42 replies to this topic

[Gemini]

sorry if it's so basic that it even sounds stupid...

I think I know the school basics of how the principal forces acting on aeroplane's wing work: drag, lift, net lift force etc...

What can make me win many few beer rounds tomorrow night is to find out how the hell the plane (well, some planes at least) can fly up side down How come the net lift does not turn into downforce then ? Or does it mean that when flying "up side down" the plane is never flying really horizontally , but has to position the wings at the angle that will allow the lift to build up?

Anyone can give me a simple explanation. Simple enough to share it with few other drunk bumps tomorrow. Pleeeeease...

[rdrcr]

Some primers:

Aircraft wings are tilted (called "angle of attack").

As they cut through the air, they force air downwards (they even force the air flowing above them to move downwards.)

For every acting force, there is a reacting force, so as the wing forces the air downwards, the air forces the wing upwards.

Because of "conservation of momentum", the wing can only fight against gravity if it throws air downwards.

The plane flys, it essentially "surfboards" across the air.

So, how can a plane fly upside-down? The pilot simply flips the plane (or performs half of a loop-the-loop), then uses the control surfaces ("flaps") to tilt the plane so the wing still forces air downwards. But this is what the pilot was doing for right-side-up flight too: tilting the plane so the wing acts downwards upon the air.

From an article that does a very good job of explanation with regards to sustained inverted flight

"...Most airfoils are cambered, or curved, on top but flat on the bottom. As a result, they fly better upright than inverted. Symmetrical airfoils, which have the same curvature on both surfaces (3 in diagram below), perform exactly the same upright or inverted, and so are favored by aerobatic pilots. In order to fly at all, however, a symmetrical airfoil must be positioned at a slight positive angle-leading edge high-with respect to the flight path; otherwise the airflow around the upper and lower surfaces would be the same, and no lift would be created..."






http://www.airandspa...02/AM/fusd.html

[dave]

I have built and flowen a few radio controled airplanes. The airplane that is desiegned to fly inverted has a symetrical airfoil. Meaning that the wing shape on top and bottom of the wing is the same. When flying upright the aircraft is desiegned so the wing has slight postive angle of attack with all controll surfaces at neutral.

When you roll to the inverted a slight amount off down elevator is required to maintain straight and level flight. This gives the wing a positive angle off attack to the air. Use of flaps while inverted will kill lift

Hope my humble expanation helps.


dave

[Top Fuel F1]

Originally posted by Gemini
sorry if it's so basic that it even sounds stupid...

I think I know the school basics of how the principal forces acting on aeroplane's wing work: drag, lift, net lift force etc...

Re:

http://www.grc.nasa....rplane/bga.html

Browse around this web site. It's very informational on the basics.

Rgds;

[Wolf]

I would explain it with angle of attack- plane is propelled by the force in it's longitudinal direction, and when flown upside-down I believe lift on wings is directed downwards. But that lift can be reduced by increasing the angle of attack (relative to the ground, which should be dereasing for the airfoil) plus reduce vertical component of the lift and at the same time propelling force counteracts thus reduced vertical component of the lift to bring the plane in the ballance, which should look like this

Fp*sin(alpha)=(Fl-dFl)*cos(alpha)+W,

where Fp- propelling force, Fl- lift, -dFl- decrease of the lift due to decreased angle of attack, W- weight, alpha- angle of attack relative to the 'horizontal flight'. Under normal circumstances (horizontal flight) the equation is Fl=W...

Note on Edit:
OOOPS! I logged off when it struck me that I left out the gravity in the whole equasion....

[Gemini]

thanks guys

[josfan]

"Aircraft wings are tilted (called "angle of attack").
As they cut through the air, they force air downwards (they even force the air flowing above them to move downwards.)
For every acting force, there is a reacting force, so as the wing forces the air downwards, the air forces the wing upwards.
Because of "conservation of momentum", the wing can only fight against gravity if it throws air downwards.
The plane flys, it essentially "surfboards" across the air."



HA! Do me a favor, pick up an elemlentary book on fluid mechanics, and look up Bernoulli's equation...

jf

[rdrcr]

He asked for a simple explaination Jos,

Bernoulli's equation states that the static pressure in the flow plus one half of the density times the velocity squared is equal to a constant throughout the flow, which we call the total pressure of the flow. Again, this is only one form of the equation and the restrictions for this form are that the flow is inviscid, incompressible, steady, without heat addition, and with negligible change in height. If we consider other properties of the fluid, we can derive other forms of the equation.

It is important when applying any equation that you are aware of the restrictions on its use; the restrictions usually arise in the derivation of the equation when certain simplifying assumptions about the nature of the problem are made. If you ignore the restrictions, you may often get an incorrect "answer" from the equation.

The equation was originally derived by considering the conservation of mechanical energies within the fluid. The molecules within a fluid are in constant random motion and collide with each other and with the walls of an object in the fluid. The motion of the molecules gives the molecules a linear momentum; pressure is a measure of this momentum. If a gas is at rest, all of the motion of the molecules is random and the pressure that we detect is the total pressure of the gas. If the gas is set in motion or flows, some of the random components of velocity are changed in favor of the directed motion. We call the directed motion "ordered," as opposed to the disordered random motion.



http://wright.grc.na...ane/wrong1.html

[DOHC]

Originally posted by rdrcr
He asked for a simple explaination Jos

...and then we'd better keep it simple.

