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Did a non-rigorous test - A-B only. (Cardboard/duct tape prototypes don't lend themselves to removal & reinstallation, so sorry, no A-B-A.)
That said, conditions were PERFECT. Next to no wind.
Results @ 55 mph (88.5 km/h)
- with partial boattail: 61.23 mpg (US) avg.
- without boattail: 59.85 mpg (US) avg.
- partial boattail gain: 1.38 mpg (US) / 2.3% above "stock"
Conditions:
Observed at: Grenadier Island 18 July 2006 4:00 PM EDT
Temperature 28°CPressure/ Tendency 101.5 kPa↑Humidity 63 %Humidex 36 Dewpoint 20°CWind calm DRLs, alternator ON, fan ON @ 3
W E
Partial boattail
59.8 61.6
60.2 63.3
59.4 63.1
61.23333333 avg
Non-boattail
57.2 61.7
58.7 61.8
59.85 avg.
Observations
This is about in line with what I predicted, based on the gains seen from grille block & wheel skirts (5.7% combined).
The difference between this mod and those, is this is a complex shape which can be optimised with tuft testing. The others were essentially no-brainer gap-fillers.
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