Aerodynamic lift- A real problem

[Nerys]

well I am curious. 92 pounds of lift. WHAT DOES THAT MEAN.

if sticking 100 pounds of sand in your trunk can improve snow handling would not removing 100 pounds have a similar opposite effect? (I really don't know)

I wanted to say but I have felt the "gusts" give me a good solid shove on the highway but then I thought well its not the same thing. one is blunt drag wind hitting the side of your car. How many pounds of force is that?

I have SEEN gusting winds MOVE a 12,000 pound RV. Right in my driveway. I measured it. Moved the thing 17 inches sideways (no joke) but was that lift or just brute force SHOVE into the side (I am guessing brute force shove on that one)

it would be interesting to figure this kind of stuff out but I certainly do not possess the skill or inclination to do it :-)

Frank I agree 99.99999999% of spoilers are PURELY for looks.

but I swear I read somewhere of a car that had lift issues making it "light" ie dangerous under certain conditions so they added a spoiler not to create down force but to "disrupt" the airflow to kill any generated lift. I thought I remembered it being an automatically extending spoiler that "opened up" at a certain speed though I could be mixing memories on that.

[Hermie]

Nerys: More like 60% of spoilers are for looks, almost all being OEM spoilers. I could find at least 200 spoilers in 5 minutes that are made for real downforce.

But that's just another example of ecomodder's heads in the sand to reality... Narrow-mindedness is not a good thing.

but I swear I read somewhere of a car that had lift issues making it "light" ie dangerous under certain conditions so they added a spoiler not to create down force but to "disrupt" the airflow to kill any generated lift.

That would be an "active" spoiler, which many cars have today, since automakers do know that lift is an issue to safety, which is a common fact that some people here seem to think is fiction...

Quite honestly, I'm laughing my rear off at the sheer ignorance of that, and that they then claim to be a "gearhead." A "Wannabe" is a more accurate description!

[JackMcCornack]

Originally Posted by Hermie

Actually, I haven't been putting too much time into looking up stuff.

Awww. I was hoping for supporting documentation. The spinning (and flying shortly after the spin) Mazda in the previous thread was an eye-grabber, but from an argument supporting standpoint, it's like arguing that water is bad for you and using the Titanic as your example.

Originally Posted by Hermie

I do have a life, and a college career to attend to.

That deserves an attaboy and a woohoo! I used to teach (before I got in the aero biz) and I have huge respect for anyone who chooses a career in education. To quote Farm Boy (in the Princess Bride again, but at least this time I got the character right), "This isn't as easy as it looks."

Originally Posted by Hermie

Besides, it's common sense that lift degrades performance. Why would people that actually work designing cars spend time and money publishing papers stating the blatantly obvious?

Hah! Now I know you're not teaching aerodynamics (and if you're teaching any of the sciences, I hope you don't use terms like "common sense" and "blatantly obvious" much in class). I would agree that lift degrades cornering force and braking force, and that at the lower end of the speed spectrum, lift degrades acceleration, but if you set up a car for less than optimum lift, it will degrade high speed acceleration and top speed.

That may not be common knowledge, because in many motorsports (e.g. dirt oval racing, and in the highest power classes, Bonneville) the course is too short or tight to achieve genuine top speed, but elsewhere there's an optimum. The NASCAR guys tune in less lift at the slow tracks than they do at the fast tracks, because at some point (determined by horsepower, speed, and the mix of tight corners to long straights), reducing lift costs more energy than it is worth. It wasn't until the mid-'60s that Formula 1 cars had enough power that top speed wasn't an issue and it was worth getting the lift down to zero (and they've gone way way past that since then, to negative lift, then to negative lift greater than the mass of the car).

Of course, having more than optimum lift costs energy too. Remember "Fastbacks"? The looked fast, they looked like they were pulling the car's wake into the dead water behind the car, but if you look at a car like a wing section with an aspect ratio of about .5, the induced drag from what the airplane folks call tip vortexes was far worse than the pressure drag. But for minimum drag, a car is going to generate lift, and if you go over or under that optimum Cl, you'll increase drag, which will cost you in top speed, in high speed acceleration, and in what matters most on this forum: fuel consumption.

[MetroMPG]

It's clear to me that the original poster isn't willing to engage in either the research (self-admitted) or level-headed discussion (my conclusion) to make this a meaningful thread.

On top of that, an insult has now been leveled generally against all forum members, which just adds to the evidence he's more interested in escalation than edification.

The moderators will usually tolerate "cranky", but only when it's typically accompanied by "useful".

I absolutely think there is merit in discussing the message (lift implications of aeromodding), but after talking with another moderator, I've decided to shoot this particular messenger. Hermie's been banned.

[thatguitarguy]

Originally Posted by Nerys

Frank I agree 99.99999999% of spoilers are PURELY for looks.

but I swear I read somewhere of a car that had lift issues making it "light" ie dangerous under certain conditions so they added a spoiler not to create down force but to "disrupt" the airflow to kill any generated lift.

This is what a true "spoiler" does. It "spoils" the airflow. There are some experimental aircraft that use spoilers instead of ailerons. You activate the spoiler - that wing loses lift and drops - the aircraft turns. They don't put unnecessary crap on airplanes just because it looks cool.

[Nerys]

hmm what airplane is that? I never heard of using spoilers to turn. you use then to burn altitude without increasing speed but to turn? I imagine it would be a sluggish method of turning but might be neat as a "backup" similar to using proportional thrust to turn etc..

[MadisonMPG]

Originally Posted by Hermie

I weigh 150, and drive solo. Try again, jackass.


Neil: Explain your fixation on drag.

Madison: An Audi TT has enough rear lift to kill someone from spinning out of control at about 120 MPH. Your exaggerations either show a lack of maturity or IQ.

*only post I want to reply to*

Once again, 120mph, something you WILL NOT see in America. Legally.

[JackMcCornack]

Originally Posted by Nerys

hmm what airplane is that? I never heard of using spoilers to turn. you use then to burn altitude without increasing speed but to turn? I imagine it would be a sluggish method of turning but might be neat as a "backup" similar to using proportional thrust to turn etc..

They're pretty common in some subfields of the av biz. The first three that pop to mind are the Mitsubishi MU-2 (twin engine corporate commuter) and of course (he said, blushing modestly) the Pterodactyl Ptiger and the Boeing PAVE Tiger. They're called spoilerons in that application and they're not sluggish at all, but they are draggier than ailerons. In fact that's their primary advantage; when banking, aelerons increase lift on the wing going up, which increases drag on that side, which makes the aircraft yaw away from the direction of the turn, but with spoilerons, drag increases on the wing going down, which yaws the aircraft into the turn. Thus they're particularly useful for low speed high dihedral recreational aircraft (Ptiger) and early UAVs that had to fly themselves (PAVE Tiger)--oh yes and for specialized aircraft flown by non-pilots (one more modest blush: the Kinetic Aerospace Switchblade in the 20th Bond film, Die Another Day). If everybody had spoilerons we wouldn't need rudder pedals any more--but we would need more Jet A because spoiler make drag. Spoilerons are not an ecomod.

[Nerys]

very cool ! I am definitely going to have to look those up and maybe try it on a model plane. Might make for smoother maneuvers for my camera platform!

[Christ]

Darin, Thank you.

Without reference material, I don't have much else to add to this thread. I really need to get back all the books and such that I've lost through the years, and get back into my studies of fluid dynamics. It truly is an intriguing study.

That said, I'll help where I can with input and experience, but I don't expect to be of much assistance in this thread, beyond what I've already provided, which (admittedly) isn't much.