December Racecar Engineering Magazine and Vees

[pillowmeto]

December's Racecar Engineering Magazine (Vol 18 No12) has a follow-up article to their earlier articles on European Vee aerodynamics. This month inspects flow through and around the front beam tubes, end section, nose, and wheels. It is a good read, the result is surprising.

Just after that is an article about Monoshocks, Z-bars, and Bump rubbers with alot of talk of Vees.

[vreihen]

In case anyone didn't hear about it yet, Racecar Engineering is giving away the online December issue for free. The URL is http://www.racecar-engineering.com/xmas . I can't seem to get the issue to load at the moment, but did read it online from the same link last week.....

[hardingfv32-1]

So what did you guys learn from the articles?

Brian

[DanRemmers]

The article describes some wind tunnel and computer model experiments that compare the aerodynamics of the stock front beam to one with an aerofoil cross section added to the tubes and shock towers.

Wind tunnel tests showed no change in drag, and computer models showed slightly lower drag with the fairings.

Both methods showed about a 10% increase in lift when the fairings were added.

[pillowmeto]

The idea is that the nose of the car, the ground, and the wheel/vertical portion of the beam form a boxed in area of compressing air and that air does not have else where to go but up. With an upward draft in the region of the beams, the addition of airfoils give more surface area for the draft to act on thus increasing lift by about 10lbs at 100mph. A small decrease in drag was seen when using airfoils. The images seem to show that air is actively moving through the beam tubes in both simulations.

[hardingfv32-1]

It would seem that armed with this study one could file a protest against the use of beam covers under the "no wing clause". They have the shape of a wing and are obviously providing lift, a common function of a "wing".

Brian

[fvracer]

Brian,

I think that wings that provide lift would be OK, the regs are concerned about generating downforce. Do you think that if we could get enough lift to have the car barely touching we could reduce the drag from those pesky tires enough to increase the top speed at Road America next year? Of course stopping and turning might be a bitch.

Doug

[hardingfv32-1]

Where does is say no downforce? I read " no wings".

Brian

[brian]

Many years ago Bill Noble and others went to a wind tunnel and, if memory serves me, they found that single body work ( I refuse to call them fairings) over both tubes worked the best. Tests with individual fairings for each tube generated reversion forcing the air back out of the hbeam. In the videos you could see the tufts of yarn jump everywhere with dual fairings. The article in question said they thought the increase in drag with the fairings may have to do with the back of the car. I think the trailing portion of some cars like the Citation helps keep the air clean down the side of the car. Either way, American vee bodywork appeares to be much more developed than the example in the magazine. Plus the upright on the h beam had been cut off ala F First. Don't know how much relevance it holds for us.

[jpetillo]

I think a double beam fairing can do better than a single - drag-wise - but it needs to be designed right. That's easy to say, but I think difficult to do. It's not clear that the benefits would be significant.

With regard to the article, I believe their first article mentioned that the fairings caused slightly more drag than with no beam fairings. Their CFD analysis didn't show that, but the analysis cannot include every detail of the car. I forget if the analysis assumed a "rolling road" or one stationary to the car. The wind tunnel tests didn't have a rolling road. That would certainly add to the updraft in the front that may not be there as much in real life.

John

[Bill_Bonow]

This article is based on the UK FV which uses the ball joint beam. The ball joint beam tubes are on a wider spacing which makes the wind tunnel data useless for king pin beams. The bodywork examples shown in the article/wind tunnel test are specifically of an AHS http://www.formulavee.co.uk and nothing else. So I would think that this could have little to do with other models of UK FV's let alone USA versions of FV's that use a different front suspension.

It does suggest that USA FST designs may favor no fairing over the front beam tubes.

[hardingfv32-1]

The article is as representative as we are going to get. It has relevance to all beam front ends. At a minimum it shows a trend from certain actions. Unfortunately this aero stuff is not that straight forward. I would say the individual beam covers have to be tuned to provide zero lift. I'm ASSUMING/hope this would reduce the drag.

There is NO WAY that the bare beam of any FV/FST can not be improved on in the aero department.

Brian

[jpetillo]

I agree with Brian - that an improvement can be made to a bare beam, and that the beam covers could be made to produce no lift and produce less drag. But if the end result is that they would be angled up, it may look to the tech crew like downforce-producing wings and then you may be disqualified!

[Bill_Bonow]

There is NO WAY that the bare beam of any FV/FST can not be improved on in the aero department.

