F1000 - Latest Spec - Small Glitch

[Dave Gomberg]

The revised F1000 specification that will appear in the October FasTrack (due out tomorrow, Wednesday, September 20) omits several editorial changes (word-smithing, grammar nits) and two substantive changes due to some confusion over version control. The two substantive changes (which will be part of the final specification in the 2007 GCR) are as follows:

In H.1.D:

7. Venturi tunnel sections are not permitted on the lower surface of the car between the rear of the front tire and the front of the rear tires; the 1 inch variation allowed in the lower surface in paragraph D.6 may not be used to circumvent this restriction.

In H.1.E:

9. The cooling system is unrestricted. Radiators, if housed in or incorporating a cowl air-scoop deflector, shall comply with bodywork rules.


Dave

[Rennie Clayton]

Dave,

What is the means used for verifying the legality of a car with respect to H.1.D.7?


Cheers,
Rennie

[RobLav]

H.1.D.7 is clearly not the same as FC rules. Is this what the CRB / BOD want? This rule, as currently written above, makes illegal almost every FC diffusor I've seen. That 1" rule is used to start the duffusor upward slope just forward of the front of the rear tres.

I think the earlier wording was better Dave.

[Art Smith]

Dave-

thanks for the heads-up on the substantive changes not appearing tomorrow.

I applaud inclusion of the FC cooling system language, H.1.E.9!!

H.1.E.7 in my view is unworkable as written; it's not close to objectively verifiable. venturi tunnel section is not defined. even if the term was defined (in my view not doable!!), it can only lead to utter chaos. can you imagine, or better yet want, tech measuring front and rear ride height of the "flat bottom" to thousand's of an inch as raced or qualified to support verification an imaginary pitch rule (0.0000" delta front to back plus or minus 0.0000") ????? weight jackers would suddenly become required on all four corners and cool down laps would be much slower just like they were during the insane rules period F1 went through........... I'll bet there isn't a car in the country running today that could demostrate compliance with the draft rule as currently written: ie: a flat bottom that's also horizontal

while some may argue I'm on a "dictionary crusade", the rules defining the bottom of the car drive the entire design for cars for this class in my opinion!!! we have to have something better than "anyone/someone (undefined) will know it when they see it".


Art
artesmith@earthlink.net

[R. Pare]

Art, Rob L, Rennie:

Apparently it will be perfectly legal to make the whole bottom shaped as a venturi - as long as you don't have the venturi-shaped restriction "throated" with vertical sides, it then isn't a venturi "tunnel" !

[Rennie Clayton]

Richard, this is why I am asking for clarification of what means will be used to objectively verify legality. If the intent is to use the ground as a reference plane for determining convergent and divergent venturi geometry, this sets a very, very bad precedent for the Club as a whole, not to mention the implications for the class.

Dave, I am not attempting to beat you about the head and shoulders with tirades and accusations of poorly written rules; As a competitor who must abide by this rule, I feel I am well within my rights to request clarification as to how said rule will be objectively verified. If I choose to design, build and campaign a car, I must have a means that I can use to verify that it will be legal. Right now, I don't see such a means.


Cheers,
Rennie

[R. Pare]

Rennie:

I've been squawking about getting a verifiable wording for over ten years now! The rule is way too open to differing interpretations from different Stewards, and as such is a joke.

As you said, the rule can also be easily interpreted to mean that the break for the diffuser cannot start ahead of the leading edge of the rear wheels, making everything in current use illegal. I brought this up originally a few weeks ago, yet they don't seem to catch on, do they!

[Stan Clayton]

Before the black helicopters start circling too closely, Dave told me last week (and reiterated yesterday) that he would be out of town all day today. He should be home this evening, but I would not anticipate any replies from him before then.

Stan

[Rennie Clayton]

I am prepared. Your non-verifiable rules writing process will not invade my brain waves, because I have shielded myself.





Cheers,
Rennie

[Stan Clayton]

We are own all your black helicopters...!

