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