Quote:
Originally Posted by freebeard
Wielding the notorious Template, this is what most people would give you. Match the ground plane and peak of the roofline.
correct
Again I would listen to Sven7 on how big a bustle you might care to drag around. |
Of course we are assuming in that photo that the rear window has attached flow. Even if it does, it may be a bit strained (pulled down too quickly but not lost), in which case it would behoove you to build a tail from the top of the rear window down, following the template's curvature.
To build the correct angle on the boat tail
from the trunk lid back only, I am told to mark the vertical line on the template that is nearest the bumper (here, in the middle of the template's rear wheel) and simply slide the image down, maintaining its angles.
Getting the right angle will be easier if you get a straight side blueprint, as so:
Edit, ok I did your homework for you
The diffuser bit is taken from Hucho's book. Compared to a horizontal belly pan, the 3* upward tilt should decrease your drag by about 0.02 Cd.
You may find the departure angle to be too conservative, but fear not, as a 15* angle will only increase your drag by 0.01 Cd compared to a horizontal pan.
Keep in mind if it's too long for your tastes you can chop it off at any point without changing the curvature. This will decrease your aero gains, though.