[Art Smith]

what, if anything, is going to be done to improve the "flat bottom" to something where all the terms are defined and the rule is objectively verifiable ??? concern about the F1000 aerodynamics rules is not new or limitted to only me. I can't afford to build a car with a "flat bottom" that isn't horizontal if the rules allow someone to cry "foul" when they suddenly recognize something they don't like and couldn't/wouldn't describe in writing. I also can't afford to build a "rolling stone" with a "flat and horizontal bottom" if others will be allowed to use their elementary school reading and geometry skills to obvious advantage..............

Lee's post to another thread clearly indicates to all that are awake or care that aerodynamics is a huge deal at these horsepower/weight ratios!!!


engines
Horsepower is really not as important as you might think in a bike powered downforce car. Maybe it's because torque remains pretty much the same no matter how much horsepower you can get.
A driver who can use the downforce is going to win, regardless of how much horsepower anyone has. This week one of our DSR's turned times .4sec under the Portland track record, with a motor 25hp less than the record lap.


Art
artesmith@earthlink.net

[Stan Clayton]

Is there a consensus that folks want a flat bottom rule that allows the rear diffuser to extend ahead of the leading edge of the rear tire so long as it doesn't violate the 1" specification?

Stan

[Rennie Clayton]

I, for one, would be happy to have my original question answered.


Cheers,
Rennie

[RobLav]

Stan - yes - absolutely. That would allow us to use the Van Diemen diffusor in conversions.

[Dave Gomberg]

Despite what some of you may have thought, a) we are listening and b) no, I haven't dissapeared from the face of the earth. Particularly for those of you who have been unhappy with D.7 (in any or all of its incarnations), but for all concerned, we'd like your reactions to an alternative. The basic change would be to delete D.7 (and renumber subsequent sub-sections) and to change the allowable deviation in D.6 to one-half inch. This means that D.6 would read as follows:

6. The entrant shall designate a flat rectangular reference area with minimum dimensions of 12 inches by 12 inches. This reference area is located on the lower surface of the chassis (the surface licked by the air stream) between the rear of the front tire and the front of the rear tire. The center of the reference area must be no more than three (3) inches from the longitudinal centerline of the vehicle.

For the full width of the body, between the rear of the front tire and the front of the rear tire, no point on the lower surface of the chassis (the surface licked by the air stream) shall be more than one-half inch (1.27 cm) above the plane determined by the reference area designated by the entrant and on a line perpendicular to that reference plane. No point on the lower surface of the chassis may be below the plane determined by the reference surface on a line perpendicular to that reference plane, except as specifically permitted herein. Compliance with these requirements shall be accomplished by placing a straight edge on the reference surface designated by the entrant and verifying that the requirements are met. A maximum of four (4) three (3) inch by five (5) inch rub blocks are allowed anywhere on the lower surface of the chassis, and may extend below the reference plane.

Dave (donning a fresh flack jacket)

[ianashdown]

Dave,

I have no dog in this race, but I would like to make a suggestion. I like the idea of a defined reference plane, I just don't think what is being proposed is large enough. It will be difficult to project that plane based only on a 12 x 12 area. I would suggest it should be at least 10" wide by as long as possible. All the way back to the 'firewall' perhaps. CART has a similar ref plane and they define 3 points I think and the have a fixture that attaches to those points that defines the referenece plane for inspection purposes. It works quite well.

Ian

[Rennie Clayton]

Dave,

As I understand the current state of affairs, most FC undertrays have diffusors which are 1" deep at the leading edge of the complete rear tire, correct? This rule would render them immediately illegal. Is this an intended consequence? It seems to me that the 1" allowance is still a necessity here.

This flat plane can be oriented any inclination you want, so long as no part other than the 4 rub blocks protrude below it, which assuming you want your engine as low as possible would preclude much in the way of funny business with tilted reference planes.

FWIW Ian, I suggested a 3 point reference plane definition. It got shot down as "too complex". Having working in Champcar for the last two years, I can tell you that there's nothing more convenient than a 30 second undertray verification via fixture.

