Rule Interpretation - Double deck diffusers

[BorisTheBlade]

Narf!!!
@Astro1
Would it be asked too much to take the context of my post over there at Autosport as well inspite of just taking one of the pictures I posted because they clearly show that it's not about the starter hole. But okay, I'll do it for you:

(...)
I'll provide you with some pictures. Red circles are the starter holes, green circles are what I estimate to be the feeders for the upper sections. Ferrari is only one single example of the starter hole of a team with normal diffuser. But you can spot it at any other team too, if you want:
Williams


Ferrari


Brawn with starter hole visible


Brawn with feeder hole visible


Brawn with what I think is the feeder hole from the outside

(...)

@jimmy8v & djos
As you can see on one of the above pictures, you can see the street through the hole. So I'd say the animation is not accurate. My bet is still what moz pictured in the very same thread over there:

[Astro1]

It wouldn't be too much to ask for, but I was trying to concentrate on the idea of the hole and not the other aspects as I think it's the only questionable issue and at that it's only the Brawn car which seems to implicitly use a hole as a device, where the actual hole is hidden within the upper device.

So when asked what is the purpose of the outer shape of the device, how can Brawn avoid saying it's not an aero device and is just for the purpose of a starter?

[BorisTheBlade]

AFAIK at least Williams are also using holes. Otherwise it wouldn't be possible to get air to the upper section. But it was mentioned that they use horizontal holes which...
1. Suggestion: Are hidden behind the suspension when looking from beneath
2. Suggestion: Are under the suspension to count as unsprung devices (sounds weird for me but nevertheless)
3. Suggestion: Are in front of the RWCL and therefore have different regulations applying.

I don't know what Toyota is doing under their car but as it appears to me, they don't need holes for their construction as they don't have a 'real' Double Decker. They only have that one small plate to circumvent the regulations that demand bodywork seen from beneath not to be higher than 175mm.

[NormanBates]

Been skulking on this forum for quite some time, thought I'd finally add something.

Might be of some use to those who wanted to hold the bgp diffuser in their hand and have a good look at it. Wondering how this italian lot got such good renderings of it, can they be considered accurate?

Admittedly stolen from the thread discussing these diffusers in the autosport forum.

http://vbox7.com/play:9c408f41

In italian though anyone want to translate.

Very interesting and informative discussion so far, thanks.

nice animation, but I don't believe the brawn difusser works as described there: that part (if you really believe it can really make a difference, which I don't) would reduce drag from the back wheels, so making the car faster on the straights, but it would also create a low pressure zone ABOVE the car's floor, so reducing downforce, and the speed at fast corners; plus, you wouldn't see the floor through the upper deck, so it can't be like that

I also think it's closer to moz's picture, but still I think that is not totally accurate either (I believe you'd need a bigger intake to get such a big effect)

edit: I was doing my own drawing, to post it here; then, looking at the "brawn with starter hole" hires picture, I converged to moz's drawing: it definitely looks like that (the central part has the minimum 30cm reference plane width, the two big vertical fins are separated by the maximum 50cm reference plane width, the air goes in to the higher deck through holes on the sides); it is still surprising to me that such small apertures can make such a big difference, so I keep my previous conclusion that the difusser definitely helps but the brawn car is fast because of many more things apart from it

[vasia]

I have no technical experience but I personally think this whole diffuser situation is a big smoke screen.

Their is no denying that the double decker is worth an extra half a second of what ever it is, but lets not forget - if this double decker design is cleared in April this wll enable developers to design a car on a completly new level, and enable them to venture areas they wouldnt have been able to previously explore!

I personally believe that McLaren will be the first to develop their interpretation of the double decker shortly followed by Red Bulll... although im very shocked that Newey didnt think of this idea being the man he is! Maybe he is loosing his touch, although their is no denying tha the Redbull is shaping up to be something special!

Red Bull have already stated that they asked the FIA last year if the double deck diffuser was legal and where told no, that is why they (and others) are so pissed off that now the story has changed!

