Floor thickness....
Richard,
Interesting point.....I need to ponder that for a while....
I also was under the impression of the rule being "shadow +1"...but I understand if all the conversions wouldn't meet it that it needed to be changed.
Matt Conrad
Phoenix Race Cars, Inc.
I'll bet if someone tries to argue that the top surface of a floor is bodywork they will loose that fight.
I do believe that we should mandate a min pod thickness which would clear up the problem above plus keep someone from building a sidepod with a "wing" off the top that extended the pod to 145cm and the floor going full width 150cm.... like this---> ].
All this aside, remember a certain Swift that was neck & neck with one of the most devoloped cars in the country for Runoffs pole. No huge floor, no big pods. In fact, just the opposite- a aerodynamic "skinny" car. Perhaps the large floor is not the end-all be-all.
Sean O'Connell
1996 RF96 FC
1996 RF96 FB
2004 Mygale SJ04 Zetec
You are correct in that assumption, as the floor has it's own specific definition in the glossary that pretty much precludes it from being also defined as bodywork.Originally Posted by carnut169
However, the floor is not what was being discussed!
Interesting thought....
Sean,
Good point on the Swift....I've seen one of those cars smoke everyone....including any newer VD or Tatuus. The car was driven by a very talented driver and the car preperation was meticulous, but so were some of the newer cars.
....and just for fun, what if we built a 10" thick floor...is it floor....or is it bodywork?
Matt Conrad
Phoenix Race Cars, Inc.
RE: Floor Width
I spent a fair amount of time looking down at this certain car and the additional floor in front of the side pod leading edge is less than five inches. The safety tape was to alert attendees who aren't normally around these kinds of cars, as the black carpet and black floor really blended in, especially for those stepping in close to peer into the cockpit. The tape was added to the carpet after a car had a front end plate cracked in the SCCA booth on day 1. Kind of like a big auto show -- many of the display cars are scratched, dented, and generally abused inside and out. And it's a shame.
Craig Vogeley
>>
Not a serious issue....unless someone gets hurt.....but pictures of a certain car from PRI also showed another problem with the floor jutting way out....people tripping or stepping on it....I noticed "Safety Tape" on the carpet around the front edge of the floor of the car where it protrudes fairly significantly.
<<
Umm, you'd sell fewer cars? :-).
Sorry. Couldn't resist.
Racer Russ
Palm Coast, FL
Matt:
Only the portion that is to the ouside of the frame (in the case of a formula car) and is licked by the airstream would be considered bodywork.
"Floor Pan - The sections of the car normally used as a supporting platform for seats and to physically separate the interior (cockpit) area from the undersides of the car."
So, according to the official definition, the floor has to satisfy two criteria to be a "floor" - it has to be a supporting platform for the seats, [i]and[i] also serve to separate the cockpit interior from the undersides.
This then would mean that if your car had a pan attached to the bottom of the frame that the seat sat on, and it stuck out past the framerails to support the radiators, etc., that portion sticking out has to be called something else besides "floor" - the portion sticking out past the frame satisfies neither criteria.
If the underside surface of the extension is at or below the official "floor", then at a minimum that surface cannot be considered bodywork; however, if that lower surface has been jogged up to be above the floor, then it IS body as per the definition. In any case, the upper surface, as long as it is above the floor (and licked by the airstream), is officially "bodywork" as per the glossary definition:
" Body - All parts of the car licked by the airstream and situated above the bellypan/floor, with the exception of the rollbar and cage. ........."
This definition needs rewording a bit - by this definition, even the suspension, wings, etc., is "body" !!!!!!!
Rules ????????
The more I read these rules the less I understand what I am reading.
It is one thing to put words on paper. At some point it is necessary to put pencil to paper and draw something.
I have put pencil to paper and I am confused.
1-- Is the maximum diffuser width the distance between the outer most vertical sides of the diffuser/tunnel? Does this exclude and drop in between the two outer edges? Is this measured at the exit or at any point behind the leading edge of the rear tires? I assume that there can be no change in the surface of the undertray forward of the leading edge of the rear tires that connects or is a extension of the shapes that develop behind the leading edge of the rear tire. How is this going to be measured in a protest?
