Wind tunnel tests were conducted during the months of January and March of 1970, in the Wichita State University 7' x 10' wind tunnel. Three-eighths (3/8) scale models of the 1971 Dodge Charger and Plymouth Road Runner cars were the test subjects. The initial test period was used to develop aerodynamic front end extensions, front undernose spoilers, backlights and various other items to improve the vehicle aerodynamics. The second test phase was utilized to develop rear stabilizer systems, a greenhouse reduced to minimum size, additional nose shapes and other subtle configuration changes.

This report presents all the data obtained from these tests and the results of the analysis. Data for the various parameters are compared with each other as well as with the "F" Series Dodge Charger Daytona data. The best aerodynamic configurations are pointed out for each body and greenhouse.

Among the features tested on the 1971 Dodge Charger 3/8 scale wind tunnel model was a windshield that extended forward almost 27 inches farther than the stock configuration. (Figure 76).

The objectives of the wind tunnel study were:

1. Define and develop the aerodynamics of five basic "G" Series, B-body Dodge and Plymouth configurations.
2. Develop the "G" Series, B-body into the lowest possible aerodynamic drag race car by adding a nose extension, a backlight plug and modifying the greenhouse area of the car.
3. Define the aerodynamics of three rear deck stabilizer systems.
4. Determine the aerodynamic effects of removing the side glass from the "F" Series Dodge Daytona and the "G" Series Dodge B-body.

The wind tunnel tests were performed in two phases. Phase I testing started January 5, 1970 and continued to February 6, 1970. Phase II testing began March 2, 1970 and ended March 26, 1970. The 3/8 scale, fiberglass models were pitched through body rake angles of 0 to -3 degrees and yawed from -3 to +9 degrees. All testing was done at a freestream dynamic pressure of 40 psf (125 MPH).

The results of the "G" Series race car aerodynamics program are comprehensively compared to the "E" and "F" Series aerodynamic results.

The basic "G" and "H" Series B-body external shapes are identical with some aerodynamically insignificant exceptions. Therefore, all "G" Series, B-body test results and analysis also apply to "H" Series, B-body.

The tests utilized two 3/8 scale "G" Series models: A Dodge Charger, GW-23, and a Plymouth Road Runner, GR-23. The models were of laminated fiberglass construction which were formed in molds taken from 3/8 scale clay models.

The models were constructed to allow flexibility of test parameters. They consisted basically of three parts: Main Body, Underbody and Wheels.

The body was a high fidelity 3/8 scale aerodynamic reproduction of the actual car, but had limited detail in the grille and tail light areas. The front end of the body shell was made separable at two locations to accommodate several basic front end configurations. Further modifications were made on the Dodge model for the Phase II tests. The roof was made removable at the "belt line". Reinforcement and attachments were provided on the body to accept a clay plug for the minimum greenhouse investigation. In addition, side glass, on the standard greenhouse, was also made removable to determine window out effect on car performance.

The engine compartment was constructed to retain the same volumetric displacement as the actual race cars, thus simulating similar cooling air mass flow characteristics. However, due to design problems, the model's firewall was located aft of that on the full size car. Ducting was installed from the air inlet area to the forward face of the radiator for the 9 and 18-inch noses and aero front end simulating actual race car conditions. Ducting on the standard and minimum change nose started at the 45 inch line. All the inlet flow was ducted through the radiator. The duct has variable geometry to accommodate relative attitude changes between the body and underbody when the model was raked. A radiator was utilized that had similar pressure drop characteristics across the core as that on the full size race car. Limited detail wood engines were utilized to simulate the racing hemi and its volumetric displacement in the engine compartment. A scale fan was mounted in the wood block utilizing a bearing which allowed it to "free wheel" during the tests. Attempts were made to simulate engine compartment air venting by providing proper cut-outs throughout the engine compartment. However, only marginal geometric simulation could be accomplished.

