Propeller Design

Discussion in 'Aviation' started by TheBadger, Jul 19, 2006.

  1. TheBadger

    TheBadger New Member

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    First off, great forum people. Now the question. I have always wondered as the war progressed why american planes went to a broad four blade design of prop while the RAF seemed to favor a slender five blade design and the germans kept a large three blade paddle type. What were the reasons or benefits of each.
    Thanx!
     
  2. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    It was all a matter of the methodology used by the engineers for squeezing the maximum amount of power from the engine while achieving maximum efficiency.
     
  3. red admiral

    red admiral Member

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    It depends how fast you want your prop to spin. More blades are more efficient for a faster-spinning prop.
     
  4. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    I think it also had to do with the design of the aircraft and how to get the most from that aircraft. Some Luftwaffe aircraft had 4 blades instead of 3. Some British had 3 blades instead of 4. Some US aircraft had 3 instead of 4.
     
  5. mosquitoman

    mosquitoman Active Member

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    I always thought that the general rule was the more hp the engine gives the more propeller blades it had
     
  6. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    I dont think so. Look at the Ta-152. It had well over 2000hp and only had 3 blades. Look at the Bf-109K and so forth.
     
  7. Twitch

    Twitch Member

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    It even got as banal as the height of the landing gear struts positioning the nose above the runway for tail draggers at least. A shorter height gear kept the nose lower but limited the diameter of the blade arc. It is much easier to steer and see on the ground and easier to take off if the nose isn't pointed heavenward at a steep angle. So 4 blades of less over all diameter gave as much or more power than a large diameter 3 blade. A fighter had to still have clearance when you brought the tail up on takeoff when the fuselage was level.
     
  8. mosquitoman

    mosquitoman Active Member

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    right, gotcha
     
  9. Jank

    Jank Member

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    The P-47 was the first fighter to feature telescoping landing gear struts to give the gear more length when extended for this very reason.
     
  10. red admiral

    red admiral Member

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    As I said before;

    "It depends how fast you want your prop to spin. More blades are more efficient for a faster-spinning prop."

    Which is why more modern wind turbines (well depending on where) have one propellor and a counterweight.
     
  11. TheBadger

    TheBadger New Member

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    Thank you gentlemen for your thoughts. I agree that height is an issue I beleve that is why the Vought F4U had a cranked wing. RPM's and horsepower may figure but as stated most late models had big HP numbers, although I'm not sure about RPM's. Maybe the materials used had an affect, (were German props made out of wood?). Tip speeds need to remain sub-sonic too. Anyway thanks again for answering this trivial question.
    Oh, the best fighter of WW2?- F6F Hellcat!
     
  12. TheBadger

    TheBadger New Member

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    Thank you gentlemen for your thoughts. I agree that height is an issue I beleve that is why the Vought F4U had a cranked wing. RPM's and horsepower may figure but as stated most late models had big HP numbers, although I'm not sure about RPM's. Maybe the materials used had an affect, (were German props made out of wood?). Tip speeds need to remain sub-sonic too. Anyway thanks again for answering this trivial question.
    Oh, the best fighter of WW2?- F6F Hellcat!
     
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