I’ve always thought there was a lot to be learned about racing while hoisting a few cold ones at the local pub. 

For instance, most of what I know about aerodynamics I learned while playing darts drunk (ie, more than one beer).  Did you ever launch the dart tail first toward the dart board?  Of course, the dart turns around in flight and still sticks the little point into the board (or the wall, or into someone who was foolish enough to not scatter when it’s my turn to throw darts).  This was my aerodynamic education 101. 

With this knowledge, I went to work for Craig Breedlove in 1964 on the “Spirit Of America” Land Speed Record project, and stayed for five years.  Even though we used the Lockheed Aircraft wind tunnel on our quarter scale model, we learned more about going fast (with stability) by playing darts and drinking beer.  We also got Craig’s weenie roaster to run over 600 MPH.  This is what we learned.

As long as the object you are sending through the air has the Center Of Balance forward (the heavy front end of the dart) and the Center Of Pressure at the rear (the feathers), the object will have stability and travel straight.  The feathers create aerodynamic drag, causing the back of the dart (or arrow) to always remain in the back.  When you see a Bonneville Salt Flats streamliner with a big tail fin sticking up, think of the feather.  That tail fin is there to create drag and nothing else.     

Now, here is another other thing about aerodynamics, and this is a critical part in keeping Pro 5.0 (or Outlaw type cars) reasonably stable at high speed.  Aerodynamic lift.  By it’s very shape, a Pro 5.0 Mustang wants to fly.  Basically flat on the bottom and rounded on the top.  If you look at a Pro 5.0 Mustang from the side, it’s almost a perfect cross section for a “wing”.  This ain’t good. 

When an object with this rounded shape on top is going through the air, it takes longer for the air on top to get to the back than the air underneath, because the air on the top has further to go than the air on the bottom.  This “speeded up” air flow over the top causes the air to have less pressure per square inch, which is what causes the object to “lift” in that direction.  Just like the wing on an airplane or a sail on a sailboat. 

To counteract this problem, many race cars use up-side down wings on the front, on the back, or both.  Anything to create a negative lift (down force).  Take a look at the wings on a top fuel dragster or an open wheel Indy or Formula 1 race car.  These cars have enough down force to literally stick to a ceiling running up-side down without falling off, if you could ever do that.

With a stock body Pro 5.0 Mustang, things are a little different.  We don’t have wings on either the front or the back to assist with down force.  Instead, we can use spoilers to help counteract aerodynamic lift.  The rear spoiler is supposed to slow the air down on the top of the car by “blocking” the flow to the rear.  A good illustration of this type of spoiler is on Funny Cars and many Pro Mod or Fuel Coupe cars.  Notice that tall fence or vertical panel on the rear of the spoiler.  That’s the “air blocker”.

Unfortunately, I have seen some very unstable Pro 5.0 cars lately.  I realize that there are many other dynamics in play here besides aerodynamics, but if it won’t go straight, it won’t go fast either.  Or let me put it this way.  It may go fast, but it’s an “out of control fast”.

Most of the spoilers I see lately on Pro 5.0 Mustangs wouldn’t spoil anything (except possibly the driver’s shorts).  Almost none of them have any “fence” (called a wickerbill) at the rear of the spoiler to block or slow down the air.  Some of the spoilers are not the full width of the rear of the car.  Why the hell not?  Many of them don’t extend back far enough to be in the stream of air coming off the roof.  We allow a full IHRA style 17 inches from the attachment point on the trunk lid to the rear tip of the spoiler.  I’ve seen spoilers as short as 10 inches.  This is insane. 

Is it possible that our Pro 5.0 racers have never seen Pro Mod or Nitro Coupe cars?  Many of the new Pro 5.0 cars have “Pro Mod horsepower” and are capable of running over 215 MPH.  All this with a spoiler that would be inadequate on a Pro Stock car at 200 flat.

Here is what Warren “The Professor” Johnson says about spoilers.  “If the spoiler is a 14 inch NHRA type, the wickerbill should be no less than 1 inch high and 90 degrees (perpendicular, not angled back) from the flat part of the spoiler.  If the spoiler is an IHRA 17 inch type, the wickerbill can be ½ inch at 90 degrees.”  This information came through Buford Heavy (Eric Duncan, Atlanta Raceway Tech) who discussed it with Warren immediately after the Fun Ford Weekend event in Atlanta.  

The addition of vertical spill plates along the sides of the trunk lid between the roof and tip of the spoiler would also assist in channeling the air over the spoiler, and keep the air from just rolling off the sides of the trunk.  On the front end, smaller “hood bubbles” will also create more down force.

With all the attention to the latest technology in engine development these days, I can’t quite understand why more attention is not aimed at the aerodynamic side of the equation.  It scares me to watch.

It makes me want to go back to the pub for a few more cold ones.  Anyone for a game of darts?  Or how about “I’ll show you mine if you show me yours”.