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Thread: Best prop size for OS55ax in p51 Mustang PTS

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  1. Best prop size for OS55ax in p51 Mustang PTS 
    #1
    Hi everybody,

    I have a quick question about prop sizes for the P-51 Mustang PTS. I bought a brand new OS55ax for my mustang PTS. It has 10 tanks of fuel through it and I am running it a little rich for a few more tanks. My question to everybosy here is what is the best APC prop size to put on it? I am currently running an APC 12x7 on it and am getting around 10,000 rpms (everything is stock). The plane weighs about 7 pounds. What would everybody suggest if I wanted more vertical performance? What would I use if I wanted more horizontal speed? If anybody makes a suggestion, please also state what the typical rpm should be for that prop. I am using 10% nitro synth/castor blend. Any help would be greatly appreciated. I will post pictures of my 'stang as I built a cockpit for it and weathered it to look more scale.

    Happy flying!
     

  2.  
    #2
    Join Date
    05-05-2012
    Location
    chardon, oh usa
    Posts
    8
    I am also looking to put an os55ax in my p51 sport 40. Any ideas??
     

  3.  
    #3
    Join Date
    08-19-2002
    Location
    Wichita, ks
    Posts
    27
    Depends on what you want to do... 12x6 will be good all-around I think, and an 11x7-11x8 will pull a little harder on the top end.

    Fun to experiment with both.

    -Eric
     

  4.  
    #4
    Join Date
    05-05-2012
    Location
    chardon, oh usa
    Posts
    8
    What is the correct was to pick out a prop? Is there a chart you use? Does it depend on weight of plane? They list some recommended props with the engine on the OS site. They show 12x7,12x8,13x6,13x7. So very confused.
     

  5.  
    #5
    Join Date
    08-19-2002
    Location
    Wichita, ks
    Posts
    27
    Mostly just experience in intuition really...

    The manual is a good reference, but I read a long time ago that OS generally recommends a little larger prop than the engine is really happy with so that the noise levels are a little lower, mainly for the Japanese market where the sound levels are more strictly enforced.

    And yeah it does depend on the weight/aerodynamics of the plane. If you had a 55AX on a Hangar 9 Twist .40, it'd probably be a 13x4 I'd recommend over a 12x6.

    "rule of thumb" if you're not making big changes is to go up two in pitch for going down one in diameter. Or if you go up one in diameter, go down two in pitch.

    -Eric
     

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