# Laminar Flow Airfoil



## davebender (Mar 17, 2013)

I'm no expert in this area but found the web page interesting.
Laminar Flow Airfoil


> The P-51 Mustang was the first aircraft intentionally designed to use laminar flow airfoils. However, wartime NACA research data shows that Mustangs were not manufactured with a sufficient degree of surface quality to maintain much laminar flow on the wing. The RAF found that the Bell P-63, despite being designed with laminar airfoils, also was not manufactured with sufficient surface quality to have much laminar flow.
> 
> The B-24 bomber's "Davis" airfoil was also a laminar flow airfoil, which predates the Mustang's. However, the designers of the B-24 only knew that their airfoil had very low drag in the wind tunnel. They did not know that it was a laminar flow airfoil.
> 
> The boundary layer concept is credited to the great German aerodynamicist, Ludwig Prandtl. Prandtl hypothesized and proved the existence of the boundary layer long before the Mustang was a gleam in anyone's eye.





Another interesting bit from the same web site.
Wing Dihedral







> Highly maneuverable fighter planes have no dihedral and some fighter aircraft have the wing tips lower than the roots, giving the aircraft a high roll rate. A negative dihedral angle is called anhedral. The AV-8B Harrier II above has a negative dihedral or anhedral


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## J.A.W. (Mar 17, 2013)

Big turbines providing excess thrust enabling VTOL/viffing/blown aero are in a different category, surely..although the Tempest was also WW2 era with a 'laminar-flow wing' claim.


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## davebender (Mar 17, 2013)

Did any WWII era aircraft have this design feature?


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## tyrodtom (Mar 17, 2013)

The He162 had anhedral on it's outermost wings.


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## J.A.W. (Mar 17, 2013)

tail di-hedral.. One of the few 1st gen jet fighters that did not exhibit hi-speed porpoising dynamics to spoil gun-aim..


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## GregP (Mar 17, 2013)

The He 162 outer wing panels are so small, one wonders why they are even there ... except to guide the tip vorticies. Really, there's almost no area there.


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## tyrodtom (Mar 17, 2013)

I think the anhedral wingtips on the He162 was to compensate for too much dihedral in the main wing, it saved them from having to redesigning the whole wing.
They were in a rush.


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## GregP (Mar 17, 2013)

They are so small I think it was to eliminate vibration in the tail more than anything else, by moving the tip vorticies.

And without VIFFing, the Harrier is not very maneuverable, though it does roll well.


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## nincomp (Mar 18, 2013)

Davebender
OK, this thread finally got me to join the forum. I studied aeronautics in college and even had a part-time job at a windtunnel, so the continual references to the P-51's "laminar-flow airfoil" has been a sore point for me.

Yup, it is true that the P-51's wing did not have any significant laminar flow. Extensive laminar flow is extremely difficult to achieve and requires incredibly exact tolerances and smoothness to achieve. In fact, until recently, high-performance sailplanes were about the only "production" aircraft to actually have extensive laminar flow over their wings. Even on these high-performance sailplanes, laminar flow could be lost from something as minor as a few bug-hits on the leading edge. There are stories of sailplanes landing miles short of their landing strips because they encountered some mist or rain. The water droplets "tripped" the air boundary layer from laminar to turbulent - increasing the wing drag and drastically reducing the glide ratio. Similar stories exist about sailplanes that happened to fly into a small cloud (swarm?) of gnats or other insects. As a sidebar... the stall characteristics of some laminar-flow wings became very ugly (abrupt) when the laminar boundary was disturbed. This might explain some of the P-51's handling characteristics.

Boy, do I feel better now that I got that off my chest! 

