High-Drag Areas on the Supermarine Spitfire

[pbehn]

To be honest, I do wonder how much the Meredith effect is fact vs myth. Obviously, there's something to it, as with laminar flow wings. But I don't think that theory 100% paid off in terms of real world results. It's like comparing the P-51 with the Spitfire. When powered by similar engines, the P-51 was a good 30 mph or so faster on top end than the Spitfire, and it took the Griffon engined Mk 14 at least 300-400 more bhp to reach the same speeds.

Overall, I think that P-51 was just a cleaner airframe than the Spitfire. The fit and finish above all on the Mustang was seemingly miles ahead of a lot of Spitfires. You have to remember that it seemed that Spitfires didn't go fully to flush riveting for all external panels until sometime in 1943. The Mustang did this basically all along going back to the NA-73X prototype.

I do believe that the laminar flow wing and Meredith radiator done well helped, but they weren't the sole magic bullets. I'd bet that a lot of why the Spiteful was so fast was just lessons learned from designing the Spitfire and gains in manufacturing and aero made since the mid 1930s.

That's why sort of my "dream" fighter would have the best attributes of the Mustang and the Spitfire. IMO, we got pretty close with the XP-51F and G, and sort of approached that with the P-51H. Or maybe if the P-51B/C/D/K was able to keep the weight to NA-73X or P-51/Mustang I levels.

If you allow 10MPH for fit finish and cleanliness, 10 MPH for reduction in cooling drag and 10MPH for lower drag aerofoils that gives you the 30MPH difference, it takes a lot of horsepower.

 

[wuzak]

If you allow 10MPH for fit finish and cleanliness, 10 MPH for reduction in cooling drag and 10MPH for lower drag aerofoils that gives you the 30MPH difference, it takes a lot of horsepower.

It was something like 8mph for the cannon installation.
A few mph for the windscreen (more upright on Spitfire than P-51).
And lots of other little things that cost a few mph each.

 

[wuzak]

Hmm - is it just me, or the Spiteful was also with a windscreen set at the shallower angle than it was the case with Spitfires?
W wuzak @Wurger etc - help

It was.

 

[pbehn]

It was something like 8mph for the cannon installation.
A few mph for the windscreen (more upright on Spitfire than P-51).
And lots of other little things that cost a few mph each.

I was just illustrating where the difference between the two comes from it was from many things, in fact things dont "tot up" in that way. The biggest difference in my opinion was that the P-51 was a generation later. If Mitchell was alive in 1940 he may well have come up with something like the P-51, just as the P-51 would not have been designed "as is" for the RAF in 1935-36 it was too heavy for the engines of that time.

 

[Aeroweanie]

No. There were two, actually, published by the Royal Aeronautical Society. The citations are here: https://ww2aircraft.net/forum/threads/ww2-fighter-and-critical-mach-speed.802/reply?quote=1308078

A bibliography of my publications on WWII aircraft:
AIAA paper 91-3288; A Retrospective - Computational Aerodynamic Analysis Methods Applied to the P-51 Mustang
EAA Sport Aviation January 1999; World War II Fighter Aerodynamics
Journal of the Royal Aeronautical Society; A CFD Evaluation of Three Prominent World War II Fighter Aircraft
SAE 2000-01-1678; Aerodynamics of the Bell P-39 Airacobra and P-63 Kingcobra
SAE 2015-01-2580; Novel World War II Aircraft Design Features
Contributions to the Birch Matthews book "Cobra!: The Bell Aircraft Corporation 1934-1946"

And, some Historic Flight Foundation talks (some of which are available on Youtube):
A Retrospective of World War II Aircraft Design; September 2012
The Grumman Cats; July 2013
The Real Story British Fighters vs. German Fighters (Battle of Britain Series); April 2015
The Remarkable History of the B-25 Mitchell; May 2017
The Grumman F8F Bearcat; September 2017
Advanced Aerodynamics; November 2018
Exceptionally Plane - People Grumman Aircraft Engineering Corporation; March 2018
The Grumman TBF Avenger; June 2018
Korean War Fighter Tactics; March 2020
The P-51 Mustang; November 2022

My favorite, which is not on WWII aircraft:
The 1937 Soviet Transpolar Flights to the United States; March 7 & 10, 2018

 

[Metrallaroja]

