Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 10-16-2020, 09:53 AM   #1 (permalink)
EcoModding Lurker
 
Join Date: Oct 2020
Location: Milwaukee, WI
Posts: 2
Thanks: 0
Thanked 1 Time in 1 Post
Drag reduction - Racecar

I am working on some drag reduction on our endurance racecar and I wanted to pick some brains from the hypermile'r world.

Our rules allow us to repurpose material from the car in other areas. If we use wood, metal or plastic stock then we are charged "points". We basically have no points left, so we are reusing some of the rear bumper, a splash sheild and door cards. I also have some metal from the bottom of the fenders and some trim pieces.

The biggest area I see is the rear of the car. I can extend out to 12" from the rear of the car and I already have a diffuser at a max angle that extends out that far.

I am running an airdam, splitter, flat floor, diffuser and a custom fast back (reused bumper). The radiator is sealed and ducted and I have a vented hood with gurney flaps to improve extraction. I also have vented fenders, on the top for pressure reduction and reduced lift and the rear of the fenders vented to relieve well pressure.

I have a mock up here of what I want to do in the rear with a splash shield and door cards. I have an approximate 14 degree slope off of the fast back.

I don't want to cover the fenders because of brake cooling and we need to change tires.

We are only at 145whp, so drag reduction is important for overall lap times.

Does anyone have any other tips and tricks, additional input would be greatly appreciated.

Attached Thumbnails
Click image for larger version

Name:	Screenshot_20201015-111323_Gallery.jpg
Views:	63
Size:	32.5 KB
ID:	29365   Click image for larger version

Name:	50406300228_1cb7c65fa5_o_sml.jpg
Views:	70
Size:	35.9 KB
ID:	29366   Click image for larger version

Name:	50406042323_9a6053ae11_o.jpg
Views:	65
Size:	48.4 KB
ID:	29367  
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 10-21-2020, 01:16 PM   #2 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
rules

Are you allowed to enclose the rear quarter panels to create some boat-tailing on the sides, while still allowing sufficient wiggle room for fast tire changes?
I'm not a racer except for Bonneville, but I believe that your diffuser would be more effective if enclosed, along with welcome drag reduction.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 10-21-2020, 01:27 PM   #3 (permalink)
Master EcoModder
 
kach22i's Avatar
 
Join Date: Jul 2011
Location: Ann Arbor, Michigan
Posts: 4,158
Thanks: 120
Thanked 2,790 Times in 1,959 Posts
Quote:
Originally Posted by LuckyKid View Post
The biggest area I see is the rear of the car. I can extend out to 12" from the rear of the car and I already have a diffuser at a max angle that extends out that far. ............
You don't have to follow the original silhouette of the car it sounds like.

I'd try something like Ferrari did in 1962 - worked back then.

See Post#2
Porsche Boxster Shooting Brake, Yes or No? - Pelican Parts Forums


Very close to the aerodynamic template Part-C most often discussed in this forum and is a sticky at the top.

I think the rear (box cavity) can remain 100% open so all the repurposed metal can go to the sides, top and belly.
__________________
George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
  Reply With Quote
The Following User Says Thank You to kach22i For This Useful Post:
aerohead (10-21-2020)
Old 10-21-2020, 06:28 PM   #4 (permalink)
EcoModding Lurker
 
Join Date: Oct 2020
Location: Milwaukee, WI
Posts: 2
Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by aerohead View Post
Are you allowed to enclose the rear quarter panels to create some boat-tailing on the sides, while still allowing sufficient wiggle room for fast tire changes?
I'm not a racer except for Bonneville, but I believe that your diffuser would be more effective if enclosed, along with welcome drag reduction.
I thought that if the back of the rear tire is enclosed that it creates drag. Maybe I could leave a cavity behind the tire but extend the rear quarter panel downward?
  Reply With Quote
The Following User Says Thank You to LuckyKid For This Useful Post:
aerohead (10-23-2020)
Old 10-22-2020, 10:49 AM   #5 (permalink)
Master EcoModder
 
kach22i's Avatar
 
Join Date: Jul 2011
Location: Ann Arbor, Michigan
Posts: 4,158
Thanks: 120
Thanked 2,790 Times in 1,959 Posts
Many ways to vent that rear wheel well, from the slot of the 1962 Ferrari Breadbox to the 993 Porsche below.

https://www.vanthulldevelopment.com/...-gt2-widebody/
Attached Thumbnails
Click image for larger version

Name:	vanthulldevelopment_porsche_993_GT2_Widebody_15.jpg
Views:	47
Size:	62.5 KB
ID:	29415   Click image for larger version

Name:	vanthulldevelopment_porsche_993_GT2_Widebody_18.jpg
Views:	52
Size:	74.9 KB
ID:	29416  
__________________
George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
  Reply With Quote
Old 10-22-2020, 09:26 PM   #6 (permalink)
Master EcoModder
 
Join Date: Sep 2012
Location: Motor City
Posts: 272
Thanks: 0
Thanked 212 Times in 131 Posts
Have you tested it without the wing?
  Reply With Quote
Old 10-23-2020, 12:28 PM   #7 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
enclosing

Quote:
Originally Posted by LuckyKid View Post
I thought that if the back of the rear tire is enclosed that it creates drag. Maybe I could leave a cavity behind the tire but extend the rear quarter panel downward?
Enclosing will definitely reduce drag if the panels are boat-tailed, when viewed from above, however, you will lose the drogue effect of the exposed wheels, affecting high-speed stability. This has been known since before 1940.
Historically, if the rulebook allows, the body will be streamlined as much as possible, then 'sail' area will be added for directional stability, of which will be partly supplied by the paneling.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 10-23-2020, 01:14 PM   #8 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
Quote:
Enclosing will definitely reduce drag if the panels are boat-tailed, when viewed from above, however, you will lose the drogue effect of the exposed wheels, affecting high-speed stability. This has been known since before 1940.
Do you have a cite or example? TIA.
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
aerohead (10-23-2020)
Old 10-23-2020, 01:37 PM   #9 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
citation

Quote:
Originally Posted by freebeard View Post
Do you have a cite or example? TIA.
Fachsenfeld, who did the research at the FKFS, addresses the relationship in his book,' AERODYNAMICS DES KRAFTFAHRZEUGS', 1951.
The turbulent wake behind the wheel acts in a stabilizing fashion, like the wake behind the transom of a ship / boat, tends to 'center' the stern in the direction of travel.
If you look at a recent ROLEX' 24-HOURS of DAYTONA race car, you'll see a fin behind the Jaray greenhouse, running the total length of the aft-body. Exactly like Fachsenfeld had done prior to the beginning of WW-II in Europe. This weather-vane compensates for some of the loss of the exposed wheel wake, and with zero drag penalty.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
freebeard (10-23-2020)
Old 10-23-2020, 02:28 PM   #10 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
Quote:
...a recent ROLEX' 24-HOURS of DAYTONA race car
One of these?

https://i.pinimg.com/originals/2a/e6...6d39a0aef7.jpg

Here's a candidate:


https://i.pinimg.com/originals/6f/7f...b596f9d1e1.jpg

Maybe this one?


https://2.bp.blogspot.com/-te8lpwrMQ...of-Daytona.jpg

__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
aerohead (10-23-2020)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com