Presented by Nine Lives Racing
Jonas350
Jonas350 New Reader
3/6/22 4:44 p.m.

Just finished making these fiberglass wheel covers for my RX7... 

I've been wondering if the decreased drag from the front covers overcomes the increase in frontal area. My intuition says it does, but I wanted to get your thoughts on it.

The widest point in the center of the cover sticks out 5" on each side. I'm primarily concerned with decreasing drag for higher top speeds.

I'm also looking for a logical justification to keep them , cause I just think they look cool laugh




Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand PowerDork
3/6/22 4:51 p.m.

I have no idea about the question but I'm torn between describing it as a barnacle or a carbuncle. wink

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
3/6/22 4:58 p.m.

Wheels are really, really ugly from an aero standpoint. The top of them have have an airspeed that's twice that of the rest of the car and they squirt vortices all over the place. I would think that you'd definitely see less drag by covering them.

Appleseed
Appleseed MegaDork
3/6/22 5:13 p.m.

You could do moon covers, and seal the gap in the opening with semi-flexible rubber. An experiment by a home builder in the Experimental Aircraft Association picked up 3kts by sealing the wheel gaps on his pants for his Acro Sport II.

Personally they are an odd look, but your car is totally  cyberpunk. I wouldn't change a thing. I'd add even more. Seriously.

03Panther
03Panther UberDork
3/7/22 3:55 p.m.

Those are absolutely ugly...I LOVE IT!!!

californiamilleghia
californiamilleghia UltraDork
3/7/22 4:12 p.m.

I am on the wrong computer , but look for the 1951 Porsche LeMans winner #46 ,

it has some cool skirts on it that increased the top speed with a small 1100 cc motor.

Jonas350
Jonas350 New Reader
3/8/22 4:29 p.m.

"The top of them have have an airspeed that's twice that of the rest of the car and they squirt vortices all over the place. I would think that you'd definitely see less drag by covering them."

I didn't realize the air speed was that high at the top... I just know they are a turbulent mess. Sounds like you know more about aero that me, so it's encouraging to hear that.

 

"Personally they are an odd look, but your car is totally  cyberpunk. I wouldn't change a thing. I'd add even more. Seriously."

Cyberpunk is exactly what I am going for. Any suggestions on how to turn it up to the next level? I love that rendering by Walter Kim. I was toying with the idea of doing a big low mounted wing like that. I went so far as to mocking one up out of foam... but I thought maybe the whale tale would be a little more tasteful. My style is tastefully overdone.

 

"Those are absolutely ugly...I LOVE IT!!!"

Haha pretty much my sentiments too. From the front and rear I'm a bit iffy about them... but when I see it from the side I'm a bit mesmerized. It's definitely the most polarizing mod I've ever done.

 

"I am on the wrong computer , but look for the 1951 Porsche LeMans winner #46"

Yes! That's exactly what I was going for. That was one of the few examples I could find of what I had in mind before I started building them.

 

Y'all might get a kick out of the aero on the C4 I'm working on. It's a long project. Dropped the body down over the frame about 6" and the aero is more focused on high down force and less about low drag. Also a high emphases on being over the top.

https://youtu.be/RZXm7K9oebU

jfryjfry
jfryjfry SuperDork
3/19/22 10:17 a.m.

Wow that is really cool

84FSP
84FSP UltraDork
3/19/22 11:24 a.m.

So dig the C4 but can't get my head around the FC.  Seems like it would work - from a realistic standpoint - how hard is it to get at wheels and brakes for maintenance? 

Appleseed
Appleseed MegaDork
3/19/22 5:50 p.m.

Crib this: Cyberpunk Corvette

 

californiamilleghia
californiamilleghia UltraDork
3/19/22 6:25 p.m.

Here is 46

eogel
eogel New Reader
5/7/22 9:01 p.m.

Can you post more pictures of the C4 you are working on or start a new thread. Thanks

 

Jonas350
Jonas350 New Reader
4/17/24 1:01 p.m.

Thought it would be fun to update this thread. Decided to eliminate the increased frontal area problem :)

The front covers are now flush. They are hinged on the leading edge and a bracket attached to the steering knuckle opens them, and I used a tool balancer to pull them shut.





Here it is at full lock. Of course I won't have anywhere near this kind of steering input at speed, and of course the side you turn into sticks out the most.

Design was inspired in part by the 1987 Chevrolet Express Concept: https://www.youtube.com/watch?v=D18OxxragVs

VolvoHeretic
VolvoHeretic GRM+ Memberand SuperDork
4/19/24 7:49 p.m.

Great job! That needs to be in a syfy movie. smiley

tgschmid
tgschmid New Reader
4/21/24 10:54 a.m.

In reply to Floating Doc (Forum Supporter) :

Agreed

buzzboy
buzzboy UltraDork
4/23/24 7:56 a.m.

What blue is this? It's fantastic!

Jonas350
Jonas350 New Reader
4/25/24 9:27 p.m.
VolvoHeretic said:

Great job! That needs to be in a syfy movie. smiley

That was my exact vision building it. Wish I could see it cruise by in the background of Ghost in the Shell or something like that. Maybe one day it will get a casting call 😁

Shot a video of it moving. Looks kinda magical. https://youtu.be/qbSDIWw-zxQ?si=MzkYUeOOOg0_lbXX

 

The color is a custom pearl called Blue Grape. I was dead set on the color. https://usa.specialistpaints.com/products/base-pearlz

Driving4fun
Driving4fun New Reader
4/26/24 6:43 p.m.

Awesome job!  Execution is near flawless imo.  Well done sir!

VolvoHeretic
VolvoHeretic GRM+ Memberand SuperDork
4/30/24 1:37 p.m.

Back to the original question about frontal area... If the underbelly isn't butt smooth doesn't the frontal area extend all of the way down to the ground?

stafford1500
stafford1500 GRM+ Memberand Dork
4/30/24 2:00 p.m.

Frontal area is really only the visible projection from the front/rear. for a typical car it is going to be in the mid-20sqft range.

The only reason to bother with it is to make comparisons between cars that are not the same. It allows you to compare DragCoefficient*FrontalArea for a more equal comparison. That is the only way to compare something like a car vs a motorcycle (car lower CD but larger frontal area, motorcycle lower frontal area but higher CD). Together they give you a rough approximation of the drag force (still missing the velocity component).

Reduced frontal area does not necessarily mean lower drag coefficient.

VolvoHeretic
VolvoHeretic GRM+ Memberand SuperDork
4/30/24 3:33 p.m.

In reply to stafford1500 :

Thanks for the explanation. I have never heard it explained that way in all of the reading over all the years that I have done.

hybridmomentspass
hybridmomentspass Dork
5/19/24 2:02 p.m.

That blue FC looks freaking rad!

StuntmanMike
StuntmanMike New Reader
6/18/24 11:22 a.m.

Very cool! I feel like it should make the Jetsons spaceship sounds when it moves

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