Boat tail easy

[redpoint5]

Yeah, I'm hoping he's saying cargo carrier, because a trailer ain't gonna work.

Hitch mounted cargo carrier is exactly how I'd implement something like this, so I could easily remove it if needed.

[freebeard]

....because a trailer ain't gonna work

There is a fine line betwixt the two.

[Phase]

Was going to get something like this and use dibond for the boat tail

[Phase]

Did a Julian Edgar style box cavity as a test on back roads. Car felt less draggy. Wasn’t really able to flare the side inwards to reduce wake size and no hard measurements. But I was surprised it stayed attached even after 60 mph.

[freebeard]

If you still have the part, you could slit the bends halfway and overlap them to add some taper.

And add a difusser section to stiffen the bottom edge.

[Phase]

yeah the hard part is trying to bend all of the angles inwards. may have to practice with some notebook paper at home or something lol

[freebeard]

Pie cuts:

[aerohead]

Originally Posted by Phase

Did a Julian Edgar style box cavity as a test on back roads. Car felt less draggy. Wasn’t really able to flare the side inwards to reduce wake size and no hard measurements. But I was surprised it stayed attached even after 60 mph.

Technically, it's not a box cavity until it has a 'bottom.'
That open underside is polluting the pressure recovery of the top and sides, compromising performance.
If you had access to General Motors' contracted B-Roll video of their land speed record Impact/EV1 land speed record 'Yellow Ferret' box-cavity, you'd have a perfect example of what to build.
Cd 0.137, and 183-mph, in 1993!

[Phase]

Originally Posted by aerohead

Technically, it's not a box cavity until it has a 'bottom.'
That open underside is polluting the pressure recovery of the top and sides, compromising performance.
If you had access to General Motors' contracted B-Roll video of their land speed record Impact/EV1 land speed record 'Yellow Ferret' box-cavity, you'd have a perfect example of what to build.
Cd 0.137, and 183-mph, in 1993!

Well the goal before having a full proper boat tail is to do a smoother under tray and work on a permanent rear diffuser

Even though it’s not a perfect box cavity, the roof lije did extend our and go a little lower past the spoiler, and the sides created much harder separation edges. A lot of newer Toyotas use some “ extended” separation edges below their tail lights. No idea how much those effect things since they aren’t the whole rear body. And then the Kia EV 6 uses a weird mid center box cavity shape thing, almost like the Audi a2 box cavity

Either way, I wasn’t going for a box cavity for this test. I was just trying to test out the angles and attachments and extensions for the actual boat tail mod down the line. I “ felt” lower drag and better coasting though with this giant cardboard shape, so it must be doing something versus the stock rear. I got some crazy looks from the 3 total cars that drove near me though

[freebeard]

I was just trying to test out the angles and attachments and extensions for the actual boat tail mod down the line.

Follow the bumper seam line down to a radius along the wheelwell flare.

Maybe the problem was calling it a 'Julian Edgar style box cavity'.