First Electric van boat tail

[aerohead]

Originally Posted by JohnForde

Hard to lower floor.
1. License plate
2. rear sensors
3. Porous everywhere

Gonna try a foam floor @ 24" continuous height

I would recommend that you add material to that area so as to extend it out to the lower 'end' of the 'magenta' line you've shown.
I don't think there's any legal requirement, as might apply to an 18-wheeler, and it's DOT rear bumper region, as implied in what Lawrence Livermore depicted.
Foam floor sounds good!

[JohnForde]

I tested for 55 miles with strong & mixed winds. I sense a small improvement. I got 1.9 mi/kWh. My goal is to get above 2 @ 63 mph. A longer test may establish success.
I still need to tape the door hinges,
Try more acute angles. It is now at 11. I may try 14 & 16.
Smooth the underside.

[freebeard]

In another thread, Logic posted a link to a PDF that includes new information on an Italian researcher's work that includes one of the more interesting designs IMHO of all time, the Morelli Urban car.



aerohead did a thread on this in 2015, IDK if he remembers. ecomodder.com: Morelli's 'Fluid Tail'

Here is the only picture from then:



Obviously the forebody differs, but that black 'cuff' Zevo provided should possibly be at 45 degrees instead of 20.

[aerohead]

Originally Posted by freebeard

In another thread, Logic posted a link to a PDF that includes new information on an Italian researcher's work that includes one of the more interesting designs IMHO of all time, the Morelli Urban car.



aerohead did a thread on this in 2015, IDK if he remembers. ecomodder.com: Morelli's 'Fluid Tail'

Here is the only picture from then:



Obviously the forebody differs, but that black 'cuff' Zevo provided should possibly be at 45 degrees instead of 20.

A prerequisite for the efficacy of Morelli's fluid tail 'ring-vortex' is all the 'roundness' of the rear cross-section.
There's a 'three-dimensional- flow- relieving- effect' at play with those generous radii, which are completely absent on the Zevo.

[Piwoslaw]

Originally Posted by aerohead

A prerequisite for the efficacy of Morelli's fluid tail 'ring-vortex' is all the 'roundness' of the rear cross-section.
There's a 'three-dimensional- flow- relieving- effect' at play with those generous radii, which are completely absent on the Zevo.

Superb photoshipist's rounded upper corners:

[freebeard]

Permalink #183

Originally Posted by myself

Closer to a circular termination is better.

[Piwoslaw]

Originally Posted by hisself

Closer to a circular termination is better.

Of course!
A circle is what the extension of the boattail should be aiming for, but if starting from a rectangle, then terminating it short of that will still give you straight edges with round corners. Like a cross section halfway up the chimney adaptor:

Originally Posted by freebeard

wiki.dtonline.org/images/thumb/c/c6/Transformer2.png/1000px-Transformer2.png

[freebeard]

But wait -- there's more --

https://en.wikipedia.org/wiki/Superellipse

The superellipse is the set of shapes between a square and a circle. Thus it is malleable.

Photoshop is a train wreck lately, pay to subscribe and they keep all your stuff. The last version I had was $2 at Goodwill (their computer store in Delta Oaks)

Blender is free and Open Source. So there's no brakes on the train. duckduckgo.com/?q=superellipse+in+blender&ia=web

There're various ways to skin that cat (oops) -- the Bevel Operator, grid-to-circle, Geometry Nodes, & etc. I like the Geodesic Dome add-on: docs.blender.org/manual/en/latest/addons/add_mesh/geodesic_domes.html

Geodesic Object Parameters
Frequency
Subdivide base triangles.

Radius
Overall radius.

Eccentricity
Scaling on the X/Y axis.

Squish
Scaling on the Z axis.

Square (X/Y)
Superellipse action in X/Y.

Square (Z)
Superellipse action in Z.

Rotate (X/Y)
Rotate superellipse action in X/Y.

Rotate (Z)
Rotate superellipse action in Z.

Dual
Faces become vertices, vertices become faces, edges flip.

[JSH]

Originally Posted by JohnForde

I tested for 55 miles with strong & mixed winds. I sense a small improvement. I got 1.9 mi/kWh. My goal is to get above 2 @ 63 mph. A longer test may establish success.
I still need to tape the door hinges,
Try more acute angles. It is now at 11. I may try 14 & 16.
Smooth the underside.

1.85 mi/kWh to 1.9 mi/kWh is an almost 3% improvement in fuel economy. A manufacturer would be dancing a jig. (That is more than adding drive wheel fairings and hub covers to a Class 8)

Before you make any changes to the tail angles I suggest running again in calm conditions. Strong and mixed winds and especially side winds can really throw off your results.


For those talking about cones and circles - remember this tail has to allow easy access to the rear door.

[JohnForde]

I did a 117 mile test this morning. It is right at the outer reaches of efficiency - 1.96 mi/kWh. But it is only point zero one better than three other runs including my first outlier run on July 13.

Conditions were good & It was a two way out and back run. Maybe the others were not.

I am within 2% of getting to two.

Here is my log:

ZEVO EFFICIENCY @ 63 mph

DATE DISTANCE X Mi/kWh = Avg kW

July 13, 72 miles @ 1.95 32kW
July 14, 112 miles @ 1.88 33.5
July 17 96.1 miles @ 1.90 33
July 21 74 miles @ 1.95 32
July 24 271 miles @ 1.67 37.6
July 25 303 miles @ 1.78 35.5
July 30 206 miles @ 1.84 34
Aug 2 90 @ 1.84 34
Aug 2 189 @ 1.73 36
Aug 2 100 @ 1.76 36
Aug 4 139 @ 1.95 32
Aug 16 194 @ 1.77 36
Aug 16 101 @ 1.71 37
Aug 17 100 @ 1.55 41
Aug 17 192 @ 1.66 38
Aug 19 209 @ 1.72 37
Sept 3 225 @1.59 40

NEW TAIL
70”L @ 12 deg (with floor)
Sept 20 117 @1.96 32