Wings/aerofoils Are they really needed? and if so when?

[Fastbrit]

Only once did I see you have an issue. IIRC that was after you'd fitted a quick acting steering rack. Think it got removed for the next meet 

Oh God, I'd forgotten about THAT! Seemed like a good idea at the time... quick-ratio, lightweight Stiletto rack'n'pinion made the car undriveable! 

[richie]

So does this mean you are coming back out to play? as thats mostly your old slogan

If I ever make it, at least one of those statements will have to be scratched out 

And I have a slightly different approach to find out what will work,no surprise there then i there
along the lines of the newbie you posted a pic off and a very long piece of desert   Its cheaper to take it there than Mira,but is kind of spelled the same

cheers richie

I just knew the ball of wool and masking tape option would appeal - you're probably unravelling your cardigan as we speak 

JM

I am currently waiting for some unsuspecting old lady to walk past so I can pinch one,even though I am getting on a bit a cardigan is not something I presently own

keith I rememeber some of the thinks you mention,will have to have a look at some photos to get them clear in my head,was it only 15 years ago you last raced,seems longer

cheers richie

[Peter Shattock]

If I were the sort of person who was old enough to have a nice woolly cardigan in the back of my wardrobe, would anyone know how fast you would need to go to get some idea of what is going on. Just wondering if its a 70mph (no faster you understand) in the middle lane of the motorway whilst a couple of equally law abiding citizens video the car? Or is this something that changes with speed so that you need to be going at your maximum trap speed to get a realistic result?

I'm not totally sure what I'm going to do with this if its possible to gain useful information this way, but it sounds like start on what looks to be a very long learning curve.

Just for the record my car (1584lbs with me in it) feels better without a wing (H helper) but my terminal of 107 - 109mph is way down relative to many on here, but as said earlier the weigh relative to speed (lift) also needs to be considered. I'm sure there is some clever maths to sort this out.

Anyone care to comment on the use of the little air deflector used above the rear window by some of the more hardcore German look cars. Form or function?   

[John Maher]

If I were the sort of person who was old enough to have a nice woolly cardigan in the back of my wardrobe, would anyone know how fast you would need to go to get some idea of what is going on. Just wondering if its a 70mph (no faster you understand) in the middle lane of the motorway whilst a couple of equally law abiding citizens video the car? Or is this something that changes with speed so that you need to be going at your maximum trap speed to get a realistic result?

I'm not totally sure what I'm going to do with this if its possible to gain useful information this way, but it sounds like start on what looks to be a very long learning curve.

Just for the record my car (1584lbs with me in it) feels better without a wing (H helper) but my terminal of 107 - 109mph is way down relative to many on here, but as said earlier the weigh relative to speed (lift) also needs to be considered. I'm sure there is some clever maths to sort this out.

Anyone care to comment on the use of the little air deflector used above the rear window by some of the more hardcore German look cars. Form or function?   

Pete,

That's a seriously anorexic street car (and driver???)   

The wool tuft test will show relevant info at speeds lower than your 1/4 mile terminals but for best results closer to the real deal is better.
It's a little like cylinder head flow bench testing.....
Industry standard test depression is genarally accepted as being 28" H2O but actual flow demand on a good head at max piston acceleration can be 70" plus.
The only benches capable of pulling that hard tend to be in the hands of the OEMs, F1, NHRA Pro Stock & Nascar. For the rest of us, 28" gives enough valid data to make useful improvements.

Terminal speed is generally a reflection of engine hp i.e. big hp equals higher terminal speeds.
That's why you often see turbo cars with modest ETs but high mph.
If you see a car make a mediocre pass but the terminal is up there, it's a dead giveaway it has some serious bhp.
With your little motor, the  lower bhp number (relatively speaking) delivers slightly smaller mph while the power to weight ratio results in super respectable ETs compared to cars running similar ETs with more cc.

No idea if the rear window deflector works or not but if it's positioned just before the air breaks away from the body it should trip the air enough to make a positive contribution (less drag).
Trick would be to identify the position at which the wool tufts start going crazy and position the lip spoiler just above that point. Should result in less drag (improved ET & mph).
Looking back at that New Beetle pic I posted you can see air stays attached pretty much all the way down the rear window. Don't know what mph the pics were taken at.
Maybe ask Martin to add it to his list of tests for MIRA? 