Cheers,
Rennie

[R. Pare]

While having a 3-point checking system would be nice - I've worked in CART/Champcar off and on for the last 20 years and can attest to the simplicity - the reality is that the club would have to spend a small fortune in equipping every region with the right equipment, plus getting guys to provide those hard points on converted cars would most likely prove to be its own nightmare. CART has it pretty simple, as they are pretty much always all together at the same track at the same time, with a dedicated crew that has ONLY those cars to check. I shudder to think how it would be handled at many regions!

As to the proposed rule change, it really does not address the question that has been asked upwards of 50 times here now : WHAT IS THE DEFINITION OF A VENTURI?

Decreasing the vertical deviation allowance DOES help mitigate the potential for downforce production, but is only meaningful IF the foolish "No Venturies" rule is dropped - you can shape the undersides as a venturi, but will get less downforce if the throat depth is only 1/2" rather than 1.0". If the "No Venturies" rule is kept in, you have accomplished nothing, as no one knows what will be considered a "venturi" any more so than they would have if the deviation was kept at the original 1.0".

As Rennie says, decreasing the allowance to .5" will render just about every converted car illegal unless they make new undertrays that rise only .5" at the leading edge of the rear tires.

And I still see nothing that outlaws spears from the front of the cars!

Horsepower is really not as important as you might think in a bike powered downforce car. Maybe it's because torque remains pretty much the same no matter how much horsepower you can get.
A driver who can use the downforce is going to win, regardless of how much horsepower anyone has. This week one of our DSR's turned times .4sec under the Portland track record, with a motor 25hp less than the record lap.

I always get a good chuckle when quotes like this one pop up - it always makes me wonder if the source ever took a course in physics!

[Dave Gomberg]

Ren:

There is considerable disagreement about just how much existing diffusers are above the reference plane ahead of the rear tire. One could argue that a strict reading of the existing FC rules allows none. But, leaving the FC rule aside, the F1000 rule (as now proposed) would allow up to a one-half inch rise at the front of the rear tire starting anywhere ahead of the front tire.

Dave

[Dave Gomberg]

Richard:

The section (D.7) containing "venturi" would be gone under this proposal.

Dave

[John Mosteller]

I am for deleting D.7 and leaving the 1 inch rule as is so that converted FC's are legal.The whole idea of this class as originaly proposed was for converted FC's and FF's which have always had the 1 inch rule.What is the reason for now wanting to eliminate almost all converted FC's? Although I am interpeting the undefined trem (Venturi tunnel sections) to have to have sides.I don't see a flat bottom with a diffuser as being any kind of tunnel so I have already started my conversion with the diffuser starting ahead of the rear tires and will plead my case with the stewards.IMHO if you delete D.7 then you have a rule that is understandable and easy to check for compliance. If venturi tunnel sections is left in the rule then an exact definition needs to be published.When the no venturi clause was put in the FF rules I made multiple calls to national trying to get a definition and no one was ever able to define that term.The basics that I got from them was you should be ok as long as the bottom of your FF is flat but if one of our stewards sees something they don't like it will probably be seen as a venturi section.I for one don't understand why you want to have undefined gray areas that end up causing controversy.

[sidney]

We have a lot of smart guys reading these posts. Isn't the intent of all this back and forth to limit the development of low pressure air underneath the car between the tires? If that is the case, and the association also wants to make it easy to measure at impound, I'm thinking Lee, Stan, Richard, and all can come up with an acceptable method of doing this. Now that I have thrown this out, I'll go back in my foxhole and cover my head!

I am personally looking for "frickin' laser beams" on the front of my car instead of spears.

[Stan Clayton]

As to the proposed rule change, it really does not address the question that has been asked upwards of 50 times here now : WHAT IS THE DEFINITION OF A VENTURI?

But then in the very next paragraph, Richard writes...

...you can shape the undersides as a venturi, but will get less downforce if the throat depth is only 1/2" rather than 1.0".

I figured that if I kept quiet long enough someone would spill their guts...and sure enough it has happened. Now, what part of a venturi don't you understand, Richard? Please explain to us again...

