than the Felt DA.

 
 
 The current model has experienced unmatched success. Just last year it was ridden to three Elite Men’s National Time Trial Championships in three diferent countries. It’s ridden by Felt’s stable of Ironman Triathlon athletes. It’s the weapon of choice for so many.
 
  But the new DA had to be better. And it also has to be legal in the eyes of the UCI, the world governing body of competitive cycling. Now that the objectives, the tools and the engineering process have been revealed,it’s time to look at the data.

The fnal phase of development was wind tunnel testing and refning. In January 2009, Felt’s engineering team went to the San Diego Low Speed Wind Tunnel to obtain objective third-party aerodynamic analysis on a prototype version of the new DA. Several modifcations were made over the next year until the fnal version of the bike, the ffth in a series of prototypes, was fnalized and tested. This was the bike that would be raced by Felt’s ProTour athletes at the 2010 grand tours.
 
  There are lots of diferent ways to gauge a bike’s aerodynamic performance, but Felt focuses on real world conditions. That means considering how a bike performs with the wind hitting it at various angles. When measuring aerodynamics, the angle of the wind is referred to as “yaw angle.”
 
  What the wind tunnel revealed was that, while some competitor bikes performed just as well as the new DA heading directly into the wind (0 degree yaw angle), the DA was untouchable with the wind hitting it at 5 to 15 degrees. Think about that. How often are you pedaling dead straight into the wind? Not too often. That’s why most aerodynamics engineers focus on the numbers produced in the 10- to 15-degree range.
 
  Not only was the 2011 DA superior to the competition at those “real world” angles, but it showed a clear improvement over the current DA.
And that was the real challenge. 

Here are five key features that contribute to the 2011 DA’s improved aerodynamics:

INCREASED SURFACE AREA

CFD analysis led Felt engineers to redesign every tube shape on the DA, including the down tube, to optimize airfoil efciencies. The new frame now has 25 percent more surface area, which in this case helped reduce drag by 14 percent.

SHARPER BAYONET

The new Bayonet 3 Steering System has similar functionality as the Bayonet 2 system on the current DA, but it was further refned for an even more aerodynamic profle. Felt created its own bearing to achieve the narrow profle—instead of a 1-inch bearing, it uses a smaller proprietary 3/4-inch bearing to reduce frontal area.

SLIMMER HEAD TUBE

Like the fork, it’s narrower than that of the current DA. The width was reduced from 42 millimeters to 35, making it even more efective at slicing through the wind.

SLIPPERY SEAT TUBE

The shape of the new seat tube difers greatly. Like the down tube, it follows a true airfoil shape instead of a cutout, and also features a fare that kicks air around the rear tire.

AERO BRAKES

This was one of the biggest challenges faced by Felt engineers—not only did the new brake system have to be more aero, it had to perform better and be compatible with the wider rims being used in aero TT wheels. The solution was this innovative new V-brake system that combines unmatched aerodynamics (internal cable routing, shelter from wind drag) with improved power and modulation.