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Just Some Aero Questions

73
46
Exp. Type
HPDE
Exp. Level
Under 3 Years
Cantley
Another aero question: I saw this part on the Faessler car and I thought I saw a vendor selling one like it but I don't know what it is called and I can't find it anymore. Not sure it is a canard or a fender extension. It seems to make sense when putting wide front wheels, as a first incremental step before adding the big wing and splitter. Thoughts?Screenshot_20210527-194442_Samsung Internet.jpg
 
Definitely a good part to run if your tire is exposed. I call them dive planes, or tire blockers. I've tested a few variations of these in the wind tunnel on a few different cars (e36, M2, and my own car. All the videos on my youtube) and they always produce downforce at an OK efficiency. Generally blocking the air from just hitting the tire is a good idea, but they didn't produce as much Df as canards.
 

Ludachris

Chris
Staff member
Moderator
1,411
1,618
Exp. Type
HPDE
Exp. Level
5-10 Years
Newcastle, CA
Another aero question: I saw this part on the Faessler car and I thought I saw a vendor selling one like it but I don't know what it is called and I can't find it anymore. Not sure it is a canard or a fender extension. It seems to make sense when putting wide front wheels, as a first incremental step before adding the big wing and splitter. Thoughts?View attachment 65629
Always wondered about those too.
 
73
46
Exp. Type
HPDE
Exp. Level
Under 3 Years
Cantley
Definitely a good part to run if your tire is exposed. I call them dive planes, or tire blockers. I've tested a few variations of these in the wind tunnel on a few different cars (e36, M2, and my own car. All the videos on my youtube) and they always produce downforce at an OK efficiency. Generally blocking the air from just hitting the tire is a good idea, but they didn't produce as much Df as canards.
Wow thanks for taking the time for me AJ. Yes I do have some tire exposed and I thought this can be fabbed easily and give me a little bit of help in the immediate.

20210603_112056.jpg
 
735
1,062
Exp. Type
Time Attack
Exp. Level
Under 3 Years
SoCal
Wow thanks for taking the time for me AJ. Yes I do have some tire exposed and I thought this can be fabbed easily and give me a little bit of help in the immediate.

View attachment 65638
I’ve seen these commonly called “tire spats” as well. Racebred Components offers a universal fit set made out of ABS plastic if you’re looking for something pre-cut, or you can buy sheets of ABS and cut your own for quite a bit less.

B583F0DE-1F81-49AE-9B1D-1896AD221B31.jpeg
 
4,515
5,004
My 2 cents on this, and it goes back to my kart racing days, we covered all the tires in bodywork whenever allowed, the reason given, and it made sense to me but I'm very far from an "expert" is that the top of the tire is cutting through the air at twice the velocity of the the lower half of the tire, so.. it would seem that if resistance is measured exponentially, that would make complete sense. To go into that a bit further, in the 70s F1 and Indy cars were starting to flair over their front tires, this was disallowed along with sealed tunnels and what not, so I'm not sure if it was the result of one, or all of those rules changes. Later the LMP cars were required to cut holes over their front and rear tires to slow them down to compete with the Daytona prototypes when the classes were blended.
The short answer appears to be there is some aero data, along with some real life experiences, that seems to justify keep your tires covered.
 
5,141
5,663
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
My 2 cents on this, and it goes back to my kart racing days, we covered all the tires in bodywork whenever allowed, the reason given, and it made sense to me but I'm very far from an "expert" is that the top of the tire is cutting through the air at twice the velocity of the the lower half of the tire, so.. it would seem that if resistance is measured exponentially, that would make complete sense. To go into that a bit further, in the 70s F1 and Indy cars were starting to flair over their front tires, this was disallowed along with sealed tunnels and what not, so I'm not sure if it was the result of one, or all of those rules changes. Later the LMP cars were required to cut holes over their front and rear tires to slow them down to compete with the Daytona prototypes when the classes were blended.
The short answer appears to be there is some aero data, along with some real life experiences, that seems to justify keep your tires covered.
Yep, additionally the air off the front tire is spinning forward, against the air stream which is what you alluded to saying its twice the velocity.....I bet its at least twice or more. Good point Rob.
 
73
46
Exp. Type
HPDE
Exp. Level
Under 3 Years
Cantley
Or you could make a drawing of what you want and have @AJ Hartman cut them out for you.
Sure it may cost a little more, but hey....its carbon!

View attachment 65640
Yes, for sure. What you have there in the pictures is what I was thinking about, with regular fenders. Now I have some thinking/measuring to do.
On the topic of canards, I don't question the downforce findings but I am surprised that they can be so effective given they are mounted on a soft bumper cover. I imagine you need a large washer behind the bumper cover to distribute the load so they don't rip off at speed?
 
5,141
5,663
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
Yes, for sure. What you have there in the pictures is what I was thinking about, with regular fenders. Now I have some thinking/measuring to do.
On the topic of canards, I don't question the downforce findings but I am surprised that they can be so effective given they are mounted on a soft bumper cover. I imagine you need a large washer behind the bumper cover to distribute the load so they don't rip off at speed?
there are some little clippy thinks that the screw goes into. its surprisingly robust.
Its also on a curve so that adds a lot of rigidity.
 
73
46
Exp. Type
HPDE
Exp. Level
Under 3 Years
Cantley
As blacksheep and bob have already noted, you need to either do both the splitter and the wing or neither.

The reason is, as also noted, aero balance. What I'm going to add is that an effective splitter and no wing has some potential for making the car "aero-loose", which would tend to get worse as speeds rise - an effective splitter works to unload the rear tires by turning the front axle line into a soft fulcrum. Oversteer in a high speed kink sounds like a whole lot more excitement and a whole lot less fun than tailhappiness in a tight hairpin . . .

IIRC, Terry Fair of Vorshlag ran into this exact issue a few years during development of the rather fast red S197. I'm sure it's included in the car's build thread either here or on another forum or on Vorshlag's own forum.


Norm
On the topic of the wing: I was thinking about mounting options and my intuition tells me I would be better off running the stanchions through the trunk lid panel and bolted to the trunk floor, putting pressure on something structural and low, and as far back as practicable, vs simply mounting on the trunk lid panel. Thoughts on this?
 

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