an option to the box-cavity
 

Returning to yesteryear, the mid-1930's inflated boat-tail offers a low-weight, and 'stowable' alternative to a box-cavity or proper boat-tail.
* The device, which contains the collapsible envelope, inflation fan, and valving attaches to the vehicle as a single unit.
* A 12-VDC umbilical cord provides electric supply.
* It can be integrated into the cruise-control logic, deploying and de-deploying at any chosen velocity.
* When 'stowed' it adds no length, is garage-able.
* I mocked-up half a boat-tail on my bedroom wall, serving as a pattern for tailoring the envelope.
* A $35, retired high-school SINGER gear-drive sewing machine provided for stitching.
* The Bosch, DC HVAC blower was from a boneyard VW Westfalia Campmobile. $ 10.
* Scrap white pine provided the box framework and envelope attachment.
* Box hardware 'hooked' over the tailgate, and was tension-strapped from below.
* Expandable Naughehyde was used. A mistake! Rip-stop Nylon is a better choice (it holds to the tailored shape! )
* I recommend Marine-grade thread, as it has UV- blocking protection.
* From the photo caption, as shown, the 'rig' pushed the T-100 to over 32- mpg @ 65-mph. Up from 26+.
https://ecomodder.com/forum/member-a...ilkisons-t.jpg

How much of that was the half-tonneau?

https://image.dhgate.com/0x0s/f2-alb...-cup-whole.jpg
Maybe a bladder inside a collapsible shell?

how much ............... half- tonneau
 

I've got that data in the rat's nest.
As MetroMPG mentioned long ago though, we had the rooftop cargo carrier in the bed also, which I don't remember testing separately.
That's why I prefaced my remark, that the results were a condition of all appliances shown.

It would be interesting to test variations on the half-tonneau. Like a semi-circular floor.

I showed a stainless steel collapsible structure, they also come in cast or injected silicone.. Very large 3D printers exist, so something like a rectangular shift lever boot could be printed in nylon or TPU.

https://external-content.duckduckgo....-Flexibles.jpg
https://youtu.be/uR_xVABJhig

curved floor
 

All the half-tonneau R&D expense for GM, Ford, and Texas Tech seems to have fallen on blind eyes.
I've never seen one since 1988 except the ones built for friends, or for Gale Banks Racing, and their land speed record.
Researchers may have figured that they were casting pearls before swine and gave up on any additional efforts to push the envelope.
The curve might have conserved vortex energy, allowing a stronger low pressure to be presented to the inner face of the tailgate, cutting drag further.
That's a good thought.:thumbup:

....and some people think I'm not being any help. :)

That's very cool - I like that. I've thought about it but never done it.

How about modifying the cab high portable canvas camper shells? AFAIK, youcan still buy them

how about?
 

we're limited only by our imagination and the established boundaries of physics.;)

CANVAS : a really sick idea
 

This is for any member, guest, or lurker, who's had the misfortune of dead-heading with a Class-8 Tractor, pulling a flatbed semi-trailer.
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You've delivered your load to the customer, you and your team driver have contacted dispatch or a logistics broker and can't find another load anywhere near your location.
Your facing a long OTR stretch, to pick up a load far away, dead-heading with one of the worst examples of modern-day truck aerodynamics!
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Not a problem!
Secured to the trailer's forward bulkhead is another 'tarp.' however, this one has a 'trick.'
It's actually an inflatable, streamlined envelope, designed specifically for this contingency.
It holds all the unused, rolled or folded cargo tarps, plus inflates into a perfectly streamlined half-teardrop, which 'disappears' to nothing, by the end of the flatbed. Powered by the charging system of the tractor. Another 'glad-hand'.
Secured with tie-downs, periodically, along the length of the trailer, you've converted one of the highest-drag 18-wheelers on the road, to the lowest.
In a few minutes.
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With an inflatable gap-filler on the forward face of the same bulkhead, you knock off another 19% drag ( NASA ).
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The upper body is now completely streamlined.
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Another inflatable fairing, under the trailer, behind the rear wheels/ DOT bumper region, trims drag even lower with an underbody 'Kamm-back.
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Then Heaven forbid, you use the five (5) feet, allowed by federal law, to inflate a final underbody boat-tail, outside, beyond the DOT bumper, creating the lowest-drag, 'air-bagged', Class-8 vehicle on Earth. And the fuel economy and range to prove it.
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Trailers are already wired. One larger conductor, to handle the increased current demand of the small blowers aren't rocket science.
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Any cargo load capacity loss of an 80,000-lb GVWR vehicle, due to the added weight of an 'air-bag' system wouldn't even register on the economic radar.
Simple software and Blue-tooth connectivity could easily 'automate' some of these features. Drivers wouldn't be out any extra effort.
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These are the 'Lost Dutchman's Mine' of real wealth. It's very strange to live in a capitalist society which allows profit potential like this to languish and lie dormant for 86-year on. Especially in times of anxiety over electrification of transport and range issues.
Aerodynamics is great for everything except when wheels are involved.
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PS 'steal this invention!'