found another aero cap
 

pretty funny site
plus this...
Hearkening Back To Automotive Glory Days - There, I Fixed It

I Thought about this, but decided to not do it.
 

http://ecomodder.com/forum/attachmen...1&d=1264222919

I'm in the process of making an Aerocap for my truck. I have done a bit of research and have gotten to understand some basics of aerodynamics. I actually considered this very design, but decided against it on account of it isn't too aerodynamic. It has to do with the fact that the air will not follow that curving slope all the way down. You will get severe flow separation about half way down those windows which will create a lot of turbulence and drag. Hear me now, believe me later, this will save some gas, but only about 5-8%.

The only place you can improve aerodynamics in the back is above the top of the truck bed and try to control the flow there, the sides of the bed and behind the tailgate area are doomed aerodynamically by the basic design of Ye Old Pickup Americanus.

I have a hunch that there is a fairly huge low pressure area created at the in the last 18 inches or so of the truck bed, the air moving along the sides will be seriously sucked into this area and create 2 large vortex which extend back behind the vehicle from the areas above the head lights. The drag created from trying to pull around 2 tornadoes while at highway speeds will be significant. Imagine the amount of energy it would take to create 20 foot whirlwind in calm air, how big a fan would you need? I think this is the amount of energy which goes into creating these trailing vortex.

Maybe if he mounted these vertically on each side of the pick up towards the back.....???? Hmmmmm

http://ecomodder.com/forum/attachmen...1&d=1264224004

Thought that thing was a Henry J until I focused in on it...

Yeah, it's not ideal or perfect but I think it looks cool. Put a modern pickup, 70s beetle, and some 50s fins in a blender and this is what you get.

On this forum there seems to be a lot of attention to speed. I'm sure that explains a lot of focus on the 15 degree rule for instance. But, suppose that guy had different goals. Say 30-55 mph is his norm. I don't expect the point of separation would extend all the way down to his bumper but would it not go past 15 degrees? I'm particularly interested in separation angle as a function of speed. Thanks in advance to anyone with a helpful link.

Thanks for sharing the pic, ChazInMT!
KB

cap
 

Looks like some Henry -J cross-breeding.
Way too fast for attached flow.Great for Pine-wood Derby racing.

Me too. What is the optimal shape? I'm new, but have seen number from 2.5 to 3:1.