Explain this and win the prize!

[gear]

[gripen]

Originally posted by Crumpp
Your saying the Spiteful has a more efficient wing than the FW-190A not be just a little but a rather large margin.  Your calculations using "K" from Focke Wulf's data say the e factor is around .78!!

This has absolute nothing to do with my calculations; the value of the K (1,24) at climb speed for the Fw 190 results value of the e 0,78. There is no other answer for this value of the K.

The Spiteful wind tunnel data gives a very well behaving Cd/Cl^2 curve, practically linear:



Again there is no other answer for the value of the e because the line is so linear despite what ever calculation method is used.

Originally posted by Crumpp
The FW-190 wing was twisted 2 degrees specifically to achieve an elliptical distribution.  As Lednicer points out it was not far behind the Spitfire and neither was the P51.

There was no washout in the Spiteful and taper ratio is near optimal, while Lednicer's analysis prove that the Fw 190 had too much washout for optimal lift distribution:

Originally posted by Crumpp
Another factor is aspect ratio.  The FW-190 had the advantage over the Spiteful with a higher aspect ratio.

6.02 = FW-190
5.81 = Spiteful

The e factor of the tapered wing decreases slightly when the aspect ratio increases, you can test this yourself with formulas given above by Badboy and you can also find them from Perkins&Hage. Again this has nothing to do with my calculations.

gripen

[Crumpp]

There was no washout  in the Spiteful

Exactly.  The whole point Gripen is:

1.  The OPTIMAL shape is elliptical.  If the physical construction of the wing is not elliptical then you must manipulate the wing structure to achieve an elliptical distribution.  This is done by twist.  The Spiteful does not have elliptical wing construction.  It has NO twist either to move it closer to elliptical.

The FW-190 does have a 2 degree twist to move it closer to elliptical.  Just like the P51.  The P51 and the FW-190 were given twist to bring them closer to elliptical.  The Spitfire was given 2 degrees of twist to move it away from perfect elliptical due to the stall.

taper ratio is near optimal,

Yeah, OK.  

Optimal taper ratio is elliptical construction, Gripen.

http://www.centennialofflight.gov/essay/Theories_of_Flight/Reducing_Induced_Drag/TH16G6.htm

Since the lift distribution is nearly elliptical, the chord distribution should be nearly elliptical for uniform Cl's. Reduced lift or t/c outboard would permit lower taper ratios.

http://www.desktopaero.com/appliedaero/wingdesign/wingparams.html

Planform taper is the reduction of the chord length and thickness as one proceeds from the root (near the fuselage) to the tip section (at the wing tip) so that the airfoil sections also remain geometrically similar. (A planform is the shape of the wing as one looks down on it from above.)

http://www.centennialofflight.gov/essay/Theories_of_Flight/Reducing_Induced_Drag/TH16.htm

I find it hard to believe.  Especially since the inclusion of taper ratio is considered
not to make a large difference at all and is generally considered unnecessary for most applications.

In fact the largest contributor to e factor is wingtip construction.

The wing-tip shape, being at the point where the tip vortices are produced, appears to be of more importance in minimizing tip vortex formation and thus minimizing induced drag. Taper and twist are perhaps of greater importance in dealing with the problem of stalling.

http://www.centennialofflight.gov/essay/Theories_of_Flight/Reducing_Induced_Drag/TH16.htm

A taper ratio of 0.4 most closely approximates the elliptical.

The FW-190's Taper Ratio is according to you - .44
The most optimal would be .40.

Since both Aspect Ratio and Taper very very slightly factor into e factor I would have to say the Aspect Ratio advantage of .21 for the FW-190 trumps the .04 Taper Ratio advantage of the Spiteful.  

So I have to call a big BS flag on your "optimal taper ratio" theory for the Spiteful.  It just does not make any sense.  

Nice power point chart BTW.


On the subject of your wooden model spitfire.  
This report was written in 1937.

Thegreat advances in monoplane fighter design in Germany made it clear to the RAF that it needed a new home-defence interceptor. Impressed with Mitchell's Type 300, the Air Ministry drew up a specification (F.37/34) around the Type 300 design, and in 1936 ordered 310 production examples of the new fighter. A prototype first flew in March 1936, and the first production Spitfire Mark Is reached No. 19 Squadron RAF at Duxford in August 1938.