2-- I understand the 50mm rule about the undertray extending beyond the side pod. What I don't understand is what part of the side pod? Is it sufficient that I have the side pod cover the top of the undertray or is the rule meaningless because the top of the undertray is body work if it is above the floor pan under the frame?
I understand the side pod rule to require what Sean's car is. The undertray can only be 50mm wider than it is because the side pods are the width they are. The way this rule is written, Sean can use any width for the undertray out to the maximum. What did the rule writers want? What is the 50mm restriction about without some minimum height to measure from? Will the fairing around the rear tire be called a part of the side pod or can I extend a small wing from some place on the side of the car and have it extend on both sides to within 50mm of the width of the side pod?
I guess that this is the open rules that everyone wanted. What scares me is the potential land mines that have been laid in the rules with poorly defined restrictions.
A lot of the restrictions in the rules have their origins in a sense that the restriction would make the cars safer. Will we be safe from the lawyers when they smell blood on the track and some "expert" says that one of the cars involved did not follow "established best practices"? There are a few features that are allowed in F1000 that would not fly in any other SCCA class.
How about some help from the experts? Lee? Stan?
I think the issue here again (like the venturi) is - What is the definition of a diffuser?
A better set of rules is to set the max width of any body or undertray panels aft of the leading edge of the front tire and be done with the fuss.
The question(s) that Steve is trying to ask is:
What exactly does the "width of the diffuser" pertain to? Is it the total of the panel within which the "diffuser" is contained, or the "diffuser" itself only? Are we talking only about the overall maximum width of its rear opening (as described by the 2 vertical walls), not including any horizontal sections that stick out farther or the thickness of those vertical walls?
If the opening is split into 2 (or more) separate openings, is the maximum width allowed the aggragate of the widths of those openings? If it is split into 2 openings, is it still a diffuser, ot the aft end of a "venturi tunnel" as historical use of the term would tell us?
What exactly is the "start" of the diffuser? What defines the "start"? We are allowed a 1" variance of the underbody between the edges of the tires. If we make full use of that variance, and start a sweep up of the undersides so as to form a traditional "venturi tunnel" that breaks somewhere forward of the front of the rear tire, is that upward sloping roof of each tunnel ahead of the tire considered part of the "diffuser"?
If whatever we have for a vertically-increasing-section, 3-sided channel considered to be a "diffuser" as soon as it reaches the plane of the front of the rear tires? If so, is it permissable to start it at that 1" height maximum?
There are good reasons for these questions: The history of the nomenclature used in other classes around the world has it that the term "diffuser" did not come into being until cars were not allowed to use "tunnels" any more - ie, "flat bottomed ground effects" cars - and did not pertain to the aft end of traditional "tunnels", even though they perform basicly the same function.
Steve and Richard,
The rules, I believe are:
1) The total width of the diffuser is not to exceed 95 cm. That means no part of the body work shall exceed 95 cm width behind the front of the rear tires. That includes all vertical and horizontal surfaces. This is the current FC spec. I can explain the reasoning as to why for this rule if you want.
2) The 1 inch deviation rule has always been intended to allow for wear and tear and imperfections in manufacturing, and rub strips. The rule is not intended to allow for designs which curve the underside of the car or intentionally start the upward deviatoin in front of the rear wheels. Again this is in keeping with current FC specs and the broad interpretation of the 1 inch deviation rule.
3) The maximum floor width is intended to not allow a floor to protrude laterally from the body work in a dangerous fashion. The rule is intended to limit the extension beyond the vertical projection of the body work to a flat surface at the floor. It should be interpreted to read as a maximum 1 inch width extension beyond the projection at that point of the extension although the extension may exceed 1 inch at other points of the projection. I would interpret this rule to not allow horizontal elements which serve no purpose other than to widen the floor as this presents a saftey violation.
Perhaps Stan will agree or sanction what I have written, but I believe these are the rules and there intended purpose.
-Rick Silver
Thanks Richard for clarifying my question.
For me the question I want answered is: When I place a streight edge against the bottom surface of the car that is aligned with the leading edge of the rear tire, what is legal and what is not?
If this comes up in a protest and it is not settled before hand, this will be decided by an appeals comittee of Stewards with or with out input from the comp. board as they choose. Do we want rules settled that way?
- Does that streight edge have to be on the reference plane?
- If the edge is on the reference plane and no part of the under tray is more than one inch above that edge/plane is this sufficient to be legal?
