Explain this and win the prize!

[Crumpp]

I've got a report as well as pictures too. The point was that the Fw data in the drag chart posted above for Ta 152 is certainly based on model testing and probably the values for the Fw 190 too because the chart contains detailed data for parts of the airframe as well as claims for interference drag which is a clear indication of model testing.

Not the report I am talking about.  I am refering to the actual polar plots of the FW-190.

We are not talking about the total drag here but the drag rise due to change of the lift coefficient (induced and viscous). And this can be estimated from the models with good accuracy given the corrections are right. A wooden model might be cleaner than a real plane but the lift characters as well as viscous drag change due to increasing AoA are about same regardless the size of the model.

We are talking about Drag ESTIMATION, Gripen.  Again give HTC a call.  Badboy has already told you on this one as well.  Specifically the efficiency factor as part of the induced drag formula.

You need to read the reports you post.  

Wood's opinions about the corrections were outdated

It's not just Wood, Gripen.  Even the report you posted about the influence of the shape of the windtunnel says the same thing!

"For studies requiring a higher degree of accuracy, lifting-surface theories have been used [as opposed to lifting line theory], but generally it has been found that the additional complexity of these methods has not sufficiently improved the predictions to warrant common use."  (NACA Report 921 - Theoretical Symmetric Span Loading at Subsonic Speeds for Wings Having Arbitrary Plan Form).

Again do the math.

Besides even Badboy claims above "Glauert also published a very nice graph".

Ok.  Barney the Purple Dinosaur publish es some nice coloring books too.  

Your taking this completely out of context.  Badboy's chart showed that the range was so narrow that correction made little difference.  Just like he explained in his post.

Twhich is a clear indication of model testing.

BS.  You would not know clear indications of model testing if it came up and bit you.  You've shown yourself to be about as knowledgeable on aeronautics as anyone else on this board inspite of the fact you attempt to pass yourself off as an expert.

Now your attempting to justify your wooden model antics with the 1/6th Spitfire polars.

Crumpp

[gripen]

Originally posted by Crumpp
Not the report I am talking about.  I am refering to the actual polar plots of the FW-190.

 
There is not much need to post further data for this thread, it has been already pointed out that there is no way to estimate e factor accurately from the aspect ratio only. But if you have finally something relevant for this thread, please post.

Originally posted by Crumpp
We are talking about Drag ESTIMATION, Gripen.  Again give HTC a call.  

To be exact, we are talking about the estimation of e factor of the whole airframe ie the change of the drag (induced and viscous) when the lift coefficient changes, not about total drag. Pyro and Hitech are most wellcome to join in discussion anytime if you need them to tell you what Pope and others have allready pointed out.

Originally posted by Crumpp
Badboy has already told you on this one as well.

Well, the problem here is that Badboy has continously misundestood what Wood and others actually wrote. The formula he originally posted was not so called gereric formula and another example is Glauert; Glauert never made corrections to the e factor because he published his work couple years before Oswald and Glauert corrections are for Prandtl's lifting line theory ie for induced drag only.

Originally posted by Crumpp
It's not just Wood, Gripen.  Even the report you posted about the influence of the shape of the windtunnel says the same thing!

Let's see the whole quote, keep in mind that mentioned modifications for lifting line theory actually mean Glauert corrections:

"Lifting-line theory in the past has been so modified and extended so that the characteristics of wings having no sweep, moderate to high aspect ratio, and any taper ratio can be determined readily with good accuracy. For studies requiring a higher degree of accuracy, lifting-surface theories have been used [as opposed to lifting line theory], but generally it has been found that the additional complexity of these methods has not sufficiently improved the predictions to warrant common use."

So actually the quote says that Glauert corrections for the lifting line theory work well. Besides I have not used Glauert or Wood, my analyses are strictly based on drag polars which even according to Badboy is the right method.

Originally posted by Crumpp
Badboy's chart showed that the range was so narrow that correction made little difference.

