Commercially produced aerodynamic pickup bed cap

[tomi_k]

Aerohead : For the tailgate section.... something like that was under planning... simpliest way to start was to open the tailgate and build a box on top of it... After that is done to certain extend... Evolution of that is to remove tailgate and fill the space of tailgate and below and blend it to with rear underbody (with some sort of diffuser)... That darn rear axle is kind middle of everything... lol... but lets see...

[freebeard]

simplest way to start was to open the tailgate and build a box on top of it...

ecomodder.com/forum/google_search_results box cavity

[tomi_k]

Latest box with vertical fins... and changed top surface... this is the one which I used on my latest record (11.20 liters / 100km)...

Fins will be moved few inches "out" (closer to the tail lights) as I have room for it... and side fairing might show up ...

[freebeard]

I saw something in 'interesting aerodynamic cars' or elsewhere and haven't been able to find it again.

It was a French or Spanish hypercar with a typical hypercar body but there was a distinctive spoon-shaped depression ahead of the spoiler. The result, supposedly, was downforce with no drag penalty.

aerohead?

[Piotrsko]

The hump at the tailgate to bed joint isn't doing weird things to the flow?

What happens when you fair the tail lights?

[tomi_k]

Originally Posted by Piotrsko

The hump at the tailgate to bed joint isn't doing weird things to the flow?

Can you point it out? Not 100% sure what you mean....

[freebeard]

I could Photochop it if you like, but essentially hold a straight edge up against the contrasting blue truck in the background and the gray part of the fin. The black line appears to stand proud by about an inch or so. It's not enough to dirupt the flow. so [shrug].

The spoon shape I referenced would have that line be a downward curve. With the box removed and tailgate closed, the top of the tailgate wold comprise a crescent-shaped wickerbill.

I did find this at Permalink #3759 in the aerodynamics thread.



Click to enlarge and look at the rear quarters. Very similar to your plywood fins.

[tomi_k]

Freebeard : I think I got it... most likely that is just a discontinuation of the duct tape which I placed from the very end of the cap (from pink foam) over the fin edge, in diagonal, which most likely looks like a bump from the direction of the picture... That was quick hack to get that area filled so air would flow closer where I want it flow (and would plan to have something in that spot in designs going forward). For this one I just wanted to test how fins work so that area was not considered too in details, yet.

[tomi_k]

The idea of blending side surfaces with the top surface and meet at the of of the bed was to create that "smooth" transition over longer length to reduce vortex happening between the side and top surfaces. And based on the tuft test, it looks like the side surface air flow "blends" nicely to top surface... and looks even that just before the cap ends, most of the airflow is getting "between the fins" hence I am pushing the fins more "out" so that happens.

As highlighted by Aerohead, the tail light areas was known to be "tricky" to blend nice with those aspects but I considered that I rather make 90% of the shape as good as I can, and deal the tail light area what is left (not saying thats not important)...Doing things other way around, I think I would have made too many compromises...

[Bicycle Bob]

What are the fins for?