The first article that you mentioned also mentioned the "Davis wing" that was used on the B-24. It too showed extremely low drag in the wind tunnel, but not in the production aircraft. I actually feel very sorry for the design teams that used the wind-tunnel data in their performance calculations. I can't imagine what they (or their bosses) did when the actual performance was very much less than predicted. 
You might recall that the original P-51's performance was good, but not spectacular. My guess is that the wing performance was well below predicted. 
- Luckily for the P-51, the British had the better performing merlin engine to use in it. In my opinion, this made all the difference. 

The main (unanticipated) advantage of the P-51's "laminar-flow" wing is now well known: it delayed the effects of compressibility, giving the plane a high critical mach-number. This allowed it to dive faster than most planes while staying in full control. - Remember that the P-51 was designed before much was known about compressibility (airflow at or near the speed-of-sound). The designers had no way to test for this, so these high-speed characteristics were a very fortunate accident.

There is a section (Chapter Five) in the NASA document sp-468 "QUEST FOR PERFORMANCE The Evolution of Modern Aircraft" that has a good discussion of the actual performance of early production laminar-flow wings vs. the perfectly shaped wind-tunnel models. 
This is a wonderful .pdf book (500+ pages) that you can download for free. I have lost the link, but you can find it by searching for "NASA sp-468."


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## J.A.W. (Mar 18, 2013)

Ah no, the P-51s V-max was not better than the thick-winged Typhoon [525 IAS] significantly less than the 'laminar flow' winged Tempest [545 IAS], in fact the P-51s developed a bit of a blue-note terminal-velocity dive wing-shedding rep..but the P-51 was fast for the power it had available, on the level...


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## nincomp (Mar 18, 2013)

As for dihedral:
Your source is technically correct, but as is often the case, the full answer is more complicated.
The mention of inherent stability is important. It includes both the center of gravity and effective dihedral. Basically, if there is sufficient inherent stability the airplane will automatically return to flying upright. If, however, the wings have too much effective anhedral (negative dihedral), the airplane will continually try to roll itself inverted. The tendency of the plane to invert itself can give it an advantage in maneuvers that require rapid rolling. On the other hand, the pilot or other control system must always actively fight to keep the plane rightside-up.

Inherently unstable aircraft are a bad idea (especially near the ground) unless there is some automated control system that is very rapid and very reliable. In some cases, a human pilot would be incapable of reacting fast enough to safely fly the plane if the automated controls fail. During the WWII era, I do not believe that the required automated systems were advanced enough to deal with significantly unstable aircraft.

Now, however, on-board computers are used to control unstable aircraft. It is therefore much safer to go after that last little bit of maneuverablilty.


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## nincomp (Mar 18, 2013)

J.A.W. said:


> Ah no, the P-51s V-max was not better than the thick-winged Typhoon [525 IAS] significantly less than the 'laminar flow' winged Tempest [545 IAS], in fact the P-51s developed a bit of a blue-note terminal-velocity dive wing-shedding rep..but the P-51 was fast for the power it had available, on the level...



No argument. Note that I said "most planes." The wing sections used in the P-51 were simply better than _many_ others in use at the time, not optimal for (or even designed for) the highest critical mach. As I said, it was simply a fortunate accident. 

It is important to remember that as the "sound barrier" was approached, many new and unexpected problems kept appearing. Wing sections were only part of the problem. There was a lot to learn about things like design and location of control surfaces, the wing-fuselage transition, effective wing sweep, etc.

The main point that I wanted to make in my first post was about the lack of actual laminar airflow on the so-called "laminar flow" wings of WWII fighters.


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## tomo pauk (Mar 18, 2013)

Maybe the real-world 'laminar flow' wings were the best real world approximations of theoretical laminar flow wings? Some designers and producers doing their job better than another?



J.A.W. said:


> Ah no, the P-51s V-max was not better than the thick-winged Typhoon [525 IAS] significantly less than the 'laminar flow' winged Tempest [545 IAS], in fact the P-51s developed a bit of a blue-note terminal-velocity dive wing-shedding rep..but the P-51 was fast for the power it had available, on the level...



