Generates rear downforce and sets the rearward end of the aerodynamic balance.
A multi-element stack on a reverse-spoon main element with variable spanwise twist. The reverse spoon exists because the air behind the driver and the air near the endplate arrive at different angles; twisting the main element keeps the stagnation point off the top surface across the span rather than only in the middle. Yaw elements at the front of the stack were identified as a weight reduction opportunity, at a cost to rear wing efficiency. Design Philosophies and Processes: The CR25 brief was to reduce rear wing weight while increasing downforce, to move the centre of pressure rearward and give the more oversteering car at high speed that the drivers had asked for. The specific proposal was to delete elements 4 and 5, which had proved to give little gain in real world testing. That saves 618 g of elements plus the bolts and whatever portion of the endplate is cut off, with each endplate weighing in the region of 800 g. Reducing from three elements to two plus a slat was the other option under examination.
ANSYS Fluent 2D element sweeps (153 two-element and 148 three-element runs on CR26E), 3D verification, integrated half-car runs with the current undertray, then full-car yaw runs. Spanwise pressure coefficient at maximum thickness is the metric used to show the spoon working.
Tooling board molds machined directly rather than fiberglass molds pulled from CNC foam plugs. Airfoils infused, spars wet laid up, assembled in 3D printed jigs. From the design reports and one-pagers: CR25 one-pager estimate: create and machine moulds for the wings 20 hours plus the drive to Knoxville and Reckless Industries' scheduling; mould surface prep 30 hours; lay up parts 70 hours; trim parts 15 hours; assemble the wing 20 hours; clear coat 15 hours. Nomex honeycomb for 1,345 square inches cost $175.
CR22 rear wing schedule, bottom skins and top skins without flanges: 0-90 Textreme (76 gsm), +/-45 stitched (150 gsm) x2, 0-90 Textreme (76 gsm). Endplates: 0-90 Textreme (76 gsm), +/-45 stitched (300 gsm), Nomex honeycomb core (0.25 in), +/-45 stitched (300 gsm), 0-90 Textreme (76 gsm). From the cost report drawings and CAD: From the cost report drawings: Carbon Fiber (Full RW combined drawings PDF).
Small flow detachment behind the driver's head, visible in constant-speed tufting on the upper surface. Leakage around elements from manufacturing tolerance and mounting wake, visible in Flo-Vis on the bottom surface.
CR26I: CLA 1.32, CDA 0.65, L/D 2.19, 11.58 lb. CR25: CLA 1.46, CDA 0.65, L/D 2.26. From the cost report drawings and CAD: Weighed mass: 4780.9 g (10.540 lb). Dimensions called out on the cost report drawings. These are the figures printed on the drawing, not a labelled specification; open the drawing itself for what each one refers to. Full RW combined drawings PDF (mm): 533.4 957.6, 1001.8 Full RW Minus Top skin (mm): 533.4 957.6, 1001.8 Full RW pdf fully assembled (mm): 533.4 957.6, 1001.8 RW 1 combinepdf (mm): 944.88, 519.98, 2.54, 13.46, 121.91, 912.88, 944.87 513.58 RW 1 no top skin (mm): 2.54, 13.46, 121.91, 912.88, 944.87 513.58 RW 1 (mm): 944.88, 519.98 RW 2 Combined (mm): 944.88, 175.26, 912.88 16.0, 2.5 Source: Subteam weight books: CR25/Initial Documents/Weight Breakdown CR25.xlsx | Cost report drawings: CR26E/Aerodynamics/Cost Report & Drawings/Rear Wing/pdfs/Full RW Minus Top skin.PDF; CR26E/Aerodynamics/Cost Report & Drawings/Rear Wing/pdfs/Full RW combined drawings PDF.pdf; CR26E/Aerodynamics/Cost Report & Drawings/Rear Wing/pdfs/Full RW pdf fully assembled.PDF; CR26E/Aerodynamics/Cost Report & Drawings/Rear Wing/pdfs/RW 1 combinepdf.pdf and 3 more
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