How to improve fuel economy with a tonneau cover

[2000neon]

I can't comment on whether or not it is better to extend past the tailgate or not. To do a partial tonneau cover, I believe it is best to separate the covered and uncovered parts of the bed. Basically have a vertical wall at the front edge of the partial tonneau cover, from the bed floor to the height of the cover.

This is what Gale Banks did on his top speed record setting Dakota.
Sidewinder Dakota:
http://www.google.ca/imgres?q=sidewi...9&tx=133&ty=70

[radioranger]

Great info, I guess i could try it both ways and check my downhill speed, fortunate to have a good testing area here,

[aerohead]

Originally Posted by 2000neon

I can't comment on whether or not it is better to extend past the tailgate or not. To do a partial tonneau cover, I believe it is best to separate the covered and uncovered parts of the bed. Basically have a vertical wall at the front edge of the partial tonneau cover, from the bed floor to the height of the cover.

This is what Gale Banks did on his top speed record setting Dakota.
Sidewinder Dakota:
Google Image Result for http://www.cumminsracing.com/images/Sidewinder-sideview-lrg.jpg

In an interview with Sport Truck Magazine,Glen Sharpf,of GM's Aero Lab (patent holder of the 1/2-tonneau cover) reported that some of the low drag performance of the 1/2-tonneau was owed to the opening underneath, back to the inner face of the tailgate.
The low pressure of the locked-vortex captured by the cover is communicated through the opening to the gate.The pressure differential created across the gate,front-to-back, is part of the drag-reducing function.

[2000neon]

There is always more to learn, thanks for clearing that up for me.

[ERTW]

Originally Posted by PaleMelanesian

That's basically what they've done with the cab on the new F150. It angles down (probably 10-12º) for a few inches at the back edge.

thank you for the pic! Visually, it looks more like 30*...

The tapered kamm on the cab is from Morelli's most recent work. It works

[radioranger]

wonder if I just lower the rear spring on the old Ranger a few innches?

[kach22i]

UPDATE: 07/23/13

2013-05-16
GMC Pickups 101: Busting Myths of Truck Aerodynamics
2014 Sierra gains fuel economy, quietness from time in wind tunnel
GMC Pickups 101: Busting Myths of Truck Aerodynamics

So what accessories can truck owners add to help aerodynamics? Tonneau covers for the bed help smooth airflow over the truck, and Bloch says soft covers are more beneficial than hard covers because they form to how the air wants to flow. Running boards can also help air flow smoothly down the truck’s sides.

I say that there are support ribs which disrupt this flow and theory, plus the flutter of the fabric adds air flow distortion. However, I'm not an aerodynamics, so what do I know? I only know what I have seen on my own truck covers.

Some tailgate up verse down discussion the article too.

Even the top of the Sierra’s tailgate and the center high-mounted stop light are optimized to guide air cleanly around the truck. And because Bloch’s team detected unwanted airflow between the cab and bed, new sealing has been added.

Mind the gap.

[Hog F150]

I installed a tonneau cover on my 2000 F150 recently. The ultra gauge tells me I'm getting 0.5mpg less. Hmmm.

[MetroMPG]

Hi. What was your test method?

[Hog F150]

Don't laugh at me now, I'm completely new to this aero stuff.

I recently bought the F150. Coming from a minivan, the gas mileage is OK. I've had the Ultra Gauge for 4 days now. I'm becoming obsessed with better driving habits, and trying to improve my mpg's. I read this thread earlier, and I had a tonneau cover for the truck, but not on it. I was getting 18.7mpg with an empty bed, tailgate up. I installed the cover yesterday, and today on the same trip to work, I went down to 18.2mpg. I'm driving in a 65mph zone, going around 62, with my eye on the gauge. 60 mile round trip. F150 is the extended cab, or super cab, with a 6.5ft bed, 4.6L engine.

Tonneau cover is a cheapo, canvas cover with 3 aluminum ribs underneath, and two of those are missing.