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Old 10-28-2009, 02:04 PM   #268 (permalink)
3-Wheeler
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Quote:
Originally Posted by COcyclist View Post
Does the fact that Basjoos has installed inner and outer side skirts (pontoon style) between the front and back tires and a totally smooth belly pan allow him to keep more airflow under the car? Would this allow him to cheat the 4 degree limit on the bottom of the boat tail? If so, this would be helpful for a daily driven vehicle that has to negotiate steep driveways.
Hi COcyclist,

I think the pontoons can certainly help to keep some of the air under the car, but the extra volume of air needed to fill that expanse under the tail, means that the extra air has to come from somewhere.

One could put side ducts by the rear tires to force air into the space, but then there's more drag because of the ducts.

At this point in time, it seems the only option is to limit the angle of the boat tail underside to some volume in which the air coming into the underside of the car at the front, can easily fill at the rear.

To keep the air attached to surfaces on the car body, there appears to be the requirement of 'pressure'. That is, if one were to attach tiny manometers to the surface of various panels on the car, the air is still attached when the pressure is at or slightly above atmospheric.

If the air is allowed to try and fill too large of a void or pocket with more than is available, then the pressure will drop below atmospheric and the air will then be allowed to become detached from the body surface.

The ideal boat tail exit angle may not be possible in situations where it needs clearance over steep inclines and such.

Jim.
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