[Piwoslaw]

Originally Posted by dremd

And a final thought, wouldn't it be great if it could be collapsed entirely just by sucking the air out? How about using the tension from the top to hold the boat tail from hitting the ground, then having tent poles (or plywood)hinged in 2 (folding so the "V" is inverted) collapse in such a manner that the entire assembly sits between the bumper and the back window?

I see it like this: The inflatable boattail would be made up of 3-5 "layers", extending horizontally from the back. You start by inflating the largest one, closest to the car. The rest of the layers are deflated and snuggled inside the first one. When you speed up you inflate the next one, slightly smaller, and so on, until at cruising speed the very tip is inflated. This lets you have drag reduction before total inflation. The hinged inverted "V" (lambda) would stick up and out while folding.

Another idea is that the boattail is in segments, like descibed above, only they're not inflatable, but stiff and they retract one into the other like a telescope. The first segment is a kammback, the others fit inside of it. This reminds me of a collapsible cup: