[bikenfool]

Originally Posted by ChazInMT

The problem with this design is that a serious downdraft and consequent very low pressure area is created above the rear window and high presure air is moving along the side. So you have air moving in 2 directions and 2 differing pressures.

Can you say VORTEX? The drag created by spinning the the air dragging along 2 tornadoes is immense.

There is a slightly more efficient shape for creating drag, but not by much.

Originally Posted by aerohead

The FKFS (Koenig-Fachsenfeld/Kamm) tested something similar to the r-pod,except that it had inboard wheels.It was reported at Cd 0.45.
The r-pod,with exposed wheels and fenders would be higher.
The 'classic' teardrops would suffer the same attached longitudinal vortices as r-pod just as ChazInMT has illustrated above.
The rooflines are all too fast,the pressure builds over the aft roofline in advance of the side flow,we get separation up there,and the pressure differential causes higher pressure air from below and on the sides to race up there attempting to reach equilibrium.As the flow fields collide at different velocity and pressure,they coil up just like a mesocyclone,spinning into horizontal tornadoes.
The sharp edges rob about 16% of Cd potential.The gap sucks energy.If they don't have belly pans,there's some more loss.
A 'gutted' VW microbus 'trailer' would pull as well as a shrunken Airstream,at Cd 0.43 (free-air),lower in train behind a tow vehicle.It would have more usable interior volume than a 'teardrop.'

Wow, so you guys are saying that the cool looking teardrop trailer design is crap? Unless it has a taper in the plan view also? I'd like to get educated, can you point me to some literature on this? My fluid dynamics education is very rusty.