In the left corner we have a single engine fighter with 1150 HP, doing almost 400 mph. At the right corner we have a SE fighter with 2150 HP, doing 5 mp/h more. So let's trash the 1150 HP airplane???
The wing-shedding got nothing to do with wing being of this or that tape, it was connected with U/C doors opening in high G maneuvers, and was cured by installation of door locks.

Hi, nincomp,


> You might recall that the original P-51's performance was good, but not spectacular. My guess is that the wing performance was well below predicted.
> - Luckily for the P-51, the British had the better performing merlin engine to use in it. In my opinion, this made all the difference.



We can take a look at the available engine power the 1st Mustangs have at disposal. With engine same as at P-40D/E, the Mustang I was some 40 mph faster. The greater top speed was not something that could be attributed to the wing, but speed difference was simply to great. 
The P-51B and later models, with Merlins comparable to the Spitfires VIII/XI, were some 30 mph faster than those Spits.


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## J.A.W. (Mar 18, 2013)

True, the Mustang was fast, for the power it had, on the level..
The P-40 similarly powered was much slower, high speed in the thick sea-level air has to be a function of a balance between power/drag, if you`ve got a 2000+hp Napier Sabre to unleash you can go [ if you`ve got a 3000hp N.S. you can do 417mph at S-L - Tempest 6 @ 17lbs boost] .
Mind you, the much maligned P-39 went pretty fast on not much hp, so did the He 100..


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## tomo pauk (Mar 18, 2013)

I'm not sure what do you mean by 'on the level'?
The high speed is always a function of a balance between power and drag (until the compressibility kicks in, that is; plus, we have the exhaust thrust, applicable for all altitudes. The P-39 was a small airplane (wing area akin to Fw-190, or considerably less than of Spitfire), the undercarriage was fully covered when retracted, the weight was not excessive. Once the wing guns were removed from the -Q, it was doing circa 400 mph. We can note that P-39 was never maligned by Soviets, they always clamored for more.


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## J.A.W. (Mar 18, 2013)

On the level, as opposed to going up or downhill.. The Mustang was not the fastest zoom/dive fighter inspite of its clean airfame..


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## nincomp (Mar 18, 2013)

tomo pauk said:


> Maybe the real-world 'laminar flow' wings were the best real world approximations of theoretical laminar flow wings? Some designers and producers doing their job better than another?



Well... not really. It was virtually impossible to get the required profile accuracy and surface finish with the aircraft building techniques of the time. The use of fiberglass and other composites has made production of these precision airfoils much easier. To give you an idea of how sensitive the NACA 6-series laminar profiles are to imperfection, sailplane owners would occasionally use 1000-grit sandpaper, attached to precision aluminum straight-edges to carefully smooth the leading edge and upper surface, even if they could not see any flaws. Some claimed significant performance gains. 



> We can take a look at the available engine power the 1st Mustangs have at disposal. With engine same as at P-40D/E, the Mustang I was some 40 mph faster. The greater top speed was not something that could be attributed to the wing, but speed difference was simply to great.
> The P-51B and later models, with Merlins comparable to the Spitfires VIII/XI, were some 30 mph faster than those Spits.



Good points. The P-51 was a very clean aircraft. As a matter of fact, when I recently read a lament that there was not a greater attempt to improve the P-40, I realized that the North American engineers were familiar with the P-40 (having been asked to build it themselves) when they decided to design the P-51. In some respects, the P-51 was, indeed, an updated P-40.

The improvements would have been much greater, though, if the theoretical advantages of the laminar-flow wing were realized. On paper, there could have been a 25-30% reduction of drag from the wing. It should be mentioned, however, that even using today's construction techniques, such an improvement would be very, very unlikely. It turns out that the wind-tunnel data for those airfoils does not scale up accurately to the long cords and high speeds of the actual aircraft.
- Sailplanes (and military drones) have much narrower wings and fly at lower speeds.