- If the edge is not on the reference plane but the sum of the deviation from the bottom surface of the undertray to the edge and then to the reference plane the reference plane (perpendicular to the reference plane) never exceeds 1 inch is the car legal?
- Is there some characteristic about the shape of undertray when it deviates from the reference plane along the streight edge that is aligned with the leading edge of the rear tires, that would make it illegal?
Rick:
I understand the rule to reference the diffuser exit only. The undertray may be 150cm wide
and may extend rearward of the rear axle by 80cm. Abviously it will have to be contoured around the rear tire. My interpertation is the distance between the vertical sides of the diffuser measured 1 inch above the reference plane may not exceed 95cm. I don't see your interpertation.
To your second point. I buy the intention of the rule. Your FC was built to a 1cm rule. That is tight enough to keep every body honest. But this rule is 1 inch. My question that has not been addressed is: what will make the underside of the car illegal even though it is in compliance with the 1 inch deviation rule?
This issue is not trivial. There are several ways to shape the bottom and meet the rule while gaining down force, shifting the aerodynamic center of pressure forward, and reducing drag.
Steve, I know what I would do.
Let me admit up front that I don't know what I'm talking about. I'm just an internet forum contributor sitting at a keyboard. :-).
Please tell me why you don't:
1) Decide what you want to do to make your car perform best within the published rules.
2) If you're worried about legality, contact SCCA. There is a formal process offered for this, right?
3) Take the following into consideration before making a decision: How much benefit is there? What is your confidence level for defending it's legality? What is the risk of losing a protest? Is the benefit worth the risk?
If the benefit is worth the risk, do it. If not, don't.
Over simplified?
I'd think other benefits to the approach above is that you may get a competitive advantage, and you may learn what isn't legal and can look for it on others' designs to make sure they don't get an unfair advantage.
Racer Russ
Palm Coast, FL
My Take
Now that the rules are in the GCR and I've had a chance to digest the posts here and re-read the rules for the 100th time, here's my interpretation:
1. The maximum diffuser width behind the front of the rear tires is 95cm....total.
2. The diffuser cannot start before the front of the rear tires.
3. There is an allowable deviation for the floor of 1" above the reference plane.
4. No part of the floor can be below the reference plane.
5. The reference plane must be 30cm x 30cm and no more than 75mm from the center line of the car.
6. The maximum floor width is 150cm...or no more than 50mm wider than the max width of the bodywork.
This is essentially limiting everyone to a flat bottom between the rear of the front tires and the front of the rear tires....but with a 1" deviation allowed above the reference plane (the lowest allowed portion of the underbody).
My take on this is that the intent was not to make the floor a 100% flat bottom or they would have written that the floor between the rear of the front tires and the front of the rear tires shall remain flat with no more than a 1cm deviation (for error, wear, etc.)
Am I all wet?
Matt Conrad
Phoenix Race Cars, Inc.
Rick (and Steve and Richard and others...),
While I agree with your analysis as regards FC, I think it is does not translate directly to F-1000. In any event, I would be interested to read your reasoning. My own thoughts run along the following lines after re-reading the relevant sections of the 2007 GCR.
The FC section, 9.1.1.B.1.b., last sentence of the 3rd paragraph (p.171) reads, "Diffuser undertrays are permitted." with no further elaboration. However, when I refer to the table of dimensions I note "J. Maximum body width behind front wheels" listed as 95 cm. Therefore, I and everyone else conclude that nothing except suspension components may reside outside that 95 cm, including the diffuser and any flat lateral elements to them.
When I look at the F-1000 section, 9.1.1.H.1.C.6., (p.221) it reads, "A diffuser is permitted behind the front of the rear tires. The maximum width of the diffuser is 95cm." So, what is the diffuser? From posts above I conclude that FC guys consider that it is all undertray elements aft of the leading edge of the rear tires.
The GCR doesn't define a diffuser, but Simon McBeath offers a good working definition in his book Competition Car Downforce, "The divergent section of a duct which slows down an airflow. On a competition car it is the upswept panel or panels at the rear of the underbody, or at the rear of tunnels." The key word is "upswept". If it isn't upswept it isn't a diffuser, it's simply the flat bottom.