Originally posted by rdrcr
If you ignore the restrictions, you may often get an incorrect "answer" from the equation.

Nothing could be more true. Look here:

Originally posted by rdrcr
Bernoulli's equation states that the static pressure in the flow plus one half of the density times the velocity squared is equal to a constant throughout the flow

So p0 + rho*v^2/2 = constant?

But how do we interpret this? Is the static pressure p0 equal to the static pressure of air when the wing profile isn't present or what? Suppose it is. Because the flow accelerates on the top of the wing (I assume it's not symmetric but has a deeper curvature on top), v increases, and therefore the total pressure on top of the wing is higher, which sounds like it's creating downforce ;) . On the other hand, maybe that static pressure is the local static pressure on the upper side of the wing, and then we see that because the velocity dependent part rho*v^2/2 is larger there than under the wing, the static pressure must be lower on top if the total pressure is constant. Now that sounds a lot more interesting, because then you might have some lift...

The point of this post is that an equation as such is almost meaningless, as rdrcr says (and accidentally illustrates). It does make sense to stay with simpler explanations, or you may have to expand on what the correct interpretation of the equations is.

[Ben]

Bernoulli's equation is only meant to be applied along a streamline, and as the wing directs the air downwards to create lift the streamlines point downwards as well, so invoking Bernoulli can't invalidate rdrcr's point.

Bernoulli is only a part of it and a wing can't violate Newton's third law so a net mass flow must be generated downwards to create lift.

Ben

[DOHC]

Exactly---the "downwash".

[Ben]

I work for a helicopter manufacturer and it always amuses me that people talk about helicopters as blowing a jet of air downwards to create lift and then talking about fixed wings only in terms of pressure differences due to bernoulli.

They're both wings so they generate lift in the same way. If the downwash argument is so obvious for a helicopter why not a fixed wing?

Ben

[desmo]

Great illustration of the point Ben. Watch a wet race and watch the quantities of heavy spray being thrown high up in the air in the upwash behind an F1 car for another illustration of Newton's third law in action, albeit inverted 180 from the helicopter (hopefully!) It seems that the action of wings can be usefully modeled using either pressure difference or conservation of momentum models. They really don't contradict at all.

[DOHC]

Ben, good point! I think that when it comes to creating lift (or downforce) you see several different "explanations", some of which are a bit tough to swallow. I like the downwash/conservation of momentum explanation, both because it appeals to simple physical principles, and because it's visible, as desmo points out. The pressure explanation is fine with me too, but the classical explanation using "circulation" around the wing profile seems utterly contrived to me---its intellectual taste is hardly better than cod liver oil on the palate ;)

And when talking about propellers, it's the same as with helicopters---a matter of mass transport induced by the rotating wing.

[MrAerodynamicist]

Thats the trouble with this argument - people always seem to take sides and claim one to be the the real truth but they both are. One may be more useful over another in explaining a particular case but they botrh still have have to hold true [within sensible limits. ]

[BRIAN GLOVER]

Ah yes, inverted flight. my favourite attitude. Most of my flying has been in the inverted mode, having owned two different aerobatic airplanes and 6 years in the Airforce.

[QUOTE]Originally posted by rdrcr
[B]Some primers:

>>>>>Aircraft wings are tilted (called "angle of attack"). >>>>>

This is called 'Angle of incidence' and on some aircraft, the left or right side of the wing has a higher angle of incidence to counter propeller torque depending on which way the prop turns. A 'wash' on the wing can perform the same function.
If you fly inverted in an airfraft with a lift creating airfoil derived from NACA section tables and assuming that you have inverted fuel and lube systems, much elevator input is required to induce lift from the wing. There is a vertical component to the propeller thrust and the elevator deflection also creates lift.
A loss of altitude is inevitible with this type of section, even in powerful planes such as Spitfires and P51s. The BF 109 had fuel injection and could be pushed over into a dive to about 7 negative gs. The Spitfire would have to roll inverted, 'split S', to stay positive to keep the German in sight. These wings are very difficult to fly inverted.

>>>>>>>.....So, how can a plane fly upside-down? The pilot simply flips the plane (or performs half of a loop-the-loop), then uses the control surfaces ("flaps") to tilt the plane so the wing still forces air downwards. But this is what the pilot was doing for right-side-up flight too: tilting the plane so the wing acts downwards upon the air. >>>>>

That would be a 'half roll' and the 'elevator' would be deflected. This is the movable section of the horizontal stabilizer on the epenage. There are`many different types of flaps systems. They generally alter the cord on the wing, to enable lower stall speeds in the upright attitude and are not used for pitch contol.


"...Most airfoils are cambered, or curved, on top but flat on the bottom. As a result, they fly better upright than inverted. Symmetrical airfoils, which have the same curvature on both surfaces (3 in diagram below), perform exactly the same upright or inverted, and so are favored by aerobatic pilots. In order to fly at all, however, a symmetrical airfoil must be positioned at a slight positive angle-leading edge high-with respect to the flight path; otherwise the airflow around the upper and lower surfaces would be the same, and no lift would be created..."