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## tomo pauk (Mar 18, 2013)

J.A.W. said:


> On the level, as opposed to going up or downhill.. The Mustang was not the fastest zoom/dive fighter inspite of its clean airfame..



Maybe some numbers, like diving speeds, would help us to qualify the Mustang? 



nincomp said:


> Well... not really. It was virtually impossible to get the required profile accuracy and surface finish with the aircraft building techniques of the time.



I agree that it was impossible to achieve 100% laminar flow with wings produced back in ww2, that's why I've used the "best real world approximations of theoretical laminar flow wings" statement.



> The use of fiberglass and other composites has made production of these precision airfoils much easier. To give you an idea of how sensitive the NACA 6-series laminar profiles are to imperfection, sailplane owners would occasionally use 1000-grit sandpaper, attached to precision aluminum straight-edges to carefully smooth the leading edge and upper surface, even if they could not see any flaws. Some claimed significant performance gains.



Thanks.



> Good points. The P-51 was a very clean aircraft. As a matter of fact, when I recently read a lament that there was not a greater attempt to improve the P-40, I realized that the North American engineers were familiar with the P-40 (having been asked to build it themselves) when they decided to design the P-51. In some respects, the P-51 was, indeed, an updated P-40.



Mustang shared appearance with most of inline-engined fighter; apart the engine, it shared next to nothing with P-40. 



> The improvements would have been much greater, though, if the theoretical advantages of the laminar-flow wing were realized. On paper, there could have been a 25-30% reduction of drag from the wing. It should be mentioned, however, that even using today's construction techniques, such an improvement would be very, very unlikely. It turns out that the wind-tunnel data for those airfoils does not scale up accurately to the long cords and high speeds of the actual aircraft.
> - Sailplanes (and military drones) have much narrower wings and fly at lower speeds.



We have "theoretical advantages" and "On paper" in one side, and the production and usage realities at another. Seems to me that NAA was able to get the grips of stuff and produce it as best as the technology of the day was allowing. The others following the suit, either as good as NAA, or worse.


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## J.A.W. (Mar 18, 2013)

According to RAE evaluation the Tempest listed the following V-max limitations:
IAS Height
370 @ 30,000ft
410 @ 25,000ft
450 @ 20,000ft
490 @ 15,000ft
540 @ 10,000ft

Comments from Tempest evaluation, "The fact is that it has the best acceleration in the dive yet seen at this unit"[ ditto zoom].


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## tomo pauk (Mar 18, 2013)

Indeed, the Tempest has better 'allowances' for dive, P-51 was redlined at 505 mph indicated at 9000 ft.


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## nincomp (Mar 18, 2013)

> Mustang shared appearance with most of inline-engined fighter; apart the engine, it shared next to nothing with P-40.



How about this: The Mustang is the P-40's third cousin, twice removed? Or that cousin's next-door neighbor?
OK, maybe not.


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## J.A.W. (Mar 18, 2013)

No nincompoop, no, the P-40 was designed by Berliner, but the P-51 was drawn-up on behalf of the British by those familiar with actual Me-werk..


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## tomo pauk (Mar 18, 2013)

The chief designer of Curtiss not being a Berliner, but from USA? 



> but the P-51 was drawn-up on behalf of the British by those familiar with actual Me-werk..



Care to elaborate this a little bit?


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## drgondog (Mar 18, 2013)

The Brits did not advise or 'draw up' anything. Schmued and Horkey did the preliminary design in the thrird week of March, 1940 - then Kindelberger flew to Britain to present the concept to Sir Henry Self - who approved the concept on April 9, 1940.

Schmued migrated to the US from Brazil in 1930 and had zero involvement with Messerschmidt.