Can we all get past that now?

[Art Smith]

Dave-

your "alternative D.6 / D.7" post was a sight for very sore eyes. I for one will
do my level best not to soil or damage your new dinner jacket; the Kevlar gold
looks stunning on you!!

given:
1.) the exisiting flat bottom rule
2.) the need to protect expected FC conversions
3.) none of us can successfully outlaw in absolute terms the Physics of ground
effects and/or downforce
4.) the need for an objectively verifiable set of rules

I'd recommend the following changes:
DELETE: D.7. Venturi sections are not permitted on the lower surface of the car
between the rear of the front tire and the front of the rear tire.
DELETE: D.8. Diffusers are permitted behind the front of the rear tires.
ADD: D.6. .......................the reference surface on a line perpendicular to that
plane, except as specifically permitted herein. The rear edge of the
flat bottom shall be a maximum of 2.50" (TBR) above the track as
raced and as qualified. Compliance with these..........

adding a maximum height for the rear of the flat bottom limits the creation of
downforce by controling both the minimum throat and maximum expansion ratio
that can be achieved within the objectively verifiable limits of the flat bottom.
change 2.50" (TBR) to anything you like keeping in mind the higher the limit the
more downforce potential it allows and the lower it's made the more trouble it will
cause members converting exisiting FC cars. higher numbers for the height
of the rear of the flat bottom will drive designers toward higher torsionally stiffness
solutions which ususally benefits enharrant driver protection.


Art
artesmith@earthlink.net

[R. Pare]

Dave:

Losing the "no venturies" rule is great - finally someone seems to understand that it is the height of stupidity to ban an undefined object!

Stan:

And just what is it about the concept of banning an undefined object that is open to massive fluctuations of interpretation that you find to be logical? The question that EVERYONE has to deal with is not whether or not R. Pare knows what a venturi is, but whether or not their local Stewards have a clue, and can actually point to a specific, DEFINED shape that they can then design around.

PS: Since you still don't seem to understand, ANY flat or curved surface on the car undersides with even a HINT of a radius at both ends is technically a venturi, and IN FACT ACTS as a venturi. With that being in actual fact what the bottom of these will have, any steward anywhere could easily protest any car out there.

Art:

As stated before, specifying a maximum height off of the track under all conditions is not workable - those conditions would include cresting sharp rises where the whole car leaves, or practically leaves, the track surface. The max bodywork and rear wing height rules have the same problem - on many tracks, there is most likely NO car that complies with the rule at certain point out on the track surface "as raced or qualified".

[Art Smith]

Richard-

given we already live in a less than perfect world (see exisiting table with its other maximum height rules), in my mind a maximum height limit for the rear of the flat bottom is infinitely preferable to any of the previous verbage with it's total lack of objective verifiability and undefined terms. there are very few places in the world that can make passive measurements of a moving object with respect to the ground with NBS traceable metrology to the accuracy that would be needed for verification of non-compliance of a moving F1000 car.

suggest adding a rule excluding any and all cockpit adjustable means to adjust ride height(s) (ie: wieght jackers) if that is your concern...........................


Art
artesmith@earthlink.net

[Rennie Clayton]

And just what is it about the concept of banning an undefined object that is open to massive fluctuations of interpretation that you find to be logical? The question that EVERYONE has to deal with is not whether or not R. Pare knows what a venturi is, but whether or not their local Stewards have a clue, and can actually point to a specific, DEFINED shape that they can then design around.

PS: Since you still don't seem to understand, ANY flat or curved surface on the car undersides with even a HINT of a radius at both ends is technically a venturi, and IN FACT ACTS as a venturi. With that being in actual fact what the bottom of these will have, any steward anywhere could easily protest any car out there.

BWWWAAAHAHAHAHAHAHHAHA! Seriously dude, you have a short in your sarcasm circuits. You should get a technician to look at that.


Dave,

I agree with Ian that the reference area is too small to extrapolate properly. Here is my recommendation:

6. For the full width of the body, the area of the underbody licked by the airstream (Underbody) between the rear of the front tire and the front of the rear tire shall be designated as a controlled area (Controlled Area).