Not true. Red Bull asked the FIA last year if a "similar design" was legal and they were told no. Red Bull has not explicitly outlined what that "similar design" is, nor has Red Bull actually stated they asked the FIA about a "double-decker diffuser". Even if it was a double-decker diffuser, who knows, Red Bull's design might have been different to what we've seen so far.

[machin]

If the lateral holes meet the rules I can see no reason why the arrangement below wouldn't be allowed:-

[machin]

Or from an alternative angle with semi-transparent parts (if only the real thing were like this!!!!)

[NormanBates]

that's quite close to what I was drawing, then I looked closer at this picture:

Brawn with starter hole visible

where it looks like the front section of the higher deck is at the lowest allowed width of the reference plane (300mm), and so the air inlets must be on the sides (as in moz's drawing), at least on the brawn design (maybe williams is more like yours?)

[machin]

From that picture you're right; it is quite clear that the Brawn's central section is 300mm wide..... This one of the Williams does look like the higher section is wider... like my model above.... although not sure if it looks to be 500mm... which is strange.. might as well use the whole width available if you're going to do it...????

[NormanBates]

From that picture you're right; it is quite clear that the Brawn's central section is 300mm wide..... This one of the Williams does look like the higher section is wider... like my model above.... although not sure if it looks to be 500mm... which is strange.. might as well use the whole width available if you're going to do it...????

true, that one looks more like your drawing, using close to -but not fully- the 500mm available (look at the height of the biggest vertical fins, which is 175mm, and it looks it's more than 2x but less than 3x)

[saiyu]

What I find interesting is this quote taken from this weeks issue of autosport:

"Ironically. the controversial diffuser set-up used by Brawn, Toyota and Williams improved the situation [cars following each other] as it reduces aerodynamic downwash."

Is this the same as the wake?

[joseff]

If the lateral holes meet the rules I can see no reason why the arrangement below wouldn't be allowed:-

3.10.1c
When viewed from the side of the car, no longitudinal cross section may have more than one closed section in this area which must be symmetrical about its major axis.

Taking a cross section of your model would definitely yield 2 closed sections IMO.
Other interpretations of the rules are welcome

[machin]

Taking a cross section of your model would definitely yield 2 closed sections IMO.
Other interpretations of the rules are welcome

You're right.. it would.... but that rule you've quoted, in full, reads:-

3.10.1 Any bodywork more than 150mm behind the rear wheel centre line which is between 200mm and 730mm above the reference plane, and between 75mm and 355mm from the car centre line, must lie in an area when viewed from the side of the car that is situated between 150mm and 350mm behind the rear wheel centre line and between 300mm and 400mm above the reference plane. When viewed from the side of the car no longitudinal cross section may have more than one section in this area.

So it doesn't apply..... this rule basically means you can only have one lower aerofoil element in your rear wing.... the next rule, 3.10.2 says you can have only two upper elements in your rear wing.

[PSfan]

If the lateral holes meet the rules I can see no reason why the arrangement below wouldn't be allowed:-

Hello, new to the forum, but I have a question regarding this post, Where did the quote "Fully enclosed holes are permitted in the surface lying on the reference and step planes provided no part of the car is visible through them when viewed from directly below"

I am assuming it relates to 3.12.7, I don't see anything in there that has the word directly below. The way I interpret that rule is, that when viewed from anywhere beneath the car, the area which lies between the rear wheel centre line and a point 350mm rearward of it cannot be more then 175mm above the reference plane.

[machin]

Its 3.12.5


All parts lying on the reference and step planes, in addition to the transition between the two planes, must produce uniform, solid, hard, continuous, rigid (no degree of freedom in relation to the body/chassis unit), impervious surfaces under all circumstances.
Fully enclosed holes are permitted in the surfaces lying on the reference and step planes provided no part of the car is visible through them when viewed from directly below.

Now you could argue this doesn't apply as concerns the floor in front of the front wheel centre line.... but as the holes are on the line which separates the two areas you could argue that the holes are perfectly legitimate... as they're covered by this rule above...