Droptail truck tailgate.
 

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I don’t think we’ve done this one yet.


Droptail

Droptail aerodynamic benefits MPG (droptail.com)


SPOILER POSITION


Computer automatically deploys tailgate into a spoiler position at highway drag inducing speeds, for best aerodynamics improving mileage, and then closes it as vehicle comes to a stop. The system may also improve trap speed and ET in the 1/4 mile. Stability can be improved in the spoiler mode through a downward force applied to the rear axle on slippery roads at speed.


https://www.youtube.com/watch?v=rBRsxC-IJ2s&t=31s


Interesting...🤔



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20 years ago, my grandfather mentioned it would be useful to hide the plate on some photographic speed traps :D

I don't see anywhere on that site where the marketers of this device have measured any reduction in drag or lift, only streamer videos which don't tell us anything (lay the tailgate flat and the streamers will point backward, but that's a higher drag configuration than tailgate up).

ETA: Under FAQ they claim 5-10% improvement in fuel economy. Snake oil.

I was actually looking for Myth busters, but I found this in Youtube's basement:

https://www.youtube.com/watch?v=xocaC15WwA0

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But this is neither up or down. It’s being tipped till the air spills over the lip at which point the air re-attaches to the gate briefly before exiting. Ford made their 2015 F150 tailgate wider at the top for the same reason, brief re-attachment for better aero. (1:40 mark in video)

http://www.youtube.com/watch?v=oEkiDsVGr9c


The lip of the tipped gate is more than likely sub optimal. However, adding a properly designed airfoil to the top edge of the gate should produce a superior result.

There are a several super cars that have active aerodynamics. Spoilers that deploy and morph as speed and conditions dictate. This wouldn’t be any different.

It’s a interesting concept.


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If brief reattachment is the reason for lower drag with the tailgate up, the tailgate fully down should be lowest drag since it has the most area for reattachment. But it isn't. There has to be more to the story.

The Droptail people could easily test their device. The SRT-10 has a mechanical throttle connection, so throttle-stop testing is possible if they want to do it for cheap. That would tell us something more useful than streamers and vague claims of improved efficiency.

F-150 tailgate
 

Some articles addressed pickup truck tailgate spoilers in psychological terms.
The automaker ( Ford ) has understood, since 1981, that a pickup ( their's anyway ) will typically get better mpg and lower rear lift if the tailgate remains upright and closed.
Ford, presuming that consumers have some limited understanding of rear spoilers, by placing a spoiler on the tailgate top, are hoping that, when not carrying long loads, owners will close the tailgate in order to 'preserve' the function of the spoiler.
It's not that the spoiler itself necessarily reduces drag, it's just that its presence, somehow encourages the owner to keep the gate closed, which absolutely does reduce drag.
In the early 1990s, the now defunct, Sport Truck Magazine, devoted a major portion of one issue to pickup aerodynamics. Aerodynamicists from all the major automakers contributed to the article. At that time they recognized aerodynamic ideosyncracies among pickups, and the reader was cautioned to approach pickup aero on a case-specific basis.
Today's ( over-bumper ) tailgate spoilers take better advantage of a truck's overall length, improving fineness ratio and flow reattachment area potential. It would be surprising to learn that they did not help.

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I hear what you’re saying. But I believe more may be at play here.
Throttle stop testing is one way. Another good indicator would be more tufts in the bed and on the back of the cab that would paint a better picture of the air currents. Also using pressure measuring sensors to measure downforce would be valuable as Julian suggests. I would assume it would add downforce. Which is probably a good thing in a pickup.

One thing is for sure.

A-B-C testing would be easy. (up, down, somewhere in between)

Just a flick of the switch. ;)



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JSCE video claim
 

I didn't experience enough data from which they could make their case. The video offered more questions than answers.
Perhaps they'll continue to refine their presentation, adding in missing conditions, caveats. Specificity related only to the RAM SRT 10.

Yeah. They should do that before selling people stuff. Their claims are really for the unicorn corral, no? I mean big sales claims contradicting known research but that are nonetheless presented without any new data is just about the definition of a unicorn: a flying uni-antlered albino horse that nobody has ever demonstrated has ever existed in the flesh. :)