Which one offers the lowest overall drag:
A. A standard shaped roof where the roof is mostly parallel to the ground
Or B. a Kamm placed over a standard roof?
The roof continues upward inclination beyond the standard shape roof height to slowly taper down.
Roof camber data seems to show that while Cd decreases with higher roof camber, overall CdA goes up as the increase in frontal area won't compensate for the lower Cd.
In This Chapter the Modifications That Were Carried Out To
But there's a catch as this data is for a symmetric shaped roof camber where both upward and downward slopes are equal.
What happens when the upward slope (front) is steeper than the downward slope (rear)? Of course the max roof camber point goes forward.