[Squirmn German]

I run a wing. I have been 111 in the 1/8 without the wing. Car was solid.

I have been 142 in the 1/4 with the wing. Car was rock solid...i'm not about to try it without it just to see.

Does it work? Who cares? Looks cool to me. 

[richie]

I run a wing. I have been 111 in the 1/8 without the wing. Car was solid.

Does it work? Who cares? Looks cool to me. 

Thats why I figure most people have them
Thankyou for you input,you sure you dont want to take it off and try it?

cheers richie

[Jon]

My street car used to squirm a little when I got of the throttle at just 164 km/t, it was then stock height at the rear.
It's now lowered 3 cm but when I go thru traps at 174 km/t it's so solid that I can just lift the throttle. The only other change is that I have fitted a pair of AVO chocks in place of the cofaps that used to be back there. The car weighs 1808 lbs.

[ESH]

... Anyone care to comment on the use of the little air deflector used above the rear window by some of the more hardcore German look cars ...

Looks daft. 

[Jon]

... Anyone care to comment on the use of the little air deflector used above the rear window by some of the more hardcore German look cars ...

Looks daft. 

Looks kind of like a two fold ragtop in open position... 

[Martin]

... Anyone care to comment on the use of the little air deflector used above the rear window by some of the more hardcore German look cars ...

Looks daft. 

they may be more effective than you think, even if they do look daft! lol

Its another thing we'll be trying.

[stretch]

I only ever drove my old car once without the wing / aerofoil.  It didn't feel as 'planted'.

I never had a problem with the car thru' the top end, although the best terminal was only in the 120mph range.  It also had the brakes jammed on a few times at the top end to avoid breaking out, is that kind of talk aloud on here?   

As for looks, I liked the look of the car with the 'big' wing.  Each to there own.  I also love what Pete has done with it.

[Bernard Newbury]

I have been following this thread with interest and it made me look at my ticket when I had my mishap. It happened at the 1/8th and my speed was 108.20 and my thoughts were for self preservation rather than weight transfer and the aerodynamics of stopping in a straght line etc etc. I have never braked so violently in all my life and the car stopped very quickly in a straght line, felt very stable and planted . I suspect that this was due to the weight, IRS and the setting up rather than any wing/spoiler/tea-tray attachment but with that in mind with the rebuild it will be having another one fitted. I do agree with Ritchie that the weight of a car is an important factor. On the plus side for wings /spoilers they do stop fires from spreading over the roof. Sissy sticks, Ritchie that's another can of worms . Bernie

[John Maher]

It takes a specific amount of horsepower to push a vehicle through the air at a given speed.
You also have rolling resistance to take into account (friction coefficient of tyres, weight of vehicle, bearing losses etc) but the major issue is wind resistance and power required to overcome it.

The lower the drag coefficient of the vehicle (Cd), the less resistance there is to forward motion.
Cd number is relative to the same frontal area turned into a flat plate as opposed to a contoured body shape...
It takes less energy to push a tear-dropped form with frontal area of 32 sqft through the air than an 8' x 4' sheet of plywood!

A 10 x scale model of a Beetle will have the same Cd as a regular one.
Multiply frontal area by Cd to make comparisons between diffferent sizes and shapes.

From memory a Beetle's Cd is something bad like 0.49. Think New Beetle is 0.38 (crap for modern car).
Not sure what frontal area is - height x width... maybe 25sqft??

25 x 0.49 = 12.25 CdA

Cd of a cabrio with the hood down could be in the 0.6-0.7 range   
CdA now becomes 15 (being generous and using 0.6)

Lower the CdA figure and it'll take less hp to travel at speed.
ie make the car slippier and reduce frontal area

When doubling speed, drag increases x 4 but the amount of horsepower required to overcome extra drag goes up by cube of speed - factor of 8
Beetle takes something in the region of 25hp to travel at steady 60mph on a perfectly flat road on a calm day.
Approx 200hp at 120mph

Working off that theory, aiming for 150mph terminal speed when you're used to maxing out at 140mph will require a 23% increase in horsepower   
... assuming aero is the factor holding you back - not traction/handling/gearing etc

(150/140 cubed = 23%)

At the bhp level required to run 140mph, dropping CdA might be less expensive than funding a 23% power increase 

Conclusion: Richie needs a New Beetle (with wheelie bars)   

JM

Note: prior to adding this edit, I'd originally calculated the percentage power iincrease reqd as 56% (!!!), rather than 23%. Thanks to Bruce for recognising the error and supplying the correct calculation (see his post on Page 5)

[Fastbrit]

A propos the New Beetle, this is interesting:
http://www.evworld.com/article.cfm?archive=1&storyid=911&first=2412&end=2411

And the Audi A2 has a Cd of just 0.25 – how about racing one of those? Perfect for the VWDRC...