Well, if we ad the effect of the washout, increased viscous drag for optimal taper ratio, and the fuselage, the values for the P-51 and Fw 190 are very close to the values taken from the drag polars ie somewhere around 0,75-0,8. Funny thing is that even Raymer uses constant value of e 0,75 in his simplified analysis.

Originally posted by Crumpp
BS.  You would not know clear indications of model testing if it came up and bit you.

There was no large wind tunnels in the Germany so it's safe to say that Fw data is at least partially based on small models.

gripen

[Crumpp]

There is not much need to post further data for this thread, it has been already pointed out that there is no way to estimate e factor accurately from the aspect ratio only.  

Only in your mind.  People who know what they are talking about use them all the time.  Why don't ask an aeronautical engineer?

To be exact, we are talking about the estimation of e factor of the whole airframe ie the change of the drag (induced and viscous) when the lift coefficient changes, not about total drag.

You did not understand what Badboy pointed out did you?  There are TWO e factors's.  Only Oswalds includes an element of viscous drag.

 

my analyses are strictly based on drag polars which even according to Badboy is the right method.

What a blatent lie.

1.  Your Spitfire is a drag polar of a wooden model which you are trying to pass off as representative of the actual plane.  

2.  You do not have a drag polar for the FW-190.  In fact most of the calculations  you have done have been off half baked theories of your own.  Such as the ones you did off Lednicer's lift distribution chart.

 

There was no large wind tunnels in the Germany so it's safe to say that Fw data is at least partially based on small models.

Guess you totally missed the pictures that have already been posted of full sized aircraft hanging in Rechlin wind tunnels.  

There is no point in continuing this conversation.  You have nothing and are simply trying to "get" the last word in and try and save a little face.  You know most people will only read the last post in a long thread and are desperately hoping to salvage something and recreate the fantasy of Gripen the expert.

Crumpp

[gripen]

Originally posted by Crumpp
People who know what they are talking about use them all the time.

I quess this claim is in the same leaque as the "wet lifting area".

Originally posted by Crumpp
You did not understand what Badboy pointed out did you?  There are TWO e factors's.  Only Oswalds includes an element of viscous drag.

There is just one e factor and it was introduced by Oswald 1931. It's for entire airframe and includes induced and viscous drag. There is no other e factor. Besides I have told you nearly two months ago that lift distribution analysis (like Glauert corrections) do not count viscous part of the drag rise (see my posts 11-12-2004 09:17 PM and 11-15-2004 02:42 PM) so I have known perfectly well that e factor contains induced and viscous drag long before Badboy posted something on this.

Originally posted by Crumpp
1.  Your Spitfire is a drag polar of a wooden model which you are trying to pass off as representative of the actual plane.  

2.  You do not have a drag polar for the FW-190.

The models can be used perfectly well to determine e factor as pointed out by Pope and others. The Fw data sheet gives the values of the K and that is all I need for drag polar.

Originally posted by Crumpp
Guess you totally missed the pictures that have already been posted of full sized aircraft hanging in Rechlin wind tunnels.  

The tunnel picture which you posted was the 8m tunnel A3 in the LFA (Brunswick) ie not a large scale tunnel.

Originally posted by Crumpp
There is no point in continuing this conversation.

So far you have posted nothing relevant to this thread, so this might be your best idea so far in this thread.

gripen

[Crumpp]

Gripen says:
The models can be used perfectly well to determine e factor as pointed out by Pope and others.

Pope says NOTHING about comparing wooden models to actual aircraft of a different type Gripen.  Pope says the CONCLUSIONS of Wooden model testing GENERALLY give good agreement with the SAME aircraft.  In other words the general conclusions hold true but not the exact numbers!!

You just can't seem to understand that.

Badboy has pointed it out.