That is correct. My Xtra 300 has identicle flight characteristics inverted or otherwise and has no glide ratio to speak of. In other words, if the engine quits on a 2000ft downwind, It will barely make it to the runway. Modern jet fighters need much thrust to keep airborn. The space shuttle does a dead stick landing from orbit and the pilots employ 'energy management' to make it to the runway.

[RDV]

....angle of attack can make any shape lift ( exept a sphere , the exception as polymorphicaly perversely symmetrical) given enough speed , think of Winklehock at Nurburgring or Weber & Dumbreck at LeMans

[RDV]

...missed commenting on the downwash vs pressure skirmish going on, so lets toss some more kindling on the fire.... on aircraft wings undersurface , which would be producing all the downwash , gives @ 25% of total wing lift, whilst upper surface (low pressure corner) gives the rest... this example can be seen on early aerofoils , which were skinned only on one side , leaving the undersurface with protruding spars and formers, or even today, where on military aircraft all the payload or armament is slung under the wings, a fully loaded tactical bomber looks as it has no wing undersurface.... you never seet his mounted on top surface of wing....

[rdrcr]

Gentlemen,

I have before you a post from a good friend of mine who is an acrobatic pilot himself. I relayed this thread to him for his opinion as he is far more knowledgeable than I about such things. Brian, you and he would get along famously I'm sure. His name is Don. He's an auto racing nut as well as his addiction to flying. He goes by the nick of Snaproll on other other forums. I've been trying to get him to start posting here as I think his contributions would be most interesting as well as entertaining. So let's give him some encouragement and prompt some questions in his direction... as I'm a bit in over my head on much of where this thread is going but I'll try to keep up... I'll relay our responses to him and perhaps he'll chime in personally.

Here are Snaproll's thoughts...

Richard,

First, never forget the F117 Stealth Fighter. Before the F117, everything flew with wings that generated tremendous amounts of lift. But when the F117 came along it proved that even shapes that weren't aerodynamically sound could fly, with the aid of computers and powerful engines. Until the F117, what actually creates lift had been argued between the engineers that believed Bernoulli and the ones that felt Newton's third law was the key.

The reality is they were both right. The wings on a F117 generate the majority of their lift from downwash or as you said surfing on the air. Small gas model airplanes have wings that are flat on top and bottom, they fly using downwash from the wings angle of attack. But only because they have enough power to weight to overcome the tremendous drag that's produced by a flat wing. Tilting your hand outside a car window when its going 30 mph is another example of downwash lift.

IMHO, Brian Glover and Ben get the prize. Brian posted: "There is a vertical component to the propeller thrust and the elevator deflection also creates lift." (I disagree that the elevator deflection ITSELF creates lift, it pushes down on the tail which causes the wing to rotate around its center of lift, increasing the wings angle of attack and this produces additional lift.)

Ben posted: "Bernoulli is only a part of it and a wing can't violate Newton's third law so a net mass flow must be generated downwards to create lift." (You can't argue with that but there is another source of lift, the engines thrust vector.)

In horizontal flight: Lift = Weight and Thrust = Drag

In horizontal flight the lift generated by the wing is a function of its shape and angle of attack to the on coming (relative) wind (which produces downwash aka lift). In climbing flight wing lift + the vertical component of thrust = climb rate.

Example: An airplane has a wing installed with 2 degrees, leading edge up, angle of attack when its upright. It weighs 2400 lbs and flies level at 150 mph with 180hp. At 150 mph the wing is producing 2400 lbs of lift and the engine thrust is equal to the drag the plane produces at 150 mph.

Lets first discuss how an airplane climbs and remember you don't get something for nothing: We increase the wings angle of attack by 5 degrees via the elevator. The plane slows to 110 mph and is going up at 500 feet per minute. Why? Lets look at the wing first. If you put it in a wind tunnel at 110 mph with (2 installed + 5 climb attitude for at total of) 7 degrees angle of attack, you'd find that it is only producing 2200 lbs of lift. SO HOW IS THE PLANE ABLE TO CLIMB! Well, you also tilted the thrust angle of the engine, now its pointing 5 degrees up (assuming it was at a 0 degree thrust angle in level flight) and the vertical component of the thrust vector is going to add LIFT. In this example, probably somewhere around 300 lbs of lift, for a total lift component of 2500 lbs which give our plane 100 lbs of buoyancy.

Now things get complicated... Turn the same plane upside down. All the principles we've discussed still apply. But, now you also have to compensate for the manufacturer's 2 degrees of installed wing angle (which is now pointing down) and with a flat bottom wing the angle of attack must be increase even more to offset the now downward lift generated by the wings (Bernoulli) shape. So to get level flight the wing will have to have an angle of attack to the relative wind of something like 10 degrees. With this high angle of attack come more drag. So, when this plane is inverted you end up with it's wing at 10 degrees, the engine thrust at 12 degrees and an inverted level flight airspeed around 100 mph because the 180 hp of thrust is acting against more drag created by the wings angle of attack (and the load on the elevator and the angle of the fuselage).

