Author Topic: P51-D vs F4U-4 & P38-L  (Read 17955 times)

Offline Bodhi

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Re: P51-D vs F4U-4 & P38-L
« Reply #15 on: March 04, 2009, 10:27:37 PM »
Why would clearance be an issue? The diameter of the prop would remain the same.

It was meant with regards to the hub size increasing to accomodate another blade.  The hub for the Curtis is very tight.  Adding a fourth blade means that the hub spreads out to accomodate another blade which WILL increase the diameter.
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Offline Bodhi

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Re: P51-D vs F4U-4 & P38-L
« Reply #16 on: March 04, 2009, 10:32:10 PM »
I was talking about a 4 blade version of the 3 blade Hamilton Standard Paddle prop used on the P-38K. They raised the gear box up and raised the centerline of the prop shaft to make it fit the P-38.

According to the study Lockheed did, the Merlin would add weight, not remove it. At least that's what Warren Bodie said, and he had access to the original study.

Thanks for the clarification. 

As for the weight, I can't believe that the Merlin installation weighed more.  Think of all the items and equipment that can be yanked if the Allison is gone.  All the steel ducting for the turbo, the stainless tub and housing the turbo sits in, the armour plate used to protect the pilot from the turbo, the intercoolers and all that steel intake structure.  It'd be interesting to weight the Allison and the Merlin, then start weighing removed components I have around the shop to see what the difference is.
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Offline Widewing

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Re: P51-D vs F4U-4 & P38-L
« Reply #17 on: March 04, 2009, 11:24:22 PM »
The F4u-4 was the best WW2 prop fighter ever built, I think the F6F-6 would have been a monster as well. The Bearcat trumps even the -4.

You may find it interesting that I have been conversing with author Robert Dorr about the F4U-4. He is also a Technical Editor for Air Power History magazine. This is the official publication of the Air Force Historical Foundation. The magazine recently published at article titled "The P-51 Mustang: The Most Important Aircraft in History?" Bob wrote, "The current Air Power History (where I am technical editor) has an article asserting that the P-51 Mustang is not merely the best fighter of the war but the greatest airplane of all time. A popular text making the rounds on the Internet claims that the F4U-4 Corsair was really the best fighter of the war; we would like to publish this in APH but cannot identify the originator."

Guess who wrote that F4U-4 piece 11 years ago? Uh huh, yours truly. Can someone say justice prevails?

I wrote to Bob and explained in detail why the F4U-4 was simply the finest fighter to see combat in WWII. I quoted a story I got from a retired USAF Brig.General. In 1941, he joined the RCAF and was trained on Hurricanes. He flew Spitfires in Britain and eventually transferred to the USAAF. He flew P-51s in the ETO. Post war, he stayed in the Air Force Reserve. Sometime prior to the Korean war, he encountered a Navy F4U-4B while flying a P-51D. The two pilots engaged in some determined mock combat. His description of the fight was simple and directly to the point. "My Mustang had nothing for that Corsair. I could not prevent it from getting on my tail and then could do nothing to shake it off."

I offered to polish up that old piece and include actual Navy test data. I also mentioned that one of our Aces High guys had recently finished the restoration of an F4U-4... I directed him to a copy of the F4U-4's detail specification. I doubt that he had any idea that these resources were out there.

It looks like I may be writing the P-51 rebuttal piece... Should be fun, and will generate some heat. It will also generate lots of light too. In August of 1945 the top three performing fighters in the US inventory were all painted blue. F8F-1, F7F-3, and the F4U-4.

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Offline Saxman

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Re: P51-D vs F4U-4 & P38-L
« Reply #18 on: March 04, 2009, 11:58:58 PM »
Grab your flame-proof undies, WW. The Pony fanboys will be coming after you with torches and pitchforks.

But it's about time the Hog got some love from a wider audience.  :salute
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Offline Captain Virgil Hilts

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Re: P51-D vs F4U-4 & P38-L
« Reply #19 on: March 05, 2009, 12:08:44 AM »
Thanks for the clarification. 