Furthermore, the F-1000 table of dimensions (p. 223) clearly states that the "J. Maximum width of body and lower surface of the car behind the front wheels" is 150 cm. The table also clearly limits the diffuser to 95 cm (see the last line of the table). Flat (not upswept) lateral extensions to the diffuser are clearly the "lower surface" of the car and appear to meet the definition of item J of the table, so may be 150 cm wide. (Whether one can fit a 150 cm wide undertray between tires that cannot themselves exceed 185 cm O.D. is irrelevant.)
Turning this issue around, given item J, if a builder decided not to use a rear diffuser and instead simply extended the flat undertray all the way to the back of the car with no diffuser section - no "upswept" part, as it were - what would be the max permitted width of that portion of the undertray? Referring to item J, I would have to say 150cm.
Therefore, I conclude that no part of the diffuser itself may exceed 95 cm wide, but that flat lateral extensions of them are permitted to be a max width of 150 cm.
Stan
Stan Clayton
Stohr Cars
Stan-
reasonable positions for the special case of the flat bottom also being level.........
that said, the more important general case of the flat bottom not being level in not addressed. flat and level are two different words. wheather it's chassis set-up or an inclined flat bottom compliant with the rules as written, sooner or later what constitutes the beginning of the undefined term "diffuser" will have to be addressed!
the inverse of:
"If it isn't upswept it isn't a diffuser, it's simply the flat bottom" (ie: if it's upswept, it's a diffuser) is unworkable. the inverse would require flat AND absolutely level bottoms................. a flat bottom that would center the bubble on the Starrett levels most of us use for chassis set-up would be a "freak happening". running the front of a flat bottom cars up to avoid being found non-compliant is just plain dangerous!!
Art
artesmith@earthlink.net
Art, the reference plane does not need to be level. Just mount a laser flat to the reference surface and scan the laser making perpendicular measurements and ensure the one inch deviationis maintained.
The question of a 1 inch deviation allowing design to that deviation versus the historic interpretation of wear and tear/manufacturing errors to 1 inch needs resolution. The literal words allow up to 1 inch, but the same is true for current FC and there has been a historic interpretation, more specically clarified by the pro series rules.
The 150 cm versus 95 cm max width behind the tires rule is also I think a rule which needs clarification.
Now is the time to get the rules and their interpretation correct. It is my opinion that the current literal reading and posts above regarding a few of the rules is somewhat at oddds with their intent. I will attempt to have some clarification on these points very quickly.
-Rick
Stan:
I think your interpertation is correct. The diffuser is that portion which rises up towards the rear and is bounded by 2 vertical sides. The undertray , that portion of the car that is an extension of the reference plane and within 1 inch of that plane, is limited to 150 cm maximum width and may extend to 80cm behind the rear axle.
The next question is where do we measure the diffuser. In a properly designed diffuser, the walls are not parallel but are curved from the outside to the toward the center. The ideal shape is similar to the water traces left after you race in the rain on a muddy track. Road Atlanta is the best.
When ChampCar and Indy car talk about diffusers they talk about the exit being limited. Bend down and measure the distance between the two vertical sides. This allows for a radiused edge. My suggestion was 1 inch above the reference plane if there was any problem with radiuses. Ideally the sides of the difusser curve outward from the center line and going forward from the exit in plan view.
How you start the diffuser is important. The edge or side of the diffuser wants to be tangent to the departure or brake line for the diffuser. All this shaping is well within the 1 inch of the reference plane of the undertray. This leads to my other question of about what would make the undertray illegal even though the shapping did not even get close to the 1 inch limit.
To me the 1 inch rule is that if you measure up from the reference plane and every thing is within one inch, you are in. Exceed 1 inch and you are out. Then you as a competitor decide how close to the limit you want to play.
If the 1 inch rule is more restrictive than this, then spell it out clearly.
Matt;
I take it you don't agree with the above statement about the undertray width behind the lfont of the rear tire?
Russ;
I see that we are squabbling over 100 lbs potential down force. If done right it is 100 lbs of very low drag down force. With all other things being equal and I have 100 lbs more down force than you do you will be well and truley beat. If this down force is available in the rules then I can not be without it. This is the name of the game -- maximize your performance within the rules. I have 39 years of dealing with SCCA rules and rule makers. The process is not as simple and streight forward as it seems even when it gets to the printed page.