Make sense? If it does and you've followed this, you should be able to answer this question. Take the same plane that in normal, right side up level flight went 150 mph and dive it down at 200 mph and level off. At 200 mph, before the speed decays back to 150 mph, what will the wing's angle of attack be and why? Hint, Bernoulli will be winning this one.

Something else to remember, F15's and the like can climb straight up. At that point the wing lift is pulling them horizontal and thrust is the only thing that is making it climb. Of course that's only possible when you can generate more pounds of thrust than the aircraft's weight. Aircraft with thrust to weight ratios less than 1:1 can go straight up, until they loose momentum then gravity takes over and they fall like a rock.

You can post this for me if you like, all I ask is a little credit. I've spent a few hours in a plane like the one in the example, flat bottom wing upside down. I swear this is how it works. I didn't understand why it flew the way if did until I got some books on aerodynamics. Once I read the books I understood better how it was going to react. Aren't aerodynamics fun?!?

Take care my friend,

Don

_________________________

Well there you go Snaproll... credit where credit is due.

So what say all of you?

[Wolf]

Rdrcr, isn't it basically what I've said, 'cept I added that at relative angle of atack of the wing (-10°), the lift will also decrease...;)

[rdrcr]

Jeez Wolf... uhhh I think so. Perhaps your equasion was a bit over the top, I know it was for me!

I did get a response from him, stating that you had some points but lost him with some of the jargon.

He had an equation in there that probably said it all but I wasn't about to review/question it. If we said the same thing, he did it in a hell of a lot less words!

I suspect he'll be in before to long to introduce himself and carry on the discussion if he wishes...

[Wolf]

Rdrcr, that's not 'a jargon'- that's my deficiencies in 'technical English' department...

[DOHC]

Very interesting posts by Brian (as usual) and snaproll/rdrcr.

But as for the Bernoulli vs downwash issue, I think that it's not a matter of two different effects. My argument is the following: a symmetric wing (aerobatics) only creates lift via angle of attack and downwash. But if we have an unsymmetric wing at zero angle of attack, you may still have lift (blame Bernoulli if you like). The point is, that wing still creates a downwash. No downwash, no lift. Also, no lift without drag. (Here, of course, I'm not talking about gound effect but free flow.)

snaproll gave us a problem to work out (not too hard). We can also consider another problem for the same plane that manages 150 mph level flight while producing a lift of 2400 lbs. Suppose that we increase the weight of the plane, e.g. by adding another 150 lb passenger. What will happen? The speed at level flight drops, not because the passenger has increased the drag, but because the wing doesn't generate 2550 lbs of lift at 150 mph level flight. There is just one way to generate that lift, and that is to increase the angle of attack. This will induce more drag, so the speed drops. The increased angle of attack is needed to produce the necessary lift/downwash. Bernoulli won't solve the problem.

In terms of downwash/conservation of momentum, I think it's neat to use Newton's second law in the form

F = dp/dt,

where F=force and p=momentum. In this particular application, it says that the force equals the change of momentum per unit time, i.e., we have to create a downwash (a vertical downward velocity component in the flow) in order to have a lift force (a vertical upward force component). If this happens due to angle of attack or due to wing curvature/geometry is immaterial.

Now, consider a completely horizontal flow (level flight); the momentum vector of the incoming flow is then horizontal. Immediately after the wing (unsymmetric or at an angle of attack) the momentum vector is no longer horizontal but points a bit downward. That vector can be decomposed into a horizontal component and a vertical component. The magnitude of the horizontal component is of course smaller than the original free flow magnitude of the momentum (Pythagoras theorem). The difference (loss) produces the drag force. The vertical component, on the other hand, emerges as a new component, and it produces the lift force, in both cases in agreement with F = dp/dt. Both lift and drag are reaction forces in this model. Of course, this model is crude and doesn't address what happens near the wing surface. It only gives an overall picture.

I think that some of the confusion of pressure vs downwash, is just that while pressure (and Bernoulli) gives a local, detailed description, the downwash/force model is a macro model.

Compare this to loads on a structure. The total load might be described by a single force (macro model), but in reality you have a force field and a stress field in the material (local, detailed description). Likewise, in hydrodynamics pressure is a force field (pressure = force/area, N/m^2), and density is a "mass field" (density = mass/volume, kg/m^3). If we choose to discuss in terms of force and mass we end up with the downwash view, but if we choose pressure and density, Bernoulli's equation is the preferred tool.

We need both models, but for an elementary understanding, you don't have to be so fancy, and the macro-style force thinking is usually easier to grasp.

All the local models require some elementary feeling for what fields are, or for partial differential equations if you prefer math language. Those are so much harder to understand than ordinary differential equations.

This post might be a bit OT as I don't address how to fly inverted, but I hope the remarks have some value just the same.

[snaproll94e]

Hi Gents, Snaproll checking in. First off, I'm no english major so PLEASE cut me some slack unless this thing has a spell check that as of yet I haven't found

DOHC,

I wouldn't argue with anything you've printed. I would suggest that Bernoulli is alive and well and lives on top of a wing in flight so he does enter into this problem. I am no aeronautical engineer so I won't try to trade equations with you. I will tell you that you can measure a pressure differentual between the top and bottom sides of a wing and its usually highest 1/3 the cord width back from the leading edge.