Badboy says"
Any designer will tell you there is only one reason they use models in wind tunnels… cost! Airplane design by building, testing, changing and retesting models is essentially a confession of ignorance of the designer, it is an attempt to make design by trial and error, less expensive than the millions involved in working with full size aircraft. No designer would ever dream of claiming that their model test results are likely to be close in terms of performance, that’s not what they are intended for. They save a lot of money, and a lot of big mistakes in terms of balance, dynamic stability, and integration, in the very early stages of the design process. More and more money has been spent refining the techniques and corrections to the point where the wind tunnel testing of models has become an essential part of aircraft design that can save billions on modern projects. In the 1940s model testing was in its infancy, and designers couldn’t use those tests for performance prediction with any hope of worthwhile results and they still don’t. That’s why development programs include the full range of tests, from scale models initially, to full size model testing, to prototype tests all before the aircraft ever gets near a runway, and eventually every new aircraft is subject to a huge range of flight tests, and even then, performance estimates will be changing as the tests evolve. I don’t normally like to be so blunt, but using model tests the way Gripen has, is just plain silly, and he wouldn’t believe it even if Kurt Tank told him in person ;-)  

The tunnel picture which you posted was the 8m tunnel A3 in the LFA (Brunswick) ie not a large scale tunnel.

Looks to me like they have an actual plane hanging in it.

So far you have posted nothing relevant to this thread

Your right you have not posted anything relevant.  

Crumpp

[Badboy]

Guys,

Please leave me out of your discussions.

Many thanks.

Badboy


But on a passing note Gripen, one last source for you, that includes some software I've been using to estimate e as a function of taper, aspect ratio, mid-chord sweep and Mach number. The software uses spanwise load distributions calculated by linearised lifting-surface theory. If you want to include every aspect of the geometry and fusilage you may find computational fluid dynamics of more value.

http://www.esdu.com/graphics/dataitem/74035a.htm

Here is a sample output from the software I just ran as an example, based on the F6F. You can see that in this case the taper ratio is only just over 0.52 and the last column in the output data can be inverted for e = 0.997:

**************************************************
ESDU International plc

Program           A7435

ESDUpac Number:   A7435V10
ESDUpac Title:    Subsonic lift-dependent drag due to the trailing
                  vortex wake for wings without camber or twist.
Data Item Number: 74035
Data Item Title:  Subsonic lift-dependent drag due to the trailing
                  vortex wake for wings without camber or twist.
ESDUpac Version:  1.0    Issued April 1996.

(See Data Item for full input/output specification and interpretation.)
**************************************************

INPUT DATA
==========

F6F                                                                        
A=5.51,MID-CHORD SWEEP=5 deg.,TAPER RATIO=0.5275                          
INPUT FILE test.txt                                                        

INPUT DATA ERRORS
-----------------

      No error detected



OUTPUT DATA
===========

----------------------------------------------------------------------
M   A     n    Ln (deg)   Taper   BetaA     AtanLh   1+Delta
----------------------------------------------------------------------
.100     5.510  .500    5.00     .527    5.48        .48     1.003

.150     5.510  .500    5.00     .527    5.45        .48     1.003

.200     5.510  .500    5.00     .527    5.40        .48     1.003

.250     5.510  .500    5.00     .527    5.34        .48     1.003

.300     5.510  .500    5.00     .527    5.26        .48     1.003

  .350     5.510  .500    5.00     .527    5.16        .48     1.003

  .400     5.510  .500    5.00     .527    5.05        .48     1.003

  .450     5.510  .500    5.00     .527    4.92        .48     1.003

  .500     5.510  .500    5.00     .527    4.77        .48     1.002
------------------------  END OF OUTPUT  ---------------------------


Hope that helps...

Badboy

[gripen]

Originally posted by Crumpp
Pope says NOTHING about comparing wooden models to actual aircraft of a different type Gripen.  Pope says the CONCLUSIONS of Wooden model testing GENERALLY give good agreement with the SAME aircraft.  In other words the general conclusions hold true but not the exact numbers!!

Actually he says that the size of the model does not affect lift curve slope despite the reynolds number changes. It does not matter how the results are used.

Originally posted by Crumpp
Badboy has pointed it out.