Except that the 1" restricted area applies only to the undertray ahead of the front edge of the rear tyres, and has no legal basis for establishing what is / isn't a diffusor aft of that line. There have been a couple of examples proferred that refer to a flat lateral extension off the side of the diffusor as somehow being a part of the "flat bottom" area, but the rules explicitly state that the controlled area ends at the front edge of the rear tyres. Outside of that area, presumably you can do whatever you want.
Why not simply make the maximum width of all bodywork aft of the front edge of the rear tyre 95cm?
Cheers,
Rennie
Diffuser Width
Steve,
My post was after Stan's very interesting postulation as to what constitutes a "diffuser" and I was only stating how I interpreted the rules....not whether I agreed with them or not. Our diffuser design is aggressive in this area (but very easily altered) so it's not a big deal, but having a clarification now might save some dremel use later.
Historically I believe that the rear diffusers on the FC cars were 95cm....in total. It's easy to find out....ask around to a few of the people making them and I think they'll all tell you that the entire unit behind the front tires was less than 95cm. Maybe they'll even respond here....
Like Rennie states.....The new rules say nothing about the max width of the floors "behind the front of the rear tires"....the 150cm floor dimensions are specifically stated as "between the rear of the front tires and the front of the rear tires". The only place where it specifies any dimensions behind the front of the rear tires is when it specifies the diffuser dimensions of 95cm.
So.....based on Stan's well thought out post I would assume the diffuser to be only that portion which rises from the level of the floor. But based on past interpretation of the diffuser rule I would say the diffuser is what is behind the front of the rear tires.
Matt Conrad
Phoenix Race Cars, Inc.
I understand your point, Art, but there is no reference in the rules to the bottom needing to be "level". Furthermore, I doubt there is any consensus of what "level" means. OTOH, the rules do specify that the bottom may not extend below the reference plane by any amount, nor above it by more than 1", between the front and rear tires.
The plain language reading of the rules as written appear quite clear to me, but it seems that some ambiguities may still exist in some minds. Therefore, I would request that those who feel the rules mean something different - or who wish for them to read differently - write the CRB with your thoughts.
Regards, Stan
Stan Clayton
Stohr Cars
I interpreted the diffuser issue the same way Stan did.
However, the other issue that Steve brought up is the 1" deviation rule between the tires. I now interpret that as being the underside is free as long as it meets that 1" rule - and not an assumed historic interpretation - like Rick S pointed out for FC. An historic interpretation does not exist for F1000.
My comments above were not meant to be an interpretation of the rules as they are written. I think you guys are interpreting the written word correctly. As someone on the formula car advisory committee which submitted the final wording to the comp board, I think that the literal interpretation here, at least for some, may not be the rule that was intended.
The 95 cm diffuser in many peoples mind meant max width, same as FC. But with the wording 150 cm behind the rear of the front tire, that kind of negates that interpretation. In writing the rules if one did not see the new 150 cm wording, then 95 cm max diffuser width meant total maximum width. I personally favor the 95 cm max total width as it keeps converted FC and FFs competitive. A 150 cm wide undertray with only a 95 cm upswepted area shaped to the wheels will generate huge down force over the 95 cm max width.
The 1 inch rule was intended, I believe, to allow for wear and tear and manufacturing tolerances, not to allow a designed, curved underside. I thought this was intended to be a flat bottom class. The F1000 wording is the same as the FC wording which uses a max deviation and not the words flat bottom. Allowing 1 inch design curvature could substantially change car performance and increase development costs.
I have always been under the impression that this class was founded on the premise of both converting older cars and building newer cars. The clarrification of these rules will have a substantial effect on the competitiveness of converted cars and total car cost. Never the less, the rules should be clarrified to reflect the intent, not simply interpreted due to oversight. Now is the time to get the rules clear and correct.
-Rick
Stan:
I agree to a point with your 95 & 150 cm interpretation. Thereare, however, still a couple of things that need to be clarified:
1: A logical interpretation of the 95 cm diffuser width would be that it means only the actual opening, and does not include the thickness of the vertical side walls.
2: If that is determined to be the case, can the diffuser be split into two 47.5cm wide openings that are separated by a whatever-wide dropped section in between? In this scenario, the actual diffuser sections when combined are still only 95cm wide, as allowed, but the overall width is greater than 95cm. I'm not sure what, if any, aero benefit there would be to this arrangement, but the logic behind this interpretation is still valid, as only the actual "diffuser" opening(s) are 95cm in total wide.
