Which car is FASTEST based on Fenders

[1reason]

Assuming the fenders have zero weight, is it better (less total drag) to:

1. Not have air handling behind the front and leave it with only a front fender

2. A rear fender behind the front wheel, and then another fender in front of the rear wheel

3. solid piece from the front wheel to the back so the back doesn't have to "re-push" the air out again?

I "think" my question comes down to is the air friction of having the air handling from the (3) front to the rear more or less than the friction from a (1) smaller fender pushing in the rear?


I know, I know..... I should have been an artist (I hear that all the time)

 

[Obsessedderbydad]

The car that crosses the finish line first /images/boards/smilies/smile.gif

 

[B_Regal Racing]

A tear drop shape is the fastest. I have thought about a rear fender before (one that would come to a point), but the rear wheel would always cause to be an aerodynamic challenge, plus the rear fender would add weight.

 

[ngyoung]

For tear drop you don't have to maintain the full tail to get the same effect. I think that is referred to as a Kamm back.

As for best fender choice I think the most common is the top option in your list. More recently a racer named Lightning Boy set a track record with a fender style similar to the second choice. I don't know of anyone having success with the full length fender style in your 3rd option.

 

[1reason]

A tear drop shape is the fastest. I have thought about a rear fender before (one that would come to a point), but the rear wheel would always cause to be an aerodynamic challenge, plus the rear fender would add weight.

Have you tried a rear fender on the front tires. I have a material that adds nearly zero weight, so I'm not worried about weight, but intuitively, it seems that one foil may be most appropriate, although I'm having a hard time getting my head wrapped around having the leading surface much larger than the front wheel in order to allow it to tear towards the rear.

 

[Kinser Racing]

The jury is still out on 1 and 2. #3 definitely not.

 

[B_Regal Racing]

Have you tried a rear fender on the front tires. I have a material that adds nearly zero weight, so I'm not worried about weight, but intuitively, it seems that one foil may be most appropriate, although I'm having a hard time getting my head wrapped around having the leading surface much larger than the front wheel in order to allow it to tear towards the rear.

Honestly, I'm not a good enough racer to be able to give a good answer. I used to build my own fenders, but I do believe weight and shape can affect the car's overall speed, and at the pro level, it can be all the difference in the world. To be sure I was not doing more damage than good, I started using GEE fenders from DD4H. I may, at some point, put GEE fenders behind the front wheels, we'll see...

 

[1reason]

The jury is still out on 1 and 2. #3 definitely not.

Is it me, or does it "seem" like number 3 should be the best given that only the front wheels have to cut through the air? In my son's race two days ago, we went number 1 (ran out of time) and took first in den and pack, but with material that weighs essentially zero, I would think one piece is faster....

That said, I read somewhere that the air being pushed is pushed on the other cars, so I wonder if that's a factor in winning, or 3 is slower regardless?

 

[1reason]

Have you tried a rear fender on the front tires. I have a material that adds nearly zero weight, so I'm not worried about weight, but intuitively, it seems that one foil may be most appropriate, although I'm having a hard time getting my head wrapped around having the leading surface much larger than the front wheel in order to allow it to tear towards the rear.

Honestly, I'm not a good enough racer to be able to give a good answer. I used to build my own fenders, but I do believe weight and shape can affect the car's overall speed, and at the pro level, it can be all the difference in the world. To be sure I was not doing more damage than good, I started using GEE fenders from DD4H. I may, at some point, put GEE fenders behind the front wheels, we'll see...

I'm in the same boat, I don't think I'm helping much, but probably didn't slow the car down in the process neither (although I'm not sure)

 

[ngyoung]

maybe in a wind tunnel #3 looks better but when there is a car next to yours deflecting air into the side of your car I think the full side panel ends up being more of a sail. Most of what you will get for explanations is all going to be theory. There have been a few that have actually tried that style but it didn't work out. Whether that was solely the fender issue or not is not certain. The guys that are pushing the track records in league have all been your #1 configuration until recently someone did it with a #2. I do not know if any of them have put a lot of effort into trying out a configuration like #3 and it never performed well enough to enter into a race or if they just haven't ever tried.

 

[Chief]

Try not to over engineer things. There are several engineers here on the forum and they will also reluctantly tell you that just because it looks good on paper does not mean that it will work on the track. Keep it as simple as possible and go from there. Look at the guys on the top of the list...and know that they are not engineers. Nothing against my engineer friends, Im just trying to keep you from trying to re-invent the wheel so to speak. Have fun and good luck

 

[HurriCrane Racing]

What would be really cool to see is the single pass times of all the finals cars when running them alone.
This may be a way to hone in on what design offers the biggest advantage when running in traffic.

Uh, I'm an engineer....

 

[Obsessedderbydad]

you can over engineer things... Just sayin.

 

[B_Regal Racing]

Uh, I'm an engineer....

So am I, but it hasn't help me much here. Just sayin'

 

[txchemist]

The part of the problem that makes it super difficult is that the loss of speed due to air drag is composed of both moving the air out of the way { thin car better} change the coefficient of friction of a plain wheel with adding a smooth fender in front of each wheel, and then dealing with the ADDED skin friction from the sides of the fender and if you continue the fender along the entire body, you increase the skin friction compared to just the thin body. All this makes it close to a wash and a super builder might do better with #3 IF they get the surface friction down with polished sides. All the calculations are at best just the start of a model. Then you have to plug in actual race results and try to modify for both the track that changes the flow on the bottom, and the interaction of cars next to you. So the short answer is-- you have to make your own cars and see- but your own variation will probably be larger than the effect you are trying to measure..