Slipstreaming in the late sixties

[Amagi]

Hello, this is my first post. I’d like your assistance with aerodynamics as implemented in a Formula One game simulating races in the late sixties. A debate has grown up over the distance at which a following car should begin to gain a drag reduction, however small, from a car ahead. There is a shortage of evidence but among the sources used was the 1995 Peter Wright article mentioned in the ‘Drafting’ thread of June 2007, which has a paragraph on the sixties.

These are my questions:

I. I’ve looked at the Advantage study from 2004, however it only extends to eight car lengths. Is it possible to extrapolate a drag reduction curve further from the one produced on page 11 of the study? How long is the wake of a 1998 F1 car?

II. The pre-wing sixties cars were very sleek but were built with little aero knowledge- they had high noses and also nose intakes. Also, there was no spoiler in front of the wheels (until 69). How would the drag of an F1 car of 1998 compare to one of the sixties?

III. If you have more than one car close together they produce a longer combined wake. How close together do the cars have to be before this effect begins? Is there a method by which the additional length of the wake at a given speed can be derived from the number of cars in a pack?

IV. What is your best estimate for the length of a single sixties F1 car wake at 190mph? Multiple cars?

[Conceptual]

Is this for a rFactor mod?

Chris

[Ogami musashi]

you can't answer that until you have empirical data, slipstream drag reduction is due to recirculation of air (the vortex) and the duration is vortex scale dependent mainly with vortex surrounding being the other main parameter.

All i know, from a simple empirical data, at the speed range you cite, an indy car has a wake of 25ft.

[Amagi]

It's Grand Prix Legends. The original game simulated the 1967 season. The 1965 mod was made with assistance from some of the original team and used the original draft code. The 1969 mod added wings and had new draft parameters. The most recent 1966 mod followed on from the 1969 mod.

There is a debate about whether the 1965 mod should be remade with the new draft parameters. As it is an old game the original code was limited by the power of early PCs: however, the parameters used by the new draft code are controversial.

A speed of 190mph is the only parameter to consider, you can assume calm dry sealevel conditions. I'm surprised that a single Indycar at 190mph would have a wake of 25ft whereas that of a 1998 F1 car is far more than eight lengths...? One of the features of Indycar racing is that large packs develop on the high-speed ovals- isn't the wake of a pack far larger?

Could a rough comparison between the drag factor of a sixties and nineties F1 car be made, independent of other parameters?

[Ogami musashi]

Well, the wake will depend on the vortex that are formed so it is more a question of the shape of the car, but still you can maybe approach it by the drag factor yes.

That won't be accurate but should at least give you a correct correlation with a 1998 F1 car;
Pay attention to have to correct Cd of you cars, as for instance the suspensions and engine did produce a lot of turbulence.

[Amagi]

Grand Prix Legends at the old Nurburgring:

http://www.youtube.com/watch?v=cYNytizUJV8

Though a pack of Indycars can go faster because the drag reduction experienced by the leader, is the wake of an Indycar pack much longer than that of a single car? Would an Indycar attempting to catch a pack get a reduction of drag at a much further distance than if it were attempting to catch a single car?