As for the weight, I can't believe that the Merlin installation weighed more.  Think of all the items and equipment that can be yanked if the Allison is gone.  All the steel ducting for the turbo, the stainless tub and housing the turbo sits in, the armour plate used to protect the pilot from the turbo, the intercoolers and all that steel intake structure.  It'd be interesting to weight the Allison and the Merlin, then start weighing removed components I have around the shop to see what the difference is.

If you consider the power the P-38 had available, you'd have to figure that the props it had just weren't getting the job done. The chin mounted intercoolers just do not add enough drag to absorb all of the HP they allowed the Allisons to produce, after all, the H model and earlier didn't have them, and they were considerably slower that the later models, especially the L model running at full Lockheed/Allison rated boost and RPM (a difference of between 15 and 30 MPH, depending on models compared, and as much as 300HP per engine). Another thing to consider is that a turbocharger loves a load, and the more efficient the prop, the more it loads the engine, since it loses less to slippage.

The performance difference between the K model mule, with ill fitting cowl panels and all, and the J and L models is considerable, not just top speed, but especially climb rate and range (top speed increase wasn't worth a lot at altitude to the P-38, since above 25K you could get it to compress at or before 465MPH), as well as acceleration. The K model didn't have a lot more power (as compared to the J and L models), but evidently those Hamilton Standard Paddle props are a lot more efficient than the Curtiss Electric props are (as well as a lot more reliable according to the pilots). According to Bodie, the K model mule was actually a well worn and abused G model that had the chin intercoolers grafted on and the gear box cowls crudely fitted as well. The gear boxes were bigger and taller, and raised the centerline of the props several inches, so the cowls that covered them had to be quickly cobbled up by hand, they supposedly didn't really fit the prop hubs and spinners or the rest of the plane either, and the same could be said of the intercooler installation. Since there were only one or two (only one K mule was ever photographed, and there are only a couple of pictures of it) were ever built and it/they were built by hand, there's no way to tell how much the poor fit hurt the aerodynamics, but they felt it was enough to make a measurable difference.

I'm pretty sure the Merlin itself weighs a good bit more, the Allison was fairly light for it's size and displacement, Allison was originally a pure racing engine company from what I've read, and the V-1710 was first designed for the Navy to be used in lighter than air craft. I think the weight gain was fairly considerable. I'd have to drag out the book, (I don't know where it is right now, we're remodeling) but I seem to remember the total weight gain for the plane was around 1000 pounds (about 500 pounds per side I guess), despite losing most of the extensive exhaust system, the turbocharger, the intercooler, and the plumbing, which I agree is strange. Best I can remember, they anticipated little gain in speed, and an actual reduction in rate of climb, and possibly range. The desire was actually to reduce cost and complexity.

I don't know that the Merlin can be reassembled to run counter-clockwise the way the Allison can (the Allison was actually designed originally so that it could be shut down and re started running in the opposite direction), that would also cause problems, as one side would have to have a gear box with an extra gear or idler gear to make the props run in opposite directions (or the engine reversed in some other manner). Those helical cut gears in gear boxes don't like running the other way, and they usually don't like having gears added in to reverse them. That's why we use straight spur cut gears in high HP applications, but they bring in their own problems, and I can see where props might not like straight cut gears (harmonics and backlash).

The Merlin, unless tuned so that it gives up power below 22-25K feet, would give up power compared to the turbocharged Allison above 26K feet, further reducing speed and climb above that altitude. The only thing holding the Allison back from performing at altitude without the turbocharger was the crank driven supercharger. Given an equal amount of boost in stock form, the Allison actually makes more power (we tested that fooling with pulling tractors). If you put a crank driven supercharger on an Allison that made the same boost as a Merlin had, the Allison would make more power. Of course, the advantage of the supercharger on the Merlin series is it could be tuned for particular altitudes, the way it was in the Spitfires (there were high and low altitude specific versions of the Spitfire). So you can move the critical altitude to suit your purpose or mission.

But it is really hard to beat a turbocharger for great performance at a wide range of altitudes. In those days, turbocharging still had a ways to go, but even then it held some pretty significant advantages.