I have witnessed the pressure differentual at work, the filler neck on my wing tank is at the top of the curve, the vent for the tank is on the bottom side of the wing. One day I looked at the wing in flight and noticed fuel being sucked out from under the cap. I landed and found the seal had split when the last time I put the cap on. When this started happening the fuel level in the tank was at least 4 inches below the top of the wing/filler neck so, as myself and others have seen for ourselves (some with devistating results) there is a low pressure on the wing, sucking it up, if you will. Another interesting thing about this experience was that there were pitch angles in level flight where the fuel stopped syphoning out. These corresponded with speed changes which to me means that as the wings angle of attack changed the center of (low) pressure changed.

I agree that as the air on top of the wing meets the air on the bottom at the trailing edge of the wing they converge and the air at the top washes down. Does this sound right to you? If you think about it if there is a low pressure on top why doesn't the air on the bottom of the wing get sucked up? Or is it that the angle of the (faster moving) air on top of the wing, moving downward along the aft curve of the wing force the air on the bottom of the wing down? The latter would be my guess. So that and Bernoulli support the plane....agree? I've seen this argued in aviation publications both ways. You'd think that with today's technology we'd have a definitive answer.

Check out my last question again. The answer has a lot to do with this discussion. I'll post the answer or you can take a shot at it. Either way is fine with me.

Best Regards,

[DOHC]

Ah, welcome snaproll!

Or is it that the angle of the (faster moving) air on top of the wing, moving downward along the aft curve of the wing force the air on the bottom of the wing down? The latter would be my guess. So that and Bernoulli support the plane....agree?

That sounds very right to me. The two velocity vectors from above and below add up to a slightly downward vector. Personally I don't see any conflict between Bernoulli and the downwash. The observable downwash is just the integral, or aggregate, effect of the local description. Net lift becomes the integral of the pressure differential over the wing surfaces.

[snaproll94e]

DOHC,

Looks like we're off to a good start! You didn't say if you wanted to take a shot at my question or if you wanted me to post the answer.



Take the same plane that in normal, right side up level flight went 150 mph and dive it down at 200 mph and level off. At 200 mph, before the speed decays back to 150 mph, what will the wing's angle of attack be and why? Hint, Bernoulli will be winning this one.

[DOHC]

Ok, here it goes: The angle of attack (pitch) is slightly negative (installed angle of attack plus this negative pitch angle might still be positive though).

Let's say, just to illustrate with some numbers (although I have no idea of whether they're realistic), that you have 2 deg installed angle of attack and -1 deg pitch for a total of 1 deg angle of attack. I think this is what happens in your example, because at 200 mph, 1 deg total angle of attack is enough to create the necessary 2400 lb lift at high speed level flight. As the speed slowly reduces to the standard 150 mph level flight condition, total angle of attack goes up again, so that 2400 lb lift is created at that lower speed.

Too bad I only took one flying lesson so far in my life!

[rdrcr]

A hearty welcome Snap! Great to have you on "board".

That rushing sound you hear is this thread discussion flying over my head.... DOHC, you need some more stick time with all that knowledge!

... I'll just go back to my reading now....

[DOHC]

Originally posted by rdrcr
DOHC, you need some more stick time with all that knowledge!

Well, wouldn't that be nice! Maybe I should work less in my profession (which allows me to know everything in theory and nothing in practice ), and spend some time in the skies instead, not just as a passenger.

Meanwhile, rdrcr, I hope you'll get some wheel time in that McLaren/Elva I read about.

[DOHC]

I'd like to ask a question about wing design though. All reasonable airplanes today have a convex lower surface of the wing (the upper is of course always convex) instead of a concave surface as could be seen in WWI airplanes, and as we see on F1 cars today (ok, tunred upside down in this application).

My question is, why are airplane wings convex on the lower surface? Clearly that leads to less lift, but also much less drag. Is this design chosen to optimize lift-to-drag ratio (and hence fuel efficiency for the airplane) or what? Or is it better to have a convex lower surface in high speed applications, while concave is desirable in low speed applications? After all airplanes do deploy flaps and slats and the like to improve low speed characteristics, thereby creating a "concave" lower surface. With these control surfaces deployed, the glide ratio typically drops significantly.

Snaproll, Brian, Ben, Wolf and the rest of you, could you clarify this?

[DOHC]

Then another version of the same question, for RDV perhaps. RDV, did you work in F1 during the introduction of wings in 68/69 by any chance?

What's interseting about that time is that many of the early wings were very much home-made and were not at all aerodynamically sophisticated. The two significant exceptions at the very beginning were Chapman's designs for the Lotus 49, and of course before that, Jim Hall's design for his Chaparral cars. If we have a look at those two, the wing profiles look pretty much like standard NACA profiles, with convex upper and lower surfaces.

Pretty soon though, when the wings became fixed, they started having concave upper surfaces to generate more downforce. Also, Gurney flaps began to appear frequently, although they had been around and called spoilers for some time already. (The Ford GT40 being one example.)

So, RDV, I just thought you might be the person to ask. What was the aero understanding like in those days in F1? Was it only Chapman and Hall who had some understanding, and do you know anything about how, in those formative years, real aerodynamics was brought in? How did it all happen?

