Debunking Lift Theories Still Taught

[turboplanner]

I still don't understand your point here. He says that from what they are taught, people expect that a wing curved on the bottom and flat on the top would produce a down force not lift. And yet that is not the case for SC wings. I'm not sure whether you are agreeing or disagreeing?

A wing curved on the bottom and flat on the top produces a downforce, as in the Sprintcar wing - the teaching is correct.

 

I'm saying his description is incorrect. A Supercritical Wing is a complex shape and not just flat on the top and curved on the bottom.

 

A Supercritical Wing does camber on the top, just a lesser amount than a conventional aerofoil, and its complex shape underneath is designed to offset the lesser camber by creating more downforce. I've attached a diagramme comparison of a conventional aerofoil and supercritical aerofoil from the NASA website.

 

 

 

[completeaerogeek]

Sorry didn't mean to overstate my point but if you see his latest clanger he says that sprint car wings have nothing to do with airliners...

 

Absolute classic!

 

Apart from using exactly the same principle of turning flow, being able to calculate their relative 'downforce' in exactly the same way and the fact that they are just an aerofoil turning the airflow to create a reaction force... Well nothing at all I suppose...

 

 

[aro]

Sprint car wings have nothing to do with an airliner? That is priceless!!!!!

IS there some alternate physics theory from your Universe you would like to share?

I said sprintcar wings have nothing to do with an airliner. Probably what I should have said is that sprint car wings are curved on the bottom for a totally different reason than the wings on an airliner.

 

 

[2tonne]

Remind me not to visit your home village they seem to be missing their idiot. Perhaps its time to go home.

I love comments like this - takes me back to the geeks at my school battling it out in the playground:laugh:. Oh, and I wasn't one of them ok.

 

 

[completeaerogeek]

A wing curved on the bottom and flat on the top produces a downforce, as in the Sprintcar wing - the teaching is correct.I'm saying his description is incorrect. A Supercritical Wing is a complex shape and not just flat on the top and curved on the bottom.

 

A Supercritical Wing does camber on the top, just a lesser amount than a conventional aerofoil, and its complex shape underneath is designed to offset the lesser camber by creating more downforce. I've attached a diagramme comparison of a conventional aerofoil and supercritical aerofoil from the NASA website.

_______________-

 

Geez you really are scrambling now aren't you? It s a long time since I have seen someone backpedalling that fast.

 

They work EXACTLY the same way. It is irrelevant which way the flow is turned. They perform the SAME FUNCTION using the same principles.

 

Time to quit while you are behind.....

 

 

[completeaerogeek]

I said sprintcar wings have nothing to do with an airliner. Probably what I should have said is that sprint car wings are curved on the bottom for a totally different reason than the wings on an airliner.

_______________-

 

How can I make this any clearer. IT IS EXACTLY THE SAME PHYSICAL PRINCIPLE AND THE CURVED SHAPES PERFORM EXACTLY THE SAME FUNCTION.

 

They change the direction of the air to suit whatever purpose is intended...

 

 

[aro]

I'm saying his description is incorrect. A Supercritical Wing is a complex shape and not just flat on the top and curved on the bottom.

Flat on the top is an approximation. So is flat on the bottom for a conventional airfoil.

 

There is more curvature on the bottom of the SC airfoil. If you measure the distance along the surface from LE to TE it is further on the bottom - which is a problem for the equal transit time theory. But I thought we had agreed that the equal transit time theory doesn't hold water?

 

 

[turboplanner]

Well since I'm just a poor country boy who had to leave school at the age of 26 to help out on the farm perhaps you could explain why this would be so classic, GIVEN your description, which you now appear to be correcting?

 

In particular a Sprintcar with an upside down aerofoil to your description, and I quoted it precisely - where the resulting effect is DOWN.

 

An airliner, which has a supercritical wing flies because the resulting effect is UP

 

I suppose there could be some airliners fitted with upside down aerofoils, but I've never seen one, and that was the context of my comment that Sprintcar wings have nothing to do with airliners, rather than an attempt to provide another start to the endless belt of your assumption that "they are just an aerofoil turning the airflow to create a reaction force", minus Bernoulli once again, of course.

 

 

[aro]

How can I make this any clearer. IT IS EXACTLY THE SAME PHYSICAL PRINCIPLE AND THE CURVED SHAPES PERFORM EXACTLY THE SAME FUNCTION.They change the direction of the air to suit whatever purpose is intended...

Settle down, I agree with you. All I was trying to say is that I don't understand the point that was being made in the original reference to sprintcar wings.

 

 

[Guest ozzie]

Aerofoils don't care about orientation or gravity they just react to relative airflow.

 

 

[facthunter]

It's a risky concept that attitude has much to do with AoA. An angle of attack indicator (by any name) will point this out. Nev

 

 

[turboplanner]

I hope you brought an apple for the teacher FH, someone needs to.