Too late for it to applied to a wooden model of the Spitfire.  It applies correction for the shape of the tunnel and the model or test aircraft being mounted off-center of the stream.  So what was the shape of the tunnel your model was tested in?  Mute point because this theory came out AFTER the 1/6th scale model of the spitfire was tested.  Therefore no corrections could have been applied.

Crumpp

[gripen]

Originally posted by Crumpp

If the physical construction of the wing is not elliptical then you must manipulate the wing structure to achieve an elliptical distribution.  This is done by twist.  The Spiteful does not have elliptical wing construction.  It has NO twist either to move it closer to elliptical.

Well, here is a typical example how you don't understand at all what has been under discussion in this thread. The lift distribution can be manipulated both ways; with taper ratio and the washout. Here is a lift distribution chart from the Glauert book which shows the effect of the optimal taper ratio:




Same can be found in the other form (Figure 2-44a) from Perkins&Hage. As Badboy pointed out above with example of the F6F, the tapered (untwisted) wing can reach almost elliptical distribution with optimal taper ratio as can be seen from the chart above.

The Spiteful, Mustang and Fw 190 all had about optimal taper ratio (around the 0,5) but the washout in the wings of the Mustang and Fw 190 moved lift distribution inwards just like washout did same thing in the case of the Spitfire. This can be confirmed from the Lednicer's lift distribution chart:



Basicly if you want to prove something else, you should prove that Lednicer is wrong. Besides, this has abolute nothing to do with my calculations.

Originally posted by Crumpp
On the subject of your wooden model spitfire.
This report was written in 1937.

If you had actually read the document you would have found out that it was written 1935 and in the NACA references it is claimed for year 1935. The wind tunnel tests of the Spitfire I have refered are from year 1943 as can be confirmed from the catalogue of the PRO.

gripen

[Crumpp]

The lift distribution can be manipulated both ways; with taper ratio and the washout.

That is funny.  For someone who "does not understand" I sure made that my whole point in the first post about the Spiteful.

You don't have a lift distribution chart for the Spiteful, Gripen.  So you can't really make any claims about it!

Other than what the math shows.

The Spiteful, Mustang and Fw 190 all had about optimal taper ratio

So tell me how any formula that uses both aspect ratio and taper ratio arrives at result in which the Spiteful beats the FW-190??

Taper ratio's are equal and the FW-190 has a higher Aspect Ratio.    Mathmatically it does not make sense Gripen.  Unless your manipulating data.

Your whole argument is not logical.

If you had actually read the document you would have found out that it was written 1935 and in the NACA references it is claimed for year 1935. The wind tunnel tests of the Spitfire I have refered are from year 1943 as can be confirmed from the catalogue of the PRO.

AS the paper says Gripen:

 

Silverstein, Abe White, James A  NACA Report 547 1937  

http://naca.larc.nasa.gov/reports/1937/naca-report-547/

It was published in 1937.
A year after the prototype Spitfire was flying.

A prototype first flew in March 1936, and the first production Spitfire Mark Is reached No. 19 Squadron RAF at Duxford in August 1938.

 

The wind tunnel tests of the Spitfire I have refered are from year 1943 as can be confirmed from the catalogue of the PRO.

Double standard here Gripen.  You won't take anyone elses word on a document and you expect them to take yours?

If it is from 1943, how can anyone be sure it was a varient that even flew during the war?  The Mk XIV was in service in October 1943.

http://www.csd.uwo.ca/~pettypi/elevon/gustin_military/spit/spit1943.html

It was not approved for (+25) boost until much later in the war.

Crumpp

[Angus]

Hello Guys.
I've not read the thread to well, but I saw you comparing the 190 wing with the one of the Spiteful.
Now, the Spiteful was supposed to incorporate laminar flow, but with insufficient success as far as I know.
Now the Spiteful was faster than the ultimate Spitfire, however not by so much I think, and also with more power (I think again)
So, just my 5 cents, but take a look at the Spiteful's performance vs say Spit XIV or 21, and compare it with the power.
As far as I remember the Spiteful wing turned out totally as a slight disappointment, - i.e., the original Spitfire wing was actually better than belived to be.
Just from my head, but please have a peek into it

[gripen]

Originally posted by Crumpp
For someone who "does not understand" I sure made that my whole point in the first post about the Spiteful.

The Spiteful has taper ratio 0,47 and no  washout which yields near elliptical lift distribution. Basicly you did not understand that also taper changes lift distribution.

