Race car aerodynamic help?

[winkosmosis]

Why not cover the engines with fairings?

[Bennett_Racing]

Originally Posted by winkosmosis

Why not cover the engines with fairings?

Could you post a simple drawing of idea?

[winkosmosis]

Originally Posted by Bennett_Racing

Could you post a simple drawing of idea?

What I mean is, cover the engine with a cowl like on a street car

[Bennett_Racing]

Originally Posted by winkosmosis

What I mean is, cover the engine with a cowl like on a street car

I get you, see what you mean but that would mean a totally new body, we need to really keep the overall look of the car really.

Hope that makes sense.

We could enclose the whole car but then its not a fuel altered, it near enough becomes a funny car.

Thanks

[fultondp]

Luke,

Your 2007 body had a engine cowling...can you reuse it, or make a similar?

I would also suggest making the front wing wider if it is allowed in the rules, to put the front wheels in the wind shadow of the wing. Also, some fender flares in the back to smooth the flow around the rear wheels. You'll have to check the rules there for "open wheel". Solid Moon disks instead of mag wheels also might help a bit.

Since you are concerned about the look as well as drag, starting at the back instead of the front might be a better approach. Is your rear wing actually doing you any good? You might be able to get rid of it altogether and get the same effect by moving the engine a few cm forward on the chassis.

We would need to see some pictures of the rear-end. If the air stream is creating a vortex "trailer" you are pulling down the track, putting a boattail with a sharp edge on it could help to reduce the size, or allow for better separation of the flow off the rear.

I think the other guys are requesting dynamic data to try and understand where in the run the aero loads are hurting you. For example, static wind tunnel testing might suggest increasing the angle of the front wing. But if you do this, it won't hurt your performance at the start, but once the front wheels come down, it might put your blower in the wind shadow, and rob your horsepower in the last half of the run.

Darren

[Bennett_Racing]

Originally Posted by fultondp

Luke,

Your 2007 body had a engine cowling...can you reuse it, or make a similar?

I would also suggest making the front wing wider if it is allowed in the rules, to put the front wheels in the wind shadow of the wing. Also, some fender flares in the back to smooth the flow around the rear wheels. You'll have to check the rules there for "open wheel". Solid Moon disks instead of mag wheels also might help a bit.

Since you are concerned about the look as well as drag, starting at the back instead of the front might be a better approach. Is your rear wing actually doing you any good? You might be able to get rid of it altogether and get the same effect by moving the engine a few cm forward on the chassis.

We would need to see some pictures of the rear-end. If the air stream is creating a vortex "trailer" you are pulling down the track, putting a boattail with a sharp edge on it could help to reduce the size, or allow for better separation of the flow off the rear.

I think the other guys are requesting dynamic data to try and understand where in the run the aero loads are hurting you. For example, static wind tunnel testing might suggest increasing the angle of the front wing. But if you do this, it won't hurt your performance at the start, but once the front wheels come down, it might put your blower in the wind shadow, and rob your horsepower in the last half of the run.

Darren

We can make similar but would look odd with the front end body work?

Front wing wider was an idea I thought but I don’t understand aerodynamics enough yet, I thought an inch wider than the wheels?

Rules wise, backs can be enclosed fronts cant

Rear wing def def works, when we started to get upto 180mph+ in 1995 the car was getting out of control so the wing was added and now drives perfectly but I do want to change the tubing for aero tubing later this year

Seen photos of a boat tail, how could we add this to the car ?

Totally understand that, the only part that needs to be in clean aie is the injector (3 holes at top of motor)

Thanks all il post some photos of rear end asap

[Bennett_Racing]

Few photos hope they help

ImageShack® - Gallery

[Nigel]

A few musings,
What deploys the parachute? What conditions are acceptable for its deployment airflow wise?
Could the front wings be extended vertically in a narrow strip to shade the front tyres from air flow? Both up and down.
Would there be any advantage in making the nose more like a cowcatcher -to move air to the sides and higher to cover more of the block.
When the rear tyres grow - do they still stick out of the body?

[Bennett_Racing]

Originally Posted by Nigel

A few musings,
What deploys the parachute? What conditions are acceptable for its deployment airflow wise?
Could the front wings be extended vertically in a narrow strip to shade the front tyres from air flow? Both up and down.
Would there be any advantage in making the nose more like a cowcatcher -to move air to the sides and higher to cover more of the block.
When the rear tyres grow - do they still stick out of the body?

2 levers deploy them seperately, or both together (depends on speed)

On our 2007 body shown on the site, we kept having the chutes fall right onto the wheelie bars, we solved it by simply moving the chute mount up only 1 inch and sorted it. must have been in dead air...

Not sure what you mean airflow wise? As long as they work we can try anything, its got to be safe.

The front wings? you say a narrow strip? can you explain please?

We have played with the idea of making the front bodywork come further back nearer to the engine to 'hide' more of it from airflow

They grow a fair bit, here is a photo of the car during burnout to give an idea as they grow about the same amount.

[aerohead]

Originally Posted by Bennett_Racing

Thats a few questions ! I will try to answer them the best I can.


is it the AA Fuel Altered that you want help on?
Yes the black Relentless fuel altered

Your all-up weight would be useful ( wet )
2200lbs race ready with driver

Are you at full lock-up with the clutch at the timing light?
Do you mean top end finish line? Or the start line?

Is there any horsepower to spare?
How do you mean?

Is the body of the car already carbon-fiber epoxy?
No fibreglass but its fairly lightweight, we were concious of this when we made it.