The entrant shall designate a flat planar reference surface (Reference Surface) located on the Underbody. The Reference Surface shall be a minimum of 10" wide, shall be symmetrical about the longitidunal axis of the car, and shall extend the full length of the Controlled Area.

Within the Controlled Area, no point on the Underbody shall be more than one inch (25.4 mm) above the Reference Surface. No point on the Underbody may extend below the Reference Surface, except as specifically permitted herein. Compliance with these requirements shall be accomplished by placing a 5 foot long straight edge laterally against the Reference Surface and measuring gaps between this straight edge and the Underbody. A maximum of four (4) three (3) inch by five (5) inch rub blocks are allowed anywhere on the Underbody, and may extend below the Reference Surface.

Outside of the Controlled Area, there are no restrictions placed on the Underbody.


Cheers,
Rennie

[RobLav]

1) When are you guys going to realize that Richard is playing with you? He knows you can't easily define a venturi without making rhe entire underbody of almost every car illegal.

The underbody of every single FC with a rear diffusor is acting as a convergent / divergent nozzle, therefore a venturi.

I am a former Navy Main Propulsion Officer on steamship destroyers. We used all kinds of devices which exploited Bernoulli's principles.

It is senseless to even try to define it. Leave it out and regulate the desired effect by the rule wording.

2) It is rather frustrating seeing all this new discussion regarding the flat floor, or the 1" rule, and now the 1/2" rule. We went through this numerous times in our rules committee and we all agreed upon the 1" rule to allow the diffusor from converted cars.

Frankly, I still believe the easiest and best wording would specify the flat floor area from the rear of the front tires through the rear roll hoop bulkhead cross section, and then free aft of that rear bulkhead. That rear section is now determined to be a "bracket" anyway. So we need a flat floor on that "bracket"? You could almost argue that it is no longer a floor - it is just a bracket.

Limiting the "relatively" flat area to remain only between the rear of the front tires and through the rear roll hoop provides a few things:

a) Provides the ability to use the diffusor from converted cars

b) Most people who convert their own cars will probably not have a difficult time fabricating a new diffusor. But we should not force that decision upon them by NOT allowing them to use the stock diffusor because of the lack of the 1" rule wording.

c) Allows the rear structure lower edge "bracket" to more closely align with the motorcycle engine's rear mounts (the swingarm mount), thereby improving structural integrity. The distance between those engine mounts and the bracket floor will be decreased.

d) Provides the ability to further exploit the higher velocity air under the car in what is realistically now a "development" class.

e) It's more fun...


In any case, at a minimum, the FC 1" rule should still still apply to allow use of the current FC diffusor.

Lastly, can we get this done soon, so we can design and build the cars?

Thanks,

Rob

[carnut169]

6. For the full width of the body, the area of the underbody licked by the airstream (Underbody) between the rear of the front tire and the front of the rear tire shall be designated as a controlled area (Controlled Area).

The entrant shall designate a flat planar reference surface (Reference Surface) located on the Underbody. The Reference Surface shall be a minimum of 10" wide, shall be symmetrical about the longitidunal axis of the car, and shall extend the full length of the Controlled Area.

Within the Controlled Area, no point on the Underbody shall be more than one inch (25.4 mm) above the Reference Surface. No point on the Underbody may extend below the Reference Surface, except as specifically permitted herein. Compliance with these requirements shall be accomplished by placing a 5 foot long straight edge laterally against the Reference Surface and measuring gaps between this straight edge and the Underbody. A maximum of four (4) three (3) inch by five (5) inch rub blocks are allowed anywhere on the Underbody, and may extend below the Reference Surface.

Outside of the Controlled Area, there are no restrictions placed on the Underbody.

Wouldn't these rules allow tunnels? Seems like the only place that would have to be flat would be your controlled area & the pods could sweep up.... (but I'm not engineer)

I think this makes sense and would allow the use od the current FC diffusers (please don't make me buy another diffuser!)