3: If the car is constructed such that the "floorpan" (which defines the vertical plane above which "bodywork" starts) is some distance above the reference surface, and also above the horizontal surfaces sticking out past the 95cm width of the diffuser, are those horizontal surfaces to be controlled by the 150cm width or the max overall car width? If they are to be controlled by the 150cm max "body" width, the official definition of "body" needs to be changed - that definition absolutely precludes them from being called "bodywork". For the horizontal sections between the front and rear tires, this question is moot, as in that area their width is controlled by the "undersides" rule. However, everything behind the front of the rear tire is not covered by that rule, nor is any lower surface that is in front of the trailing edge of the front tire!
4: What determines the "start" of a diffuser? Is it to be defined as a "break" from the plane of the surface immediately forward of that "break"? If so, that does not preclude it starting 1" above the reference surface as some would believe. Or is the definition of a "diffuser" going to be the complete panel within which it is formed? If so, then that panel can be only 95cm wide in total, not the 150cm dimension - you can't have two conflicting definitions for the same feature.
If the desire is to force the builders to "start" the upsweep of a diffuser at the front of the rear tires (as a maximum forward location) much in the manner of the majority of current FC cars, you need to state that the lower surface immediately ahead of the front of the rear tires has to be located vertically at, and parallel to, the reference surface. That will not, however, preclude the use of 1" deep "tunnels" sweeping up and forward of that point.
As an aside, but very relevant as to "why" we ask these questions: Any use of the "history" of the FC rules to determine the meanings of the F1000 rules is a bit disingenuous - the use of the FC history of mandated stressed floorpans and crushable structures was ruled out in those discussions as being "irrellevant as F1000 is a new class and therefore has no history" !
Since that was the stance taken by the senior CRB member here on this board, the only possible conclusion is that if there is to be consistancy in the use or non-use of historical thought processes and definitions, then F1000 is a clean sheet of paper with no history at all. As such, these items need addressing so as to establish what will in the future be F1000's "history".
Actually, according to the Glossary definition of "body", suspension and tire are included in the definition!
Think we can finally get that fixed??
Not so. Many of us cut our teeth on these rules way before there were official definitions of thing like bodywork, and always thought of the panel within which the diffuser was formed as being subject to the bodywork width rules, but that a "diffuser" was only a distinct shaping that was included in that panel - ie - the panel in total while being generally called a diffuser is in fact not the definition of a diffuser.
Oops - missed the "undersides" caveat in J. - Ignore my previous post of the width control behind the rear wheels!
Matt;
When I wrote my post I had looked at the description following the diagram; "maximum width of the body and lower surface of the car behind the front wheels ... 150 cm".
The written rule states: "The maximum permitted width of the bodywork is 150 cm." The next sentence says: "The width of the entire lower surface of the car between the rear of the front tires and the front of the rear tires shall not exceed the maximum width width of the bodywork by more than 50mm and shall not exceed 150cm." This is consistant with the diagram and table.
The rules makers dropped any reference to a minimum height of the body work. Further more that sentence only referrs to the lower surface. I would say that as long as the body work covers the lower surface, you can make the body work and the lower surface 150 cm wide and extend 80 cm behind the rear axle.
That's how I read it too Steve.
I have raised these arguments because it is now time to start building something that meets the rules. For me, I wish we had stayed with the FC rules.
We have clarified the following:
We still have yet to address the following:
- The body width and undertray width is 150 cm maximum to the end of the car.
- That which slopes upwards behind the front of the rear tire is the diffuser and can only be 95 cm wide.
- As long as the body covers the lower surface of the car between the tires any shape is fine.
Rick: FYI DW's diffuser starts 1" before the front of the rear tire. The car might not make the 1cm rule but it will certainly make the 1 inch rule. Now that the pro series is using SCCA rules you will see this rule being streached.
- What would cause a to be illegal even though the entire bottom surface between the tires is within 1 inch of the reference plane?
- How and where will we measure the diffuser for 95 cm.
Last edited by S Lathrop; 01.12.07 at 10:28 AM.
Steve,
In your first #2 above, did you mean 95 cm wide?
