EV build aero.

[mistareno]

G'day,

I'm in the process of planning an EV build.

We have a fairly new Family car that we replace every few years, so I was going to convert a small ute/truck that I could use both as a commuter vehicle and for it's practicality.

I was looking at a Kia K2700 which are a few years old now and can be picked up quite cheap.

I was going to rip off the heavy steel tray and make a lightweight alloy tray with enclosed sides. I was going to use semi flexible solar panels for the top section because they are almost as light as straight aluminium and I can probably fit a kw of panels on the top.

I was intending to have it hinged at the front so I can prop it in an 'up' position if I need to carry bigger objects.

This is what I was planning on from the side, with only a small amount of taper on the sides.

I can't add images or links, but an image can be viewed at rccv.info/temp/k2700.jpg

I may not be legally allowed to extend the teardrop to the end of it's natural shape (due to overhang regs) so may have a slight kamm tail (where the last line is on the tail) where I would incorporate lights and number plate etc.

It does have a fairly smooth transition into the roof and is quite curved in plan view also. It' probably the closest I could make a vehicle to the template without building it from scratch.

[NeilBlanchard]

Welcome to EM!

Here's the image of this project:


When you say "tray" you are referring to the cargo bed, right? I am not familiar with this model - is it a truck or a van? Does the wheelbase match (more or less) the aero template?

It's an ambitious project!

[mistareno]

It's a Cab chassis mini truck.
It's basically a Van with the rear end lopped off.
It's not that heavy.
About 1100kg without the steel tray.
Here is a picture of what it looks like normally -

[freebeard]

Yes, welcome to ecomodder.

What is the use case, IOW will you be hauling liquids (easy aero), books, or grain (still not bad) or refrigerators (do the math)? If you carry through with the underside and wheel spats this could be an excellent base vehicle, but it carries a lot of cruft between the wheels.

About the lack of plan taper: Air has both a pressure and a velocity (relative to the vehicle). Because of this air moving down the flat sides at the same speed as the air moving down the sloped top migrates upward. If it encounters a sharp edge a vortex forms, tiny at first, but growing into counter-rotating dust devils following behind the vehicle. That's why the Template is a half body of revolution.

Would your truncated rear be a rectangle or a half-circle?

Here is an ordering of similar shapes. Circle=>squircle=>square:


...and something for inspiration:

[Xist]

[mistareno]

I was going to use the same radius on the edges as the roof of cab and start the side taper after the rear wheels so they are enclosed. So probably closest to the square example but with radiused edges.

I was going to cut some 100 mm pvc pipe into quarters (length ways) to use as the radiused edges. If you heat it up it bends well too.

I only need to transport timber and plants and other household stuff. It won't be a 'transport' vehicle as such. The tray will be flat and long which will suit my needs ok even if it does have a bit if taper at the back.

the truck will have a smooth under side with the batteries between the chassis rails.

[mistareno]

This is pretty close to how I'd like the rear to look. Not ideal, but not terrible either.

[Daox]

Looks like a great project. Any idea what you want to use for drivetrain components? range? etc?

[NeilBlanchard]

The Schlörwagen (aka Pillbug aka Göttinger Ei) is an excellent model to follow. Its Cd is 0.18, which is amazing. Elsewhere here on EM, there is a picture of it with tufts, in a wind tunnel and if the tail was broader (more like a beaver tail) than the drag would be even lower.

[freebeard]

I was going to convert a small ute/truck that I could use both as a commuter vehicle and for it's practicality.

I found the answer to one of my questions. Maybe a mobile office/party van?

This is pretty close to how I'd like the rear to look. Not ideal, but not terrible either.

I would respectfully disagree. That is the ideal.

I was going to use the same radius on the edges as the roof of cab and start the side taper after the rear wheels so they are enclosed. So probably closest to the square example but with radiused edges.

The middle example is 1/2 way between a square and circle. Toward the square limit you get round cornered rectangles, like the iPhone. Aerodynamically, you'd be better off closer to the mid-range, like an Airstream trailer.

PVC is nasty stuff. Brittle and it doesn't play nice with wood or metal. How about bamboo slats?

Wainscoting - Wall Slats for Bamboo Ceiling & Island Decor | Cali Bamboo


You'd have a dimensional, millable outer face and bamboo on the interior. Much nicer than PVC