My intention is not to hi-jack the thread here, but I take the liberty of bringing race car downforce in, as an application of flying upside down...

[Ben]

The Chaparral G.S.2G used what was pretty near to a NACA 0008 or 0009 (symmetric wing with max thickness either 8 or 9% of chord). I suspect any considered efforts at this stage were based on NACA aerospace research.

As for DOHC's question - not a clue I'm afraid. I now on some of our rotor blades we use a reflex curvature on the trailing edge to minimise the pitching moment of the section.

Ben

[Wolf]

DOHC- some early day amusement with aerodynamics... http://www.atlasf1.c...&threadid=41445 (recent thread in TNF).

As for origins of aerodynamic devices in GP racing, I believe Brabhams were first to sport the nose mounted 'fins', and the first cars to use rear wings were Ferrari (apparently it was 'started' by Chapman who intended to mount helicopter blade behind the driver, but Clark would have none of it... ). Lotus also sported moveable wings (driver controlled) that were in min. drag position on straights and tilted into 'downforce position' by a pedal. I liked those high strut front and rear wings (suspension mounted) Lotus sometime in '69 (Kyalami, IIRC) had...

And a bit of trivia for Indy bashers- I believe Smokey Yunick designed a Indy roadster with centrally mounted wing in '62, and ran with it. http://www.carousel1.com/4408_lrg.htm - see the pic.

Here's the link to one of TNF's relevant threads: http://www.atlasf1.c...&threadid=30405.

[BRIAN GLOVER]

This thread is just great. Is there more to life than cars and planes? My wife just walked in. 'Hello Darlin, just talking to some friends.' I wonder if she knew that I would never mature when she married me?

DOHC, are you telling me that all that stuff takes place when I go barrelling around the skies on Sundays? Who is this Bernulli guy anyway?

Hey Richard, nice of you to persuade Don (Snaproll) to come and dog fight with us.
Howdy Don. Shame on you, you didnt do a preflight check. Its in writing now.

All I know is that when you pull back, you go up and when you pull back a little more , you go down. Damndest thing.

A 'snap roll' is one of those nice things to do, like smoking your tires at the lights. You dont plan it, you just do it when the urge takes you. After any manouvre, you just snap the thing for good measure. It clears your head for the next thing. That's a 'Whip Stall' for you Brits.

I suppose that you are all waiting for some sort of sensible comment from me on this matter. I regret that there will be none forthcoming, I just fly for the #%^*"~ of it.

Originally posted by DOHC

....very beginning were Chapman's designs for the Lotus 49, and of course before that, Jim Hall's design for his Chaparral cars. If we have a look at those two, the wing profiles look pretty much like standard NACA profiles, with convex upper and lower surfaces. .....
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I remember those White winged Chaparral 2e's at Riverside. Many firsts in auto racing were attributed to this genious, named Jim Hall. much of the design still remains shroaded in a cloak of mystery and the clandestine link to General Motors and its connections to aerospace industries. Many autoracing firsts came from that little shop in Midland Texas, where the great man and his wife, who did a lot of the fabrication. still live in reclusion.
Firsts include:
Fibre Plastic monoquoc 'Tub' chassis, 16" forged aluminum racing wheels with special low profile firestone tires. First real racing brakes, first two way telemetry to the pits, first 'dog clutch' auto transmission with locking torque converter.

GM engineer, Frank Winchell, the head of R&D, and Jim Musser, ( Car nuts like you) took note that Jim( MIT grad) was no ordinary weekend racer. This relationship led to special race engines which led to the(ZL1) all aluminum engines, auto transmissions, paddle shifts and most of all the first driver opperated airfoils and the first use of the phraze, 'Aerodynamic balance'.
Chapman's Lotus 49 double chassis car used much of this technology.

Did you know Chapman was an aviation buff also. He left Lotus to build aircraft with Burt Rutan in California, using Irish tax payers money. He died shortly afterwards of a heart attack. Jim Clark and Chapman's relationship had been strained for some time prior to Clark's death, but that is another story.

Anyway, where was I? GM's R&D division aided Jim in exploring' Aerodynamic balance' in Hughes aircraft wind tunnels. Some devices had been used on race cars before, but untill Hall, none had worked in concert before. Musser was working on a mid engine Corvette and was intrigued by Hall's locking torque converter and auto 'dog cam' transmission and incorporated it into the GS11a experimental car. Some Chapparel lap records were never broken. Hap Sharp, Jims partner and Roger Penske started the modern way of making racing big bussiness and both drove early Chapparals. George former could not believe Hall lapping him whilst driving a Lotus 23 in the USRCC series in 64. Jim went on to Can Am with the 6th generation of the car, the best auto racing series of all time, and pulled out when GM did, and was never heard of again till now.

The 2E was the first car to be designed around its aero package with input from Firestone(sound familiar ?) There was a 3rd pedal that drivers such as Phil Hill and Jo Bonier, experienced downforce and g foces of unprecedented proportions, when balancing the front and rear wing lift using NACA type inverted airfoils with struts mounted directly to the cast magnesium suspension uprights. Another first for cars.

