Wing vs. Whale Tail spoiler

[akeller]

I've searched and not found anything covering this subject.

I want to know which would provide more down force - a whale tail spoiler or a wing.

Have any of you used a wing? If yes which one?

 

I've seen a few pictures of S30s with wings that looked pretty good.

 

Thank you for your help and guidance

 

Al Keller

330-877-9189

al_keller@earthlink.net

[JIM73240Z]

Search in here.

 

http://forums.hybridz.org/index.php?/topic/55944-windtunnel-test-data/

 

Your answers are in there with the #'s of drag from each one and the amount of downforce.

 

Jimbo

 

 

fyi, i have a wing.

[69sroadster]

I apologize if I missed this in another thread somewhere...but the numbers listed under the lift/downforce on the thread for the windtunnel test results, does a negative number = downforce? The legend at the top said otherwise, but then the numbers didn't make sense that way. I saw something like -.2xx for the whale tail spoiler and then +.1xx for the test mule. Also, how can you take those numbers and extrapolate into an equivalent weight in lbs? I could really use some downforce over the back of my ZX and want to decide which type to go with. Also, with the blue Z did those fender vents go through to the engine bay?

[jt1]

The heading on the chart is lift, so a negative number indicates downforce. A way to verify that is that as we increased the angle of attack on the wing, the negative number gets larger.

 

The blue car had vents in the inner fenders to allow air from the engine compartment to pass into the wheelwells and then out the fender vents. This mod is discussed in detail in one of the threads about the bonneville cars if you want to hunt it up.

 

jt

[SHO-Z]

There was an article in one of the car mags on the 911 Porsche on its spoiler. It was had faster lap times around the track without the spoiler. This was due to higher straight away speeds. Spoilers look neat on a car, I am not into the wing thing, but will reduce straight away speed and gas mileage

[JMortensen]

There was an article in one of the car mags on the 911 Porsche on its spoiler. It was had faster lap times around the track without the spoiler. This was due to higher straight away speeds. Spoilers look neat on a car, I am not into the wing thing, but will reduce straight away speed and gas mileage

That's one car on one track, and shouldn't be used as a "spoilers make your car slower" proof. C&D tested various spoiler configs on a Z car and found that they gave varying degrees of downforce and drag and some of the less aggressive configurations IMPROVED drag and mpg.

 

What's more, if spoilers and wings made your car slower, you wouldn't see so many spoilers and wings on race cars. If you look at LeMans Prototypes though, you can see that they have more slippery, less downforce setups for LeMans than they run in other races in the ALMS for example, and this is because the higher downforce IS created along with increased drag. There is a happy medium, but they're running into it at 230 mph down the Mulsanne straight. The situation might be a little different for a stock Z car, but most of us here at Hybrid Z, if we are interested in downforce probably don't need to worry about drag too much because we have V8's, turbos, and V8 turbos powering lightweight cars, and most tracks we'll be running on max out at ~150 or so mph.

 

Have a look at McBeath's books Competition Car Aero and Competition Car Downforce or Katz's Race Car Aero Designing for Speed if you're really interested in how it all works.

Edited March 24, 2011 by JMortensen

[thehelix112]

Side note: Jon, I've got Comp Car Aero and Katz, but not Comp Car Downforce, is it worth my getting do you think? The other two seem pretty comprehensive.

 

Dave

[JMortensen]

I just got it myself. In browsing through, I'd say yes. It has info on building wings (that's why I bought it--gonna give that a go pretty soon). It does have a lot of repetitive info if you already have CCA, but there appears to be enough new stuff in there to justify the price. I bought it used on Amazon. There is a later version that goes for about 5 times the cost, I got the cheaper version.

[Tony D]

OK, two cars and two tracks. The BRE/OEM style spoiler cost us 3mph compared with simple ballast in the spare tire well.

 

Frankly we went much quicker without the spoiler, as we could add more ballast to get equivalent downforce on the wheels without the drag penalty of the kick-tail.

 

Most of the original stuff was designed to work at speeds below 125mph---they give maximum downforce at the expense of drag. This is discussed in detail elsewhere. John C posted a typical low-drag spoiler configuration that works great, but I wouldn't put it on my street-car...

 

I see now driver-adjustable wings are back and legal in F1 again... If they are so great, why make them adjustable? Because on the straights you don't need nearly as much downforce as you do in a turn. A fixed spoiler is always a compromise. Always.

[JMortensen]

Who is that advice really for? How many people in the world are doing land speed racing in a Z and trying to decide whether to add ballast to the spare tire well or put an aero device on their car Tony? Ten? Five? Less?

 

In realistic terms, what is allowed in a given racing class is probably severely limited, and only within the narrow confines of what can be done does one have to weigh drag and downforce. The end result is usually that everyone will run the biggest aero device they can within the confines of the rules. Streamlining left automobile road racing in the 1950's for a reason. That's not a mistake, and it comes from the fact that cars with downforce can turn faster than cars without, and that is because downforce gives the traction of ballast without having to manage the weight of ballast in the turns. If you're racing is done in a straight line and you're power limited, then what works best will probably be less drag. Even in a straight line, without power limitations, downforce is a good idea. Funny cars make 14,000 lbs of downforce at 320 mph. If your racing is done on a course with turns, you should use downforce (or more likely minimize lift to the greatest degree possible) to add traction, and ballast should only be a tool used to come up to minimum weight in the most advantageous way possible.