A late P-38 with the Hamilton Standard paddle props would have been far easier to produce and offered a lot more than a Merlin conversion. Removing the Curtiss Electric props would have removed a great deal of electrical load (the electrical system was almost overloaded if everything worked properly, and if the props acted up the generators were toast) and solved reliability issues. It would have also increased performance significantly by all measures, top speed, rate of climb, acceleration, and range. It would have required far less work with regards to changes. The gear boxes would fit the plane, props, and engines, all that was really required was a new set of dies to properly form the spinners, shrouds, and cowls. I'd be willing to bet it would have been a lot easier to get more Hamilton Standard paddle props than it would have been to get that many more Merlins. It would likely have been cheaper as well, since Packard was paying a license fee to Rolls Royce to build Merlins.
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Offline Captain Virgil Hilts

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Re: P51-D vs F4U-4 & P38-L
« Reply #20 on: March 05, 2009, 12:16:02 AM »
Grab your flame-proof undies, WW. The Pony fanboys will be coming after you with torches and pitchforks.

But it's about time the Hog got some love from a wider audience.  :salute

Shoot, he's been wearing Nomex long johns and a fire suit for years. And the P-51 guys have been on him like white on rice for a long time, a real long time.

I've always felt the blue rides have been overlooked. While the P-51 is without a doubt an excellent aircraft, and admittedly one of the finest of its time, it has always gotten far more credit than it earned, at the expense of several excellent aircraft.
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Offline Saxman

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Re: P51-D vs F4U-4 & P38-L
« Reply #21 on: March 05, 2009, 12:24:12 AM »
For that matter, the P-47 was far more important than the Mustang.

Hell, I could argue that for all the derogatory press she's been given, the F4F was the fighter that won the Pacific War, and therefore was ALSO by FAR more important than the Mustang. Guadalcanal broke the back of Japanese air power and its dominance of the Pacific, and it wasn't the Henderson P-400s that did it. The F4U, F6F and P-38 were really just the final nails in the coffin.
« Last Edit: March 05, 2009, 12:28:20 AM by Saxman »
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Offline Wmaker

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Re: P51-D vs F4U-4 & P38-L
« Reply #22 on: March 05, 2009, 03:41:29 AM »
It was meant with regards to the hub size increasing to accomodate another blade.  The hub for the Curtis is very tight.  Adding a fourth blade means that the hub spreads out to accomodate another blade which WILL increase the diameter.

Rgr, thought about that after posting, but didn't think it would be significant enough increase but there actually wasn't too much room after all. The new blade already increased the diameter and after that the distance to the fuselage wasn't too great anymore...


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Offline Captain Virgil Hilts

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Re: P51-D vs F4U-4 & P38-L
« Reply #23 on: March 05, 2009, 08:33:29 AM »
Rgr, thought about that after posting, but didn't think it would be significant enough increase but there actually wasn't too much room after all. The new blade already increased the diameter and after that the distance to the fuselage wasn't too great anymore...

(Image removed from quote.)
http://home.att.net/~C.C.Jordan/P-38K.html

The propeller in that picture is the Hamilton Standard High Activity paddle prop, so the change in hub diameter would be different, since the Hamilton Standard is hydrostatic and not electric like the Curtiss Electric prop. There isn't a lot of room there for the hub and spinner to get bigger without the cowl covering the gear box and joining to the fuselage getting almost as big as the fuselage, but there is room. A four blade Curtiss would have been close to useless as far as gains go, because the three blade was so terribly inefficient. The spinner covering a Curtiss prop hub is full, I noticed that when I was talking to Steve and Bob one day up at Middlesboro. But I don't think the spinner covering a Hamilton Standard prop hub is quite as full. The easy thing to do is to compare the spinner covering a Hamilton Standard 4 blade P-51 prop to the one covering the Curtiss on a P-38. I don't have a reference photo handy. I know Widewing did some scale comparisons for the article you got that photo from. Maybe he has done others that he has not published, or maybe he has photos he can use to do a quick and rough comparison. Or maybe Bodhi has access to the parts, photos, or drawings.

