Quote:
Originally Posted by Hersbird
I realize it's not a classic teardrop but then I wonder if the classic teardrop is also doing the same thing just on a smaller scale.
I mean the 18' rpod with a slide is only 2500#, people with a 18' 2500# classic box travel trailer get better then 10 with a modern v6 tow vehicle.
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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.'