6. The entrant shall designate a flat rectangular reference area with minimum dimensions of 12 inches by 12 inches. This reference area is located on the lower surface of the chassis (the surface licked by the air stream) between the rear of the front tire and the front of the rear tire. The center of the reference area must be no more than three (3) inches from the longitudinal centerline of the vehicle.

For the full width of the body, between the rear of the front tire and the front of the rear tire, no point on the lower surface of the chassis (the surface licked by the air stream) shall be more than one inch above the plane determined by the reference area designated by the entrant and on a line perpendicular to that reference plane. No point on the lower surface of the chassis may be below the plane determined by the reference surface on a line perpendicular to that reference plane, except as specifically permitted herein. Compliance with these requirements shall be accomplished by placing a straight edge on the reference surface designated by the entrant and verifying that the requirements are met. A maximum of four (4) three (3) inch by five (5) inch rub blocks are allowed anywhere on the lower surface of the chassis, and may extend below the reference plane.

[Rennie Clayton]

Mr. Laverty,

With regard to your first point, I will refer you back to my original question in the second post of this thread: what is the means used to verify legality of the car with respect to H.1.D.7? That question, and the subsequent removal of "venturi" wording from Dave's response are not coincidences.

The question of underbody rules is unaffected by whether it's a bracket, the chassis, or a block of green cheese. The underbody is defined as the "lower surface of the car licked by the airstream". Period.

I would be very, very leery of making the controlled area any smaller, because of downforce generating ability. These cars are already going to be very fast, and if they're allowed unfettered underbody aerodynamic freedom outside of a small zone between the rear edge of the front tires to the rear rollover hoop bulkhead, they will be dangerously fast. I know y'all don't want to hear it, and there's plenty of dissent and disbelief on this forum about how fast it will make the cars. But trust me: it really will. If you don't believe me, then make your choice, but don't even think about complaining when a newly designed car comes blowing by around the outside of you in the middle of a corner. If I thought such a car would be safely crashable with the current chassis rules, I would design, build and drive one myself to prove it to you.

For what it's worth, Lee Stohr was equally incredulous and ridiculed the idea of putting tunnels on his DSR's, because they "don't have the torque to pull that much drag." Stan and I kept on hammering the point home to Lee that tunnels would be remarkably effective, and I think we all know where that went.


Sean,

Wouldn't these rules allow tunnels? Seems like the only place that would have to be flat would be your controlled area & the pods could sweep up....

Not to be obtuse, but... uh, yeah. That's exactly what it means. That's exactly what the rules you posted mean, as well. In fact, the only material difference (other than munged wording from the Department of Redundancy Department in what Dave posted), is that my proposed rule expands the reference surface size requirement. Because having a 12" x 12" area at the front of the car makes it really tough to get an accurate measurement reference to something that's 8 feet away at the rear of the car. Otherwise, there's no difference between the two, so your question / comment applies equally to your own rule proposal.


Cheers,
Rennie

[R. Pare]

1) When are you guys going to realize that Richard is playing with you? He knows you can't easily define a venturi without making the entire underbody of almost every car illegal.

The underbody of every single FC with a rear diffusor is acting as a convergent / divergent nozzle, therefore a venturi.

I am a former Navy Main Propulsion Officer on steamship destroyers. We used all kinds of devices which exploited Bernoulli's principles.

It is senseless to even try to define it. Leave it out and regulate the desired effect by the rule wording.

Nice to see that someone else with real world experience and a decent education in this area sees the obvious that others here are so willingly turning a blind eye to!

2) It is rather frustrating seeing all this new discussion regarding the flat floor, or the 1" rule, and now the 1/2" rule. We went through this numerous times in our rules committee and we all agreed upon the 1" rule to allow the diffusor from converted cars.

In any case, at a minimum, the FC 1" rule should still still apply to allow use of the current FC diffusor.

Lastly, can we get this done soon, so we can design and build the cars?

