AI Aerodynamics Discussion

[JWL]

Folks-

 

Couldn't fathom how to split this out of the "hAterZ" thread, so let's move the aero discussion in here.

 

Thanks.

 

-JWL

 

From the other thread:

 

Will ask my IT folk how to split the threads...might be above my PlaySkOOL internet skillz.

 

As for the aero rule, would something easy like no aero devices allowed between the centerlines of either axle or beyond 2" inboard of the rocker panel? We could also limit how far forward a splitter can stick out, but I am hesitant to do that without looking at how far folks have them sticking out now so we don't cause Sawzall madness over the Winter.

 

Keep on thinking and posting...

 

-JWL

[b_tone]

From other thread:

 

Scott, while I don't disagree that it can't be done, I do think it can't be done our our types of budgets. Sure people may start throwing stuff under the car, I say go ahead and let them. Having been part of aero development I have an understanding on what it would take to make it all work, and its way outside of most of our budgets.

 

Here is a simple rule that will kill this:

 

"No underbody devices allowed between the centerlines of the front and rear wheels."

 

With that inplace there will be no way to control the flow under the car (because there are no flat bottomed cars) thus removing nearly all potential underbody cars.

 

It's not that difficult to curb this right now with my suggested rule.

 

EDIT: JWL beat me by a few minutes, I guess that's what I get for refilling my coffee in the middle of my post. To his point yes in my opinion that would work to limit what would work, and in reality without a flat bottom a diffuser won't work.

 

Length of splitters - if you have more than 3-4 inches of flat surface out front you've probably got too much as without a huge amount of rear downforce you'll have a ridiculous center of pressure (from an aero perspective) to the front and most likely result in a big push and slow straight speeds.

[horsewidower]

Nice simple rule, I like it. Let's define the device as an "aerodynamic device." And no "mass damper" interpretations.

 

edit: I also assume that it only applies to AI, not AIX. I don't believe any of those gentlemen have commented.

 

Bob Holmes

[firehawkclone]

We could also limit how far forward a splitter can stick out, but I am hesitant to do that without looking at how far folks have them sticking out now so we don't cause Sawzall madness over the Winter.

 

Keep on thinking and posting...

 

-JWL

 

From other thread:

 

Length of splitters - if you have more than 3-4 inches of flat surface out front you've probably got too much as without a huge amount of rear downforce you'll have a ridiculous center of pressure (from an aero perspective) to the front and most likely result in a big push and slow straight speeds.

 

This one would basically have me remove my splitter all together. And if it couldn't hang closer than 3", there goes the stock setup!

 

 

 

We all don't drive mustangs guys....

[b_tone]

What does vehicle type have to do with how much horizontal surface should be allowed?

 

I did not mention anything about vertical height off the ground, so what are you talking about in your reference about "hanging closer than 3 inches"?

[nape]

What does vehicle type have to do with how much horizontal surface should be allowed?

 

I did not mention anything about vertical height off the ground, so what are you talking about in your reference about "hanging closer than 3 inches"?

 

I think John is saying that his splitter sticks out past the nose of the car, yet the vertical part of the splitter (air dam?) is not at the tip of the nose. F-bodies typically don't have the front of the nose flat like the Mustangs I've seen.

 

As far as "hanging closer than 3 inches", I believe he's refering to Scott's post in the other thread about a ground clearance rule.

[firehawkclone]

What does vehicle type have to do with how much horizontal surface should be allowed?

 

I did not mention anything about vertical height off the ground, so what are you talking about in your reference about "hanging closer than 3 inches"?

 

Vehical type has everything to do with how much DF is made from the same amount of horizontal surface area! And yes my splitter has more than 4"

 

I did say "you " did! It was a genral statement bud form othter posts! Relax!

 

A stock f-body air deflector(engine cooling) hangs that close(3") for a RR setup suspension.

[firehawkclone]

What does vehicle type have to do with how much horizontal surface should be allowed?

 

I did not mention anything about vertical height off the ground, so what are you talking about in your reference about "hanging closer than 3 inches"?

 

I think John is saying that his splitter sticks out past the nose of the car, yet the vertical part of the splitter (air dam?) is not at the tip of the nose. F-bodies typically don't have the front of the nose flat like the Mustangs I've seen.

 

As far as "hanging closer than 3 inches", I believe he's refering to Scott's post in the other thread about a ground clearance rule.