The P-51B/C experienced four types of failures in the 1st Qtr 1944. First the engine bolts from a specific contractor failedcausing several catastrophic failures. Second the ammo doors were 'ballooning' in terminal dives. Third the aft fuselage/eppenage structure was failing in high speed slow rolls (NAA originally designed tail to Army specs which were not satisfatory for the Q loads encountered by any of the P-47/38/51 high speed fighters) and last the wheel uplocks were not sufficient in some cases to prevent the main gear from lowering through the wheel cover doors during high G pullout.

Secondary issues included similar 'ballooning' with fabric elevators.

The primary difference between the 23xxx and 45-100 airfoil was the location of Max t/c. For the 23xxx it was 24.5% and for the 45-100 it was 49%. The 45-100 was designed by specifying the pressure distribution at high reynolds numbers that NAA wanted - then applying LaPlace/Theodorsen transformation methods to extract the wing co-ordinates.

True - that Laminar Flow is near impossible holy grail for WWII methods, but the Mustang fill and prime and sand undercoat was far superior to other metal fab techniques. The primary point to make however is that the profile drag in the wing tunnel was about 40% Less than the 23xxx - so not hard to extrapolate that even absent laminar flow that the 45-100 had accompanying superior boundary layer to turbulent flow transition which resulted in reduced profile drag.

Further the location of the max T/c provided for a more gradual velocity gradient from LE to max T/c which explains the delay from Drag Divergence to Critical Mach shockwave despite having a much fatter wing than the Spit. I don't offhand know what the Tempest wing T/c is - but that is the single most important factor - all else being equal - to Mcr point. The Mustang shock wave originates near the max T/c which is 25% Chord farther aft from conventional airfoils of the day.

And No - there is Zero in common with any aspect of P-36 through P-40 airframe 

The P-51D/Mustang IV reached .84-.85M in an RAF test which was halted at that point when the test pilot witnessed the beefed up ammo doors deflecting and knew the next stage was too much 'local' lift which would cause structural failure.

While not the fastest zoom and dive fighter aircraft during WWII, it was at or near the top comparatively speaking and the retained energy resulting from clean fuselage combined with exhaust thrust and low airfoil drag were major factors.

I am not one that believes that the radiator/cowling design was a major thrust producer but I do believe that it does create enough added energy to overcome the drag of the 'scoop'.


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## tomo pauk (Mar 18, 2013)

From Wikipedia, referenced to authors Thomas and Shores:



> A laminar flow wing adopted for the Tempest series had a maximum thickness to chord ratio of *14.5%* at the root, tapering to *10%* at the tip.



P-51, from Gruenhagen's book:
-16,5% at root, 11,5% at tip


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## drgondog (Mar 18, 2013)

That would give the edge to the Tempest re: Mcr, all eles equal.


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## tomo pauk (Mar 18, 2013)

The talk about laminar flow wings brought a question: how come the Sea Fury was deemed as a superb carrier plane, while P-51 was not regarded as such by USN? The Sea Fury having less wing area than Tempest, while the wing thickness to chord ratio was lower than at P-51. Was the flap system of S. Fury better suited for low velocities?
How good/bad was the Seafang as the CV bird, having also laminar flow wing?


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## drgondog (Mar 18, 2013)

First and foremost, the Mustang was an in-line engine recip and there was no logistics supply chain for it nor was the USN thrilled about In-Line. Second, the Mustang's long Nose vs Hellcat was a detracting feature. Third the low speed handling characteristics was less suitable than the Hellcat, Bearcat and Corsair -

Last but not least - the F4U already had more range than any USN bomber it might be pressed to escort, leaving a range capability of the Mustang looking for a mission.


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## tomo pauk (Mar 18, 2013)

As in most of the cases, it's hard not to agree with your analysis. We could add that USN was about to receive the F4U-4 and F8F, performance of those two would negate any performance edge Merlin Mustang had over 1944 USN fighters. The RN probably wanted to replace their LL fighters, along with Firefly and Seafire with an indigenous fighter of both greater performance and better CV suitability.
OTOH, I was hoping to get a plausible assessment of Sea Fury and Seafang's capabilities in the low speed handling.