Thanks,

Rob

Rob: You are correct. If the diffuser rule is changed to just state that "rear diffusers are allowed" ( dropping the original "behind the leading edge of the rear tires" caveat), then that, coupled with the elimination of the "no venturies" rule will keep all current FC diffusers legal, as long as the 1" deviation allowance is kept intact. This is pretty much what the FC rules state, so there really shouldn't be any interpretation issues, and is exactly what I have been pushing for wording for over 6 months now.

And you are correct : No one here can provide a measureable definition of what an illegal diffuser shape is without making every current car illegal, and has been repeatedly stated by myself and others quite a few times. The only way out of this mess is to define what can and cannot be done with shaping the undersides in a manner that circumvents the effectiveness of any venturi sections that one might try to incorporate, and I've posted what I think are reletively simple means to that end at least twice so far since the first version of the rules was published.

Rennie is right : the current rules will allow undersides shaping that will create enough downforce to make these cars blindingly fast, IF someone decides to make use of what is allowed, never mind the drag reductions that can be used with the wide bodywork allowance.

You really don't want to go there if the idea is to keep this class "reletively" inexpensive and within decent margins of what most tube frames can stand for stress levels.

[carnut169]

Not to be obtuse, but... uh, yeah. That's exactly what it means. That's exactly what the rules you posted mean, as well. In fact, the only material difference (other than munged wording from the Department of Redundancy Department in what Dave posted), is that my proposed rule expands the reference surface size requirement. Because having a 12" x 12" area at the front of the car makes it really tough to get an accurate measurement reference to something that's 8 feet away at the rear of the car. Otherwise, there's no difference between the two, so your question / comment applies equally to your own rule proposal.


Cheers,
Rennie

Hard for you to be obtuse, even when answering one of my questions which almost force uh...obtusity.
but bear with me...
Wouldn't this part rule out tunnels?
For the full width of the body, between the rear of the front tire and the front of the rear tire, no point on the lower surface of the chassis (the surface licked by the air stream) shall be more than one inch above the plane determined by the reference area

[Rennie Clayton]

Sean,

No, it most certainly doesn't rule out tunnels. They'd have to be very shallow tunnels, but as long as you were within the allowable reference measurements, you can do whatever you want. Outside of that controlled area, you can do whatever you want of course since you're permitted to have bodywork, and there are no regulations controlling its geometry.

I.e., outside of the controlled area which is the full width of the body, between the rear of the front tire and the front of the rear tire, the underbody can sweep up and do whatever. Make sense?


Cheers,
Rennie

[carnut169]

I'd be ok with allowing 1" deep tunnels as I doubt they would be very effective. I think what you might see more of is the current style FC diffusers... the up-sweep would begin just ahead of the rear tires. I'm also ok w/ allowing open aero outside (before and behind) the tires.

[RobLav]

I'm fine with that too Sean.

[Art Smith]

Guys-

the conversation and rules have to be moved beyond undefined term(s) to either terms that are defined AND objectively verifiable OR other objectively verifiable constraints that achieve pragmaticly the objective(s) of the committe/membership. either define tunnels in an objectively verifiable manner or drop the word from the discussion. it's continued use is blocking progress on the central problem; ie: the current rules include undefined terms and are not close to being objectively verifiable.

the Physics of ground effects / downforce can not be edicted illegal in absolute terms; all cars run in ground effect to a greater or lesser amount without regard to the shape of the bottom!! therefore after finally recognizing/accepting that, the only viable choice left is to limit / control the amount that can be achieved with the current state-of-the-art. controll the height of the rear of the current plus 1.00" / minus 0.00" flat bottom and the amount of downforce that can be generated is controlled in two ways: 1.) it establishes an absolute maximum objectively veriable expansion ratio that can be achieved between the rear of the front tires and the front of the rear tires (look at Bernoulli's equation carefuly for sub-sonic flow); 2.) the"zero" ground clearance to achieve the maximum expansion ratio in item 1 above is increased by suspension travel there-by further reducing the achievable expansion ratio. continue to use Richard's method of objectively verifing the bottom is flat; add a rule that establishes a maximum height of the flat bottom at its rear; delete all current references in the rules to tunnels, venturis, and diffusers and you're got something that works and achieves your stated goal of limitting ground effects.