And John, you're right about the Beetle: 0.38–0.39

I know the Karmann Ghia is almost as bad – in fact, the Type 25/Vanagon has a lower Cd than a Ghia, but I can't find the figures at present. If I recall, the Ghia coupé is around 0.36, the convertible about 0.40.

[benssp]

It would be interesting to know what difference the 'snow plow' front end made to the handling of the outlaw anglias

[John Maher]

A propos the New Beetle, this is interesting:
http://www.evworld.com/article.cfm?archive=1&storyid=911&first=2412&end=2411

Interesting article. Despite the Cd improvement it's yet more evidence for the "wings look shit" posse 

Seriously though, the wing position confirms placement in an area normally subject to turbulent flow decreases drag (see wool tuft pic posted previously).

And the Audi A2 has a Cd of just 0.25 – how about racing one of those? Perfect for the VWDRC...

Yeah... it'd fit right in with the Golf, Polo and Skoda.

All they need now is a Netto Car Park sign in the pit area and it'd look perfect   

[ian c]

hey john
how yoiu doin .

when you say a beetles cd is bad , this figure is for a standard trim car yes ?

with bumpers removed and front end lowered the cd would come down .

how much , i dont know

i also suggested earlier that richies car changes shape at speed .
as the roof bellows up , this would also effect the slipstream in a good way ?

(as long as he remembers to latch it )

[benssp]

i also suggested earlier that richies car changes shape at speed .
as the roof bellows up , this would also effect the slipstream in a good way ?

(as long as he remembers to latch it )

Not sure if he's allowed to run the roof anymore, that's why he had a haircut due to lower the CD the ponytail caused

[ian c]

shoulda kept the tail , would have helped with the "wool-tuft" experiment

[ian c]

i suspect with the roof down , air will be going over richies head , and tumbling back in towards the windscreen

helping to push him along !!!

[richie]

Mmmm so I need 56% more power,ok I think I can find that

I actually thought a ghia was better  than that? starting to wonder now if my Fridolin is such a goos idea

cheers richie

[richie]

i suspect with the roof down , air will be going over richies head , and tumbling back in towards the windscreen

helping to push him along !!!

Not sure if its helping me go forward but I already proved that one when the breather box burped a little!!! oil and it ended up coming over me onto the windscreen

cheers richie

[ian c]

i could have warned you about this one .... 
had my directions writ on a piece of a4 on the passenger seat .....
they did a couple of loop-de-loops and shot out of the car at 120 on the m62 

[ian c]

brainwave !!!

you seen the mesh screens that mount behind the seats on modern cabrios to stop wind blasting the back of your neck ?

you could make one easy enough and do back-to-backs to see if times alter !!

SOME CARS use a polycarb one i think , so this HAS to affect earodynamics

[richie]

brainwave !!!

you seen the mesh screens that mount behind the seats on modern cabrios to stop wind blasting the back of your neck ?

you could make one easy enough and do back-to-backs to see if times alter !!

boxter uses a polycarb one i think , so this HAS to affect earodynamics

I am sorry but using the word boxter in the same sentence as anything I own is deeply offensive

cheers richie

[ian c]

SORTED !!! 

[John Maher]

With all this talk of cabrios, Boxsters, pony-tails being cut off, hair blowing in the wind.....
I reckon there's a frustrated hairdresser itching to come out

Coming soon: Richie's new styling salon.....

HAIR-O-DYNAMIC   

"Not working today?"
"Been on holiday yet?"

[Fastbrit]

HAIR-O-DYNAMIC

The PERFECT name for Richie's racer! 

[Martin]

HAIR-O-DYNAMIC

The PERFECT name for Richie's racer! 

lmao!

[Peter Shattock]

John, the car is actually quite heavy, but with the excitement of a days racing ahead, I normally loose a few pounds in the morning before getting in the car!