A day at the San Diego low speed wind tunnel with Felt and Project 1T4i

The Project 1t4i team (the 2012 incarnation of the Dutch Skil-Shimano Pro Continental squad) is in San Diego for two weeks of training and wind tunnel testing

Editor’s note: will not be releasing photos from this session at the San Diego wind tunnel until next year to maintain confidentiality of the 2012 team kits

“Stand by for zeroes. Hold still — OK, we’ve got our zero Patrick, you can start pedaling.”

Patrick Gretsch blazes the course in the Garden of the Gods to win the prologue of the USA Pro Cycling Challenge. Photo: Brad Kaminski © VeloNews (file)

Inside a boxy building on the edge of of the San Diego airport, the disembodied voice of San Diego Low Speed Wind Tunnel engineer Steve Ryle fills a tube that surrounds Patrick Gretsch like a gleaming white cocoon.

Gretsch, the 24-year-old German winner of the 2011 USA Pro Cycling Challenge prologue in Colorado Springs, begins pedaling a black and green Felt time trial frame.

With the bike wheels resting on rollers and suspended by front and rear mounts that protrude from a raised platform like tuning forks, an array of instruments captures the German’s position as he plows into a steady wind generated by the wind tunnel’s 2,250 horsepower motor.

Along with teammates from the Project 1t4i team (the 2012 incarnation of the Dutch Skil-Shimano Pro Continental squad) Gretsch is in San Diego for two weeks of training and wind tunnel testing.

This facility opened in 1947 to test the World War II bombs and airplanes being churned out of Southern California’s aircraft and munitions factories. Today it’s used to test human missiles like Gretsch as well. He’s been in the tunnel for nearly three hours, and the results of those hours of minute tweaks to bar extension and height, as well as the testing of various aero helmets, is promising.

After Gretsch pedals for a few minutes, he settles into his bike with an effortlessly supple pedal stroke. His upper body is so still you could rest a cup of tea between his shoulder blades without losing a drop. In the control room adjacent to the tunnel, Felt Bicycles engineer Ty Buckenberger picks up a dry-erase marker and traces the contour of Gretsch’s back and shoulders on a closed-circuit television screen.

Felt Bicycles founder Jim Felt takes the microphone: “Bury your head, Patrick,” he instructs. The German sinks his chin into his chest the way he would in the waning meters of a time trial. Buckenberger traces another line around Gretsch’s now-lower head profile. Felt watches another monitor closely as a scrolling graph shows the amount of drag the rider has created over the last five minutes. Other numbers show watts, cadence, wind speed, effective bike speed, and time.

The graph does not move much when Gretsch puts his head down, so Felt tells Buckenberger it is not something that warrants further investigation. Felt ends data collection for this helmet. “OK Patrick,” Ryle says into the microphone. “You can stop pedaling. You are done.”

A swarm of Felt and Shimano technicians flood into the wind tunnel. Gretsch puts on another helmet and the procedure starts anew. During the test, Ryle writes figures on a massive white board. After about 20 minutes of riding, Gretsch gets the word to stop pedaling again.

Kristin Armstrong in the wind tunnel, February 2011. The San Diego tunnel has a NASA vibe (unlike the A2 wind tunnel in North Carolina, which has a NASCAR vibe). Photo: © VeloNews (file)

Felt, Ryle and a huddle of other Shimano, Felt and Pearl Izumi technicians gather round the white board and discuss the numbers. Tapping one key data point with two fingers, Felt chews on an adjustment idea that’s been posited, then says, “OK, let’s do it now.”

They put another helmet on Gretsch, only to discover that the eye shield is not the right match for the helmet. Stepping back into a room lined with wheels and Felt frames, someone grabs a roll of thin silver tape. After taping the shield to the helmet and ensuring that it is seamlessly attached, the next testing cycle begins.

With wind tunnel rental running $850 per hour, resourcefulness is critical, and the work being done here is serious. Along with Felt, Shimano is monitoring the aerodynamic efficiency of its Di2 electronic components and Pearl Izumi is doing the same with the skin suits that fit the forms of the 1T4i riders so well that they seem to be painted on.

Crouched in front of the observation window and tapping notes into his computer as Gretsch rides, Pearl Izumi Director of Innovation Ted Barber notes that clothing has an enormous effect on aerodynamic efficiency. “The rider, out of the bike-rider combination, is about 80-percent.” With so much air dragging over the rider’s massive surface (relative to the tiny surface area of the bicycle), changes to all that body area can make big differences over the course of a time trial. “Bike companies are looking at improvements of five to ten watts,” he explains.

Meanwhile, through improvements to clothing surfaces and form fit, “we are making improvements of 15, 20, 25 watts, just with the surface textures, seam placement, the cut, the fit. It all makes a huge difference.”

Barber gestures at Gretsch’s stock-still shoulders:  “You see the texture of the surface on his upper arm?” Fabric covering the rider’s shoulders and wrapping slightly down his arm has noticeable weave to it.