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## J.A.W. (Mar 18, 2013)

As far as low speed stall/wing drop characteristics,[ it might be simplistic to extrapolate] but don't semi-eliptical planforms have a rep for being a bit more forgiving in this?
Obviously purpose designed USN carrier fighters always had generous wing areas, but Hawkers did change the planform to a semi-elipse, as well as the thickness aspects when they developed the Typhoon into the Tempest-Fury.
The USN did have a parochial view towards 'Army ships', witness the Airacobra losing its tricycle undercart at their behest..


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## drgondog (Mar 18, 2013)

The primary contribution of the elliptical wing was minimum induced drag... has nothing positive or negative to contribute to Stall characteristics.


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## GregP (Mar 18, 2013)

Hi Tomo,

According to two Sea Fury pilots I know (both are signed off in P-51's), the stall speed in landing configuration at relatively light weights is 87 knots. The stall speed in landing configuration for the P-51D at relatively light weight is 78 knots. The difference is that Naval aircraft have to meet certain handling characteristics for safe flight around the carrier and the Sea Fury DOES, is very stable and forgiving in landing configuration, and has a good view of the deck (has a raised cockpit) compared with that from the P-51. Near the stall the Sea fury is much more responsive than the P-51D is, as most Naval aircraft are. With the Bristol radial, the aircraft is very speed-stable and it is much easier to “hit a spot” with a Sea Fury after some training than it is with a P-51D.

That says nothing bad about the P-51D except it doesn’t make as good a Naval aircraft as a Sea Fury. That isn’t too bad considering the P-51D was never intended as a Naval aircraft to start with. Great planes with different missions. The Fury was not a Naval aircraft either as designed and had to be modified to meet Naval requirements before they arrived at the "Sea Fury" configuration.

If you get a chance, you might peruse MIL-F-8785C, Flying Qualities of Piloted Airplanes. Quite interesting and covers a LOT of ground. The "C" version was released in 1980, but earlier specs were around when Naval piston fighters were still there and being procured.


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## nincomp (Mar 18, 2013)

drgondog said:


> True - that Laminar Flow is near impossible holy grail for WWII methods, but the Mustang fill and prime and sand undercoat was far superior to other metal fab techniques. The primary point to make however is that the profile drag in the wing tunnel was about 40% Less than the 23xxx - so not hard to extrapolate that even absent laminar flow that the 45-100 had accompanying superior boundary layer to turbulent flow transition which resulted in reduced profile drag.
> 
> Further the location of the max T/c provided for a more gradual velocity gradient from LE to max T/c which explains the delay from Drag Divergence to Critical Mach shockwave despite having a much fatter wing than the Spit. I don't offhand know what the Tempest wing T/c is - but that is the single most important factor - all else being equal - to Mcr point. The Mustang shock wave originates near the max T/c which is 25% Chord farther aft from conventional airfoils of the day.



This is a better explanation than mine. Thanks.

Despite my comment about fiberglass composites, it is indeed possible to achieve significant laminar flow on a metal wing. The Schweizer 2-32 sailplane did (although at lower Reynolds and Mach numbers). It does, however, require painstaking attention to detail and a lot of fill and prime and sand to get a smooth and accurate profile.

The NAA engineers did an impressive job with the design of the P-51. They were simply pushing the boundaries of aeronautics of the time. 

OK. The P-51 being related to the P-40 was really more a romantic notion rather than a technical one. Sorry.


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## drgondog (Mar 18, 2013)

No apology required - other than to Horkey who would have puked over the comment..


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## J.A.W. (Mar 18, 2013)

Seafang didn't make the cut against the Seafury, as a last gen prop carrier plane, but Supermarine did graft the wing on to their Attacker turbojet..


