JoeS
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Re: Aerodynamic Mods to Reduce Drag

Tue Dec 31, 2013 3:47 pm

PV1 wrote::!: :?: :!: Why is there an i-MiEV laying on its side? :o :shock: :? :cry:
Didn't you know, it's much easier to work on the underside of the car when it's on its side! Looks like they forgot to put down the obligatory mattress. :roll:

Yes, I had seen that emergency response training photo - they evidently had a hard time getting the iMiEV to stay on its side in the first place.

With drag force proportional to the product of Cd and cross-section area, in the example Mart provided the Dart still has a lower drag force than the i-MiEV for any given speed.

The NA iMiEV appears to have a fairly-clean underside until we get to the drivetrain area. When I was lying under the car yesterday I considered perhaps a flexible (heavy fabric?) cover under everything and connecting to the aft bumper; however, such a cover would unfortunately trap everything from snow to water to pebbles…

We're planning a long (>200-mile) trip on New Year's Day with the iMiEV - the fender skirts have survived about 50 miles so I'll leave them on - probably it's my imagination, but the wind noise in the back seems a bit more muted.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
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NeilBlanchard
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Re: Aerodynamic Mods to Reduce Drag

Tue Dec 31, 2013 3:50 pm

The rear wheel skirts should help noticeably. You might want to use better tape like 3M white/translucent duct tape: http://www.amazon.com/3M-Transparent-1-88-Inch-20-Yard-2120-A/dp/B0000DH8I8 which will also look better. And I think you will have less noise as the drag is lowered - the turbulence is what produces the drag and the noise.

And yes, a full belly pan would be a big help. Bridging the gap from the rocker panels to the battery pan would be good, and the front and rear knarly open portions, too.
Sincerely, Neil

http://neilblanchard.blogspot.com/

PV1
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Re: Aerodynamic Mods to Reduce Drag

Tue Dec 31, 2013 4:34 pm

Did they have to get a blue one? ;) I remember hearing about it. They called it "Weeble", as in "Weebles wobble but they don't fall down (over)."
I guess sacrifice one to save us.

The fender skirts definitely make the i-MiEV look different. Haven't decided if it's for better or worse, but it should help with noise and range. Perhaps the steel wheels have the advantage here being mostly closed. Nice work, either way.
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JoeS
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Re: Aerodynamic Mods to Reduce Drag

Thu Jan 02, 2014 1:43 pm

NeilBlanchard wrote:The rear wheel skirts should help noticeably. ..
Drove 80 miles to Monterey with the skirts on and then took them off for the return trip. No noticeable difference. Mileage was worse than normal in both directions because car was loaded with two people and about 250# of 'stuff'', and we had a significant (1600ft) climb. Fender skirt experiment inconclusive. I happen to think they looked 'cool' 8-)
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

NeilBlanchard
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Re: Aerodynamic Mods to Reduce Drag

Tue Jan 07, 2014 8:18 pm

Yeah, you need to keep running them and see how it goes. Smooth and flat wheel covers (stretch cloth over the plastic ones, and glue it with a waterproof glue, and then spray paint 'em.
Sincerely, Neil

http://neilblanchard.blogspot.com/

NeilBlanchard
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Re: Aerodynamic Mods to Reduce Drag

Tue Sep 02, 2014 9:32 am

I am in the midst of remaking my rear wheel skirts / strakes for my Scion xA, which is relatively close to the i MiEV. I am using 1/4" Dow XPS fanfold foam and 3oz fiberglass - here are some pictures:

Image
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Image
Image
Image
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Image

I have them back off the car, to fiberglass the back of the skirt, and I need to put in a panel "roof" inside the strake (last picture) to keep the water out. I also have to fiberglass the skirt panels, and the rest of the Kamm panels, and work out a joint between the side Kamm panels on the hatch with the panels at the taillights. I will probably be replacing the arcing slots with acrylic panels; for seeing the taillights from the side.
Sincerely, Neil

http://neilblanchard.blogspot.com/

JoeS
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Re: Aerodynamic Mods to Reduce Drag

Tue Sep 02, 2014 10:44 am

Neil, looking good! Exactly what scheme do you plan on using to attach the (removable) skirts to the body panel?
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

NeilBlanchard
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Re: Aerodynamic Mods to Reduce Drag

Wed Sep 03, 2014 9:53 am

I am going to pop rivet the main peices to the car. I bought some #10 stainless steel screws and nuts that I was planning on fiberglassing the nuts onto the back of the lip, to hold the skirt panels in place. But if I can fine some threaded clips that are not going to rust, and that spread out the pressure a bit, I will use those.

Some more pictures:

Image
Image
Image
Sincerely, Neil

http://neilblanchard.blogspot.com/

jray3
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Re: Aerodynamic Mods to Reduce Drag

Thu Sep 04, 2014 3:48 pm

Neil, I realize I'm addressing a master Ecomodder, but why not use rivnuts rather than rivets? They seem like the best of both worlds- install 'em blind and re-install the panel as many times as desired.
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NeilBlanchard
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Re: Aerodynamic Mods to Reduce Drag

Fri Sep 05, 2014 10:31 am

Ray, that's a new one on me - I have not heard of rivnuts. I like the sound of them.

Edit: I looked 'em up and found a short video on installing them. They look like they would be fine for all metal situations, but they may require more strength / crush resistance than a pop rivet; though maybe it's the other way around? I also already own a decent pop rivet tool. I'll have to test rivets with my fiberglass / foam / metal and plastic, and see if they work.
Sincerely, Neil

http://neilblanchard.blogspot.com/

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