Is what I want to do under the car legal? I still see that it is until the rules get clarified.
I disagree. IMO any curving of the walls, bulges or other design elements which result in the width of the "air space" within the diffuser walls to exceed 95 cm at any point within the diffuser would not be legal. The walls do not have to be straight vertical, but the 95 cm limit is absolute, and not restricted to measuring at the opening (or exit, or anywhere else).1: A logical interpretation of the 95 cm diffuser width would be that it means only the actual opening, and does not include the thickness of the vertical side walls.
Section 9.1.1.C.6. reads "A diffuser is permitted behind the front of the rear tires." The term "A diffuser" is singular, so I would think two diffusers are not legal....can the diffuser be split into two 47.5cm wide openings...?
Given our general agreement about the literal reading of the plain language of the rule as written, I agree with this interpretation.What determines the "start" of a diffuser? Is it to be defined as a "break" from the plane of the surface immediately forward of that "break"? If so, that does not preclude it starting 1" above the reference surface as some would believe.
Yep...just as soon as we can get them to define "suspension" and "tire"...Actually, according to the Glossary definition of "body", suspension and tire are included in the definition! Think we can finally get that fixed??
I stand corrected. Some, but definitely not all, FC guys equate the diffuser with total bodywork width. BTW, I agree with your analysis here. The panel does not define the diffuser.Not so. Many of us cut our teeth on these rules way before there were official definitions of thing like bodywork, and always thought of the panel within which the diffuser was formed as being subject to the bodywork width rules, but that a "diffuser" was only a distinct shaping that was included in that panel - ie - the panel in total while being generally called a diffuser is in fact not the definition of a diffuser.
Steve, (1) as the rule is written, so as long as the +1" deviation rule is not exceeded, IMO the answer is "nothing". And (2) since the 95 cm width rule is not caveated in any way, then IMO so long as the "working space" doesn't exceed 95 cm in width, you're good to go, curved walls or straight.We still have yet to address the following:
- What would cause a to be illegal even though the entire bottom surface between the tires is within 1 inch of the reference plane?
- How and where will we measure the diffuser for 95 cm.
Stan Clayton
Stohr Cars
For sure. Thanks for catching that mistake.
Stan;
I think we are getting some where.
However, I think the diffuser should be measured 1 inch above the reference plane. The maximum width is 95cm measured 1 inch up from the reference plane. This would include any surface from horizontal to vertical that is continuous with the under tray. I think this is easier to understand and enforce.
Any variations in the surface of the bottom of the undertray is acceptable as long as it is within 1 inch of the reference plane. The 1 inch rule would allow you to say that this will be an "as raced" rule. If there is any chipping or damage to the diffuser, it would likely not cause the car to be illegal. But if the damaged is such that it was wider than 95cm and above 1", then you can be disqualified.
Forward of the rear tire, any surface (to exclude holes) 1 inch above the reference plane and the car is illegal. Behind the front edge of the rear tire any surface wider than 95cm and above the reference plane plus 1 inch and the car is illegal.
I would accept that if you have a hole through the bottom of the car, that any radius or chamfer on the edge of the hole has to be included in the 1 inch deviation. Only that protion of the surface that is perpendicular to the reference plane is excluded.
If this is the rule, I think it is good. A car is legal or illegal by simply measuring what you see. You only need a streight edge and a scale to determine if a car is legal.
Where do we measure this difusser
I took these pictures from the Pennon site.
Is the flare at the front legal?
Last edited by Mike Devins; 03.27.13 at 7:02 PM.
It will depend upon where it is mounted in relation to the front of the rear tires.
Mike;
I would like to see the diffusers positioned on the car so that at the front edge of the rear tires no portion of the lower surface of the diffuser is more than 1 inch above the reference plane and that the widest protion of the diffuser is 95 cm or less. The flat surface on the sides of the diffuser can extend rearward to the end of the car if you want. That would be 150cm wide and 80cm behind the rear wheel center line.
Either one is perfectly acceptable if it meets the above limitations.
Now that is only what I think should be. I would say that the restrictions and definition for legality purposes is that the diffuser is any thing that is more than 1 inch above the reference plane and behind the front of the rear tires.
Quote: R. Pare :
1: A logical interpretation of the 95 cm diffuser width would be that it means only the actual opening, and does not include the thickness of the vertical side walls.
