Explain this and win the prize!

[gripen]

It's quite simple, pressure distribution of the one side of wing tells absolute nothing about the lift distribution.

Basicly the pressure distribution tells how the pressure caused by the airflow varies around the airframe.

And yes, the model included washout.

gripen

[Crumpp]

It's quite simple, pressure distribution of the one side of wing tells absolute nothing about the lift distribution.

Where do you get that?  Since induced drag is cause by an interaction of the pressure differentials between the TOP and the bottom of the wing it is safe to say that the Spitfire did NOT have an elliptical distribution by any means.  

 

For a lifting wing, the air pressure on the top of the wing is lower than the pressure below the wing. Near the tips of the wing, the air is free to move from the region of high pressure into the region of low pressure. The resulting flow is shown on the figure by the two circular blue lines with the arrowheads showing the flow direction. As the aircraft moves to the lower left, a pair of counter-rotating vortices are formed at the wing tips. The line of the center of the vortices are shown as blue vortex lines leading from the wing tips. If the atmosphere has very high humidity, you can sometimes see the vortex lines on an airliner during landing as long thin "clouds" leaving the wing tips. The wing tip vortices produce a down wash of air behind the wing which is very strong near the wing tips and decreases toward the wing root. The local angle of attack of the wing is increased by the induced flow of the down wash, giving an additional, downstream-facing, component to the aerodynamic force acting over the entire wing. This additional force is called induced drag because it faces downstream and has been "induced" by the action of the tip vortices. It is also called "drag due to lift" because it only occurs on finite, lifting wings and varies with the square of the lift.

http://www.grc.nasa.gov/WWW/K-12/airplane/induced.html

No what is laughable is your continued insistance in the face of the facts that the Spitfire recieved some huge benefit from it's "elliptical" wing other than more room to put landing gear and of course more drag.  At best it was barely ahead as the formulas show.

Crumpp

[Angus]

Well, wings it is.
The downwash btw pushes the tips upwards right?
The Hurricane had no dihedral, but I know of an instance where a pilot dived from 30K to the deck and got way to fast for a Hurricane.
He deformed wings, - they had a 4 degree dihedral afterwards, as well as wrinkles on the upper surfaces of the wing.
Looking for info on dihedral anyway.

Induced drag, is as you say, LIFT induced drag. All lift creates drag.
So the Spitfire's big wing both gives benefits and suffering.
It has a low wingloading which enables it to fly at lower A.o.A. at lower speeds, - A.o.A. creates drag.
Hence the maneuverability in the low speed region as well as good climb.
However, it has to pay at higher speeds.

[MiloMorai]

Originally posted by Angus
The Hurricane had no dihedral,

The top of the wing might be flat but the lower side had dihedral.

How does this figure into every thing?

[Angus]

Not really sure.....

[Crumpp]

Induced drag, is as you say, LIFT induced drag. All lift creates drag.So the Spitfire's big wing both gives benefits and suffering. It has a low wingloading which enables it to fly at lower A.o.A. at lower speeds, - A.o.A. creates drag.
Hence the maneuverability in the low speed region as well as good climb.

Yep, as I understand it.  In the low speed realm even a small advantage becomes HUGE.  At higher speeds the force of induced drag is hardly a factor.  

http://www.av8n.com/how/htm/4forces.html#fig-power-ias

As you go slower and slower, induced drag increases dramatically and parasite drag becomes almost negligible.

Notice the shap of the curves for the power of induced drag.  It stays pretty much steady until airspeed drops to a certain point.  Get slow enough and the wall comes up!

Crumpp

[gripen]

Crumpp,
Don't create theories without understanding, you can't say anything about lift distribution based on pressure distribution of one wing side only.

All we can see is that the Fw 190 has a relatively bit thicker and wider profile in the wing tip. This is natural outcome of the wing shapes.

gripen

[Crumpp]

Don't create theories without understanding, you can't say anything about lift distribution based on pressure distribution of one wing side only.

It's in black and white Gripen. Just read the link.  Besides we saw your understanding by creating theories off Lednicer's lift distribution as you came up with gooble-dee gook to solve for the wingtip efficiency off of it!!

