fenders vs. no fenders

which one is more aerodynamically efficient? and no speculation, either. I have a friend that says that no fenders are more efficient cause of more surface area, and stuff, while I can swear I remember reading about an aerodynamicist who said that open wheel designs are inferior because the 4 protruding wheels disturb the air flow severely. anyone know?



Joseph.

on a street car, fenders are better. only time no fenders are better is if you can put aero on the car that makes the wind not notice the wheels. like big canards and splitters and stuff.

The boundary layer on the top of the tyre is doing twice the forward speed of the vehicle.
That should let you answer your own question.

I don't know what that means.


Joseph.

Fenders are way way way way better.

I didn't even think of it, but kiwibacon is right about the wheels too.

As for frontal area - unless the wheels protrude out further than the side of the car (and they don't for any road car I can think of), it is redundant, and even if they did, aerodynamic drag is made up of both frontal area and drag coefficent. FYI, they are multiplied together to get an idea of the efficency of whatever is moving through the air. Without fenders, you have a bunch of tubes, hoses, arms, springs, shocks, and other such bullshittery which makes the drag coefficent sky rocket.

In short, fenders. Functional and sexy.

I think we are talking about something like an open wheel roadster, not a normal street car.
if the car has inboard shocks and springs, and the max speed doesn't go above 80 or so, then it doesn't matter weather you have fenders or not. On something that goes faster, fenders are better.

This is assuming you are talking about something like a chatterham roadster or something. Not a camry

I'm talking about like a high performance racing car. like Indy car, or something. I know that fenders are more aerodynamically effecient than a traditional open wheel design (Indy cars, or F1), and my friend thinks the opposite. I just need some proof that he's wrong.


Joseph.

There are too many variables to say yes or no. Take any car... lets say a camry... obviously it will be worse if you remove the fenders. Now, take an F1 car and add fenders to it... now you just made two cars worse. Now, if the F1 car had street tires (tread), what kiwibacon said "The boundary layer on the top of the tyre is doing twice the forward speed of the vehicle.) would come into effect (more so than with slicks, anyway) and the fenders would probably help, but still wouldn't be as good as slicks with no fenders. Now, put race slicks on that camry... nah, j/k, don't do that :biggrin:

and to answer your question to him, it means the top of the tire is moving forward, cutting through the wind at a speed of 2x the speed of the vehicle, which means 2x the wind resistance (at least) as opposed to having a stationary piece of metal in it's place (such as a fender)

I don't know what that means.


Joseph.

If you're driving along at 100km/h, then the top surface of the tyre is doing 200km/h (the bottom of the tire is doing 0).
A layer of air trys to stick to the tyre and when it comes up over the top it meets air coming the other way at 200km/h relative, creating a lot of drag.

Does anyone know if fenders are regulated out in F1?

i would imagine they are.
not sure, but i would think that it would decrease wind resistance and since nobody uses them...

hence the frontal aero on f1/indy cars. it makes the air not see the tires, since the wind is pushed above the tires it creates a sort of low pressure area that the tires can move through creating less drag.

hence the frontal aero on f1/indy cars. it makes the air not see the tires, since the wind is pushed above the tires it creates a sort of low pressure area that the tires can move through creating less drag.

If the F1 guys were allowed fenders (mudguards) then you can bet your life savings they'd be using them.
The only way to completely eliminate air resistance is to have it turning in a vacuum, the difference in high/low pressure zones over a moving vehicle is insignificant in comparison.

I am pretty sure I have read before that F1 cars have horrible drag coefficents, partly because of being open wheeled. Also, probably partly because of all the wings and such.

I am pretty sure I have read before that F1 cars have horrible drag coefficents, partly because of being open wheeled. Also, probably partly because of all the wings and such.

That's the wings. I've seen figures showing the extra drag was roughly 1/3 of the downforce.
Given that these could potentially drive upside down, they're pulling maybe 1/3 of their weight as drag to create that downforce.

That's the wings. I've seen figures showing the extra drag was roughly 1/3 of the downforce.
Given that these could potentially drive upside down, they're pulling maybe 1/3 of their weight as drag to create that downforce.

Yeah, but the wings and the wheels, is what the book was saying.

If the F1 guys were allowed fenders (mudguards) then you can bet your life savings they'd be using them.
The only way to completely eliminate air resistance is to have it turning in a vacuum, the difference in high/low pressure zones over a moving vehicle is insignificant in comparison.

i understand. but the lower the pressure around the wheels, the less resistance they face when moving. its not even close to eliminated, but most of the front aero thats not used for pure downforce is focused on reducing drag across the wheels. its why the new chassis has a front wing that mimics the "3D" wings that touring cars use in back. with a more sloped profile on the ends, and a smoother transition in the middle. plus the mid chassis aero that directs air over the rear wheels.

http://www.formula1.com/photos/597x478/manual/bmwsauber02_170106.jpg