Generates front downforce and sets the front end of the aerodynamic balance.
A dual main element wing on Eppler-series airfoils, with a flap stack behind each main element and endplates carrying a fence and a half-tube. The half-tube seals the bottom of the endplate to preserve the low-pressure region on the wing underside; the endplate curve outwashes air around the front tire. Design Philosophies and Processes: 2D CFD sweeps place elements and set angle of attack, then the best candidates move into a 3D half-car model at 35 mph, then into the full-car performance map for yaw, roll and cornering.
From the CR22 aero write-up, the first Crimson Racing car with an undertray. Preliminary constraints came from the rest of the package: with a floor added, the front wing had to make enough downforce to balance the car, and efficiency was prioritised over raw downforce because the point mass lap sim showed that is where endurance and autocross points come from. The real limiter was ride height. The front wing is the most forward part of the car, so maximum pitch angle set how low it could sit, and pitch and roll combined set the endplate height. Arriving at the final height was iterative with Suspension, and the answer was that the wing had to stay above roughly 1.8 in at the endplate. Split main plane. After looking at CR21's wing and other single main plane designs, the only two ways to add meaningful downforce were lowering ride height, which Suspension had just ruled out, or splitting the main plane. Split it: CR21's single element made 35 lb at 35 mph with a 1.55 in endplate ride height; CR22's split main plane made 45 lb at 1.73 in at the centre and 1.9 in at the endplate. Endplates were the year's focus, and all three changes were tested one at a time against the same baseline: - Half-tubes along the bottom of the endplate, to seal off the low pressure region under the wing from high pressure air coming in underneath. Iteration 002 without one made 37.73 lb; iteration 003 with one made 45.08 lb, everything else identical. Pressure contours show the difference out at the outer span. This was the largest and clearest of the three effects. - Curvature, to block the face of the tire. Curved (iteration 007) gave car L/D 2.333 with 4.58 N front tire drag and 6.9 N front tire lift; flat (008) gave 2.288, 6.05 N and 8.1 N. The change was greater than 10%, which clears the known 2 to 10% CFD run-to-run and real-world variation, so it counted. - A gurney on top of the endplate, parallel to the ground and extending outwards. With it (006) the wing made 48.66 lb; without (007) 43.88 lb, with no significant change to drag or to other components. All three went into the final design. The page notes that half-tube diameter, endplate curvature and gurney size were never refined beyond this, so there is more there. The lesson recorded with it: design through independent variable analysis. Making one change per run is the only way to see what each change actually did, and not doing that at the start cost a lot of time.
Minimum ride height and roll angle in dynamic conditions set how much angle is available. Front wing span must leave suspension setup freedom. Rules bound the width and the forward extent. From the design reports and one-pagers: From the CR25 Front Wing Design Report: maintain or decrease weight; limitations on parts available; all related rules; the move to 16 in wheels moved the bounding box 1 in toward the driver; and manufacturability, since the team did not want to completely rebuild the front wing. Note that the CR25 Front Wing Design Report was never filled in beyond its goals and constraints sections; the remaining headings are still the template prompts.
ANSYS Fluent, k-omega SST, pressure-based coupled solver, poly-hexacore volume mesh, wall y+ monitored on all lift-producing surfaces. Endplate configuration sweep: flat endplate FW CLA 1.16 / CDA 0.128 / tire CDA 0.241; no half tube with fence 1.13 / 0.132 / 0.220; no fence with half tube 1.23 / 0.133 / 0.231; fence and half tube 1.34 / 0.148 / 0.225.
Tooling board molds for all significant airfoils, milled on the 5-axis gantry. Airfoils are infused; spars are wet laid up. Small airfoils use 3D printed molds. Endcaps, spars and skins are made independently and bonded in 3D printed jigs with glass alignment beads controlling bond gap. Leading edge finished with polyester filler and satin clear coat. From the design reports and one-pagers: From the CR25 front wing one-pager: infusion layups for skins and outer endplates, flat layups for inner endplates, wet layups for half-tubes and spars, and waterjet for mounting holes and inner endplates. Costs: Nomex honeycomb $90, mounting screws $91.84 (28 bolts at $3.28), estimated total $181.84.
CFRP skins and spars, Nomex honeycomb core in endplates, EA 9460 and LC-E224 film adhesive, DP420 and structural paste adhesive for bonding, aluminium hardpoints in the laminate at mounting locations.
Fault Vault, CR26I, Design, Compromised Failure (joint Aero/Suspension entry). Improper ride height integration between the front wing and the undertray required packers to be added. Manufacturing tolerance leakage around elements is also visible in Flo-Vis, which is what the 3D printed bonding jigs and glass alignment beads address.
Endplate manufacturing moved to a two-piece mold, which integrates the fence into the part rather than bonding it on. Ride height integration with the undertray needs to be resolved in design rather than with packers at the track.
CR26I: CLA 1.35, CDA 0.15, L/D 8.86, 6.38 lb as built. CR25: CLA 1.34, CDA 0.15, L/D 8.75, 6.44 lb. From the cost report drawings and CAD: Weighed mass: 3098.0 g (6.830 lb). Source: Subteam weight books: CR25/Initial Documents/Weight Breakdown CR25.xlsx