Discussion in 'Gallery & Designs' started by Jimi, Feb 11, 2005.

  1. Jimi

    Jimi Member

    Hi all. In regard to nobi's question of how i made the propellers of my fokker 50 in rhino, i decided to post it here in order to make future browsing of specific topics easier.. :) It's better if we can include all the other different propellers (ship or plane) and building methods. :)

    Anyway, Here's a shot of a propeller blade of the fokker. One will observe that the blade angle at the root of the propeller is greater than the tip chord. Therefore, there's a twist. why this is so has many reasons in the aerodynamics and structural aspects. Aside from looking really wicked (let's face it. Twisted stuff are really cool! :twisted: twisted metal, twisted poems, twister fries, twisted doughnuts), a twisted blade design assures that the thrust produced at varying distances from the root to the tip are equal. Also, since the tip travels at speeds greater than the root of the blade, a large angle of attack would create unwanted loads in the propeller and engine. also well, greater noise levels.

    Anyway, here's how i built the props. :) It's really simple. since the props will really be small, not much details are needed. It's also important that the designer/modeler has enough data about the props to be made.
  2. Jimi

    Jimi Member

    hi all. next..
  3. Jimi

    Jimi Member

    Final product. rotate the props using the array polar command or any equivalent command.
  4. Leif Oh

    Leif Oh Member

    Great work Jimi.

    A comment and a question: I think most propellers have a Clark Y profile (or similar), curved on the front part and rather flat on the back. Perhaps this is different on modern turboprops?

    A propeller blade is nothing but a wing. The twist is necessitated in order to keep the same angle of attack in relation to relative wind (the resultant of rotation and the aircraft's speed throught the air). Since the tips go through the air at much higher speed relative incoming airflow (aircraft speed) than the part closer to the hub, they have seemingly less angle of attack (but not so when the aircraft is in motion).

    For an attempt to build this correctly, see the thread: "Getting it right with a large, three-bladed prop".

    Best, Leif
  5. Jimi

    Jimi Member

    leif- Thanks! hehehe. the old props use the good ol' clark y airfoil. the reason for people using it is because an airfoil with a larger upper camber and a smaller lower camber produces a lot of lift compared to a symmetrical airfoil but a clark y also has a lot of disadvantages. one is because of it's thick profile and high lift characteristics, it produces a lot of drag. nowadays, there are many different airfoils used for different purposes. so there are still symmetrical airfoils in use today. In the modeler's aspect, on really small scale planes, the subtle differences of the props to be modeled and the model itself arent really noticable so it's ok to cheat a bit. :wink: but if it's large, the modeler has to pay particular attention to the props.
  6. NOBI

    NOBI Active Member

    Hi Jimi,

    Thank you very much, im very appreciate your tutorial, real cool guy

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