Actually that was "Dweeb" who said for example that Glauert made corrections for Oswald's efficiency and other quite questionable claims...

Basicly the model testing has allways been most common way to test properties of the airframe before flight testing and the corrections have been good enough for accurate analysis since forties.

Originally posted by Crumpp
Looks to me like they have an actual plane hanging in it.

As pointed out earlier, the wing tips are out of the tunnel area and lift coefficient analysis are practically impossible. The most advenced wind tunnel in the LFA was the high speed wind tunnel A2 which was a 2,8m tunnel and that was the tunnel were the germans tested advanced planes (with scale models).

Originally posted by Crumpp
Your right you have not posted anything relevant.  

Hm...I have posted several drag polars, sources, a true flight test, calculation methods etc. Besides original question of this thread has been solved long time ago, no need to post more data.

Badboy,
As you can read from my latest reply to your post, I'm not looking trouble with you.

Regarding computer analysis I can say that atleast the CFD analysis underestimates viscous drag. You might allready know from where this comes...


gripen

[Crumpp]

Actually that was "Dweeb" who said for example that Glauert made corrections for Oswald's efficiency and other quite questionable claims...

Basicly the model testing has allways been most common way to test properties of the airframe before flight testing and the corrections have been good enough for accurate analysis since forties.

Great!  WE can inform the aerospace industry that they can save millions on test flights!

Gripen says the data from their 1/6th scale models is exact.  Therefore we can just skip the test flight stage and go right to production!

As pointed out earlier, the wing tips are out of the tunnel area and lift coefficient analysis are practically impossible. The most advenced wind tunnel in the LFA was the high speed wind tunnel A2 which was a 2,8m tunnel and that was the tunnel were the germans tested advanced planes (with scale models).

Yeah ok.  Get some glasses.

Again though.  The Focke Wulf report uses the windtunnel in :



Which is definately large enough.

Hm...I have posted several drag polars, sources, a true flight test, calculation methods etc. Besides original question of this thread has been solved long time ago, no need to post more data.

BS You have posted your "theories" on calculating e from lift distribution graphs, used the drag polar from a wooden model (Spitfire), and ONE drag polar from the an unknown source on the 109.  Don't sell yourself to dearly there Gripen.

Crumpp

[gripen]

Originally posted by Badboy

Here is a sample output from the software I just ran as an example, based on the F6F. You can see that in this case the taper ratio is only just over 0.52 and the last column in the output data can be inverted for e = 0.997:  

The Glauert correction gives about same result for taper ratio 0,52 so it seems that this software calculates just induced drag.

Originally posted by Crumpp

Great! WE can inform the aerospace industry that they can save millions on test flights!

They allready know this and they have allready saved millions with model testing.

Originally posted by Crumpp
The Focke Wulf report uses the windtunnel in :

Chalais-Meudon was a large scale tunnel (16x8m) but it was also a low speed tunnel and the germans lost it summer 1944. All high speed tunnel testing of Fw was certainly done with models and probably all testing of the Ta 152 series.

gripen

[Crumpp]

with models and probably all testing of the Ta 152 series.

That's a really great piece of fiction.  Please PROVE IT.  Based on the actual report, your full of it.

In the world according to Gripen, the Germans could never do any testing!  You always try and come up with something to support your agenda.

They allready know this and they have allready saved millions with model testing.

And now according to your findings they can just eliminate the whole test flight stage of the development process!!



Crumpp

[Badboy]

Originally posted by gripen
The Glauert correction gives about same result for taper ratio 0,52 so it seems that this software calculates just induced drag.
 