 

Adjustable aero is great. Unfortunately it is also banned in almost every class of racing. So if you have it available and have the means to make your spoiler or wing adjustable, go for it. But you probably won't. Again, I think it's best to focus on real world situations. In most of those that involve Hybrid Z members who also aren't likely to sign up for the hp limited classes, the rule of thumb is going to be bigger is better. Need proof? Look at unlimited time trials cars. Not a streamliner in the bunch.

[Tony D]

Your Contention:

"That's one car on one track, and shouldn't be used as a "spoilers make your car slower" proof."

 

My statement:

"Make that two cars, two tracks."

 

If facts of individual instances cause you that much problem I suggest medication.

 

You totally ignored the statement that comes after it, which is absolutely valid but doesn't fit your 'cookie cutter mentality of generalizations' apparently. Change my time slips and I'll change my statement. Otherwise it's as valid as your rant on parsing a statement that says if you are under 130, the BRE is O.K. but above that you should look for something else as IT WILL COST YOU ON AN S30.

 

(Is that paraprhasing better stated so you can understand what I actually said in my post, instead of what you decided to concentrate upon???)

 

Take a pill man. Focus.

[JMortensen]

Nevermind.

Edited March 31, 2011 by JMortensen

[thehelix112]

As to the OP's original question, (which if I'm reading it was about maximizing downforce, and had absolutely nothing to do with top speed) I don't think too may people would disagree that in general (considering commonly available parts for the S30) a wing has more potential to make downforce than a spoiler. Additionally, it would seem far simpler to mount a wing up nice and high in clean air to increase downforce, than it would be to get a spoiler to generate similar levels.

 

Of course, you could always run both. My plan is to get one of these: http://www.prestostore.com/catalog.php/azcarbum/pd2118883 then later on mount a proper wing above it if I get that serious.

 

Maybe something else to consider is that the car may not be that fun to drive with a tonne of rear downforce without the same consideration given to the front.

 

Lots of other threads in here touch on improving front lift by venting the engine bay, so that'd be a good place to start.

 

Dave

[Tony D]

Helix, I agree! There was no mention of sanctioning bodies, racing, or anything. Just which would give downforce.

 

The obvious answer is 'they both do' but one does so more efficiently I.E. several hundred pounds of downforce without additional drag from traditional BRE-Style Spoiler (whale-tail)---this is borne out in the tunnel testing I believe.

 

And as you rightly stated, the big wing out back really acts as a lever lifting the front, so a 'balance' is needed--something to push that front back down. I believe the answer was a Whale Tail and G-Nose worked well. I don't remember the numbers offhand, but the MSA Type 3 worked well, but I'm not sure on it's front downforce numbers if they were as high as a G-Nose.

 

As I mentioned, John C linked to a very efficient wing for the back of the car and my comment was I don't know if I'd want that on my street car.

 

For as much as people pooh pooh drag versus downforce, realize that most interstate driving now occurs very close (within 20%) of the speeds where a lot of this stuff was 'terminal'---the ZXR wing gives 300# at 100mph... that's linear boys and girls, on the interstate at 80mph, that's like putting some sacks of concrete back there as ballast! But it doesn't affect transient handling. The Turbo Wing was the answer to traction problems at speed (boiling the tires at 70mph when boost comes on may be entertaining to some, but it's not very quick...) The choice then becomes 'Have Tony ride along as ballast to keep the rear end hooked up' or install the turbo wing so you have 240# on the back wheels at 80mph and no extra weight to accelerate.

 

Really for the street it comes to Asthetics I suppose. A wing is great because you can adjust it---problem is that 'balance thing' you have to balance the front end with whatever you do with the back end. One affects the other.

 

How this went O.T. to racing and that...well that came well before my first post in this thread. I'm not guilty in that one.

 

Simple answer: Whaletail gives fixed downforce, wing gives variable, and can be adjusted so a smaller airfoil effectively gives more downforce. But it comes as a function of drag. The Whaletail was high-downforce, low drag (oil cooler, actually) answer back in the day. There are more effective methods, but almost all come at a price of drag.

 

And at highway speeds today, drag means less fuel efficiency. A low drag, high downforce Whale Tail may be the answer. But he really didn't state what he was doing or why he needed it. I had to put the whaletail on mine due to traction at speed issues. JeffP is now in the same boat with his ZX. If it's low-speed slalom N/A power he's looking for, a high angle of attack wing could work really well. (Even around town.)

 

Short of him giving more information on why he wants/needs it...it's all conjecture!

[thehelix112]

Tony, I agree on all points.

[260DET]

This is a "how long is a piece of string" thing. As Tony indicated, people need to get specific with their questions and requirements when starting this sort of topic.

[Tony D]

String is never long enough when wrapping packages. It doesn't matter the size of the package, or what you think the length of the string is before you start. Once you wrap it all up and get to the final point of actually trying to place the two ends near each other to tie it all up...it's short.

 

So a piece of string is NEVER long enough. That is how long a piece of string is.

 

Next question?

 

[JMortensen]

Lift is not linear, it is a function of velocity squared, so it is exponential. Formula here: http://wright.nasa.gov/airplane/lifteq.html

 

Does anyone actually have a whale tail in hand? I am trying to figure something out and wondering if anyone can give me a rough idea of the area of a 240Z whale tail as viewed from above.

[Tony D]

Is lift negative downforce?

 

You can estimate downforce simply by marking strut pistons with rings and calculating spring compression at various speeds on a smooth road. From what I've seen with the whale-tail, you get 70% compression at 70mph. My springs are 275#-in at back, and they are compressed at speed roughly .75-1" more with the tail there than not.

[JMortensen]

You want to rethink that estimate just a bit?