I had no wind tunnel data to calculate e factor of the Fw 190. But Lednicer calculated span loadings and here is estimated e factors calculated by taking 8 samples (semispan fractions 0,2-0,9) and measuring distance to the elliptical span loading:

If this guy can't figure it out from Span Loadings:

http://www.grc.nasa.gov/WWW/K-12/airplane/benson.html

I highly doubt you can either.  So don't hop on your high horse about creating theories.  You throw your fair share around.

Crumpp

[gripen]

Crumpp,
Well, all I see here is that you see something like an elliptic shape in the pressure distribution picture and somehow you conclude that it tell something about lift distribution.

Regarding estimating e factor from the lift distribution. We know that there is a strong correlation between relative  lift distribution and e factor. And that is what my calculations show. Only suprising thing is the accuracy, apparently rise of the viscous drag correlates strongly with the rise of the induced drag

gripen

[Crumpp]

Well, all I see here is that you see something like an elliptic shape in the pressure distribution picture and somehow you conclude that it tell something about lift distribution.

It's not really what you see Gripen.  It's more like what you do NOT see in the Spitifire.  Obviously the "theoritically perfect" ellipse you give the Spitfire credit for having does not exist.

And that is what my calculations show.

Yes, Heavily slanted towards you favourite plane and performed with pseudo-logic.  

Crumpp

[gripen]

Originally posted by Crumpp
It's not really what you see Gripen.  It's more like what you do NOT see in the Spitifire.  Obviously the "theoritically perfect" ellipse you give the Spitfire credit for having does not exist.

I see the the same thing as Lednicer and everybody else:



The lift distribution of the Spitfire "is not elliptical, though it is probably the most optimum of the three from the induced drag standpoint".

And the wind tunnel data and Fw data confirm this:

P-51 e=0,77
Fw 190 e=0,78
Spitfire e=0,88

And as noted several times you are the only one to claim e factor value 1 for the Spitfire.

Originally posted by Crumpp
Yes, Heavily slanted towards you favourite plane and performed with pseudo-logic.  

Well, if someone is heavily slanted towards something in this thread, it's you.

And your logic is generally laughable; your theories on swept wing and pressure distribution as seen above are good examples.

gripen

[Crumpp]

P-51 e=0,77
Fw 190 e=0,78
Spitfire e=0,88
 

Oh Yeah!  These are the values calculated from HOW again?

I had no wind tunnel data to calculate e factor of the Fw 190. But Lednicer calculated span loadings and here is estimated e factors calculated by taking 8 samples (semispan fractions 0,2-0,9) and measuring distance to the elliptical span loading:

Off the "span loading"....

That is quite the feat of calculator jockying.  You should publish a paper on your technique and inform the rest of the aeronautical engineering world.  No trained aeronautical engineer seems to be able to do it.

They all say the same thing.  You can tell the wings had some washout but it does not tell you much about wingtip efficiency.

Crumpp

[gripen]

Originally posted by Crumpp
Oh Yeah!  These are the values calculated from HOW again?

As shown above and in the Perkins&Hage.
 

Originally posted by Crumpp
That is quite the feat of calculator jockying. You should publish a paper on your technique and inform the rest of the aeronautical engineering world.

The rest of the world all ready knows that the lift distribution and the efficiency factor have a strong correlation.

Besides these values are calculated from wind tunnel data and Fw data not from lift distribution chart, still the estimates from the lift distribution chart are suprisingly accurate as seen above.

gripen

[Crumpp]

As shown above and in the Perkins&Hage.

Show us in Perkins & Hage were you can calculate wingtip efficiency factor from span loading.

What page?

Besides these values are calculated from wind tunnel data and Fw data not from lift distribution chart, still the estimates from the lift distribution chart are suprisingly accurate as seen above.

Surprisingly accurate??



Crumpp

[gripen]

Originally posted by Crumpp
Show us in Perkins & Hage were you can calculate wingtip efficiency factor from span loading.

I say above that these values are calculated from the wind tunnel data and the Fw  data, not from span loading. The system is described in the Perkins&Hage (p.90-95)

Originally posted by Crumpp
Surprisingly accurate??
 

The values of e calculated from the wind tunnel data and Fw data:

P-51 e=0,77
Fw 190 e=0,78
Spitfire e=0,88

The values of e estimated from the span loading chart:

P-51 e=0,80
Fw 190 e=0,79
Spitfire e=0,86

gripen