Why don't vehicles have aerofoils to partially take the weight of the car?

[AeroMcAeroFace]

Doing a bit more research yields this, https://core.ac.uk/download/pdf/195212282.pdf

Very interesting, not wings technically but use of blown aerofoils, that selectively increase lift in order to reduce rolling resistance, and increase downforce for grip. Interestingly, they also use the same effect on the sides for stability.

The gordon murray t50 used similar principles though only for downforce, so the precedent is there.

"Lift coefficient was increased
for rolling resistance reduction by blowing only the
top slot, while downforce was produced for traction
increase by blowing only the bottom. Also, side force
and yawing moment were generated on either side of
the vehicle, and directional stability was restored by
blowing the appropriate side slot"

[Ecky]

I skipped over a few pages in this thread, so this may have been addressed, but my ultimate questions are these:

1) Does generating lift necessarily generate drag? All else being equal? Certain you can take an aerodynamically dirty vehicle and clean up the wake in a way that creates lift and may not add drag, but that's not what I mean.

2) If creating lift *does* create drag, wouldn't it be the case that, at the speeds where this lift matters, rolling resistance is a much smaller component of total drag? At 30mph/50kph, where rolling resistance is dominant, very little lift would be generated. At 80mph/130kph, where aerodynamic drag is the vast majority of total wasted energy and rolling resistance approaches negligible, is it worth adding more aero drag to cut rolling resistance?

[aerohead]

Originally Posted by JulianEdgar

So, one of the lowest drag cars ever created in the world to run on a public roads had driver handling issues with just 14 per cent rear lift in crosswinds, but you're suggesting 50 per cent lift would be fine?

Anyone can construct in a 'thought experiment' a series of scenarios where anything is possible, but I'd much prefer to look at the real world - what has been achieved, and what the problems were.

As far as I am aware, there has never been a road car of any type, ever created anywhere, where aerodynamic lift was a positive.

1) 1969 Volkswagen Squareback
2) 1969 Volkswagen Karmann-Ghia
3) 1973 Porsche 911
--------------------------------------------------------------------------------------
These three examples satisfy the requirement for prima facie counterfactual evidence to Julian's comment, as worded.
I don't believe Julian actually meant what is implied by his comment, however, unfortunately, the linguistics is loose enough to undo the intended premise.( 'Check your premises' Ayn Rand / Jesse Stone )
I might have commented that, ' there has never been a road car of any type, ever created anywhere, where aerodynamic lift was deemed a positive attribute, and intentionally designed into the vehicle.'

[Isaac Zachary]

Originally Posted by Ecky

1) Does generating lift necessarily generate drag?

Maybe. But I don't think it's significant. An airplane at a low level of attack can have a Cd as low as 0.02, or maybe even lower. At a very high level of attack that can go up to 0.18 or 0.20 or so. But even then the overall Cd is lower than the great majority of road going vehicles.

Ironically, the faster you go the more it might make sense to add wings, with or without following a road.

Or maybe we all should be driving airplanes that have modified to apply the power to the wheels.

[Ecky]

Originally Posted by Isaac Zachary

Maybe. But I don't think it's significant. An airplane at a low level of attack can have a Cd as low as 0.02, or maybe even lower. At a very high level of attack that can go up to 0.18 or 0.20 or so. But even then the overall Cd is lower than the great majority of road going vehicles.

Ironically, the faster you go the more it might make sense to add wings, with or without following a road.

Or maybe we all should be driving airplanes that have modified to apply the power to the wheels.

Intuitively, this is tough for me. If you're displacing air in order to provide an upward force on the vehicle, my intuition says that energy is lost. But, it's been proven many times that what is intuitive often isn't reality.

[aerohead]

Originally Posted by Isaac Zachary

Maybe. But I don't think it's significant. An airplane at a low level of attack can have a Cd as low as 0.02, or maybe even lower. At a very high level of attack that can go up to 0.18 or 0.20 or so. But even then the overall Cd is lower than the great majority of road going vehicles.

Ironically, the faster you go the more it might make sense to add wings, with or without following a road.

Or maybe we all should be driving airplanes that have modified to apply the power to the wheels.

* We probably ought to have an example of one of those.
* A laminar wing by itself, cruising at 41,000-feet above sea level would be one thing.
* When the fuselage, horizontal and vertical stabilizers, gapped control surfaces and such are all added, Cd 0.02 would seem extremely liberal.
* The 1957 MG EX 181 race car had the same drag as the 1935 Douglas DC-3/ C-47 aircraft, Cd 0.12 ( one of the lowest drag aircraft ever reported [ for a non-laminar aircraft ]).
* Laminar aircraft can't exist in ground proximity.
* We'd have to be extremely specific.

[aerohead]

The Indianapolis 500 demonstrated some interesting quanta:
* six tanks of fuel per car, at 18-5-gallons (US)/ tank [ 70-litres / tank ]
* 95-miles ( 153-km ) range per tank
* six sets of tires per car ( changed at each pit stop )
* to average 233-mph ( 376-km/h )
* 1,655-pounds empty
* In recent past, Indycars have produced up to 6,500-pounds downforce
* Dynamic 'weight' up to 8,155-pounds
* 111-gallons of fuel
* 500-miles
* 4.5 miles per gallon
* The Corvette Stingray Official Pace Car, at interstate velocity, is capable of over 32- mpg
* Speed, lateral g-forces, and induced drag is costly

[JulianEdgar]

Originally Posted by AeroMcAeroFace

It doesn't say that the lift wasn't wanted you have added that bit yourself. They pitched the nose up, increasing lift and reducing drag.

Don't take my word for it. Read the 'bible' on solar car aero next, and the references to lift.



I just got it off the shelf, and of the seven references to lift, none deems it as a positive. And that's the most authoritative reference on the lowest drag cars in the world.

[freebeard]

Originally Posted by aerohead

These three examples satisfy the requirement for prima facie counterfactual evidence to Julian's comment, as worded.

In what way are they counterfactuals? Esp. the 1969 Squareback. 1970 was the first year for the long nose IIRC. And that was about luggage capacity and the safety bumpers. What was different about the '69 to the '62?

[JulianEdgar]

Originally Posted by j-c-c

Well in as few words as possible it you really think, and apparently have doubled down on your point, "ideas alone are worthless", narrowing your cover in this discussion to include the key word "alone", we disagree strongly.
I'm open to all ideas, from anyone, including yours shared here on this topic, and hope I never, at the least, try to squash them before shared and well understood. My personal life experiences have shown to me, which path is best, for the best outcome.

Interesting.

If you are "open to all ideas from anyone", and there are others who think the same, then I imagine that's why crackpot ideas spread.

Most people apply some sort of critical analysis to ideas, rejecting those for which there is no evidence, but I guess there's no requirement to do so.