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## GregP (Mar 18, 2013)

I believe the Tempest max T/c ratio was 14.5% at the root tapering to 10% at the tip compared with 19.5% and 12% for the Typhoon. It may have changed later (not sure), but the early Tempest were as stated above. Not too sure about the Sea Fury's ratios just now.


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## J.A.W. (Mar 18, 2013)

Fury used Tempest wing, except for being mounted differently-due to the Fury going to a full stressed skin mono construction - which resulted in a shorter effective span, of course in the case of the Seafury, navalised/folding wings.


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## barney (Mar 18, 2013)

*Yup, it is true that the P-51's wing did not have any significant laminar flow. 

As a sidebar... the stall characteristics of some laminar-flow wings became very ugly (abrupt) when the laminar boundary was disturbed. This might explain some of the P-51's handling characteristics.*

I'm thinking you can't have it both ways. If the wing wasn't laminar flow you can't use laminar flow to explain handling characteristics.


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## nincomp (Mar 18, 2013)

Barney,
My answer was a little too broad. To clarify this case, I should have said that some of these airfoils have nasty stall characteristics, even if the flow is turbulent.


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## GregP (Mar 18, 2013)

The Fury didn't quite use a Tempest wing ... it used the outer wing panels, and I don't know the T/c ratio of the innermost part of the outer wing panel, and the 10% at the tip isn't 10% anymore since the root tapers from the Tempest root and is smaller. I suspect it won't change much, but it will change from the tempest figures. Probably drops by about a percent each or so, but cannot be sure just yet.

If anyone knows the span of the Tempest center section, we could figure it out easily. While I have access to a Sea Fury FB.11 (is not stock since it is a Reno racer and has been profiled to an unknown degree ... but fast. It finished second last year at Reno in Unlimited Gold), I don't have access to a Tempest and can't really take anything off the Sea Fury FB.11 since it belongs to a private owner. We pretty muich leabe privately-owned planes alone except for cleainign them. To get the root T/c, I'd have to remove the wing fillets and take measurements. Can't do that.


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## J.A.W. (Mar 18, 2013)

If you can visualise the Tempest wing where it bolts onto to the centre fuselage space-frame being flush butted together under the monocoque Fury fuselage, you will get the picture. For all intents puposes inc' aero proflies armament etc they are pretty much the same [with the naval caveat, natch].


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## GregP (Mar 18, 2013)

The Tempest center section is MUCH wider than the fuselage, so your visualization cannot be correct.

So, does anybody know the span of the Tempest center section?


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## J.A.W. (Mar 18, 2013)

The Tempest does have a greater wing area/span : a consequence of fuselage joint/effective wing root width differential, however the aero-aspects of the wing are indeed, virtually identical to the Fury;

Fury span 38' 4.75"; area 280 sqft.
Tempest 41'; area 302 sqft.

If you look at an underneath plan-view, the comparison shows the identical landing gear layout to be almost meeting in the centre on the Fury, vs the wider-set extra span-wise distance of the Tempest tubular fuselage centre section arrangement.


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## Aozora (Mar 19, 2013)

GregP said:


> The Tempest center section is MUCH wider than the fuselage, so your visualization cannot be correct.
> 
> So, does anybody know the span of the Tempest center section?



In fact Greg is right in that the Fury/Sea Fury didn't quite use the Tempest wing panels, but adapted modified outer panels to a different, narrower centre-section:







Dimensions of Fury/Sea Fury major components: one _major_ problem is that the centre section is given as 18' wide, while the outer (folding on Sea Fury) wing panels are 11' 6" (x2 = 23') so overall wingspan = 41', which just happens to be that of the of the Tempest! Wingspan of the Sea Fury was 38' 4.75". Thus the centre section was more likely to be 15' 4.75" wide - the 18' centre section is more likely to be the Tempest's width, noting that the Tempest had a wheel track of 14' 10.5". 