Originally posted by Crumpp
You don't have a lift distribution chart for the Spiteful, Gripen. So you can't really make any claims about it!

Other than what the math shows.

Glauert corrections are well known and accepted part of the wing theory. Actually the modern definition of the e factor still contains Glauert correction embedded in it as can be seen above.

Besides I'm not making any particular claims or comparisons other than testing if the modern version of the e factor formula works and it seem to work rather well in the case of the plane which had no washout (the effect of the washout is much more difficult to calculate).

Originally posted by Crumpp
So tell me how any formula that uses both aspect ratio and taper ratio arrives at result in which the Spiteful beats the FW-190??

Glauert made corrections for aspect ratio and taper ratio as well as for the washout. Get his book if you are interested to calculate, I have no any particular need to calculate or prove something else than what the drag data shows.

Start a new thread if you want to compare planes this thread is about determination of the e factor not about comparisons.

Originally posted by Crumpp
It was published in 1937.

It was part of the 1937 periodical (starting from  p. 135) it was written 1935 and published same year as can be confirmed for example from here. NACA periodicals are large collections of reports which were published individually earlier.

The wind tunnel tests for the Spitfire which I have been refering are from year 1943. The reference number in the PRO is DSIR 23/12576, get the report if you don't believe and the year can be confirmed from the catalogue too.

gripen

[Angus]

were you guys in the PRO?
I was there once, and definately want to go again.
It needs some planning if you want to get something out of it  though, you may need to place orders in advance etc.
Anyway, I am planning for London, if (economically) possible, this autumn.
If you guys want to meet up, join up, team up, etc, just let me know!!! All for it, and this applies to you all. (even Izzy)
I mean, this is no joke, quite serious. And if you haven't been to London, well, some have (me like 10-20 times), and of course some AH'ers live there. So, anyway, if on the hunt for documents, pictures or data, London IS the place, and I'll be all ready to assist.

Regards.

Angus.

[gripen]

Originally posted by Angus
were you guys in the PRO?
I was there once, and definately want to go again.
It needs some planning if you want to get something out of it  though, you may need to place orders in advance etc.

I've been there couple times, at least in my case there have been no need to order something in advance. Their catalogue is very usefull. Nowadays they allowe digital cameras in the reading rooms.

gripen

[gear]

[

[Crumpp]

The Spiteful has taper ratio 0,47 and no washout which yields near elliptical lift distribution. Basicly you did not understand that also taper changes lift distribution.

Proof you did not read my very post on the Spiteful and are simply flamebaiting.

The Spiteful has taper ratio 0,47 and no washout which yields near elliptical lift distribution. Basicly you did not understand that also taper changes lift distribution.

Near Perfect elliptical distribution is .45 according to this report.


.47 is too high.  Again.  Simply post the Lift distribution chart for the Spiteful.

Start a new thread if you want to compare planes this thread is about determination of the e factor not about comparisons.

Facts are Gripen.  You can't explain it. It does not work out mathmatically with any formula using Glauerts corrections.   The Spiteful should not have an e factor significantly higher than the FW-190.

Taper ratio for the Spitful = .47
Taper ratio for the FW-190 = .44

Aspect Ratio for the Spitful = 5.81
Aspect Ratio for the FW-190 = 6.02

As Glauerts corrections show.  Higher Aspect Ratio is more beneficial to wing efficiency and the taper ratios are near equal.


 

The wind tunnel tests for the Spitfire which I have been refering are from year 1943. The reference number in the PRO is DSIR 23/12576, get the report if you don't believe and the year can be confirmed from the catalogue too.

So it it's not even a varient used in World War II.  

Crumpp

[Badboy]

Originally posted by gripen
Generally the values in the Oswald's chart are probably a bit on high side; the value of e must be always be less than 1 as Wood notes. Practical maximum is probably around 0,95 for the flying wings. Here is some values for modern planes from Navy web site:

"The value e can be estimated for a particular model of aircraft by various methods.
One of the simplest is by comparison with aircraft of similar configuration. For most
aircraft e has a value of about 0.6 to 0.8. Some values of e for various aircraft as
measured at Mississippi State University are

Bellancer Crusair (low-wing) 0.55
Learstar (twin engine mid-wing) 0.67
Cessna 170 (high-wing) 0.74
RJ-5 Glider (high-wing) 0.79"

I’m still not happy to use those values in the context of WWII aircraft because the aircraft in the list above are not really intended to operate efficiently under high load factors, they rarely pull more than 3g, while WWII fighters were intended to be more efficient during loaded maneuvers.