 

 

[turboplanner]

Flat on the top is an approximation. So is flat on the bottom for a conventional airfoil.There is more curvature on the bottom of the SC airfoil. If you measure the distance along the surface from LE to TE it is further on the bottom - which is a problem for the equal transit time theory. But I thought we had agreed that the equal transit time theory doesn't hold water?

Well most of us do, but I think the geek seems to be implying that there are instructors who don't.

 

 

[facthunter]

If equal transit time worked you would have no drag. You can't get something for nothing. There is no reason to believe particles which separate have any reason to get together later after passing through some processing independently. It would be a baseless assumption. For air to move through a curved path there must always be more pressure on the outside of the curve, or if you want to interpret it another way, the pressure will be lower on the inside. Nev

 

 

[aro]

Well most of us do, but I think the geek seems to be implying that there are instructors who don't.

There are certainly instructors who teach the equal transit time theory, and CASA appears to require it. From the part 61 MOS:

 

"Apply Bernoulli’s theorem of constant energy flow to describe how an aerofoil produces lift, limited to the variation of kinetic energy (dynamic pressure) and potential energy (static pressure) as air flows through a venturi or over a aerofoil"

 

Explaining how an aerofoil produces lisft using the variation of pressure as air flows through a venturi seems to require an incorrect application of Bernoulli, presumably equal transit time.

 

In fact, a venturi doesn't explain lift at all, because the air comes out the other end travelling in the same direction at the same speed, so it cannot possibly produce lift.

 

 

[bexrbetter]

Sprint car/F1

 

_______________-How can I make this any clearer. IT IS EXACTLY THE SAME PHYSICAL PRINCIPLE AND THE CURVED SHAPES PERFORM EXACTLY THE SAME FUNCTION.

They change the direction of the air to suit whatever purpose is intended...

Yeah, nah, they don't - you're out of your league now, stick to your 1 dimensional aircraft thinking.

 

 

[aro]

Explaining how an aerofoil produces lisft using the variation of pressure as air flows through a venturi seems to require an incorrect application of Bernoulli, presumably equal transit time.

Actually I take that back - it doesn't require it at all, since the venturi is only one surface. It just demonstrates that static pressure reduces as air speed increases - which is OK. It is the step comparing half a venturi to a wing that is incorrect - which is commonly taught.

 

 

[turboplanner]

In fact, a venturi doesn't explain lift at all, because the air comes out the other end travelling in the same direction at the same speed, so it cannot possibly produce lift.

Dafydd has just posted on the original Bernoulli thread, and that shows the bigger picture of an aerofoil rather than just Bernoulli/not Bernoulli.

 

 

[geoffreywh]

Dear Oh Dear , Mr Turbo planner. what were you thinking when you wrote that?......... I was a little bit on your side for a while there, well, sympathetic to your situation anyway....... Here comes Mr. Completeaero geek, trampling all over your beliefs and

 

theories, Then you go and drop a howler as bad as ever I've seen. Quote" That's what he said, and a sprint car wing is curved on the bottom and flat on the top, so the resulting force is down, not up."

 

What Resulting force? Set the cord centre line level with the ground, where's your lift now? Did you ever take a look at the angle those "wings" are held at? It's like, 30 degrees! It's the ANGLE OF ATTACK that gives them the (Down)thrust. I wouldn't mind betting that the downforce would be almost the same were the "wing" a flat plate. Just a whole lot draggier......Please continue the debate, But don't post in anger....it's not helping you....Cheers, and good luck....

 

 

[turboplanner]

________________Remind me not to visit your home village they seem to be missing their idiot. Perhaps its time to go home.

I note that you have not addressed the many errors you made in your statements.

 

My flat plate reference was directly aimed at your nonsense about military aircraft.

 

It is fairly apparent that you have no idea what you are talking about and every time you are caught out you ignore your past sins and try to insult me.

 

• You were wrong about the development of SC wings.
   
   
  

This is what I said: "Supercritical wings were introduced originally to help break the sound barrier and are irrelevant to RA and GA flying and irrelevant to supersonic flying, and seem to have been used just as distraction by the geek."

 

This was the Wikipedia paragraph I quoted from:

 

"Research aircraft of the 1950s and '60s found it difficult to break the sound barrier, or even reach Mach 0.9, with conventional airfoils. Supersonic airflow over the upper surface of the traditional airfoil induced excessive wave drag and a form of stability loss called Mach tuck. Due to the airfoil shape used, supercritical wings experience these problems less severely and at much higher speeds, thus allowing the wing to maintain high performance at speeds closer to Mach 1."

 

Your point about the sprint cars was moot. F1 cars have spoilers not 'deflectors and they work on exactly the same principle as sprint cars.

