Some general thoughts on Adrian Gaylard's 2013 Land Rover:
1) On page-72 he gives a 'baseline' Cd 0.340 for the SUV.
2) On page-2 he mentions that ' the wake flow generated by a blunt ended cars typically causes more than one-third of their aerodynamic drag.'
3) If we take Cd 0.340 as the Rover's drag, and if one third of that is 'wake' drag, then we're looking at 'wake drag' = Cdw = 0.1132.
4) If the addition of a boat-tail eliminated the wake, then Cd 0.340 - 0.1132 = Cd 0.2268.
5) A 'boat-tailed' Land Rover would come in between a Tesla Model S, and a Porsche Taycan Turbo. Much like Kamm's Cd 0.23 K-car of the 1930s.
6) Similar to Thomas Scott Breidenbach's GM full-size SUV, wind tunnel-tested boat-tail, which would quantitatively drop the Chevy Tahoe hybrid from Cd 0.34, to Cd 0.2414. A 98-count reduction. ( US Patent # 8590961, February 21, 2012 )
Only Ockham's Shaving Cream improves upon his Razor!