Originally posted by gripen
A practical comparison can be done with the Spiteful (no washout) wind tunnel data and calculation for entire airframe using the estimated value of K 0,01 (viscous drag) from Perkins&Hage and Glauert correction factor 0,011 for taper ratio about 0,5 (induced drag):

Wind tunnel => e=0,81
Calculated => e=0,84

Which is a pretty good result given the generalized form of the estimation.

Agreed, and that’s much more like the sort of value I think we should expect for fighters. Also, I would expect the theoretical value to be slightly higher, as they are, because the calculations don’t allow for a number of factors, such as distortion of the wingtip vortices due to viscosity, that reduces the efficiency.

Here are some more comparisons between calculated and experimental values for e shown in the last column on the right.
 


The author of this chart claims to be comparing Oswald’s efficiency factor, but he actually only appears to have tested flying wings. Though I can’t be certain. For example, the elliptical wing in that table has an experimental value of 0.92 and a calculated value of 0.93 and all of the wings with an aspect ratio 6 and taper ratio of 0.5 are very close to an e of 0.9 both experimentally and calculated. You can compensate for the incomplete value of e by including an estimated value for k in the calculation, but the value should be lower than normal because a flying wing would already include some of it in the original value. Doing that would, I anticipate, bring the value back down between 0.8 and 0.85 as before.

Badboy

[gear]

Vmax (IAS) @ 5000’ @ WEP

By Rank Order

By Year

Rank Order – Current Version
Rank
 Aircraft
 3.05
 
1
 262
 461
 
2
 190D9
 358
 
3
 Ki84
 354
 
4
 J2M2
 353
 
5
 109K
 353
 
6
 Yak 3
 349
 
7
 P47D
 349
 
8
 J2M3
 346
 
9
 F4u1a
 344
 
10
 F4u1D
 344
 
11
 Corsair II
 344
 
12
 Corsair IV
 344
 
13
 F4u4
 344
 
14
 P51D
 342
 
15
 Spit 14
 342
 
16
 P51B
 341
 
17
 Fw190A4
 339
 
18
 P38J
 329
 
19
 P38L
 329
 
20
 190A8
 326
 
21
 109G6
 323
 
22
 C205
 322
 
23
 F4u1
 321
 
24
 Corsair I
 321
 
25
 P47C
 321
 
26
 Yak 9
 320
 
27
 Ki44-IIb
 317
 
28
 P39Q
 315
 
29
 P38F
 313
 
30
 Mossie NFII
 313
 
31
 P400
 312
 
32
 Mossie VI
 312
 
33
 P39D
 308
 
34
 Spit 9
 308
 
35
 Ki61-1b
 308
 
36
 F6F5
 308
 
37
 Ki61-Ic
 308
 
38
 C202
 306
 
39
 109F4
 303
 
40
 109G6R6
 303
 
41
 A6M3
 295
 
42
 A6M5a
 295
 
43
 SPIT 5
 294
 
44
 109F1
 292
 
45
 Seafire 2
 291
 
46
 110G2
 290
 
47
 Ki43
 288
 
48
 P40E
 288
 
49
 P40B
 287
 
50
 Spitfire 1
 285
 
51
 109E4
 284
 
52
 FM2
 284
 
53
 A36
 279
 
54
 A6M2
 271
 
55
 Hurri2c
 269
 
56
 F4F3
 267
 
57
 F4F4
 263
 
58
 Hurricane 1
 262

[gripen]

Originally posted by Crumpp
Proof you did not read my very post on the Spiteful and are simply flamebaiting.

You said in your post that:

"If the physical construction of the wing is not elliptical then you must manipulate the wing structure to achieve an elliptical distribution. This is done by twist. The Spiteful does not have elliptical wing construction. It has NO twist either to move it closer to elliptical. "

You simply did not understand that the about optimal taper ratio of the Spiteful  yields near elliptical lift distribution despite it had no elliptical construction nor washout.
 

Originally posted by Crumpp
Near Perfect elliptical distribution is .45 according to this report.

As can be seen from the Fig. 2-44a in the Perkins&Hage, the taper ratio of the untwisted wing around the 0,4-0,5 yields near elliptical lift distribution, as an example see Badboy's post on taper ratio 0,52 which yielded induced drag factor (u) over 0,99 with computer analysis.

