Laminar Flow Airfoil
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J.A.W.
Banned
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..
drgondog
Major
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'.
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'.
drgondog
Major
That would give the edge to the Tempest re: Mcr, all eles equal.
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?
How good/bad was the Seafang as the CV bird, having also laminar flow wing?
drgondog
Major
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.
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.
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.
OTOH, I was hoping to get a plausible assessment of Sea Fury and Seafang's capabilities in the low speed handling.
J.A.W.
Banned
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..
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..
drgondog
Major
The primary contribution of the elliptical wing was minimum induced drag... has nothing positive or negative to contribute to Stall characteristics.
GregP
Major
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.
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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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.
drgondog
Major
No apology required - other than to Horkey who would have puked over the comment..
J.A.W.
Banned
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..
GregP
Major
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.
J.A.W.
Banned
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.
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.
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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GregP
Major
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.
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.