(Hawker Typhoon, Tempest and Sea Fury, Kev Darling, Crowood 2003, pages 140-141)


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## J.A.W. (Mar 19, 2013)

Ah yes, there's a diagram, that graphically shows the text visualisation, with the Fury utilizing virtually wholesale the aero/armament/under-cart wing componentry of the Tempest, as suggested, earlier..


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## tomo pauk (Mar 19, 2013)

As for Sea Fury being naval aircraft: it 1st took the basic Tempest airframe to be modified, and THEN we can call it naval fighter. Not like this: Sea Fury was all of the sudden a naval fighter, and by default it is better for that purpose than a shoehorned/modified land-based fighter. In other words, I'm interested in particulars that enabled the Sea Fury to become one of the best post-war naval fighters. Bill mentioned one thing: raised pilot's position, allowing for better over-nose view field. Another thing that comes to mind is roll rate at low speeds, so any good data about that is welcomed. Anything else (apart from engine type) that could set apart the two fighters?


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## drgondog (Mar 19, 2013)

I would look at the aileron size to get clues regarding low speed roll response - would also look at wing wash out to get an idea regarding tip control at low speed.


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## davparlr (Mar 19, 2013)

Laminar airflow is still the holey grail of wing design and still elusive. The X-21 was specifically designed to investigate laminar flow control. While it provided good data, maintenance was a problem.

Northrop X-21 - Wikipedia, the free encyclopedia


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## tomo pauk (Mar 19, 2013)

drgondog said:


> I would look at the aileron size to get clues regarding low speed roll response - would also look at wing wash out to get an idea regarding tip control at low speed.



According to the schematics Aozora kindly posted, the Sea Fury aileron's span was 98 in, vs. 83.3 in (6ft, 11 3/8 in) at P-51D. The aileron's chord was 25 inch, the same value for P-51D seem like only half of that (area was 6.7sq ft). Ie. ailerons of the Sea Fury have had the area was 17 sq ft, if my math is okay. The wing areas are 280 sq ft for S. Fury and 235.75 sq ft for P-51D. Wing span was 38' 4.75" vs. 37.03 ft, S.F. vs. -D.


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## barney (Mar 19, 2013)

nincomp said:


> Barney,
> My answer was a little too broad. To clarify this case, I should have said that some of these airfoils have nasty stall characteristics, even if the flow is turbulent.


 
Okay, thanks.


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## stona (Mar 22, 2013)

You must be very careful comparing speeds between aircraft,particularly different types and drawing such broad conclusions. There are many,many factors involved.
I am reminded of a story told by Murry White who worked as Ernie Mansbridge's assistant on the Supewrmarine Spitfire. The prototype K 5054 had only managed a disappointing 335 mph flown by Quill on 27th March 1936. Supermarine decided to fit their own propeller,with modified tips. At 1800 hours Quill took of for another series of tests. It was White who calculated the new true air speed,his calculation checked by Mansbridge. This time K 5054 managed 349.5 mph, very close to Mitchell's estimate.
That's nearly 15 mph simply by changing the propeller.

White's reaction also gives an idea of how fast this was at the time.

"I went to Ernie and told him that I had made a mistake,but couldn't see where. He looked through my figures and said that I hadn't made a mistake,and that my figures were exactly right,and was what they expected. I said I thought it would have been more like 250 mph,but he said that if it had been it wouldn't have been very good,350 mph was what they were aiming for." 

Cheers
Steve


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## GregP (Mar 22, 2013)

Look what Roy Lopresti did with the humble Globe Swift.

Ny changing the location of the wing-fudelage joint, he added some pweor and rewrote the performacne. The old Globe Swift had 125 HP and went 140 mph. The Swift Fury has 200 hp and goes 222 mph with basically the same airframe except for drag reduction. Without the drag reduction I'd expect maybe 163 mph. But with Lopresti's genius, he added another 60 mph or so.

The same can be done with fighters if the original design has flaw, and they all did to various degrees.


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