Yes, it just determine the subsonic lift-dependent drag due to the trailing vortex wake for planar straight-tapered wings in inviscid subsonic flow. The theory from which the data was derived is linearised and relates to inviscid flow. These restrictions are known to be relatively unimportant for most practical purposes in calculating the lift and lift-dependent drag due to the trailing vortex wake provided the flow remains fully attached over the wing surface. The paper also says that in applying this software it should be borne in mind that camber and twist and the presence of a body, engine nacelles etc, all affect trailing vortex drag to a greater or lesser degree. Of those mentioned the body effect is considered to be the most important and is stated to be generally detrimental owing to the distortion of the spanwise loading in its vicinity. This is the effect that Wood is accounting for in applying his fuselage factor.

Hope that helps...

Badboy

[Crumpp]

Thanks Badboy.  

Crumpp

[gripen]

Originally posted by Crumpp
That's a really great piece of fiction.  Please PROVE IT.  Based on the actual report, your full of it.

As noted earlier it's up to you to prove that there was a large scale tunnel in the Germany.

Originally posted by Crumpp
In the world according to Gripen, the Germans could never do any testing!  

Great logic again. The Germans had several advanced smaller scale high speed tunnels, which they used for testing.

Originally posted by Crumpp
And now according to your findings they can just eliminate the whole test flight stage of the development process!!

I'm not saying that but the e factor (change in the induced and viscous drag due to change of the lift coefficient) can be estimated with good accuracy regardless the size of the model.

Originally posted by Badboy

Yes, it just determine the subsonic lift-dependent drag due to the trailing vortex wake for planar straight-tapered wings in inviscid subsonic flow.

Yep, so the viscous part of the drag is missing and we can't calculate e factor for the wing.

Originally posted by Badboy
Of those mentioned the body effect is considered to be the most important and is stated to be generally detrimental owing to the distortion of the spanwise loading in its vicinity. This is the effect that Wood is accounting for in applying his fuselage factor.

Wood's system to estimate the effect of the fuselage is based on NACA 236 which is a compilation of tests results on various fuselage, nacelle etc. data from year 1927. In most of these tests there was no tail surfaces in the fuselage and the effect of the interference drag is not counted.

gripen

[Crumpp]

As noted earlier it's up to you to prove that there was a large scale tunnel in the Germany.

How many times do I have to tell your dense self.  FRANCE Gripen, the report says FRANCE!  In fact it names the wind tunnel.  You do not need a high speed wind tunnel to do drag estimations or polars.  OBVIOUSLY!!!

I'm not saying that but the e factor (change in the induced and viscous drag due to change of the lift coefficient) can be estimated with good accuracy regardless the size of the model.

No Gripen it cannot.  The CONCLUSIONS in a generalized fashion can be determined from a wooden model NOT the exact numbers!!

Crumpp

[gripen]

Originally posted by Crumpp
How many times do I have to tell your dense self.  FRANCE Gripen, the report says FRANCE!

As noted several times the germans lost France summer 1944, therefore it is safe to say that at least Fw data for the Ta 152 is based on tests with scale models and even the data for the Fw 190s seem to be at least partially based on model testing because it it contains detailed drag values for different parts of the airframe and claims about interference drag.

Besides the Chalais-Meudon was a low speed tunnel (IIRC about 45m/s) and Fw data sheet values for K are for much higher speed, about 80m/s at climb and well over 100m/s at high speed flying. So probably all values in the Fw datasheet are based on model testing.

Originally posted by Crumpp
You do not need a high speed wind tunnel to do drag estimations or polars.

No one has stated otherwise here. But the the most advanced German planes under developement reached transonic (compressibility) speeds so the need for high speed tunnels was obivious for drag and other analysis. Therefore they developed smaller and advanced high speed tunnels instead large low speed tunnels.

Originally posted by Crumpp
No Gripen it cannot.  The CONCLUSIONS in a generalized fashion can be determined from a wooden model NOT the exact numbers!!

Pope is very clear on this, lift curve as well as drag rise due to lift coefficient change can be determined with good accuracy despite changes in the value of the Reynolds number. Besides we don't need to be very accurate here; wind tunnel data as well as flight tests indicate that the value of the e factor for the WWII fighters was typically somewhere around 0,75 just like Raymer uses in his simplified analysis.


gripen