First Electric van boat tail

[freebeard]

If you cut a triangle out of a cylinder, the result will have three curved edges.

While you want two straight edges with the straight trapezoids.

Alternatively you could bend the trapezoids, which might be preferable.

The [rule of thumb/first approximation] used on the leading edges is 4% of the gross lateral width. IOW 4" for 8ft.

Longitudinal at the rear??? In any case it would reduce the wake area.

The roll-up rear door makes it livable, doesn't it.

[aerohead]

Originally Posted by JohnForde

Structurally, I need a square corner on top at about 44" behind the bumper. After that I could soften the corners by cutting up a 16" diameter concrete forming tube and using that 8" radius to coroplast the corner from sharp to rounded.

Could this be effective in addressing the vortices problem?

The attached longitudinal vortices are symptomatic of separated flow, just like turbulence. And like turbulence, once you have it, it cannot be 'mended.'
All you can do is 'avoid' it, or 'minimize' it.
An 'all-soft', radiused tail would 'avoid' it, but that conflicts with the 'door' situation, if I'm understanding things properly.
The only tool available for 'minimizing' it, is, to keep the slant angles 'small', as the vorticity grows 'geometrically' with increased slant angle. Very non-linear.

[Piotrsko]

Turbulence is only a problem if it increases drag overall. Otherwise there would be no use for Turbulence generator on A stalled wing other than regaining flow across control surfaces. Cars i don't know

[JohnForde]

Originally Posted by aerohead

The attached longitudinal vortices are symptomatic of separated flow, just like turbulence. And like turbulence, once you have it, it cannot be 'mended.'
All you can do is 'avoid' it, or 'minimize' it.
An 'all-soft', radiused tail would 'avoid' it, but that conflicts with the 'door' situation, if I'm understanding things properly.
The only tool available for 'minimizing' it, is, to keep the slant angles 'small', as the vorticity grows 'geometrically' with increased slant angle. Very non-linear.

I am going on a 1500 mile drive beginning Thursday (Black Hills SD). I needed to settle on a configuration. I just rounded the top corners today. Took all day. I used 16" diameter concrete forming tubes. Very short term experiment as they will weaken if rained on. I may have time do do the lower corners by mid day Thursday, but it would not be full length, only blending from a corner to an 8" radius over the last 24" of length.

[Piotrsko]

Quick coat of whatever is mis mixed paint at the orange store tends to solve the melting problem on the concrete form tubes. So does a coat of engine oil, but not as long.

I suppose one could color match the paint but that effectively quadruples the price paid.

Was loking at a departure angle aft the high point on a NACA 43 series laminar wing section when I realized it was curved all the way to the rear. That's not helpful here.

[aerohead]

If the 'upper' radii were also applied to the 'bottom', you would essentially have re-created the 'GM OPTIMUM Fairing' ( boat tail ) of 1980, a 'known quantity'; and I could, with a clear conscience, tell you that a 20-degree top, 10-degree sides, and 10-degree bottom, would net you the lowest drag coefficient.
One of the singular advantages of 'monkey see, monkey do.'
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ZEVOs looking really 'aerodynamic.' I won't be surprised to hear good things after the trip.
I leave this Friday on a 1500-miler to the Mississippi River and back with the BOLT.

[JohnForde]

2 Pre trip photos with 4 rounded corners.
Length 70" All 4 slopes 11 degrees

[aerohead]

Originally Posted by JohnForde

2 Pre trip photos with 4 rounded corners.
Length 70" All 4 slopes 11 degrees

You may want to alter your 'flight plan' and drive Zevo directly to New York's Museum of Fine Art!
That's where she belongs.
And wherever you're going, I suspect that you're gonna have some 'conversations' with other motorists.
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At 'all-elevens', with trigonometry, and using the 'tangent' of 11-degrees, a back-of-the-envelope calculation puts your new wake at roughly 39.27-square-feet, compared to the OEM of around 72.87-square feet; a 46% smaller wake.
If Zevo had a smooth underbody, like PhD Jeff Howell et al's Windsor Body, you'd be looking at a 46% drag reduction. Cd 0.1886, if you were starting with Cd 0.35 ( I wish GM/ Brightdrop would publish the data )
A BIG on the 'whale tail'.!
If you fail to get some 'tasty' kW/ mile data, next time you're near Dallas-Ft Worth, dinner's ( or lunch or breakfast ) on me.

[JohnForde]

2 more pics of the tail, pre trip.
Second one shows L bracket for structure hanging out in the wind.