At first glance this rough patch seems counterintuitive;  like trying to speed up snow skis by covering their bottoms with 220-grit sand paper. But Barber explains that the weave in the fabric surface  “induces just a slight amount of turbulence in the boundary layer so that we can get it to stick and run all the way around   his arm instead of separating and leaving a big drag.” In other words, the basket weave on Gretsch’s shoulders (and also on the front of his legs) effectively coats the rest of his body in a slippery layer. “What we found is that particular texture can reduce the drag on a cylinder by 15 percent across a fairly wide range of speeds,” Barber points out.

Pearl Izumi also keeps up to speed on progress in swim suit clothing technology, a field which has famously borrowed from the highly-evolved design of shark skin for its fabrics. But Barber says cycling clothing is more challenging than swimming kits because cycling apparel needs to be far more flexible and breathable. Swimsuits can be tighter and stiffer, he says, because, relative to the pretzeled position of a time trialing cyclists, in swimming “so much more of the body is kind of static.”

Finally, after hours of tailoring his bike, helmet, clothing and position with the care of a Savile Row suit maker, Felt and his team of equipment collaborators are satisfied with Gretsch’s position. Even after all this spinning and stopping like a hamster on a wheel, the German is in good spirits. He walks out of the tunnel, ducks into a bathroom and puts on an HTC kit (the team he is riding for in 2011) and heads out the door for for more hours of training on the sunny San Diego roads.

This test was relatively simple, as Gretsch did not need a lot of major adjustments. It’s not always that way, Felt points out. “The guys we had in here yesterday,” he says of the muscled sprinters who were in the day before, took a lot more tweaking to get into aero form. “It was like testing a school bus,” he recalls of their blocky frontal area.

After Gretsch, it is 23-year-old Marcel Kittel’s turn in the tunnel. Kittel just got back from a three hour ride up the San Diego coastline, including a series of hill repeats above Torrey Pines State Beach, a staple for San Diego racers. “It was nice,” Kittel says of his first ever San Diego coast ride on his inaugural trip to the United States.

Because Kittel uses a different sized bike than Gretsch, the wind tunnel technicians have to rearrange the position of the rollers on the raised wind tunnel platform. (The riders and their bikes bikes are raised to avoid dead air space that forms along the floor of a wind tunnel). This technicians carefully remove metal plates that surround the rollers, move the rollers to a position that matches the wheelbase of Kittel’s bike, replace the plates, then carefully seal all the plate seams with the paper-thin silver tape. Meanwhile, the Shimano techs pull the crankarms off of the bike Gretsch used and put them on Kittel’s.

Kittel has never been in a wind tunnel, and he is clearly relishing the opportunity. As the wind tunnel engineers set up the rollers for his bike, he takes out his iPhone and snaps photos of the tunnel and the control room, a space so lined with computer monitors that it looks like a combination of the flight deck of the starship Enterprise and a investment analyst’s stock-trading station.

The German is a monster talent; in 2011 he won more major races than Mark Cavendish. Among those, stage seven of the Vuelta a España, four stages of the Tour of Poland, two stages of the Herald Sun Tour and four stages of the Quatre Jours de Dunkerque. In 2011 Philippe Gilbert was the only pro with more wins than the Skil-Shimano rider.

Kittel clips into his bike in the tunnel and gets a tutorial. The bike is locked into one gear, so he can’t shift. His speed, cadence and power output are projected onto the wind tunnel floor in front of him.

While Kittel feels his position is pretty well dialed in from earlier tests on the indoor velodrome in Apeldoorn in the Netherlands, Felt begins the test by extending Kittel’s aero bars to the UCI-mandated maximum of 180 centimeters.

When he starts pedaling, Kittel looks a bit rough. His position does not give him the upper-body stillness that marked Gretch’s test. And it shows in the high drag numbers displaying on the screens in the control room.

“How did that feel,” Felt asks Kittel after the test. Kittel puts his hand on the back of his butt and says the position hurt his hamstrings. He also points out that being so far forward may affect his ability to control the bike.

As his enormous legs make clear, Kittel is a sprinter, and “for me the most important thing on the time trial bike for the prologue, where it’s more aggressive, is control. It is not all about aerodynamics, you have to have control.” Also, Felt points out, in the extended position, “he was hitting his stomach with his thighs.” Not good.

After several rounds of testing where Felt adjusts both Kittel’s bar extension and elbow height, they strike a position that is aerodynamic, yet not sketchy and power-sapping. “If I go halfway back (from the UCI maximum extension) and down two centimeters,” Felt tells the German, “we are stretching you out, but it’s minimal stretched out.” Referring to the earlier fitting and testing done on the Dutch track, Felt adds, “this was his position last year, but down. It’s halfway between last year’s position and the track test.”

With the bars tightened down, Kittel gets back on the bike and starts pedaling. A wide grin spreads across his face. This feels right, he tells Felt.

With that, the technicians clear out of the tunnel, Ryle takes the microphone and tells Kittel,  “Stand by for zeroes. Hold still—alright, we’ve got our zero Marcel. You can start pedaling.” Another round in the collaborative, methodical process of finding the perfect reconciliation of aerodynamic efficiency and rider power output starts anew.