You beat me to it, Thanks TJ

[Red Tornado]

Although I would be fine with my stock cobra r aero setup this would be a major change for a number of folks and is likely unfair to do at this point.

Besides Robin, Dave, and I certainly proved no to minimal aero seems to work fine. Same with Jay the past two years.

[swhiteh3]

BPT-

I like that rule idea a lot honestly. Good call. Let me brainstorm a few ideas out loud...

 

I like the idea of having a rule about how low AND how long the splitter can be.

 

The splitter length should be defined by the distance the splitter extends forward from the overhead view of the front bumper cover. Cars with front bumper covers that "overhang" more would be allowed a little longer splitter since some of that plan area downforce is countered by lift created by the bumper. Also, it eliminates changing front fascias to gain more splitter length (if the "length" is measured at the splitter itself by "Horizontal area"). For instance, a Saleen Mustang front airdam might extend further forward than a GT piece, giving an unfair advantage. I'd be a fan of 3" forward from the profile of the front bumper.

 

Splitter height would help eliminate ground effect from the splitter, making them a little less effective. Somewhere around 3" would be good. I think it's really important to generally keep these cars less aero dependant, and softly sprung.

 

I like the idea of ending splitters at the front axle CL. I don't see any reason to allow aerodynamic devices behind the rear axle CL though. Do we really want people running big diffusers hanging out the back of the car, 24" back from the rear bumper?? I'd like to see the rule just say "no underbody aero devices behind the rear axle CL". That would include skirt extensions, flat bottom panels, etc.

 

Of course, we're going to be, for years, arguing of what constitutes an aerodynamic device, which is why I avoided this approach. Hopefully we're ready to play the game of interpreting people's intentions. That's my only concern. I've played this game in numerous professional series, and it's tougher than it might sound.

 

On Edit: Just realized that JWL and BPT both had a similar idea, so I should have credited them both with the idea....

Edited October 18, 2008 by Guest

[swhiteh3]

Although I would be fine with my stock cobra r aero setup this would be a major change for a number of folks and is likely unfair to do at this point.

Besides Robin, Dave, and I certainly proved no to minimal aero seems to work fine. Same with Jay the past two years.

As Fidelity reminds me in every mailing:

 

"Past performance is no guarantee of future results"

 

The amount of downforce that is available is a major game changer. Waiting for it to arrive, and then dealing with it will catch even more people out.

[swhiteh3]

We could also limit how far forward a splitter can stick out, but I am hesitant to do that without looking at how far folks have them sticking out now so we don't cause Sawzall madness over the Winter.

Respectfully, if you're not capable of, or don't have the time to cut 1" off your splitter to accomodate a simple rule change, then you probably should not be racing in a series like this. The longer we wait, the more people who will need to change this. I already have my splitter made for next year, and I'll likely need to trim it to comply with these rules, but so be it. Also, I have about 10 hours or so into a CAD drawing of an undertray, and I'm campaigning hard so that I don't have to build it. With a little inginuity, I think I can build it from carbon for about $1000. It's a full underwing.... I really don't want to build it, because I think it's COMPLETELY out of the spirit of the rules.

 

There are certainly several common packages out there, like the 2000 Cobra R bodywork. We should certainly make sure we don't write a rule that outlaws common packages like this. Anyone want to measure the extension from the overhead profile of the Cobra R splitter?

[b_tone]

I like to see the Aero rules read something like this:

 

• " *Splitters are allowed, but with a profile, when viewed from above, which does not extend more than 5" forward from the profile of the bumper (also when viewed from above). This forward length is measured parallel with the CL of the car. All splitters must terminate no further rearward than the centerline of the front axles. Air dams may be mounted to the front of splitter. Underbody panels and devices are not allowed including but not limited to: underbody pans, underwings, tunnels, diffusers etcetera.
   
  *Minimum height of splitter is to be 3" from the ground when measured on a flat surface. Wings are allowed up to a width of XX and a height of XX under the top of the roofline as viewed from the side.
   
  *No side skirt extensions are allowed which extend further down or out than the OEM skirts.."

 

I'm just tossing this out there for discussion sake, but I agree with Scott that right now its far too open

Edited October 18, 2008 by Guest

[swhiteh3]

I like to see the Aero rules read something like this:

 

• " *Splitters are allowed, but with a profile, when viewed from above, which does not extend more than 5" forward from the profile of the bumper (also when viewed from above). This forward length is measured parallel with the CL of the car. All splitters must terminate no further rearward than the centerline of the front axles. Air dams may be mounted to the front of splitter.
   