Two underbodies were fabricated, one for each of the basic car models. The construction was also laminated fiberglass. Proper geometric simulation of the race car underbody was a basic requirement for aerodynamic similitude. Particular attention was directed toward exact simulation and location of the "K" member and other parts essential to the aerodynamics of the underbody. The underbody was also cut and hinged at the 12-inch side view line to provide body to underbody attitude simulation.

A set of scaled 9-inch race wheels were constructed for each model. They were made of plastic with balsa wood cores to reduce weight. The front wheels were mounted to brackets attached to an inner steel frame. The brackets were slotted allowing vertical height adjustment. At the rear, the wheels were also attached to brackets on the inner frame. An axle was utilized with a simulated differential and affixed to the wheels. Slots were provided in the wheel brackets to permit the body to move vertically relative to the front wheels and rear wheel-axle combination. All wheels were rigidly attached to the wind tunnel balance.

A steel inner frame was constructed to implement the rake angle (body attitude) changes required in the tests. The frame consisted of two interconnected longitudinal steel angles. The forward part of the frame was attached to the front part of the underbody, forward of the hinge line. The aft section was fixed to the aft portion of the body. Two bolts were attached, in a vertical plane, to plates that were mounted on the body in the dutchman area. These bolts screwed into nuts welded to the fixed inner frame. Access to the bolt heads was provided by body shell clearance holes located in the dutchman. These bolts were the mechanism to rake the body relative to the ground. The aft portion of the underbody was bolted securely to the body and the forward part of the underbody was secured to the frame. The body attitude change was achieved by turning the bolts, located at the dutchman. This allowed the body and aft section of the underbody to move in the pitch plane relative to the wheels and inner steel frame. The front portion of the underbody, forward of the hinge line, remained a constant distance above the ground (minimum race clearance of 6.5" full scale) for all body attitudes.

The effect of spoilers was investigated on all configurations tested. Figures 6, 7, 8, 9, 10, 11 and 12 presents all spoiler locations investigated.

Spoilers were fabricated of sheetmetal and fastened to the various front ends with screws and tape. In all configurations, Position "A" was located at the aft edge of the air inlet opening.

Both the Dodge and the Plymouth models were constructed to accept various front ends. The basic models were cut at the 45-inch side view line and at the cowl area. This provided the flexibility of investigating nose shape changes as well as complete front end modifications, i.e., the aero front end.

Pedestals were constructed for each model to accept the various vertical-horizontal stabilizers systems. This made it possible to adapt the same sets of stabilizers on each model.

The greenhouse on the Dodge model was removable. This feature provided the flexibility of installing various greenhouse configurations and allowed minimum tunnel "down" time. A clay greenhouse "buck" was utilized for the various major roof changes investigated.

Four front end shapes (from the 45" S. V. line fwd.) and one complete front end configuration change, from the cowl forward, was investigated for both the Dodge and Plymouth. The front ends tested were the standard, minimum change, 9-inch extension, 18-inch extension as well as a completely modified aerodynamic front end (Figures 4 and 5). In addition, a 12-inch nose was also tested on the Plymouth model only. The various noses and front ends were developed for their optimum performance, utilizing various combinations of front undernose spoilers (Figures 6, 7, 8, 9, 10, 11 and 12) and air inlet size and locations. The standard and aerodynamic front ends were constructed of fiberglass and attached by means of steel bulkheads and bolts. All the other noses were made of clay to allow for ease of modification.

Various backlights were investigated on both the Dodge and Plymouth models. In addition to the standard backlights, clay was used to define and test minimum change, semi-fastbacks, and full fastback backlights. Figure 13 presents the three backlight modifications tested on the Dodge model. Tests of the Plymouth model, however, were limited to only two backlight modifications, a semi-fastback and a rev. 1 semi-fastback, as shown in Figure 4.