Much was known about the mathematics of wing sections from 2nd WW planes, but for race car applications, Jim learned the hard way. The Chapparals should have won every race they entered, but for that damn rear wing. It was under developed and it took a while to understand the dynamic forces acting on this inverted airfoil suspended in space attached to the car's suspension. Remind you of some F1 teams??

Go to the Petroleum Museum in Midland Texas. They have 6 Chapparals. The 2E is made up from parts and the full story is told on video and a wonderfull account from Phill Hill and the driving techniques he employed, using the 3 pedals. One gas one brake and one for the wings.

DOHC, you are right about the under surface been curved as a trade off between L/D ratios for a
given application.

One last thing, in surface effect, the downwash interferes with the relative wind that can not be deflected downward. This increases lift coeficient by up to 20% when the wing is within 10% of its span from the surface. The angle of attack is reduced and so is the drag by the same proportions. Ever see a pelican fly over the water?
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My intention is not to hi-jack the thread here, but I take the liberty of bringing race car downforce in, as an application of flying upside down...

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Yeah sure.;)

[DOHC]

Originally posted by Brian Glover
Ever see a pelican fly over the water?

Awesome. They have that infinite glide ratio that we just dream of!

[DOHC]

It looks like I got you fly guys sky high! Great!

But Wolf and Brian, hold your horses a little, we got to set the tech history record straight here.

Nose spoilers, tabs, fins and the like had been tried from time to time and started becoming more commonplace on F1 cars in 1967. Real wings appeared for the first time on the 49B in Monaco, 1968, but only as nose wings. Come Spa a few weeks later and most cars sported wings, with Ferrari having a nice wing over the engine, one that later had variable angle of attack through a driver operated hydraulic device. (BTW, the Ferrari 312's wing had a concave upper surface!) Brabham too had "wings", but they looked more like home-made deflectors to me. (This is also clear in the TNF link Wolf posted.) As a response, Chapman introduced the high wings, mounted on struts attached to the uprights (Hall had of course done that already). To my eyes, Chapman's wing profiles looked fairly close to an inverted NACA 0012, but I have no clue to how they chose the shape. By the British GP 1968, it was hard to see the cars under the forest of wings and struts on the grid. Soon the 49 also had variable angle of attack, but it was a mechanical arrangement, with bungees and a steel wire, operated by a fourth pedal. And not long after that, the wing excesses and the unexpected (?) structural loads got it all breaking (again, for an example see Wolf's link) and within a year (2nd practice at Monaco, 1969), movable, as well as high wings were banned. Thank heavens -- those cars looked they weren't sure if they would go flying on a clear day.

Wolf's helicopter blade story on the Lotus comes in many different forms. In Michael Oliver's book about the 49, the story is told in a different way. In the Tasman series early 1968, Clark wanted to try out a wing, and his mechanics overnight got a scrapped helicopter rotor blade, sawed off a suitable piece, and mounted it on the car. The proper angle of attack, writes Oliver, was determined by hanging the blade out of the window on the way back from the airfield. Anyway, next morning Chapman saw it, and ordered it removed from the car right away -- it was not his idea. A picture of this car with winglet appears in Oliver's book, which is great reading (at least for those of us who remember the heat of the racing in the 60s).

Well, this all sounds a lot like TNF, but tech and tech history are never far apart IMO.

[DOHC]

Originally posted by Brian Glover
Who is this Bernulli guy anyway?

There are five Bernoulli's at least, father Johann and sons Nicolas, Daniel, and Johann II, and uncle Jacob. They were all famous mathematicians. The one we're talking about here, in hydrodynamics, is Daniel. The even greater mathematician Euler studied with Johann, the father, and also made ground-breaking contributions to the theory of fluid flow.

There's a whole lot to tell about the Bernoullis, and it would fill pages and pages here. They were incredibly creative! And so modern in their thought that you are completely stunned when you consider that they did their work more than 250 years ago...

Should you by any chance be interested in knowing more about Daniel B, have a look at the site

http://www-groups.dc...lli_Daniel.html

[RDV]

DOHC

did you work in F1 during the introduction of wings in 68/69 by any chance?

...came in just at the cusp in 70, but was around Hethel in 69 .... had already designed a sports-proto with wings on stilts off uprights a la Chapparral in 66..which eventually got built with wings off chassi as banned around then. OT must say I had my eyes opened to vehicle dynamics by a series of very clearly written articles by Jim Hall in Car & Driver in 67 as had been struggling with Olleys papers from IME , Stonex & Dr Kamm`s reports and some badly translated papers by Uhlenaut...

just thought you might be the person to ask. What was the aero understanding like in those days in F1? Was it only Chapman and Hall who had some understanding, and do you know anything about how, in those formative years, real aerodynamics was brought in? How did it all happen?

...the love of airplanes and fast cars seems to go hand in hand , so there were a lot of people from the aircraft millieu involved in racing, although in a practical way as most were from the operating side, not design. My own background being aircraft , my first love, and having done my first year at uni in aircraft design , getting sidetracked afterwards into automotive design , on arrival on the motor racing side was surprised to have found a lot of empirical design going on.