  *Minimum height of splitter is to be 3" from the ground when measured on a flat surface. Wings are allowed up to a width of XX and a height of XX under the top of the roofline as viewed from the side.
   
  *No side skirt extensions are allowed which extend further down or out than the OEM skirts.."

 

I'm just tossing this out there for discussion sake, but I agree with Scott that right now its far too open

Brian and I worked on this phrasing together, and while it certainly has some room for improvement, I agree completely with it, in concept. Exact numbers are negotiable.

[nape]

$5000 - carbon fiber nose, fenders, hood, and decklid = legal

$6000 - Triple adjustable shocks = legal

$3000 - Stoptech brakes = legal

$1000 - belly tray built by a guy in his garage = legal (by my interpretation of your proposed rule.)

$50 - roll of plastic for side skirts = ILLEGAL

 

 

"My splitter does stop at the CL of the front axle, but my belly pan starts there!"

 

Please let someone prove that this stuff works before you legislate rules against it. I think we all have improvements to be made in chassis and driver that will far surpass the amount gained by any of the proposed rule changes.

 

[edit] I'm tired of the rules witch hunts.

 

Oct 2nd, 2007:

 

Please for the love of god can we please not change any rules this year for the sake of continuity and common sense?

 

viewtopic.php?p=115998#p115998

[b_tone]

TJ - my position is that this is a clarification on current rules which are well within the intent of the spirit of the original development of the series. Keep in mind my intent is not change for changes sake, rather closing the loopholes that currently exist within the rules (and have not been exploited yet) are they are written now.

 

To speak about not changing rules until someone proves it's an advantage - I don't think i'll agree with that since I spent 10 months building what was arguably the nicest AI car in the country only to have the readily available rear suspension ruled illegal because it was assumed that it would prove to be an advantage an start the series spiraling into a black hole of slippery slopes rather than reviewing data presented, logical argument concerning geometry advantages/disadvantages and letting the car run to see how it would do in the real world....but that's water under the bridge and I'm not bitter.

 

I do thank you for your interpretation as I'll now add definition to my original post which SW and I talked about but somehow omitted prior to posting.

 

The reason for my side skirts notion is to prevent the cars from deviating from the OEM appearance anymore than they currently do.

[nape]

Bryan, I can live with your 1st proposed rule now, and I would suggest that you use the current 7.4.10 rule for wings and propose a new rule (7.4.14?) to address all the splitter concerns.

 

"7.4.10 - Spoilers and airdams are unrestricted but must be fixed for competition. Rear wings or rear spoilers installed on AI cars must not extend rearward more than 1.5 inches beyond the outline of the rear bumper and may not have an airfoil width not to include endplates or bolts greater than 72 inches."

 

 

Proposed "7.4.14 - Splitters are allowed, but with a profile, when viewed from above, which does not extend more than 5" forward from the profile of the bumper (also when viewed from above). This forward length is measured parallel with the CL of the car. Minimum height of splitter is to be 3" from the ground when measured on a flat surface. All splitters must terminate no further rearward than the centerline of the front axles. Air dams may be mounted to the front of splitter. Underbody panels and devices are not allowed including but not limited to: underbody pans, underwings, tunnels, diffusers etcetera. "

 

However, I think your side skirts rule is a slippery slope basing them on OEM dimensions. I'm not intricately knowledgeable when it comes to Mustang body parts, but how does this car fit into your idea of the rules:

 

http://hyperperformance.smugmug.com/gallery/4715803_LntnW#279107709_Cd7Ae" onclick="window.open(this.href);return false;

 

If we are going to make rules, I would like to see them made easily enforceable. I don't want to see people have to document the height of factory side skirts with pictures just to keep running their current aftermarket skirts.

 

I'll also state that I don't want to see the side skirts rule, because I already have the aluminum angle stock (from Home Depot) and roll plastic in my garage to do it in the off-season. I have a $100 lexan dirt track spoiler, an $80 circle track plastic nose, and $50 worth of roll plastic. That's my aero plan while everyone else builds wingsplittercarnarddiveplane aero packages.

