aero opportunity
 

https://www.youtube.com/watch?v=lzNiOeqwmFQhttps://ecomodder.com/forum/member-a...ed-micro-r.jpgSomething germane to my own situation. A 'cheap' used EV, with limited range, and prospects for a 'trip to Grandmothers' for Thanksgiving Day'...............
So you slap on a range extender trailer, with its added battery capacity .
The added length allows a perfect streamlining opportunity, as 'elongation' = drag reduction, if done right.
Extend the body of the tow vehicle to simulate the 'entire' vehicle, without as much truncation, as a trailer/ gap-filler system.
Not only have you gained the kW-hrs of the trailers pack, you've also dropped your drag coefficient into the 'unobtainium' region.
You have the length. Why not take advantage of it for all it's worth?
https://electrek.co/2020/02/19/frenc...nge-extenders/
At around 10-minutes into this video there's a brief shot of a Tesla battery flat-bed trailer someone fabricated.

https://images.fastcompany.net/image...origami-04.jpg
https://www.fastcompany.com/3021937/...ff-the-streets

I've been thinking lately about what one could do with Coroplast and origami. Similar to articulated buses. If the trailing edge is left standing proud, would it help as a wickerbill to assert reattachment?

origami wickerbill
 

We'd need to look at it in the context of a specific application. As a gap-closure it would be way out ahead of nothing, but with respect to the following structure, a 'wickerbill' could hurt if it caused an overshoot 'jump' situation, especially since it would be in a contracting cross-section, increasing pressure gradient environment. Flow could separate and never re-attach. It's an 'it depends' thing.

Leading edge of the trailer stands proud?

If you increase the number of folds, the shape approximates to a vault. Adjusting the folds could give it a compound curve.

In a turn, the outside could be [almost?] straight, while the inside bunches up or buckles.

leading edge of trailer
 

The leading edge of the trailer and gap-filler connection point, optimum-wise, would be matched, and both would have a smaller cross-section than at the beginning of the gap-filler, respecting the elevational and plan-view taper of a streamline profile.
Since all the aft-body is immersed in an increasing-pressure gradient, and all the air would like to flow 'forwards' if given the chance, the only thing keeping this from happening is the streamline profile. This is its 'job.'
So we've got to be especially careful about any pressure 'spikes' along the pathway. The 'smoother' the better.
Some 'accordion' bellows flow perturbation might be tolerated. Expensive wind tunnel, or CFD testing would verify that or not.