3 blade vs. 2 blade prop

Discussion in 'Scratchbuild Talk' started by jcrankshaw, Jul 27, 2010.

  1. jcrankshaw

    jcrankshaw Ace Pilot

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    Can someone explain what situation permits 3 blades as opposed to 2?
     
  2. flycap93

    flycap93 Rookie

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    3 bladed props are for more scale looks and soft accleration. 2 bladed props are more for speed and lots of punch for accleration.
     
  3. JettaManDan

    JettaManDan Administrator

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    yeah i have tried 3 bladers and they feel like they have 1/2 the power...for any of the parkjets you need the 2 blade props...if you go multi-motors like Dave did with his Hawk Sky then the 3 blades ones work good...if you want quiet and softer performace then 3 blade ones work..they usually have more flex..
     
  4. kaptondave

    kaptondave Rookie

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    I have tried 3-blade props, both on the test bench and on planes. I do not agree that they have half the power. A 3-blade generates thrust that is roughly the same as 2-blade that is one number larger in diameter. In other words a 9x6 3-blade is equates to a 10x6 2-blade. The advantage of a 3-blade is that it swings a smaller arc, which is sometimes helpful on planes like the park jets that have enclosed props, and quieter.
     
  5. JettaManDan

    JettaManDan Administrator

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    might have been the prop i used....it just didn't have nearly the thrust or the power of the 6x4 i was spinning before...
     
  6. RCPlattu

    RCPlattu Airman

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    It's like an extra wing that gives more lift but also more drag. More drag (it's probably more than just "drag" as we know it but anyway...) means higher load on the motor. Don't fry it! (Use a watt-meter to make sure you don't exceed limits.)
     
  7. ScottLott

    ScottLott Administrator

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    Kapton Dave covered most of it, but let me polish it off:

    If your speaking of GWS 3 bladed props, you will experience quite a loss of power vs like an APC prop. You can thank the flimsiness of the GWS props for that.

    Speaking specifically, adding another blade to the prop is like adding another inch to the length. You'll get better acceleration, a slight speed decrease, and an increase in amp draw.

    So if you had a 6x4x3 prop it would be roughly equivalent to like a 7.5x4(two bladed). Really, the only good thing the third blade gives you is the advantage of a larger prop without the higher diameter. (Which is perfect if you have a scale warbird like the P-51 with low sitting landing gear)

    I'm positive there are other, more subtle characteristics, but they are negligible at the speeds we fly at (under 100mph). Thanks!
     
    vspeeds likes this.
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