aero shaped windsock on a truck bed?

[kalifornia]

do you think there is any merit in a aero shaped "sock" velcro'd and strapped to the cab & bed and leave enough gaps at the cab area to inflate the sock? Or do you suppose it would have to be inflated and sealed to have a chance of working?

[Frank Lee]

I predict a lot of flapping about and rarely "inflating" to the desired shape.

[wyatt]

I think Frank's right. I have observed enough tarps that this would give me reason to believe it wouldn't work as well as a hard top. BUT, if you have a cheap/easy concept you want to put together and test out, I will gladly read about your results .

[Frank Lee]

Perhaps a framework that mostly holds it's shape would help. Still, flapping about is all aero badness.

[wyatt]

That's what I am thinking, but I would like to see how much benefit would come from the unsupported system -vs- supported system -vs- hard top. Especially when I am not the one paying . I remember one member making a boat tail for his car and seeing very small returns. He used a plastic shower curtain as the rear windshield and reported it flapping a bit, they may be related...

[shovel]

The flapping is the same thing the air would be doing without the membrane in it. So your membrane does nothing.

[aerohead]

Originally Posted by kalifornia

do you think there is any merit in a aero shaped "sock" velcro'd and strapped to the cab & bed and leave enough gaps at the cab area to inflate the sock? Or do you suppose it would have to be inflated and sealed to have a chance of working?

There's a fellow in Lubbock,Texas by the name of Rufe who is doing this with big trucks for a boat tail.I think he's applied for a patent on it.Texas Tech's Aero Lab was helping him with wind tunnel work.
When I did my pickup I had a fan forcing air into mine to help prevent aeroelastic effects that Frank Lee has mentioned.
You can try it and if it 'hunts' you can go to plan-B and install any 12-VDC ventilation fan out a car ,van,or pickup.The power liability from the alternator load to provide the current will be drowned out by the savings from drag reduction.I know this for a fact.
PS in the commercial vehicle section of Hucho's textbook he shows the Koenig-Fachsenfeld/Kamm inflated bus tail of the 1930s which he said might be worth re-visiting.(you're barking up a popular tree)

[Frank Lee]

I should have clarified that I was only thinking and commenting on the "autoinflate" idea; as Aerohead points out, an inflatable that achieves a high enough level of rigidity should work.

[euromodder]

Originally Posted by kalifornia

do you think there is any merit in a aero shaped "sock" velcro'd and strapped to the cab & bed and leave enough gaps at the cab area to inflate the sock? Or do you suppose it would have to be inflated and sealed to have a chance of working?

The air you need to scoop up for it to remain inflated, causes extra drag.
It's essentially a parachute / ballute.

You'd need to accurately size the scoops for the minimum required scooping of air, position them where you can't get much or any aerodynamic advantage out of the inflated "sock" - then hope the advantage of the sock is enough to cancel out the drag from the scoop(s).

[BamZipPow]

You could inflate it with the exhaust...but you'd have to be very careful about any leaks.