I would also like to echo Rennie's concerns about opening pandora's box at the eleventh hour. it's my sense with a +1.00 / -0.00 flat bottom whose height is limitted in the rear the cars will be best-on-best on the ragged edge safety wise for tube frames. keep in mind both explicit and implicit safety requirements found in older class rules were not included for F1000...........................


Art
artesmith@earthlink.net

[R. Pare]

I'd be ok with allowing 1" deep tunnels as I doubt they would be very effective.

Sean, tunnels of even only 1" deep are extremely effective, especially when you understand that the throat(s) can be restricted in the horizontal plane as well as the traditional vertical. Remember also that the incoming air does not have to come from the leading edge of the sidepod undersides, nor decellerate and/or exit solely thru the rear diffuser.

I'm also ok w/ allowing open aero outside (before and behind) the tires.

Not really sure if you want to specify that or not. While it will create all sorts of fun things to do, the performance increases via tire lift and drag reduction that can be had are far beyond what you want to see if part of the objective is to keep costs somewhat in control.

........in my mind a maximum height limit for the rear of the flat bottom is infinitely preferable to any of the previous verbage with it's total lack of objective verifiability and undefined terms. there are very few places in the world that can make passive measurements of a moving object with respect to the ground with NBS traceable metrology to the accuracy that would be needed for verification of non-compliance of a moving F1000 car.

Art: For our purposes, verifying that the car has risen to a point beyond the legal height limit is extremely easy with a decent digital camera and a grid pattern (this is done a LOT all over the world in different arenas of scientific study)- after all, you only have to show that it has risen beyond the allowed vertical height plane, while it is not necessary to verify scientifically that it was at a specific measurement.

And I still see no means for outlawing spears from the front of the cars!

[Art Smith]

Richard-

quality digital photography and radar enforcement of speed laws suffer from the same challange: cosine uncertainty. getting the focal plane of the camera normal to the dimension being "measured" at the correct time and location(s) on the track sounds like a "fetch-a-rock" task to me. don't get me wrong, my Nikon gets used for any number of remote sensing assignments on both test days and race days.


Art
artesmith@earthlink.net

[R. Pare]

Art:

'tis true that those factors are important if you are trying to measure the difference between 5.0" and 5.1", and any protest claims where that sort of resolution is required would be easy to squash. However, the difference between 5.0" and 7.5" is a piece of cake.

But, the mechanics of the dynamic measurement problems inherent are not what is important nor being argued about here : it is the imposition of a performance (measurement) spec that cannot be measured under the dynamic conditions actually specified as to when the car has to be compliant.

As with the max bodywork and rear wing height rule, and others, it is rediculous to impose a dynamic specification rule wherein it is a known and accepted fact that the cars can/will easily be non-compliant in a dynamic state out on the track, therefore my opposition to the words "as qualified and raced" - these words impose a dynamic compliance issue that cannot be adhered to, nor even be accurately predicted ahead of time and compensated for under all possible conditions.

This would be like imposing a maximum rotor diameter as raced (which means out on the track at all temperatures and rpms), yet allowing the measurement to be done at rest with the rotors cold rather than under the conditions specified by the rule.

I think we can agree that the rotors, while at the maximum allowed diameter at rest and cold, most assuredly will not be compliant under the conditions stated in the rule.

And neither will a diffuser measured at rest at the max allowed height when it is cresting a sharp rise at speed - exactly the measurement conditions imposed by the rule wording!

Something about wording a rule that way should make no sense at all to even the most technically illiterate!!

[Rennie Clayton]

Art & Richard,

You guys keep on keeping on with the mental masturbation vis a vis measuring the car whilst it is in motion. Let me know when the stewards start trying to enforce the rule that way. Until that day comes, I will be content to have the stewards direct me straight from the track to impound after each session to check the car... wait for it... as raced or qualified.




Dave,

Any thoughts or response to the concrete feedback you've read in this thread?


Cheers,
Rennie