On Tuesday, following the race at Atlanta Motor Speedway, NASCAR made the announcement that both Ryan Preece and Noah Gragson had been penalised 35 points for "non-conforming air deflectors" on the rooves of their cars.
On Friday before the race, NASCAR confiscated the offending parts and made Stewart-Haas Racing fit new parts to the cars; then watched SHR very very closely.
The 35 point penalty means that both Ryan Preece and Noah Gragson go into the third race of the season without any points.
The question which I was asked is my most favourite question in the world... "Why?". Why would you do that if you know that you are possibly going to be picked up for it? Because this is sport and everyone who is not currently seeking an advantage should immediately seek to do so, and given that this is motor racing where everyone is cheating all of the time if they can get away with it and/or invent solutions not yet covered by the rules, then this kind of thing is as expected as the sun rising in the morning.
This particular infringement is a classic physics question and at its heart is entirely to do with fluid dynamics and how air flows around an object and how you can control that air flow. Air, water, fluid, traffic, crowds, electricity, politics, moods: these are all things that flow and where resistance can be controlled.
An object which is moving through the air creates wind resistance which is variable depending on how slippery the object is through the air (drag coefficient), as well as the surface area being presented to the wind, as well as the relative air speed, and the pressure of the air (or water, or other medium). Very obviously, a dart or torpedo shaped object with a pointy end is going to pierce the air more easily than a brick. Also reasonably obviously, an object which is not moving but which has air moving around it, is also going to create wind resistance; which is true for a building, or a person in a storm with an umbrella, or when MY HAND IS A DOLPHIN!¹
Stewart-Haas Racing were pinged for unauthorised roof rails at Atlanta Motor Speedway and while NASCAR has not specified what the infringement was, given that every team is likely to be cheating all the time in some way because they want to gain even the smallest advantage, it is reasonable to suggest that SHR was trying to chase a very wee bit of speed by affecting the wind resistance due to the spill which comes off of the roof rails at speeds of 190mph.
The roof rails exist in principle, so that when a car is turned sideways, they create turbulence over the car because a sideways car and the attached air flow is a bad analogue of an aircraft wing. If this was a purely clean object designed to create laminar flow of air over it, then that produces a high pressure area above and behind it, which induces a suck pull force which is lift. It seems almost absurd that a 4000 pound thing can be lifted into the air but flying and flipping motor cars is a thing which does happen and is unwanted; as opposed to a thing weighing many many tons which you do want to fly inside of².
My suspicion is that SHR have altered parts A and D in some way, to affect the swirl patterns coming off of the roof rails as they pass through the air. Again, a thing moving through the air creates wind resistance but there is also wind resistance caused by the attached air presenting itself as an area of turbulence in the wake of the object. I have no idea what the actual effective area of that attached air flow is but that leading edge of those roof rails creates a force of about 0.1 of a Newton (at 180mph); which of itself is small but is enough to affect the shape of the air behind it.
Most big passenger aircraft which have cruising speeds of about 500mph, have little turn ups on their wing tips. When wind resistance is drag and drag is inefficient, then drag costs money. The objective of an airline is to create profits by not spending money. Those wee little turn ups on the ends of the wings, help to shape and minimise the size of the cone shaped swirling vortices which spill off the ends of the wings. The objective of an race car is to create speed. When wind resistance is drag and drag is inefficient, then drag costs speed³.
The distance between first and third place in that same race was 0.003 seconds; which at the instantaneous velocity of 177mph worked out to be about nine inches. Nine inches multiplied by 200 laps is 150 feet; and if you are conceding 150 feet to the opposition, then it is absolutely worth the effort to chase down 0.003 of a second per lap. Stewart-Haas Racing literally are trying to control the distance between coming first and being an also ran.
¹From that same race, Joey Logano was fined $10,000 fine for modification of a driving glove. His left glove had webbing added between the thumb and forefinger. Again, this is about controlling air flow by putting your hand out of the window to create MY HAND IS A DOLPHIN! out of the side of the car. That also creates vortices and affects air flow.
²except when the doors fall off.
³A NASCAR Cup car also has roof flaps which blow open when a car is facing backwards. These act as automatic air brakes; which present all kinds of air resistance and turbulence.
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