First Electric van boat tail

[aerohead]

Originally Posted by kach22i

Since this is the latest box tail / box cavity thread I'll post this here.

Looks to be part of an expandable camper scheme.

Next Honda Element?
https://tflcar.com/2024/08/ask-natha...otive-messiah/




Just looking at the angles, the lower departure angle looks to be for off-road and NOT aerodynamics.

Both, 'approach' and 'departure' angles are 'non-aerodynamic' in the sense of Cd.

[JSH]

Originally Posted by JohnForde

Current plan: Cuff using HDPE. Cuff is 11 degrees and 18"L.
Doors of 55", just reaching 48" behind the bumper (legal). They can adjust the second break angle. Or just stay at 11 deg. I am hoping to tuft test and maintain attachment at 16 or 18 deg. This is to follow Aeroheads advice that drag is porportional to wake size, or as I call it, the 'aperture'.
Once I succeed on the basic tail I will put tail lights at the tips and add a foldable or detachable polycarbonate extension to ~96".

I think you will start to see results with a new 11 degree angle at the vehicle. I like that your design allows for multiple angles for your main panels. I expect you will see separation at 18, 16, and 14 degrees but it doesn't hurt to try if you have the time.

(You will save me the time on my similar project too )

[JohnForde]

Originally Posted by JSH

I think you will start to see results with a new 11 degree angle at the vehicle. I like that your design allows for multiple angles for your main panels. I expect you will see separation at 18, 16, and 14 degrees but it doesn't hurt to try if you have the time.

(You will save me the time on my similar project too )

Thanks JSH! You clarify for me that I should begin testing at 11 and go up, not the dumb-ass other way which I could have easily embarked on.

JF

[JohnForde]

Newest overhead drawing of Zevo WT

[JSH]

Originally Posted by JohnForde

Newest overhead drawing of Zevo WT

With that design you have basically replicated a commercial trailer tail. You should see similar results - maybe a bit better as you van is closer to the ground and the commercial tails start much higher.

[JohnForde]

Originally Posted by JSH

With that design you have basically replicated a commercial trailer tail. You should see similar results - maybe a bit better as you van is closer to the ground and the commercial tails start much higher.

Yes. And the weight is 90% less. On an 18 wheeler Aero drag is only half. With the Zevo aerodynamics is 75% of total drag. Cutting aero by half leaves total drag at 5/8 of original. The reciprocal is 8/5 or 160 %.
A 60% increase in range that would yield is a very worthy goal.

[JohnForde]

Latest plan.
Frame of doors ~54"L & 48" behind the bumper.
Doors are covered by 72" polycarbonate twin wall, leaving 18" of twin wall sticking ~ 64" behind the bumper.
My research shows this rear overhang is out of compliance in only 5 states.
The images show an additional 48" sheet of twin wall bolted on as an extension to 96"L.
You can see why the angle is important at this length. 17 deg gets the aperture @ 96"L down to just 26".
To maintain attached flow I may use two layers of vortex generators: One in front of the cuff and a second in front of the hinge.
If I cannot maintain attached flow at 14 deg I will settle for 11.
SCIENCE!

[aerohead]

I just lost all everything I typed for the last 30-minutes, and I'm not going to try it again.
You have a chance at 17-degrees with the VGs. There was a global competition, invited by the US Air Force, to 'fix' the Lockheed C-130 Hercules'( 'highly upswept after-body, high adverse ( pressure ) gradient / fuel consumption.' ) tail section drag by using the same VG approach.
Re: Tobj'o'rn Gustavsson, KTH, Department of Aeronautical and Vehicle Engineering, Royal Institute of Technology, Stockholm, Sweden, 2006.

[Piotrsko]

Turbulent is attached? If that's true, gonna have to do some serious rethink.

[freebeard]

https://en.wikipedia.org › wiki › Boundary_layer
Boundary layer - Wikipedia
The layer of air over the wing's surface that is slowed down or stopped by viscosity, is the boundary layer. There are two different types of boundary layer flow: laminar and turbulent. Laminar boundary layer flow. The laminar boundary is a very smooth flow, while the turbulent boundary layer contains...

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