Easy Aero Fix? (Modding a pickup?)

[ebacherville]

I had a turismo, had the same nose as the rampage, was a very fuel efficient car, and looked decent too, I had a buddy with a 2.2 turbo Shelby like the one above that he had went through the motor and beefed up a bit, he was the fastest guy in town... there muscle cars would want to race him at stop lights and he'd race, then and after launching and beating the muscle car a bit, he let them pull up on him then he'd get back into it and pull ahead again just to annoy the led sled drivers.. totally insane car.. was basically the Honda civic of its day.

[OneBadBird]

Back to this "fastback crap"....I've been wondering what the deal is with the Kammback since I saw AndrewJ glue one on his buggy...

From Wikipedia: "Kamm showed that a better drag-reducing tail-end design for a car is a tapering teardrop shape that cuts off abruptly.

Prior to his thesis, the teardrop tapering smoothly to a point was considered optimal. Kamm showed that an abbreviated teardrop actually worked better; the air still flows as if the entire teardrop were still there, but without the surface drag of the long point."

Also more reading at http://homepage.mac.com/christopher....backStory.html


Gleaned from my research, apparently the optimal shape is a teardrop that's cut off where the cross-sectional area of it is 50% of the maximum of the whole drop. To me, that means that the truck-fastback would be right on the money, it seems like the top part of the cab is half and the tailgate is half. The only bad thing (apparently) is that the slope back is actually a bit too shallow. A shorter bed would be better for a bit until you start looking like a CRX, then you're good.

So oddly enough to me, what Smoky says is correct except the part that it wouldn't work....he notes that the aero experts want an abruptly truncated tail like the CRX, 300ZX, etc....but not a fastback truck. Yet, I look at a fastback truck, it has the truncated tail like those cars, just a bit longer in the tail.

The truncated thing fascinates me...not necessarily in a good way. Why the heck would that be BETTER than a full tail? I read why, but it still seems counterintuitive to me.

[ajohn7211]

Originally Posted by Smoky

That fast back crap won't help a bit, it will only add weight. A pickup truck already gets that effect by the turbulant air behind the cab with no extra weight.

If you want to better the aero in the bed area: use a tonneau cover and put a 6-8" piece of aluminum extending the roof off the back of the cab and tonneau cover over the tailgate. that should get you up to 2mpg at highway speeds with minimal weight. A truck cap with the extension off the back would also do.

Plug any holes in front, lower truck, add a front air dam, remove trailer hitch and replace rr bumper with roll pan, remove all extra weight. Get smaller mirrors. Use under-drive engine pulleys. tune up the truck. Increase gearing

I get 29mpg in my '01 tacoma with a "fastback" style camper shell that I made with EMT tubing and duct tape. I got 23ish before. Cost me $50 and added maybe 30 lbs to my truck overall? Nothing considering I largely use my truck hauling my stuff across the state on my way to and from school.

[aerohead]

Originally Posted by Smoky

That fast back crap won't help a bit, it will only add weight. A pickup truck already gets that effect by the turbulant air behind the cab with no extra weight.

If you want to better the aero in the bed area: use a tonneau cover and put a 6-8" piece of aluminum extending the roof off the back of the cab and tonneau cover over the tailgate. that should get you up to 2mpg at highway speeds with minimal weight. A truck cap with the extension off the back would also do.

Plug any holes in front, lower truck, add a front air dam, remove trailer hitch and replace rr bumper with roll pan, remove all extra weight. Get smaller mirrors. Use under-drive engine pulleys. tune up the truck. Increase gearing

I'm going to have to differ with you with respect to the fast back in a contextual way.
'Fast back' is designated to pseudo-Jaray rooflines which exceed contours which will support boundary layer attachment and are associated with separated flow as well as significant longitudinal vorticity of very high drag.
Here at the Aero Forum we've been promoting what is typically referred to as a 'Kamm' roof contour.
Alfa probably started it in 1913 with their airship car built for Count Ricotti.
Jaray included it in his patent application of 1922.
Walter Lay used it in 1933.
Kamm in 1935.
The list goes on to some of today's highest performance vehicles,land speed record cars,economy champions,and solar racers.
The' boat-tailing' which this form facilitates is historically proven to be the path to the lowest drag.
Also,its ovoid form,next to a sphere,is one of the strongest forms known and consequently can be one of the lightest structures for its surface area and contained volume.
When pickup trucks are modified with this form they can achieve fuel economy which meets,or exceeds many smaller.lighter passenger cars when on the open road.