Ute Aerodynamics?

[JacobLeSann]

Hey all,

I got a 1998 Civic Sedan for free recently. I want to use it as a winter beater, and as such I’ve been thinking of silly mods to do to it. Somebody told me to make a Ute. Now I’m obsessed. I carry a lot of large volume, low weight cargo; I don’t really drive with more than one passenger; I don’t like four doors; I carry bicycles and my sub-200lb scooter around; I don’t pull or tow anything. A Ute seems like a good idea to me.


What about the aero of modern utes, though? I can’t really find much info on drag coefficients or anything really. Just modern pickup trucks. Holden seems to be on the ball with it with their HSV Commodore “Maloo” Ute. I love the look of it.





Anybody ever mod one? Same or less drag than a notchback? Cool aero ideas for the rear end? Open to anything you guys know about them. Only thing I’ve ever seen in person was a 70’s El Camino.

[freebeard]

They're no help with your particlaur donor vehicles, but the standard would be Smyth Performance. www.smythkitcars.com/

The closest match would be their Jetta/Golf kit. Here are the parts they use laind out:



As for the aerodynamics -- You could take the whole roof off, or do a slant chop. An aerolid might be improvement over the stock top. Else you could do a half-tonneau.

[JacobLeSann]

The Smyth kit was where the idea came from. My dad seen one for sale in Alberta. The guy who makes them is great.

When it comes to the aero, I don’t really want to slant-chop it (thought I do have future slant-chop ideas). An Aerolid would be a great improvement over stock, but I’d have to determine how to integrate a window into it, and then how would I defrost that window when it’s freezing cold outside? My issues with it only start from there.

The design of the Holden looks coolest, and likely most practical as well. Keep the window small to keep the weight low, and having it right behind the rear seats means I can easily use the dashboard heater vents to defrost it. The Gen 1 Ridgeline seems similar in the rear, so I wonder if that design is effective in reducing drag. I guess you could study the flying buttress design of cars like the MR2 or Lotus Esprit, but those aren’t very low drag. Look awesome though.

I want it to be nice-looking, simple, reliable and low-weight. The pickup functionality is important to me. I want a simple rear window.

[freebeard]

The pickup functionality is important to me

Do you need a tail gate? If you're keeping the rear seats, maybe just take the trunk lid off and add some side racks?

[JacobLeSann]

You’re thinking of something like a GMC Avalanche. I’m thinking more like a Subaru BRAT, El Camino, Ranchero, etc. I’m not a fan of four doors, plus having a single “cab” in such a small vehicle should make interior heating very efficien as well as keeping the curb weight lowest. The end goal is pretty much the same rear end as the Holden Maloo Ute I posted, with a bit of aero mods. A tailgate would be perfect for loading up bikes, so yes.

[JacobLeSann]

I’m still getting the hang of perspective and such, so this sketch is very square. This a variation of aerohead’s “IT-works Double Geometry Aero-shell”.

[JacobLeSann]

And here’s me having fun.



Attack of the sideways image!

[aerohead]

She'd be a good one to mimic!
Cd 0.309 if memory serves me.
Only RIVIAN and CYBETRUCK are lower ( except SPIRIT ).
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If you left the bed open, but with the flying buttresses, you'd be sequestering the vorticity and turbulence within the confines of the cab roof, sides, and tailgate. If you're never going to haul sheets of plywood or the like, the width inside the box is less of an issue, allowing plan-taper of the buttresses, for more drag reduction.
For times when you weren't hauling 'tall' loads, you could panel in the upper opening to the 'vault,' creating the, circa 1982 slant-back topper CYBERTRUCK is riffing off of.
( C-channel attached to the inner faces of the buttresses could receive 10-mm
Coroplast, slid in from the open tailgate ). Cheap 'n Dirty!
My brother does this on his Tundra with custom-made steel panels.
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You'll create quite a 'blind-spot' to the passenger side. And even if you glaze that buttress, there'd be no way to 'defrost' it.
I drove 18-wheelers in the Air Force, and got a CDL when I left in 1975. I'm okay with only sideview / blind-spot mirrors.

[JacobLeSann]

Thanks aerohead, all very good advice. I plan to integrate some plan taper, but keep the box the same width all throughout. The blind-spots will definitely be rough, but I think it will be manageable. I do want my rear window though, as I plan to use very small side view mirrors to reduce drag. On the flip side, the drag of a rear window design could cancel out savings from smaller mirrors. I’m not very good at reversing with mirrors, and much prefer to look out the rear glass.

I was thinking similarly as you with a slant-back topper, though I would use a flip-top tonneau cover like most pickups use. Coroplast would be lighter, though.

Leaving the bed open may be better, is what you’re saying? I like the idea, but I want to use a clamshell tonneau design like the Holden, so as to keep the bed clean. When tall loads are in the back, I could unbolt the hinges and remove it, leaving just the buttresses.


0.309 for the Commodore Ute? If that’s so, then wow! I’d bet money that is far better than a 1997 Civic Sedan.

[aerohead]

Originally Posted by JacobLeSann

Thanks aerohead, all very good advice. I plan to integrate some plan taper, but keep the box the same width all throughout. The blind-spots will definitely be rough, but I think it will be manageable. I do want my rear window though, as I plan to use very small side view mirrors to reduce drag. On the flip side, the drag of a rear window design could cancel out savings from smaller mirrors. I’m not very good at reversing with mirrors, and much prefer to look out the rear glass.

I was thinking similarly as you with a slant-back topper, though I would use a flip-top tonneau cover like most pickups use. Coroplast would be lighter, though.

Leaving the bed open may be better, is what you’re saying? I like the idea, but I want to use a clamshell tonneau design like the Holden, so as to keep the bed clean. When tall loads are in the back, I could unbolt the hinges and remove it, leaving just the buttresses.


0.309 for the Commodore Ute? If that’s so, then wow! I’d bet money that is far better than a 1997 Civic Sedan.

' was just thinking that, if you weren't carrying 'tall' goods, and could tolerate losing the view through the rear window, enclosing the 'top', on long hauls, would offer meaningful drag reduction. It would be like CYBERTRUCK with the 'roll-top' cover in place.