I stand corrected, by the way, I remembered the P-38K mule as being a heavily reworked G model, and it was actually an E model that had seen even more use, abuse, and modification.
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Offline CAP1

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Re: P51-D vs F4U-4 & P38-L
« Reply #24 on: March 05, 2009, 09:10:46 AM »
Shoot, he's been wearing Nomex long johns and a fire suit for years. And the P-51 guys have been on him like white on rice for a long time, a real long time.

I've always felt the blue rides have been overlooked. While the P-51 is without a doubt an excellent aircraft, and admittedly one of the finest of its time, it has always gotten far more credit than it earned, at the expense of several excellent aircraft.
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i thought i had read somewhere a long time ago, that the f4f, f6f, and corsairs were the first american fighters actually designed to dogfight? whereas the p51, p47, p38 were more intended to intercept enemy bombers....and to protect friendly bombers?
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Offline alskahawk

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Re: P51-D vs F4U-4 & P38-L
« Reply #25 on: March 05, 2009, 10:51:40 AM »
P-51D vs. P-38L with equal pilots, unless the P-51D is going to Boom and Zoom with a significant energy and altitude advantage, the P-38L is going to win.  In a co-Energy fight, the P-38L will be able to gain the advantage by keeping the fight in the vertical, where it excels far better than the Mustang.  If the P-51D tries to turn, the P-38L again has the edge. 

Basically, the best chance is for the P-51D to come in fast from an altitude advantage and try and BnZ or if you're like most P-51 drivers, wait until the Lighting is engaged with another bandit and then come in for the pick.

The P-51D driver also has to be careful when he makes his high speed passes.  The good P-38 drivers will know how to wear you down and bleed enough of your energy to either steal the advantage from you and match your energy state and get you as you go vertical or force you into a turn fight and get you that way.


ack-ack

 Actually in real life the p51 had a much better climb rate, and accelleration rate than the P-38. As did most single engine fighters verse the P-38. A function of mass.  In AH the difference is barely noticible or non-existant. Co-alt, equal energy states the P38 will outturn the P51. The P51s advantages are to out dive and return with a higher energy state.

« Last Edit: March 05, 2009, 11:01:45 AM by alskahawk »

Offline alskahawk

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Re: P51-D vs F4U-4 & P38-L
« Reply #26 on: March 05, 2009, 11:04:32 AM »
Well, yeah, I left a little bit of room there, didn't I? To be more clear, the F4U-4 is the best piston engine prop driven fighter to see actual serious combat. The F8F is actually a World War II piston engine prop driven fighter. As is the F7F. But neither saw real serious combat, if any combat at all. Wasn't their fault the enemy was already done. Sort of like the fact that it was not Lockheed's fault that the WPB and the USAAF couldn't see the real potential of the P-38K. I've always wondered what the P-38K could have done with a four blade version of that prop.

 I would have liked to have seen the A-1(Spad, skyraider?) make it in.

Offline Captain Virgil Hilts

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Re: P51-D vs F4U-4 & P38-L
« Reply #27 on: March 05, 2009, 12:53:49 PM »
Actually in real life the p51 had a much better climb rate, and accelleration rate than the P-38. As did most single engine fighters verse the P-38. A function of mass.  In AH the difference is barely noticible or non-existant. Co-alt, equal energy states the P38 will outturn the P51. The P51s advantages are to out dive and return with a higher energy state.



Wrong. The P-51 did not outclimb the P-38, ask the guys who flew both, Stan Richardson and Art Heiden will both tell you that the P-51 could not out climb a P-38, and they flew the real thing, in the skies over Europe, fighting for their lives. Nor did it out accelerate the P-38. Only at certain speeds and certain altitudes, and not many of them, either, did the P-51 out accelerate the P-38. You can talk mass all you want, but you're ignoring an important factor, HORSEPOWER.
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Offline Yeager

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Re: P51-D vs F4U-4 & P38-L
« Reply #28 on: March 05, 2009, 03:50:08 PM »
this is a real world thread, not a game thread?
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Offline Steve

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Re: P51-D vs F4U-4 & P38-L
« Reply #29 on: March 05, 2009, 03:57:30 PM »
Back to the OP.  Pilots and E states being equal , the 51 finishes a distant third.

As far as AHII goes,  compared to the other late war rides, the 51 is really quite mediocre.
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