Lessons In The Science Of Aerodynamics In Dirt Late Model Racing

Father-and-son duo Barry (left) and Lance Wright with one of their new Icon Dirt Late Models. Wright says that Late Models have gotten so effective at producing downforce over the last few years that no matter if you are racing Supers or Crates, you have to pay attention to aero if you hope to have success on the race track.

These days it’s only the most ignorant of Philistines that believes aerodynamics only apply to asphalt racing. Dirt track race cars, especially the Late Models, have come a long way in the last few years. Yes, Sprint Cars make excellent use of aerodynamics with their absolutely massive wings. But Sprint Cars have mostly looked the same for decades.

Driver Jonathan Davenport (right) takes a big role in the preparation of his race cars. This is a customer’s crate car that he “borrowed” to win 20 grand over Thanksgiving weekend at Swainsboro Raceway’s Turkey 100 event. Davenport says it is always important to consider how a car will behave in traffic when contemplating any changes to aerodynamics.

Dirt Late Models, however, have evolved quite a bit in the last 10 years. Yes, Late Models still retain the same wedge shape of their predecessors from the previous decade, but there’s actually been a great deal of development on these cars. The changes, at first, may appear subtle to the untrained eye, but you’d better believe practically every angle and crease is created for a purpose.

The driving force for all Dirt Late Models is the modern nose. It is so effective at creating downforce over the front of the car, that everything else must be driven off of it. Wright uses an MD3 Evolution nose and fender kit from Performance Bodies. Notice how the right-side fender (left in this photo) isn’t as tall as the left-side. The purpose of pulling the fender down is to allow more air to flow across the front of the car as the race car slides through the turn.

So we thought we’d take a closer look at some of the tricks that Super Late Model chassis builders and race teams are currently employing. Most of these came about because of a recent trip to the shops of Barry Wright Race Cars to check out Wright’s new Icon DLM chassis.

 

Here’s a look at the underside of the nose. There is so much downforce created care must be taken to make sure that it is properly supported and won’t buckle. Wright also makes the bumpers height adjustable so that they won’t drag the track depending on your suspension setup.

Driver Jonathan Davenport, who is returning to drive for Wright after a very successful couple of years with other teams, was also in the shop, so we had an opportunity to hit him up for some info as well.

Both Wright and Davenport said that creating downforce in the Dirt Late Models is critical these days if you expect to be able to keep up with the competition and have any success on the track. Interestingly though, Davenport says that as a driver he doesn’t need different aero tricks depending on whether he’s driving a Super or a Crate with approximately half the horsepower. (The suspension setup is a different story, however.)

One last look at the fenders before we move on. Notice how every line is designed to add rigidity to the nose as well as additional downforce.

The difficulty, when it comes to developing a comprehensive aerodynamics package for a dirt track race car, is it’s quite difficult to gather useful data from a wind tunnel test.

Check out how far the fender sticks out beyond the door panel just behind it. The door panel flares out from front to back to help create more side force, which allows the driver to dive into the turns that much harder.

Wind tunnel testing is no longer prohibitively expensive, and asphalt teams can take advantage of them to fine-tune their aero packages. But it isn’t as effective for dirt teams because the cars are yawed so extremely through the turns that it is impossible to replicate the conditions in a wind tunnel. They simply aren’t designed to test cars that are practically sideways.

Tight wheel openings help keep air from getting underneath the car where it can add drag and reduce the car’s ability to create downforce. A small lip in front of the wheel pushes air away from the tire while having the sheet metal rolled in behind the wheel helps pull air out.

Aerodynamics on the straights simply aren’t important compared to the need to create downforce to help keep the car planted through the turns.

Use the lower support on the right side of the car to push the bottom of the panel out just a bit. If the bottom of the panel gets pushed in, it will allow air to funnel down the door panel and underneath the car.

“These cars are so big now,” Davenport adds. “They move a lot of air. Going through the turns they yaw so much that they take up about 15 feet of track. So you want to look at how they react when following other cars. You’d love it to lead every race from the green flag to the checkers, but we all know that isn’t going to happen, so how the car handles in traffic is important.”

Check out how the left side of the body bends back toward the right as it gets to the rear spoiler. That’s because sanctioning bodies will have a maximum width that they will check at the rear of the car. You always want the spoiler as far to the right as possible so that it catches maximum airflow as the car is yawed through the turns.

Check out the photos and tips we’ve gathered for you. Much of what you see comes from our conversations with Wright and Davenport, but others are from what we’ve gathered by just keeping our eyes open at the race track–so don’t blame Wright if everything doesn’t work for you.

Speaking of the rear spoiler, Wright says he adjusts the spoiler angle practically every night of racing. As a general rule, as the track dries off and goes slick, more spoiler angle can help keep the car from getting too loose.

Wright also allowed us to photograph practically anything we wanted of two new cars going together in his shop. Both are Wright’s new Icon car design, and the #49 that is practically complete is a customer’s car that Davenport borrowed to win Swainsboro Raceway’s $20,000 to win Turkey 100 Crate Late Model race over Thanksgiving weekend.

You can take advantage of the acreage of sheet metal that makes up the deck of the car to help funnel more air to the spoiler. Notice how it drops in the center from the sides to help keep the air from falling off the sides of the deck. A sharper angle on the left side also helps trap air while the car is in yaw.

That, by the way, was Davenport’s first race back with Barry Wright Race Cars, so it appears from the outside that this matchup will be paying big dividends in the future.

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About the author

Jeff Huneycutt

Jeff Huneycutt has been in the automotive industry long enough to collect more project cars than he can afford to keep running. When not chasing electrical gremlins in his '78 Camaro, he can usually be found planning unrealistic engine builds.
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