A bibliography of my publications on WWII aircraft:
AIAA paper 91-3288; A Retrospective - Computational Aerodynamic Analysis Methods Applied to the P-51 Mustang
EAA Sport Aviation January 1999; World War II Fighter Aerodynamics
Journal of the Royal Aeronautical Society; A CFD Evaluation of Three Prominent World War II Fighter Aircraft
SAE 2000-01-1678; Aerodynamics of the Bell P-39 Airacobra and P-63 Kingcobra
SAE 2015-01-2580; Novel World War II Aircraft Design Features
Contributions to the Birch Matthews book "Cobra!: The Bell Aircraft Corporation 1934-1946"

And, some Historic Flight Foundation talks (some of which are available on Youtube):
A Retrospective of World War II Aircraft Design; September 2012
The Grumman Cats; July 2013
The Real Story British Fighters vs. German Fighters (Battle of Britain Series); April 2015
The Remarkable History of the B-25 Mitchell; May 2017
The Grumman F8F Bearcat; September 2017
Advanced Aerodynamics; November 2018
Exceptionally Plane - People Grumman Aircraft Engineering Corporation; March 2018
The Grumman TBF Avenger; June 2018
Korean War Fighter Tactics; March 2020
The P-51 Mustang; November 2022

My favorite, which is not on WWII aircraft:
The 1937 Soviet Transpolar Flights to the United States; March 7 & 10, 2018

Awesome list, thanks a lot. Already made a list to watch the ones that I found on youtube
Im very interested in the F8F one, where can I watch it?

 

[Aeroweanie]

Awesome list, thanks a lot. Already made a list to watch the ones that I found on youtube
Im very interested in the F8F one, where can I watch it?

I don't think the F8F presentation ever got recorded. Attached are the slides

 

[Metrallaroja]

I don't think the F8F presentation ever got recorded. Attached are the slides

Thanks! Awesome presentation, the best one that I saw about F8F!

 

[WAFU]

Some solutions are just 'right'

 

[pbehn]

Some solutions are just 'right'

View attachment 702049

That is a late solution to a problem that was fixed.

 

[WAFU]

That is a late solution to a problem that was fixed.

Thats a logical development of the Spitfire like MB3 and 4 to reduce the high drag from underwings radiators - as per the P-51, that design utilises the Meredith Effect to improve cooling, significantly reduce drag and actually gain some thrust.

 

[z42]

What about wing leading edge radiators? These don't seem that much used, so evidently the simplistic argument that they add little frontal area and are thus low drag is invalid? So what's the verdict on them?

 

[tomo pauk]

What about wing leading edge radiators? These don't seem that much used, so evidently the simplistic argument that they add little frontal area and are thus low drag is invalid? So what's the verdict on them?

Depends on the judge? The judges at De Havilland and Hawker judged affirmatively wrt. the LE radiators.

 

[pbehn]

Thats a logical development of the Spitfire like MB3 and 4 to reduce the high drag from underwings radiators - as per the P-51, that design utilises the Meredith Effect to improve cooling, significantly reduce drag and actually gain some thrust.

Germany and UK had jets in squadron service in June 1944. The MB 5 flew the month before for the first time, it was too late or everything.

 

[z42]

Depends on the judge? The judges at De Havilland and Hawker judged affirmatively wrt. the LE radiators.

Yes, I'm aware of those. I guess my question is more of a theoretical nature. What is the aerodynamics of a wing with LE radiators? And given they are such an obvious idea that even yours truly can imagine them being a good design, why didn't world+dog adopt them?

 

[Metrallaroja]

Depends on the judge? The judges at De Havilland and Hawker judged affirmatively wrt. the LE radiators.

Looks better when you fit a sabre, Sabre Fury

The true evolution of the Spitfire retains the underwing rads but looks like a better design than the original. (Someone already mentioned it)

 

[Metrallaroja]

Some other LE radiators: J21, I225 and I220

 

[pbehn]

Yes, I'm aware of those. I guess my question is more of a theoretical nature. What is the aerodynamics of a wing with LE radiators? And given they are such an obvious idea that even yours truly can imagine them being a good design, why didn't world+dog adopt them?

The wing leading edge needs to have enough volume to hold the whole cooling system. The Mosquito was a bomber not a fighter and the engines were changed to allow the installation (water flow was reversed). On the Hawker Sea Fury the LE radiators were cooling the oil, the engine was air cooled.

 

[Metrallaroja]

On the Hawker Sea Fury the LE radiators were cooling the oil, the engine was air cooled.

The Hawker examples were the Griffon Fury and the Sabre Fury. Not the Centaurus Fury

 

[pbehn]

The Hawker examples were the Griffon Fury and the Sabre Fury. Not the Centaurus Fury

I was discussing the in service fury.