FIRST PRINCIPLES AEROBYTES
TABLE 2: the effects of splitter end plates CD
1. Stock position, flap at mid- position
2. 33mm below stock 3. 66mm below stock 4. 100mm below stock
5. 100mm below + 135mm forward 6. 66mm below + 135mm forward
7. 100mm below + 135mm fwd + flap to minimum angle
0.582
0.573 0.566 0.555 0.556 0.572 0.517
1.065
1.041 1.015 0.983 1.058 1.069 0.960
-CL -CLfront -CLrear %front -L/D 0.360
0.705
0.373 0.390 0.400 0.437 0.429 0.466
0.668 0.625 0.582 0.620 0.640 0.494
33.80
35.83 38.42 40.69 41.30 40.13 48.54
1.830
1.817 1.793 1.771 1.903 1.869 1.857
retained at this new, 100mm lower height (position 5) total downforce jumped up again to almost the same level it was before the wing was moved. It also increased by roughly equal amounts at each end of the car, with virtually no change in drag with the forward shift. Efficiency also improved markedly, and balance was now over 41 per cent front. The obvious conclusion here was that the wing’s interaction with the underbody had improved, hence the roughly equal downforce jumps front and rear with no drag increase. [Pic 63-5]
The sweet spot The wing was then raised to the 66mm
below stock height at this new, more forward position (position 6), but the numbers changed for the worse, so position number 5 was elected as the best available. This raised the obvious question about whether position 5 was actually the ‘sweet spot’ for the rear wing, but with a tight timescale there wasn’t the opportunity to explore this further. It did demonstrate the point though that a car with a downforce-generating underbody can sometimes benefit from
The stock rear wing position was at the maximum permitted height, often best for maximum downforce
“the constructor was keen to ensure cooling would not be compromised”
running the rear wing at lower than maximum height, and with a fore / aft location over the rear body that brings the low-pressure region generated under the wing into more intimate interaction with the underbody diffuser’s exit. Finally, the rear wing flap was adjusted to its minimum available angle (position 7). As might be expected, this made a pretty big difference to the coefficients and, for the first time, a result reflecting the target balance was obtained, together with a decent efficiency level in the context of this session. More on the ADR 3 next month.
Lowering the wing and moving it forwards produced almost as much total downforce but improved both balance and efficiency
Racecar Engineering’s thanks to ADR Engineering, Carbon Weezel and Simon Marsh.
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