Yes, but how legal will your improvements be?

There were many people involved in those Wichita State wind tunnel tests some 15-20 years ago. A whole load of data came out of that including the best (lowest drag) legal method to fair in king pin beam tubes. For the miniscule amount of drag developed by the king pin beam tubes, the UK tests on a ball joint beam does not have much bearing (if any) on "how to" with the typical US king pin beam FV.

But than again, I always love to see those wacky FV concoctions that will render their car un-draftable.
Looking forward to a new batch of them for '09

[hardingfv32-1]

I say ALLOW WINGS.

What is it going to matter. No one in their right mind is going to use downforce and wings would add a modern touch.

As long as the wheels are exposed, ALL Vees are easily draftable.

Brian

[Bill_Bonow]

Brian,

Here you are, Formula Vau (German FV). All the wings you wish.

[ external image ]


These are GAC-04's (UK built) with a ball joint beam, disc brakes, 1300 cc water cooled VW Polo engine, all that modern touch stuff.

[jpetillo]

There were many people involved in those Wichita State wind tunnel tests some 15-20 years ago. A whole load of data came out of that including the best (lowest drag) legal method to fair in king pin beam tubes. For the miniscule amount of drag developed by the king pin beam tubes, the UK tests on a ball joint beam does not have much bearing (if any) on "how to" with the typical US king pin beam FV.

Bill, do you know where the results of those tests can be found? Did they publish it anywhere?
John

[Bill_Bonow]

John,

Nothing was published (that I know) but a video tape of tunnel time was made available ($75?) shortly after the test. Most of those directly involved with the tests are members of this board. My bet is because a majority of the funding for the tests came from FV constructors or body builders, that most of the info learned from those tests have been applied to cars and bodies built after the early 90's.

Al & Mike Varacins developed the body for the AM-5 in a wind tunnel (WSU as well?). I'd guess that their car has more tunnel time than any other car by a significant margin.

[G.B.]

Brian,

Here you are, Formula Vau (German FV). All the wings you wish...

But note how little wing they are actually running.

[hardingfv32-1]

Thats my point. We don't need them, but they could be used as a marketing tool. Look at the pictures. You don't even notice the beam front end. The wings are what your eyes are drawn to.

Great pictures, Bill.

Brian

[jpetillo]

Bill, thanks for the reply - John

[dd46637]

You can bet those Polo motors are making more than 60 h.p.

Wings on a current Vee would probably knock 10mph off the top end.

Note the diffuser at the back.

They do look cool though

[jrv]

Wings on a current Vee would probably knock 10mph off the top end.

Over 30 years ago Harvey Templeton gave me a simple rule of thumb on wings and race cars; "If you spend more time in the straights than the corners, wings will only make you go slower (on a lap)."

Jim Vaseff

[robert]

I'll pretend I know something . . .

A round tube has something like 10 times the drag of a like sized streamlined tube.

Modern open wheel cars employ streamlining to every chunk (a-arms, tie rods, etc. even brake hoses are inside the arms) of suspension exposed to the air.

That suggests to me that exposed beam tubes offer more drag than when streamlined.

To get good information from computers and wind tunnels require a good operator. I know I've mentioned this before, but there was a lot of debate about the design of the inlets for the engines for the 777. Would they function properly when the aircraft rotated on take off, which presented the engines to a new angle of attack. The air had to wrap around the inlets, or the engines could starve for air. Despite arguments that all would be fine, a 777 engine was hung on a 747 for flight testing. Sure enough the motor farted and spewed black smoke and flame at rotation. Imagine had that occurred on both engines of the plane's first flight . . . could have been a disaster.

My point is that if those guys are still learning aerodynamics, it might just be possible that aero studies of Vees may be less than spot on.

[Larry Bradley]

I'll throw in my 2 cents.

In 1974 we took my Lynx into a "wind room"

A room with a fan which could generate a 80mph wind out of a 4x8 foot fan area.

We put the car in front of the exit for the fan on 4 scales.
Body work tested was the Lynx body with the 72 era "wedge nose" (narrow nose with a wedge cut into it) and another lynx body with a shovel (nose Full width) and windshield.
The results were: Wedge nose = 5 pounds of downforce
Shovel nose = 15 pounds of downforce.

The drag was measured and all I can report is the shovel nose and windshield had less drag.

No decent data at the rear of the car.

Larry