spoiler angle

[dkibel]

I think we're saying the same thing dkibel. Speaking of quarter panels...take the LR quarter panel off and see how she does. It's been done before.

This man has it all figured out. haha

[RW57]

On my son's car with maybe 350 up we started with the spoiler at probably 45 degrees car was always tight getting in one nite for the hell of it I laid it back as far as it would go probably at 30 degrees car was much better getting in and thru middle.

[RCJ]

How did you arrive at those calculations?

[dkibel]

Using bernoullis equation (basis for all of fluid dynamics) you can find that Pressure= (1/2) * density of air * Velocity^2 . Once you find the pressure that is on the wing you can easily find the force on the wing, for this calculation pressure is essentially a constant or a multiplier in this case since we are only solving for the difference between the 8" spoiler and the 12" spoiler. Then you can find that Force= Pressure * area. This will just find the force on the wing. We want to find the correlation to angle so when you have flow over the spoiler you will have a vertical and horizontal component. To find the down force (in the vertical direction) DF=F*sin(angle). Typing this out on a computer is quite hard to explain so im doing the best i can. A degree in engineering really helps show the results behind the theories on these forums. If anyone needs further explanation feel free to pm me.

[turtle1hp]

Matt49 What exactly does happen when the LR quarter is removed? I was actually thinking about making it shorter on a car that we run that has a closed rear section. In hopes of lowering the pressure under the car while the body is rolled through the corners.

[dkibel]

Essentially when you take the whole fender off you are creating a high pressure point right behind the driver. This is act like a vacuum at high speeds trying to turn the front of the car at high speeds. With all of the bars on the chassis being exposed on the bottom of the car there is enough turbulent flow to create a large low pressure zone underneath the car. Im interested to see what matt has to say about this! Side note, this is probably one of the most interesting threads ive been apart of!

[Matt49]

I can't speak for a closed rear end car but SOME of this still applies. The key to downforce is to create high pressure above the body and low pressure under it. The LR quarter panel is part of the low pressure discussion. The more air you can prevent from going under the car (by sealing the nose to the track) and the more air you can get to escape from under the car (open rear end), the lower the pressure will be under the car = more downforce. To understand the importance of the LR quarter panel in all of this, it is important to understand how the bodies are constructed. The rules state the body can be 76" wide (max) above the rear axle and 72" wide (max) at the spoiler/end of the rear deck. The rules also state that this taper must be even on both sides but this rule hasn't been enforced in decades and almost everybody builds their bodies so that the right side is flat and all of the taper from 76 to 72 is in the left side. Now think about the car's angle of attack (yaw) on the race track and you can begin to see how the LR quarter panel is kind of "holding" a lot of air under the car...this is bad. Several years ago, some touring guys cut the LR quarter panels so they were only about 6 inches tall and they were bad fast. The sanctions quickly wrote new rules to make that illegal. Lucas Oil has a rule stating that the quarter panel must be at least 27" tall without plastic and 31" with plastic.
If you just look at recent pics of some of the touring guys cars you can see that most of them run the LR quarter panel as short as possible with the plastic trimmed more like you would be accustomed to seeing on the right side.

[billetbirdcage]

I can't speak for a closed rear end car but SOME of this still applies. The key to downforce is to create high pressure above the body and low pressure under it. The LR quarter panel is part of the low pressure discussion. The more air you can prevent from going under the car (by sealing the nose to the track) and the more air you can get to escape from under the car (open rear end), the lower the pressure will be under the car = more downforce. To understand the importance of the LR quarter panel in all of this, it is important to understand how the bodies are constructed. The rules state the body can be 76" wide (max) above the rear axle and 72" wide (max) at the spoiler/end of the rear deck. The rules also state that this taper must be even on both sides but this rule hasn't been enforced in decades and almost everybody builds their bodies so that the right side is flat and all of the taper from 76 to 72 is in the left side. Now think about the car's angle of attack (yaw) on the race track and you can begin to see how the LR quarter panel is kind of "holding" a lot of air under the car...this is bad. Several years ago, some touring guys cut the LR quarter panels so they were only about 6 inches tall and they were bad fast. The sanctions quickly wrote new rules to make that illegal. Lucas Oil has a rule stating that the quarter panel must be at least 27" tall without plastic and 31" with plastic.
If you just look at recent pics of some of the touring guys cars you can see that most of them run the LR quarter panel as short as possible with the plastic trimmed more like you would be accustomed to seeing on the right side.

[billetbirdcage]

[zeroracing]

So what would they do if they passed a new rule? Your allowed to trim the LR as much as you want, you cannot run any covers, and back to 2015 suspension rules... Be interesting to say the least.

[RCJ]

I don't think your calculations take enough real world problems in to account.The amount of force at the contact patch of the tire is what I'm think about.Let me get some measurements from my car to explain better.

[dkibel]

My calculations were purely based on how much down force the wing would see. I was just trying to get to the point that everyone could see the correlation between wing angles and heights. I'm sure i could find out exactly how much weight was on the tires but i would need to know the geometry, percentages, wheelbase at full hike, a model of the acceleration and deceleration (if you wanted to see how much force it would give at any given point), so on and so forth. Actually, that would be an interest project this weekend.Thinking about those pictures it actually makes a lot of sense. Pretty cool stuff.

[billetbirdcage]

So what would they do if they passed a new rule? Your allowed to trim the LR as much as you want, you cannot run any covers, and back to 2015 suspension rules... Be interesting to say the least.

First sorry about the huge pictures and messing up the screen size on page. Also for getting off topic on this but I gotta say something about the rules deal.

I think I been clear on how I feel about closing the box but that is another story. The problem is enforcement and the consistency of what is checked and what isn't.

1. At the Show-Me, there was a car that was told 3 times to take something off the LR over the whole weekend. He didn't, it wasn't until the final A feature that they supposedly made him or finally got him to take whatever they didn't like off.

2. Another guy asked a Tech official (it was not schwallie) if he could run what he had on his car. It was a split birdcage which is clearly defined in the rules as Illegal. The Tech guy told him, he was fine because everyone was trying stuff and they couldn't keep up with all of it so as long as it only had 2 (non compressible) links on the LR they where fine with it.

SO WHAT THE HELL IS THE RULES?????? Is it what is written in the rule book or what the tech guy said or just what they going to check that day, I'd really like to know.

I'm leaving out a bunch of stuff because it's not my place to call out guys, throw anyone under the bus, or ETC: but I just want to know what the MOTHER F'ing rules are.

End of my rant

[billetbirdcage]

They write 2 pages of suspension rules, when the can't or more importantly won't enforce the body rules they have. Half of the cars have more then 1" of rise or drop on the right side body line, which is clear as day in the rules as NOT LEGAL

[MBR Performance]

Off topic but related to billet's rant. What gets me is they say no split birdcages yet the option to split them has been around for a long time. Stupid