 

Like I've said before, I've come to terms with the fact that this series allows big bucks to be spent, but I've also realized that I can do a lot of things within my means to try to counteract the spending. I would rather see someone show up and kick my ass with a $1000 home-brew CF underbelly pan then show up and run dead last with Motons, but that's just my perception of what the class should be.

 

My mindset is still "No new rules changes!" but if I have to live with them, I'd rather not have them be convoluted.

[b_tone]

Personally I would be ok with that type of body work I am trying to prevent the plastic roll from the rocker to the ground from appearing.

 

For reference my stock 93 Cobra mustang body work is just about 3.5" off the ground at ride height.

[nape]

Deviating from the OEM appearance any more?

 

These pics are from Nationals 2007. Which one is more stock appearing to you?

 

Jay Andrew:

 

 

Mark Luna:

 

 

I'll go on to add that, stock appearing racing is expensive. Look at WC TC for an example. People think that those cars are "stock". Well, under the stockish bodywork, they are very nice, very fast race cars with very few stock parts left.

 

If you want to limit side skirts to a certain height, write the rule that way, but don't mandate stock type parts. It'll cost me $100+ for beat up (heavy) OEM ground effects + prep + paint for something that can be accomplished in an afternoon with some pre-colored plastic and aluminum. The other nice part about plastic? If I tear it up, all I have to do is cut another piece.

 

I did see a few pictures of a very nice stock appearing class last week though:

 

 

They look really stock, but the $10-15k motors really turn off the average person who wants to have a shot at competing on a National level.

[b_tone]

How does stock appearance relate to motor costs, and I am confused how you made the jump to engines?

 

To answer your question, ML's car is more in line with my thought process as it utilizes a splitter/airdam and wing only.

[edhunter]

If splitters are allowed on the front ends that extend back to the front axle centerline, why not make it legal on the rear of the car, from the centerline of the rear axle extending back to a certain length behind the rear of the bumper as viewed from the top... whatever the wing and/or spoiler can extend to? Make it simple, set a minimum ride height, including side skirts, with a rule that there can be no tray between the axle centerlines? I know some over on the CC site are playing with rear diffusors, no idea if they've found any benefit....

 

 

... at least it'd allow a bit of experimentation for those that want to play with it.... Just a thought from someone still in the HPDE ranks with a future goal of taking my AI car into W2W....

 

 

... No, it's not mine, but it's got some sweet aero mods done to it! would love to do something similar with my foxbody, esp with the wider track that's being discussed as well ....

[Jim P.]

I have tried various iterations of aerodynamics and am working on some cooling issues with my current car, but here are examples of what I have tried in the past for "aerodynamic improvements":

 

Classic Lawn Edging:

 

Colored Plastic Airdam w/Home Depot Splitter (cheap and easy to maintain)

 

Fiberglas Airdam made from scratch w/removable bottom section:

 

The firberglass airdam has a disposable bottom section that was easy to make new when off track excursions caused too much damage:

 

-Jim Pantas

www.WildHorsesRacing.com

[King Matt]

Jim, I don't think your name is big enough on the windshield. Isn't there something in the CCR about that?

[firehawkclone]

Respectfully, if you're not capable of, or don't have the time to cut 1" off your splitter to accomodate a simple rule change, then you probably should not be racing in a series like this.

 

Respectfully, This is an AI aero discussion, not AIX!

 

Its back to the school yard once again poking at one's ability's

[nape]

How does stock appearance relate to motor costs, and I am confused how you made the jump to engines?

 

To answer your question, ML's car is more in line with my thought process as it utilizes a splitter/airdam and wing only.

 

My point was that AI was created as an alternative to classes like AS where everything is set in stone and "if the rules don't say you can, then you can't." We all like this playground because it leaves the car as an open canvas and creativity can be rewarded. I like my "skinny little rulebook" as we have it now and don't want to see it change. I think the average AI racer has more to worry about in the off-season then making the bottom of the car flat, I know I do. If they don't, more power to them if they can make the car flat, get the spring rates right, and go faster without wasting their entire career to do it.

 

I'm honestly more worried about people with MM and Griggs SLAs then I am someone with a belly pan. The chassis rules we run by are so wide open and no one has scratched the surface yet.

 

As far as your thought process, I don't agree with it when it comes to getting rid of side skirts. I think the side skirts make it look more like a race car. If you want stock appearing, there are plenty of other sandboxes to play in.