Does the rule-book allow any enclosure of the body/chassis for that class?
Pretty much do what we want...thinking an undertray?

Are the wrinkle-walls slipping presently at speed ( roof-top negative-lift airfoil )?
Don'y get this one...sorry

Can the driver see around the engine/blower/bug-catcher at present time?
Yeah has about an inch over the injector

Do you have your front/rear axle weight bias ?
It is around 800lbs over front and 1400lbs rear end

Do you have a sense of the car's dynamic weight distribution at upper speed?
None

Do you have a time/velocity table so we can see your residence time through a velocity regime?
Not sure what you mean...

Can you show us where the center-of-gravity of the car is?
Not sure how can I find out?

Have you ever put a model of it in a windtunnel to determine it's aerodynamic center-of-pressure?
I am currently trying to get it sorted, have someone ready to put a model in there but need a CAD drawing done first.

Does the car do a wheel-stand,with chassis-flecture at launch?
Yes, chassis must flex to enable it to put the power down

If so,at what distance and velocity does the front wheels touch down?
Front wheels come down at around 60 feet out or about 100mph

Do the small outboard winglets at the front axle keep the wheels firmly planted near top-speed?
So far yes, we have only tested the car so far but at 160mph the car was very stable.

Can you say how much the cabin raises as the drag slicks grow to full sidewall height?
The tyres grow about 8-10 inches in total

Is the length of the car at it's maximum or could it be any longer?
We are restricted by wheelbase (centre of wheels) which is 125 inches. Everything else we can do what we want.

Can the wheelie-bars be enclosed?
Yeah


I agree safety is paramount its my dad in the car so I'd like it right.

Even if there are some little things I can do/make it might be the difference between a 6.200 and a 6.1999

Thanks again all appreciate your time.

Luke

Luke,apology for late response and thanks for the data.Since many dragsters have so much power that they might go through 32-partial clutch engagements before actually reaching lock-up close to the finish line,to avoid wheelspin.----------- If that were the case for your car,then,perhaps you might have some power available for some additional mass,in the form of aero add-ons.------------------- Or,with substitution of carbon-fiber epoxy,you could add structure and simultaneously LOSE weight.------ If your clutch is fully engaged by the finish line,and you are not experiencing wheelspin,is the car still accelerating strongly? or is the power and gearing playing out?---------------------- With respect to the time/speed curve,some drag racers believe that they're at speed so briefly,that power-to-weight is the most important parameter and to hell with aerodynamics.-------------------------------------- I have very little data regarding dragsters and what I have is from the work of Don and Gerald Arivett who were developing a low-drag AA Fuel Dragster,fully-enclosed,with Cd0.20 ( Cd 0.18 @ 12-degrees yaw ).This was 1987,and at that time,no complete windtunnel tests had ever been performed on a dragster.--------------------------- They looked at Indy cars,since they were also open-chassis,so to speak,and the best of those cars had Cd 0.69,and they believed the best funnycar had Cd 0.60.---------------- The Arivett Bros. believed that their car,in 250-mph territory,would free up over one thousand horsepower.------------------------- So it looks like drag reduction does pay.--------------------------------------- Looking at Relentless,my thought is that (1) the integral nose/wing combination lowers the efficiency of the wing.My intuition tells me that a smaller front wing,moved forward,would provide as much downforce with less drag penalty,operating in "cleaner air". (2) The abrupt chopping-off at the back of the nose section is accompanied with complete flow separation and turbulent wake trailing back to the engine.(3) The engine itself poses a "torture-chamber" to the air,both in it's leading aspect and flow separation behind it.(4) The firewall of the altered's body is so sharp-edged,along with the windscreen frame,that I'm fairly confident that you've got complete flow separation at that point,with little recovery if any,which may be why you had to raise the drag chutes up so their droque-chutes could catch some "clean" air.(5) The rear fenders are sharp-edged enough that flow is torn up there,although it may not be a problem due to the separated flow ahead of them.(6) As mentioned by others,the tubing and padding for the roll-cage could be streamlined like aero struts on aircraft,along with the support structure for the rear wing.(7) The Goodyears,as exposed wheels,have been windtunnel-tested and themselves have a drag coefficient of 0.57.------------------------------------------- If any of these areas can be faired in,or enclosed without violating class restrictions,especially the rear wheels I think it would pay you dividends.The entire wheelie bar,if enclosed like a boat-tail,tapering to 50% of the cross-sectional area of the body ( like drag-bikes )with some fairings in front of the wrinkle-walls would dramatically reduce drag,but also might violate rulebook.(8) My final thought for now,is the rear wing.And you may have fully investigated this already but back in the 1980s,Joe Amato ran an Eldon Rasmussen "high-wing" spoiler which is credited for Joe's victory and 260+ mph runs.The wing was small,placed very high,and behind the car,operating in very clean air,with max downforce,minimum drag,and more "leverage".If Relentless is stable now,your starting from a good place.------------------------------ If you can get that windtunnel model going you could do a lot of "safe" shakedown runs without risk to your dad.I don't know if you'd have access to the MIRA facility.There is a Donald Campbell tunnel at London's Imperial College and at Southampton.Williams Grand Prix Engineering has it's own tunnel.If these can't help,perhaps another university with Mechanical Engineering Dept.and windtunnel might take your car on as a undergraduate or graduate project if you threw a few hundred Pounds their way.Keep us posted,and we'll keep thinking about Relentless.Race safe,Phil.