GCR 9.1.1.D

[S Lathrop]

JohnPaul:

One of the problems we all have in reading the GCR is that there is no "case history" recorded about how the rules came about.

When Ed Zink and I were working on the Citation-Zink Z16, there were no rules governing the shape of the bottom of FF cars. FC was old F3 cars at the time. FSV and Formula B (FA today) were the popular small bore open wheel classes along with FF and FV.

The Z16 frame was 37" wide. In part this was to support the tunnels under the sides. The shape of the tunnels was derived from the FW07 Williams F1 car. Zink was working on an Indy car based on that design. We introduced the car at the 1978 run offs and needless to say, we were required to change stuff right away. The flat bottom rule was an outgrowth of that episode.

As Dustin has correctly observed, the rule and its interpretation was intended to limit the potential for generating down force from a flat bottom car. The first generation IRL cars had a very similar shape at the front of the side pods to that on Jesse's car. The IRL cars were intended to be full ground effects cars but with limited performance.

Over the decades, the science of flat bottom ground effects has advanced to the point that such cars can generate more than their weight in down force at speeds of 150 mph. But the rules for this technology go back to the late 1970 in the US and UK. For many years FC ran under the UK rule of 1 cm deviation vs. 1 inch for the US. The cars were all built to the UK rules because that was what was used for the pro series.

The simplest interpertation of the rule is that when viewed from the bottom of the car, every thing you see has to be within 1 inch of the bottom surface/plane of the car. This holds for the defined area and that is different for FF, FC, and FB. The one inch deviation was chosen because that was the same as the belly pan. Nathan's contribution to the rules now is to separate the bottom of the car from the belly pan.

[R. Pare]

The "logic' is/was that the rules had to start somewhere, and that was with using the FF/FC rules as the basis. Those rules were designed to minimize the production of downforce off of the bottom of the car by severely limiting the amount of shaping that could be done.

Unfortunately, while the wording at first glance seems perfectly logical when one knows what is the intent, that wording also covers areas of the cars that it was not intended to cover - like outward sloping cockpit side panels. Again, this is why I included the "primarily vertical" wording in the FF rules proposal.

At this point, it would be best if someone in the class proposed a slight change in the wording to the CRB, otherwise just about every car out there could be considered illegal.

And no, more downforce does not make the cars safer - with more grip possible, it just means that when you go off, you do so at a higher speed and hit harder.

[Wren]

Downforce equals corner apex speed and FB is already up there with the best Atlantics. The cars are going fast enough already. Going faster is not going to make things safer.

The easy answer for why not to change the rules is that everyone else built their cars to these rules and we shouldn't move the goal posts now without going through the entire rules making process.

[Rick Kean]

I don't think that is it as I don't see the cars being faster because of it. It's about downforce and I'd think having more downforce would be make them safer. That's what I mean, where is the logic?

Unfortunately, the green flag dropped, and it's a race.

I think that, in general, the logical cause->effect sequence is:
More Downforce allows the competitive car to be raced faster;
Faster speeds mean much higher kinetic energy levels, as the velocity term is squared
{Kinetic Energy = (Mass*Velocity^2)/2};
If crashed, the car's tube frame must now successfully dissipate this much higher level of energy, while not cracking through the driver-survivable deceleration x time period shell.

This higher energy crash scenario is logically less safe than before.

Rick

[Northwind]

Thanks Wren and Rick for explaining my point. Down force with out much drag penalty clearly adds up to more speed on the track.

[F1000champ]

No one is looking to move the goal posts. Just claify the rule already in existence.

Changing rules of adding clarifiaction wording to the rules is like trying to pass a bill in congress in SCCA. Too many committies to go through and lot's of egos to overcome from the rules original writers.

[R. Pare]

Not really a problem if the reason why things got this way are explained correctly, and in this case it is pretty easy.

Getting such a change should be fairly easy and straight forward.

[Northwind]

The diffirential rule clarification is a prime example of how easy a rule change can be. What was it, a well written letter from Brandon. Done deal.