Of course there were people like Maurice Phillipe who come from DeHaviland (was on the structures side) also Robin Herd and Gordon Coppuck , also with aviation backgrounds and of course Frank Costin who was by trade an aerodynamicist. Most of the subcontractors in metal work fabrications such as space frames and metal fuel and oil tanks also had an aviation background.

The transposal of aircraft aerodynamics into cars was fraught with practical difficulties, and was not very scientific , more by trial and error, remember most people had to earn a living from racing , and anything which would involve spending in R&D or reduce reliability was very strenuously avoided. The emphasis initialy was on low drag, the benefits of downforce not having quite been understood in the UK , despite the Chapparrals example , but this was mainly in 66/67 , by 69 downforce was definitely understood, even if not predicted exactly by calculation.

A lot of design was by seat-of-the-pants feeling, remember that this period was probably on of the most innovative in racing, the basic concept of racing cars not having changed much in several decades, so we had incremental steps in chassi , engine , suspension , tyre technology and aerodynamics.

This thread is very pertinent , as the downwash/pressure argument was going on then , and remember being horrified to see cars with wings mounted on rear crossmember , in very dirty air , with a brace of oil coolers completely blocking flow under wings, (check out photos of the period in TNF or elsewhere) , was very proud to have modded a F2 with rear wing cantelivered as far back as I thought reasonable , which then was picked up on the F1.

As for wind profile choice, was quite aleatory, most cars seemed to run a variation of Clark Y`s a very std profile. The explosion in winged cars after the banning of the high wings is a good example of Pandoras box, which is still with us.....

This thead can go on an on , but probably better described and chronicled in severall books, any book on Lotus at that period would tell the tale better, as I know of only a particular teams view , and as a very junior engineer..

[BRIAN GLOVER]

Interesting read DOHC, Thanks man.

I was kidding, or at least I thought I was. This is serious stuff.


I could barely understand that stuff at college in the 60's, and to think guys like Bernoulli and Newton invented calculus and 'discovered' laws of motion and fluid dynamics, etc.

Hey,there were a lot of things to distract a body in the 60's. 'Dont Bogart that Joint, my friend.....'

Some guys get up early in the morning.

On another matter, I remember a thick book called' Rigidity of Rotating Masses in Space' or some thing like that. "Bout 3" thick. I coudnt tell you a damn thing about it, then or now, other than I have to squeeze the right rudder when I pull back and the left, when I push forward.

My son asked me how a Boomerang climbs and comes back, when thrown. He was 5 years old and I handed him this big book and told him that the answer lies within.

The gyroscopic forces on a propeller and crankshaft, during a snap roll are awesome, even with a composite propeller. You pull back the throttle to reduce torque. A helicopter also in abrupt manouevres, requires a reduction in torque first.

The laws of physics involved when flying a plane is mind boggling and race car engineers are encountering many of the same problems. Ask Ben about rotating masses in suspension design.(wheels and brakes)
Most Aerobatic champions were engineers and with a thorough understanding of these phenomena, gave them huge advantages over their competition. Art Schroll was Prof. of Aeronautical Engineering at the University of California and with the help of his students, built the world champion plane that he flew at many airshows. The inverted ribben cut just above the runway was a crowd pleaser. He died during the filming of Tora tora Tora.
John Ronch is a self taught aerodynamiscist and was a child genious and works with Burt Rutan on many projects. He wrote a series of columns in Sport Aviation on aerodymanics. Back issues can be gotten from Fantastic reading.

An interesting little point when flying 'seriously'( Excuse me, but I get carried away on this subject, but so many car guys are fly guys also) Lift acts perpendicular to the relative wind, therefore, in a roll, the wing going down, also goes forward and the wing going up, goes bacwards. To prevent adverse yaw, a dance must be performed on the rudder pedals. Gyroscopic precesion, adverse roll yaw, assemetric thrust from the prop at high angles of attack and lastly, engine torque, all require specific rudder input. You must understand this in aerobatics with prop driven airplanes.
Modern fighters are flown by wire. Even F4's had auto yaw damping. Different skills are required to fly these aircraft.
A truly amazing book, is 'Fly for Your Life" by GC Standford Tuck. He describes the use of the controls during the Battle of Brittain. If you have yaw in a Spitfire, the guns weren't accurate.

See the RAF Museum in Hendon, just north of London, the next time you are there. Meca for me.

Airplanes and race cars are governed by the same laws.

Originally posted by DOHC


Should you by any chance be interested in knowing more about Daniel B, have a look at the site

http://www-groups.dc...lli_Daniel.html

[DOHC]

RDV and Brian, thanks!

[BRIAN GLOVER]

DOHC and RDV, thanks RDV, you sure write well. Content is up there also.

Originally posted by DOHC
RDV and Brian, thanks!

[RDV]

....yeah, Brian , but I`m not getting any flying, like you do.........

[DOHC]

Originally posted by RDV
This thread is very pertinent , as the downwash/pressure argument was going on then , and remember being horrified to see cars with wings mounted on rear crossmember , in very dirty air , with a brace of oil coolers completely blocking flow under wings, (check out photos of the period in TNF or elsewhere)

Here's an example of what RDV mentions:

http://www.forix.com...70/06017_RY.JPG

but there were of course many more.