P-47 with a healthy dose of hindsight?

Discussion in 'Aviation' started by tomo pauk, Mar 31, 2014.

  1. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Another big brute - how would it looked like if you were on helm of the design team? By 'P-47', I mean a fighter that is mandatory designed around a R-2800 with turbo charger
     
  2. Shortround6

    Shortround6 Well-Known Member

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    What trade-offs do you want to make?

    The engine and turbo (and inter-cooler) and prop aren't going to change much unless you can come up with the paddle blade props sooner. You have to put 300 gals or more of fuel somewhere or have even shorter range. Since early versions are going to have tooth-pick props (unless you can change that) and only 2000 hp for take-off sticking in a lot more than 300 gallons brings problems of it's own.
    Real P-47 was more than a bit of a ground hog so unless you do something real tricky with the wing you can't make the wing much smaller without making runways longer.

    Only real saving would be to limit guns to 6 and the ammo supply but that option was already available but seldom used. Many of the weight charts show 6 guns standard and the 2 additional guns as "optional".

    Please note that distance the Americans placed the turbo chargers from the engine may have allowed for longer turbo charger life and greater safety. Moving the turbo closer would have meant higher inlet temperatures to the turbine and a higher rate of blade failure. Failed blades on a turbine spinning 22-25,000rpm can mean things get real nasty, real quick.
     
  3. pbehn

    pbehn Well-Known Member

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    I am surprised it was ever designed as a "razorback" when visibility is so important to the pilot.
     
  4. drgondog

    drgondog Well-Known Member

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    Sure would have designed the wing to accommodate fuel early on, along with provision for wing racks
     
  5. davebender

    davebender Well-Known Member

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    Put those R2800 engines in F4U airframes with a supercharger / turbocharger suitable for the bomber escort mission. Or else fix P-38 for the bomber escort mission and use F4U for the multitude of missions taking place below 20,000 feet.
     
  6. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Some ideas: use the metal ailerons from starters, and make sure the air-frame is strong enough for dive pull-outs the 6-7 ton fighter might be doing. (Historically fixed with the P-47C) Big fighter with big engine needs great amount of fuel - use up all of the height above the main fuel tank ASAP, for 370 gals in fuselage. (Historically fixed with late P-47D models). Introduce 2 wing racks, instead of 1 belly rack; even the 2 x 75 gals make difference, let alone bigger tanks (some P-47s were ferried via Iceland with 2 x 165 gal wing tanks in Aug 1943; wing racks were standard from early 1944 on; maybe copy/adopt Lockheed system from P-38s? - even seem like a less draggy thing). Use broader prop blades - maybe take a look at F4U (but use 4 shorter blades, not 3 long ones)? Agree that razorback spoils visibility - maybe take a look at P-38 again, this time on the canopy? Later - take notes from Whirlwind?
    As a bigger change - opt for a two-spar wing, retract the main wheels in front of the front spar, so there is ample space in the wings for consumables, predominantly fuel?

    BTW, does anybody have data about the thickness of the S-3 wing profile found at the P-47s?
     
  7. Shortround6

    Shortround6 Well-Known Member

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    You stick the turbo in an F4U airframe and you wind up with either a very fat F4U or one that looks like a pregnant kangaroo.

    The F4U used the best two stage supercharger the Americans had at the time and it wasn't good enough. There was NO mechanical drive supercharger, regardless of the number of stages, that would allow the R-2800 to make 2000hp at 25,000ft.

    You seem to have a real dislike of the P-47 but you don't seem to come up with any facts to support your position of why it was so bad.
     
  8. Shortround6

    Shortround6 Well-Known Member

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    #8 Shortround6, Mar 31, 2014
    Last edited: Mar 31, 2014
    Even if you can come up with the better propeller sooner, you still need to improve the the engine sooner to handle all the weight you want to throw into the plane.
    The paddle blade prop was about 120lbs heavier than the tooth-pick one. The 370 gallon fuel tank set up was 90lbs heavier than the 305 gal tank/s. Self sealing is not light and big square or oval tanks have more volume per unit of surface area than long skinny tanks in the wings.
    P-47N gained almost 900lbs over a late model bubble top D and the late model bubble top D was 300lbs heavier than a C and the C was 550lbs heavier than a B. These are empty weights without guns, gun sights, trapped oil, etc.

    Expecting the early P-47 to perform with 3/4 of ton of "improvements" before you fill up the fuel tanks with only a 2000hp engine is asking for a lot. :)
     
  9. bobbysocks

    bobbysocks Well-Known Member

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    what you are able to put on it is going to be driven by the technology at that moment. you probably cant start out with a bubble canopy at the onset since they werent manufactured at that time...unless you are reseaching and developing that technology hand in hand with your plane.
     