The Dodge model was reworked for the Phase II tests, with a removable fiberglass greenhouse. A clay roof "buck" was provided for studies dealing with a minimum envelope greenhouse (Figure 15). In addition, the standard greenhouse included removable sideglass to investigate a side window out configuration. Two Daytona type noses were evaluated. The tests include a 13.3-inch and an 18-inch nose extension. The effect of aerodynamic fairings on the underbody was evaluated by fitting the Plymouth model with belly pans. Three belly pans were tested; (1) from the "K" member to the hinge point on the model, (2) the second was from the hinge point on the model to the forward part of the rear wheel axle, (3) the final configuration was from the "K" member to the aft part of the rear axle.

This BIG wing thing for 1971 was the largest wing tested in terms of girth. On a full-size car, this air foil would have been 19-inches in width! (Figure 92).

Three rear deck stabilizer systems were evaluated utilizing both models. A 10-inch chord (full scale) single and bi-wing configuration (Figure 16) and a 19-inch chord (full scale) system was used (Figure 17).

The horizontal stabilizer section was a Clark-Y airfoil section. Section characteristics for both the 10- and 19-inch chord stabilizers are shown in Figure 18. An N.A.C.A. 0012 airfoil section was used for the vertical stabilizers, and the section characteristics are presented in Figure 19.

All body configuration changes (i.e.-- flush sideglass, backlight modification, pull out lower front sheetmetal, etc.) were obtained with the use of modeling clay.

The standard "G" Series car with a front spoiler and both a standard and semi-fastback greenhouse are compared to the "E" Series (1968-1969) race car in Figures 167a, 167b, 168a, 168b and 168c.

The "E" Series Daytona 500 is, generally, a better aerodynamic configuration than either "G" Series configurations. However, the "E" Series car front lift is significantly higher (450 pounds) and the directional stability is lower (center of pressure is 2 inches further forward) than the "G" Series car.

Development tests were conducted for the minimum change, 9-inch, 18-inch and aero front end in addition to the basic car. The model with the 18-inch nose or the aero front end, without front undernose spoilers, were found to have the best aerodynamic characteristics as shown in Figures 169a, 169b and 169c. The 18-inch nose configuration has the lowest axial force of all the nose configurations but has a high down force at the front wheels that is undesirable. On the other hand, the aero front end has good front and rear wheel lift characteristics but the axial force is slightly greater than the 18-inch nose data. Lateral stability of the aero front end is better than that of the 18-inch nose, CP is about 4.6-inches further aft. From an overall aerodynamic standpoint, the aero front end without a front spoiler is the best configuration.

The 18-inch nose and aero front end were found to be the best configurations by the Phase I tests and were, therefore, the only Phase I noses tested in Phase II. Two new noses were evaluated during the Phase II tests, the 13-inch and 18-inch Daytona noses. A nose evaluation was made with the minimum and standard greenhouses as shown in Figures 170a, 170b, 171a and 171b. Once again the 18-inch nose configuration, in this case, with a front undernose spoiler, exhibited the lowest axial force. The 18-inch Daytona nose was next best for low axial forces.

Lift characteristics of the 18-inch nose configuration are not desirable, i.e., there is a large down force at the front wheels and high lift at the rear wheels. Lift characteristics of the vehicle with the 18-inch Daytona nose are more desirable than that attained by the 18-inch nose configuration.

The effect that front undernose spoilers have on the vehicle aerodynamic forces have been evaluated for various spoiler positions, nose, backlight and greenhouse configurations as shown in Figures 172, 173a, 173b, 173c, 174a, 174b, 174c, 175a and 175b. Most of the nose configurations, except the minimum change and 13-inch Daytona, indicate the axial force reduction due to the spoiler is greatest at zero degrees and diminish when the rake angle is increased from zero to -3 degrees.

