Aerodynamic development

originally posted 6.22.2024

page 385 section 9.1.3. Improved Touring Category Specifications under 9. Body/Structure
b. A front spoiler/air dam is permitted. It shall not protrude beyond the overall outline of the body
when viewed from above perpendicular to the ground, or aft of the forward most part of the front
fender opening. This body outline does not include bumpers or bumper mounts. The spoiler/air dam
shall be mounted to the body, and may extend no higher than four (4) inches above the horizontal
centerline of the front wheel hubs. It shall not cover the normal grille opening(s) at the front of
the car. Openings are permitted for the purposes of ducting air to the brakes, cooler, and radiator.
Dealer installed or limited production front/rear spoilers/air dams/wings are prohibited. The spoiler
shall have no support or reinforcement extending aft of the forward most part of the front fender
wheel opening.
NOTE: Integrated bumper assemblies are defined as those designs where an external non-metallic
bumper cover completely encloses the primary energy-absorbing bumper and where this cover
could be installed in its normal position with the underlying bumper removed. On cars with integrated bumpers, the front spoiler or air dam may be attached to the bumper cover.
Where an air dam/spoiler is used, two total openings may be cut in the front valance to allow the
passage of up to a three (3) inch diameter duct leading to each front brake/rotor assembly.
Where no air dam/spoiler is used, two total openings of a maximum size five (5) inches by seven (7) inches maybe cut in the front valance so that brake ducts can be added with a three (3) inch diameter hose leading to each front brake/rotor assembly.

originally posted 7.2.2024
Enclosing the driveshaft is impractical so aft of the transmission the underbelly pan will be split longitudinally into two halves. The pan will run from the edge of the transmission tunnel to the inside of the rocker panels. In the front every effort should be made to start at the bottom of the firewall and extend as far rearward as is practical, ideally with one continuous sheet of HDPE. Forming a curve at the leading edge under the firewall would be beneficial to funnel and smooth airflow from the engine compartment into the venturi. The transmission tunnel will form the opening of the venturi. From the firewall aft, the airflow under the car will be constrained by the underbelly and the road surface. Attaching the HDPE sheet to the undercarrage of the car must be done without damaging the unistructure. Crash damage and replacement must be considered.

originally posted 7.5.2024
After further consideration enclosing the drive shaft should not be ruled out if the benefit warrants. Perhaps the drive shaft could have it’s own cover to make service easier. It should be noted that the main driveshaft requires very minimal service even in racing conditions. This could be incorporated with safety loops which could also provide a possible mounting point for the underbelly. The main drive shaft moves vertically a very minimal amount. The exhaust pipe will need an opening in the underbelly and also occupies space in the tunnel.

Indeed a drive shaft loop (or two) has been in development for some time. The sheet metal transmission tunnel in all likelihood would not contain the driveshaft in the event of a catastrophic u-joint failure. The driver is a few inches from the tunnel.
This could possibly be used as a mount for the under tray
The engineering department has made it very clear that no new holes may be created in the unistructure of the vehicle without a full review. Driveshaft safety loops may be considered.

The key would be constructing the support structure for the under tray light enough that the extra weight doesn’t offset any performance gains. A sheet of HDPE 1/8" x 48" x 96" weighs 20 lbs. (3.175 mm x 1.2 m x 2.4 m weighs 9 kg) $98 usd (fall 2024).
Target weigh would be 30 - 40 lbs for tray and mount.
The outward side can be secured on the pinch welds on the bottom of the rocker panels. Side skirts of some kind are also being considered because they would increase the effectiveness of the under tray. The diffuser tunnel could be partially formed from the HDPE or a separate panel built from composite or thin sheet aluminum. Vertical strakes (or fences) in the diffuser tunnel would create more down force and could be used to exclude turbulent airflow from the rear wheel area.