  10. Shortround6

    Shortround6 Well-Known Member

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    REPUBLIC S-3 AIRFOIL (s3-il)
     
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  11. tomo pauk

    tomo pauk Creator of Interesting Threads

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    Thanks for the link :)

    I'm not trying to make a 'P-47B' hauling 560 gals of fuel internally. Paddle blade prop was heavier, but it more than pulled it's own weight.

    Hello, bobbysocks
    I'm after the canopy of the P-38 - it was around before ww2 started. Granted, it was not that polished item as the true bubble top, but it was far better than the razorback's canopies.
     
  12. gjs238

    gjs238 Well-Known Member

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    My thoughts exactly.
    Historically this took much too long.
    It should have been clear to most that US efforts would be expeditionary in nature, so making better use of those wings is a must.
     
  13. gjs238

    gjs238 Well-Known Member

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    Interesting point.

    How did the US Army reconcile the P-38 P-47?
    That is, why the need for two high altitude turbocharged fighters?
     
  14. gjs238

    gjs238 Well-Known Member

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    Does this mean that the F4U could in no way have provided high altitude escort in the ETO?
    This has come up in other threads, but I've never seen it articulated this way.
    (Not challenging the facts, just very interested.)
     
  15. pbehn

    pbehn Well-Known Member

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    Hi Bobbysocks what I meant was the Spitfire first flew in 1936, I dont know when it was first seen in public but surely someone must have thought "thats a good idea". Mind you Hawkers didnt with the Typhoon.
     
  16. tomo pauk

    tomo pauk Creator of Interesting Threads

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    It is not so much about the need for two high altitude (= turbocharged; USAF was not sold on mechanical two-stage engines well until Pearl) fighters. It is about the USAF feeling that, with it's new generation of fighters (P-38/-39/40), it has all of their eggs in one basket - basket's name was V-1710. Hence the push for R-2800 and (Packard) Merlin in 1940. Compared with so called hi-per engines in development, those two were actual, workable engines, and not much could went wrong.
     
  17. Shortround6

    Shortround6 Well-Known Member

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    Did it?

    Or did it pull it's own weight when the engine was cleared for 2300-2600hp using water injection or 150PN fuel?

    It might have helped the 2000hp version but the improvement may not have been as dramatic, both due to the HP difference and the fact that the original prop may have been a closer match (even if a bit 'undersized' for 2000hp) than it was for 2300hp ( way 'undersized').
     
  18. Shortround6

    Shortround6 Well-Known Member

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    I don't know about "F4U could in no way" because the P-47 did not use exhaust thrust (early F4Us didn't use it very well either though) and was smaller in diameter fuselage Drag figures are still being argued.
    What is true is that the turbo supplied enough air to the engine supercharger to allow the R-2800 to make 2000hp at 25,000 or above ( newer turbo models and controllers pushed it to over 30,000ft) because it used the power of the exhaust to drive the 1st stage compressor, While the two stage supercharger on the Navy engines took 350hp or so to run the 1st stage compressor high gear.

    Please note it took until after the war for P&W to get this engine
    R-2800-32Wst.jpg
    To give 1800hp at 30,000ft using 115/145 fuel, two parallel superchargers feeding the main (2nd) stage for a total of 3 impellers and a variable hydraulic drive.

    Standard F4U engine gave 1650hp at 22,500ft (no RAM) and the -18 engine in the F4U-4 could give 1800hp at 23,000ft.

    If you want to add a 3rd stage mechanically driven you have to take the power from the crankshaft. The limit is how much power are you making in the cylinders and where is it going. To the prop or to drive the superchargers?
     
  19. tomo pauk

    tomo pauk Creator of Interesting Threads

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    On military power (2000 HP), the 14500 lb heavy P-47D-23, with paddle blade prop, was climbing every bit as fast (or slow ;) ) as the 13500 lbs heavy P-47C and early D with toothpick prop. Judging by a look at AHT charts at pg. 278 and 281.
     
  20. gjs238

    gjs238 Well-Known Member

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    In this light...
    Then perhaps pre-war US Army emphasis on turbocharging was not so off the mark as some seem to imply.
    And expectations that Allison could have just "done it" (i.e., produced two-stage supercharging for the V-1710) if given enough resources might not be so realistic.
    And Sir Stanley Hooker was truly a genius.
     
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