Variation of the spoiler axial location affects the front and rear wheel lift primarily. The forward most position (A) yields the greatest reduction of front wheel lift and increase of rear wheel lift. Moving the spoiler aft from position A to position B causes almost a 50% decrease of the front and rear wheel lift increments with virtually no change in axial force. An evaluation was made of the effect the backlight configuration has on spoiler effectiveness. The results of the evaluation for the 18-inch nose and aero front end configurations are presented in Figures 174a, 174b and 174c. These data indicates the spoiler effectiveness is independent of the backlight configuration with the exception of _B=0 degrees. At _B=0 degrees, the minimum, semi and full fastbacks exhibit the higher spoiler effectiveness.

The greenhouse effect on spoiler effectiveness was also evaluated (Figures 175a and 175b). The axial force increment is most sensitive to the greenhouse configuration. Max. C_X reduction is achieved with the minimum greenhouse and minimum C_X with the standard. The only change of front wheel lift occurs for the minimum greenhouse. Rear wheel lift slope relative to rake angle changes with the greenhouse configuration.

The minimum change 1971 Plymouth nose, like its Dodge counterpart, was convenient from a design standpoint but didn't offer suitable aerodynamics when compared to other more radical snouts tested. (Figure 118).

The best "G" Series Dodge race cars are compared with the "F" Series Daytona in Figures 176, 177a, 177b and 177c. Consideration was made for the standard and minimum greenhouses plus side glass removal on the minimum greenhouse. From an overall aerodynamic standpoint, the 18-inch nose with spoiler and minimum greenhouse (side glass out) configuration is best. If the minimum greenhouse configuration cannot be considered, then the aero front end on the standard greenhouse with semi-fastback (side glass out) is the best configuration. It is interesting to note that the "G" Series car indicates an additional axial force margin over the "F" Series Daytona when the side glass is removed. This is attributed to the fact that the Daytona side glass is closer to being flush than the "G" Series side glass, therefore, removing the side glass on the Daytona increases the axial force much more than it does on the "G" Series cars.

The "G" Series Plymouth with either a standard or minimum change front end and front undernose spoiler have axial forces greater than the "E" Series race car without an undernose spoiler as shown in Figures 178a and 178b. Front lift of the "G" Series cars is about 350 pounds lower than the "E" Series car and considered an improvement. The "E" Series front wheel lift is high because of the absence of an undernose spoiler. The rear lift of the "G" Series cars is 300 pounds greater than the "E" Series which results in a degradation of the handling characteristics.

Five nose configurations were tested on the Plymouth during the Phase I test, the minimum, 9-inch, 12-inch, 18-inch and aero front end. The 12-inch nose with the undernose inlet has the best overall aerodynamic characteristics of all the noses tested on the Plymouth (Figures 179a, 179b and 179c). Rear wheel lift is greater than desired but this can be over come with a rear deck spoiler. All the noses tested reduced axial force below the standard car values.

Addition of a front undernose spoiler affects both axial force and lift as shown in Figure 180. Axial force coefficient can be reduced as much as .046 by adding a spoiler to the 18-inch nose at zero rake angle. For this configuration and set-up, the front lift is reduced 650 pounds and the rear lift increased 370 pounds. Spoilers are most effective when the body is at zero rake. As rake angle is increased, the spoiler has less of an effect on the aerodynamic forces. The "F" Series Daytona spoiler is more effective for axial force reduction than any of the "G" Series spoilers but the lift changes are within the same order of magnitude.

Two configurations emerge from the configurations tested which are better than the others; the aero front end and 12-inch nose both having 45 square inch air inlets, flush glass and semi-fastbacks. Data for these configurations are compared with the Daytona data in Figures 181a, 181b and 181c. Data points are not shown for the aero front end configuration because the measured data had to be adjusted for an air inlet area change. The 12-inch nose exhibits the lowest axial forces, but the aero front end has slightly better lift characteristics. Neither of these "G" Series configurations is as good as the Dodge Charger Daytona.

The following conclusions are made from the analysis of the "G" Series Dodge and Plymouth B-body test data presented in this report.