Originally posted by Crumpp
You can't explain it. It does not work out mathmatically with any formula using Glauerts corrections.

If the tapered wing has about optimal taper ratio it also has near elliptical lift distribution. Now if washout is added, it moves lift distribution inwards which yields less optimal lift distribution as can be seen from Lednicer's chart and can be calculated with Glauert corrections. It's up to you to prove that they are wrong.

Originally posted by Crumpp
So it it's not even a varient used in World War II.  

It's up to you to prove that the Spitfire I was not used during WWII.

Originally posted by Badboy

I’m still not happy to use those values in the context of WWII aircraft because the aircraft in the list above are not really intended to operate efficiently under high load factors, they rarely pull more than 3g, while WWII fighters were intended to be more efficient during loaded maneuvers.

Neither I'm using those values for the WWII fighters. The drag data I have checked so far indicate that the e factor was typically around 0,75-0,8 in the Cl range say 0,2-1,0 (assuming that there was a linear stage around these Cl values). The problem here is that near Clmax (generally around Cl 1,4-1,8), like in the high g maneuvering near corner speed, the Cd/CL^2 curve is no more linear and it's difficult to say if the e factor defined normal way works well for performance calculations in this kind of maneuvering.

Another problem in the wind tunnel data is that in most cases measurements are made without propeller so slipstream effects are not counted.

Originally posted by Badboy
Agreed, and that’s much more like the sort of value I think we should expect for fighters. Also, I would expect the theoretical value to be slightly higher, as they are, because the calculations don’t allow for a number of factors, such as distortion of the wingtip vortices due to viscosity, that reduces the efficiency.

Yep, very true, I used purely approximated value of the K 0,01. The range for the value of the K (viscous drag multiplier in the e factor formula) given in the Perkins&Hage is 0,009-0,012 which yields e factor range 0,8-0,85 for a plane with about optimal taper ratio and no washout.

gripen

[Crumpp]

You simply did not understand that the about optimal taper ratio of the Spiteful yields near elliptical lift distribution despite it had no elliptical construction nor washout.

Way to manipulate words Gripen!

I simply understand the english adjectives, "Perfect" and "near perfect".

the taper ratio of the untwisted wing around the 0,4-0,5 yields near elliptical lift distribution,

So now it's a range!  What happenend to:

The Spiteful has taper ratio 0,47 and no washout which yields near elliptical lift distribution.  

You seem very hung up on lift ditribution for the entire wing.  While it does effect efficiency, a "perfect ellipse" is not a desirable feature in a practical aircraft, Gripen.  The most important part of lift distribution for induced drag is the tip.  Designers will strive to get elliptical distribution for the wingtip.

The rest of the lift distribution is usually manipulated to improve the stall and avoid the stall characteristics of a perfect ellipse.

 

The other problem with elliptical wings is the stall characteristics.  It is much safer to design an airplane so that the wing stalls first at the root, leaving the outer portion of the wing, (where the ailerons are) still flying. An elliptical wing however, will tend to stall uniformly all along the span (see the diagram below.) The "fix" for this situation is washout, but that will reduce the theoretical gains in induced drag. Therefore, we are unlikely to see a great resurgence in the use of elliptical wings, except in situations where appearance dictates.

http://142.26.194.131/aerodynamics1/Drag/Page8.html

The wing-tip shape, being at the point where the tip vortices are produced, appears to be of more importance in minimizing tip vortex formation and thus minimizing induced drag.

Taper and twist are perhaps of greater importance in dealing with the problem of stalling.

http://www.centennialofflight.gov/essay/Theories_of_Flight/Reducing_Induced_Drag/TH16.htm

So in effect you cannot explain why your math gives the FW-190 a much lower e factor than the Spitfeful.  

You keep avoiding the question of how that is possible with the aircraft having near perfect taper ratios and the FW-190 having a significant advantage in Aspect Ratio?

As for your wooden model, now I am confused about it.  First it was a 1943 report so that it could have used an NACA report calculating corrections of off center flow around the tail which included formulas that brought the model closer to the actual aircraft published in 1937.  

Gripen says:
The wind tunnel tests of the Spitfire I have refered are from year 1943 as can be confirmed from the catalogue of the PRO.

Now it is a Spitfire I?

Gripen says:
It's up to you to prove that the Spitfire I was not used during WWII.

Which is it?

Great chart Badboy.  Interesting the wide range of shapes with very similar efficiency.

Crumpp