Response: Stan:
I disagree. IMO any curving of the walls, bulges or other design elements which result in the width of the "air space" within the diffuser walls to exceed 95 cm at any point within the diffuser would not be legal. The walls do not have to be straight vertical, but the 95 cm limit is absolute, and not restricted to measuring at the opening (or exit, or anywhere else).
That is another logical interpretation, and if that is to be what the "official" interpretation is to be, then it might help for the future to state the rule as such.
Quote: R. Pare
...can the diffuser be split into two 47.5cm wide openings...?
Response: Stan:
Section 9.1.1.C.6. reads "A diffuser is permitted behind the front of the rear tires." The term "A diffuser" is singular, so I would think two diffusers are not legal.
That's one possible, logical conclusion. However, what if the forward part of the diffuser is all one cavity, and only the aft portion (the last foot or so) is split into two sections to where it's widest point is at the exit? Do you have one diffuser, or two? Again, this question pertains to exactly what we are defining the "diffuser" as as opposed to the panel within which the diffuser is formed.
Rear Diffuser
Steve,
Our diffuser would meet your interpretation. I think the only point of contention is going to be what constitutes the diffuser. Is it everything behind the front of the rear tires....or is it only that portion which rises above the legal floor height behind the front of the rear tires....that is the question.
Matt Conrad
Phoenix Race Cars, Inc.
Matt:
I have done all of the diffusers on my cars. I know what the manufacturing problems are.
Look at the pictures Mike posted. See how the diffuser flairs out towards the front? Most of the flairs will be below 25mm (1 inch). I would like to be able to do that type of shaping without it being a rules issue.
The real problem with this set of rules is the 25mm gap. If it had been 1cm as it was in the pro FC rules (not SCCA) we would not have this discusion. 1cm is a reasonable tolerance for maintaining a flat bottom. But 2.5cm is inviting all this fudging. Practically all FCs were built to meet a 1cm rule. Me, I will built to 1.5 cm and leave 1 cm for tollerence.
I think that pushing the rules to the limit will yield a 100 pound down force increase or, at least, a very significant and favorable change in the center of pressure of the under body. The rules makers wrote these rules and now you and I have to live with them.
I am trying to flush out an interpertation of the rules that will get through a protest. I may have way more experience with the SCCA protest process than Stan or any other member of the Comp. Board. I do not mean to insult anybody. I make that statement because I have been involved in the rules process since the late sixties. Old age brings certain benefits along with senility.
I don't want to get to the track and find that another competitor has pushed the rules to the limit and I have been played for the fool because I built what the rule makers thought they wrote not what they infact wrote. I have been there, done that and I can show you the chapter and verse in the rule book that resulted from similar issues. Any body remember the "basket handle engine covers" in the FV rules or the current wording for the undertray rules in FF, or how about the "no diffusers or tunnels if FF"?
Right now I would be very happy to see the rules changed to 1cm. I will bet that almost every body doing a car now will accept that. Wait a few months and it will not be possible.
Stan:
You may have backed yourself into a corner!
To reiterate:
R. Pare
...can the diffuser be split into two 47.5cm wide openings...?
Response: Stan:
Section 9.1.1.C.6. reads "A diffuser is permitted behind the front of the rear tires." The term "A diffuser" is singular, so I would think two diffusers are not legal.
If that is the logic flow that is to be used, then any car with a 2 (or more) piece stressed floorpan would be illegal.
F1000 rules, B.1.4 : "A stress bearing floorpan/undertray is permitted.......[/i]
Using your logic method, any car with more than one stress bearing floorpan would be illegal (and that would be most of the stepped-undersides cars!), whereas a car with one that is stress bearing and one that is not would be legal.
Somehow, I doubt that you want this scenario to take hold!
I would propose, therefore, that the rules be amended to state that the width of the diffuser opening as viewed from the underside be a maximum of 95cm wide for its full length, from the leading edge of the rear tire to its rear edge.
If you combine this with stating that the measurement plane is to be 25mm above the reference plane, it will also address the concerns about the difficulties of measuring to the tangency point of radiuses, etc, and would allow the "start" of the diffuser to be in harmony with any shaping of the controlled undersides area.
There are currently 1 users browsing this thread. (0 members and 1 guests)
Posting Permissions
Reply With Quote