Since despite, explanations you've been unable to comprehend that this comment was solely used due to your assertion that a supercritical wing has a flat top and a curved bottom, I'll leave you to work through this one yourself.

 

And it is clear despite you blathering that you still don't understand what the Aero book was saying. A bit sad really.

Don't be sad, I only quoted a passage verbatim from the book and recommended people buy it. How that translates into understanding/not understanding I don't know.

 

I didn't say Tobago I said Tomahawk

Yes, I'm sorry Tomahawk

 

The point is that even RA aircraft are using non-traditional aerofoils and to perpetuate nonsense serves no-one.

Let's not get off the subject, you were talking about supercritical aerofoil sections, so you can bite your tongue on this one.

 

Powered hang gliders, parafoils another recreational aircraft use single surface aerofoils which debunk ETT and venturi theory.

You were corrected on this one by another poster but appear to have overlooked it.

 

I have never claimed Bernoulli is wrong, just that we don't need it to understand lift (it is after all derived from Newton's 2nd law and incorrect explanations offered to 'prove' Bernoulli leads pilots to have a totally false idea of what is holding them up.

I didn't say you did although you certainly didn't emphasis that in the NASA material you supply to cadets NASA says it is right. What you did say is that Bernoulli is irrelevant and that's BS.

 

And it is your assertion that no pilot flying recreationally will every go onto the airlines?

No that's not my assertion - you said "A SC wing (that most pilots will spend most of their careers sitting on top of)"

I pointed out you were talking to the wrong audience on this site where most of the people fly for recreation and only three or four are involved in airline flying. I also gave you a link to a site where professional pilots, instructors and students wo will go on to fly for airlines hang out.

 

Nevertheless: You are welcome to keep making silly non factual and unsupportable statements if you like. it is quite amusing.

It is amusing that virtually all your triumphant winning bullet points appear to have flaws; what's not so amusing is that this two dimensional garbage could be coming out the end of one of our Universities.

 

 

[turboplanner]

Then you go and drop a howler as bad as ever I've seen. Quote" That's what he said, and a sprint car wing is curved on the bottom and flat on the top, so the resulting force is down, not up." What Resulting force? Set the cord centre line level with the ground, where's your lift now? Did you ever take a look at the angle those "wings" are held at? It's like, 30 degrees! It's the ANGLE OF ATTACK that gives them the (Down)thrust. I wouldn't mind betting that the downforce would be almost the same were the "wing" a flat plate. Just a whole lot draggier......Please continue the debate, But don't post in anger....it's not helping you....Cheers, and good luck....

The only reason for using the Sprintcar reference was that it was a quick example of a conventional aerofoil upside down which the geek was describing - i.e. flat on the top and curved on the bottom, which was his description of a supercritical wing at one point in the discussion.

 

However, since you've commented on the sprintcar wing, it actually started out as a flat plate - the same as the side plates, but quickly changed to a conventional aerofoil for better performance.

 

Yes, the angle of attack can be around 25 degrees on some tracks, but I've attached a photo of one which is about the reverse of the angle you'd see on an aircraft. The wings are hinged and have adjustment fore and aft to change the location of the downforce in relation to the wheelbase, and also have hydraulic jacking to raise or lower the angle of attack.

 

In addition to these adjustments, a lot of pitch and roll is built into the supension to improve traction at various points on the track.

 

So, or example, a wing adjusted for high angle of attack, will be sitting back under the squat of hard acceleration down of the straight producing downforce with lower drag but will transit several degrees under dive into the corner producing maximum drag at that point, which is immediately released when the driver hits the throttle in the turn.

 

So yes, at times the wing acts the same as a plate, but at other times it is a true aerofoil. The side plates are just that, and are so effective that when the car flicks around sideways, and would normally roll outwards, the plates have enough drag to pull the top inwards as the tyre footprints are sliding out.

 

 

 

[dlegg]

This is great, settling in with a carton of Boag's, nasty on the left vs's all comers on the right.

 

All I know is birds have it right, follow them and lift just happens...........

 

 

[ianboag]

This is great, settling in with a carton of Boag's

I went to Tassie once and they all looked sideways at me every time my credit card came out. All I could say was "I wish". I still had to pay for the brewery tour and t-shirt ...

Orright orright. Off topic. Sorry.

 

 

[kgwilson]

No, No, No, No, No. YOU ARE ALL WRONG. It's simple It is just MAGIC. See one of Ozzies posts somewhere. AAaargh who cares anyway, just go & fly.

 

 

[dlegg]

I went to Tassie once and they all looked sideways at me every time my credit card came out. All I could say was "I wish". I still had to pay for the brewery tour and t-shirt ...Orright orright. Off topic. Sorry.

So just dip you in a river and a better model shows up eh......